_ Git - rust-lightning/blob - lightning/src/routing/router.rs

   1 // This file is Copyright its original authors, visible in version control
   2 // history.
   3 //
   4 // This file is licensed under the Apache License, Version 2.0 <LICENSE-APACHE
   5 // or http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your option.
   7 // You may not use this file except in accordance with one or both of these
   8 // licenses.
   9
  10 //! The top-level routing/network map tracking logic lives here.
  11 //!
  12 //! You probably want to create a NetGraphMsgHandler and use that as your RoutingMessageHandler and then
  13 //! interrogate it to get routes for your own payments.
  14
  15 use bitcoin::secp256k1::key::PublicKey;
  16
  17 use ln::channelmanager::ChannelDetails;
  18 use ln::features::{ChannelFeatures, InvoiceFeatures, NodeFeatures};
  19 use ln::msgs::{DecodeError, ErrorAction, LightningError, MAX_VALUE_MSAT};
  20 use routing;
  21 use routing::network_graph::{NetworkGraph, NodeId, RoutingFees};
  22 use util::ser::{Writeable, Readable};
  23 use util::logger::{Level, Logger};
  24
  25 use io;
  26 use prelude::*;
  27 use alloc::collections::BinaryHeap;
  28 use core::cmp;
  29 use core::ops::Deref;
  30
  31 /// A hop in a route
  32 #[derive(Clone, Debug, Hash, PartialEq, Eq)]
  33 pub struct RouteHop {
  34         /// The node_id of the node at this hop.
  35         pub pubkey: PublicKey,
  36         /// The node_announcement features of the node at this hop. For the last hop, these may be
  37         /// amended to match the features present in the invoice this node generated.
  38         pub node_features: NodeFeatures,
  39         /// The channel that should be used from the previous hop to reach this node.
  40         pub short_channel_id: u64,
  41         /// The channel_announcement features of the channel that should be used from the previous hop
  42         /// to reach this node.
  43         pub channel_features: ChannelFeatures,
  44         /// The fee taken on this hop (for paying for the use of the *next* channel in the path).
  45         /// For the last hop, this should be the full value of the payment (might be more than
  46         /// requested if we had to match htlc_minimum_msat).
  47         pub fee_msat: u64,
  48         /// The CLTV delta added for this hop. For the last hop, this should be the full CLTV value
  49         /// expected at the destination, in excess of the current block height.
  50         pub cltv_expiry_delta: u32,
  51 }
  52
  53 impl_writeable_tlv_based!(RouteHop, {
  54         (0, pubkey, required),
  55         (2, node_features, required),
  56         (4, short_channel_id, required),
  57         (6, channel_features, required),
  58         (8, fee_msat, required),
  59         (10, cltv_expiry_delta, required),
  60 });
  61
  62 /// A route directs a payment from the sender (us) to the recipient. If the recipient supports MPP,
  63 /// it can take multiple paths. Each path is composed of one or more hops through the network.
  64 #[derive(Clone, Hash, PartialEq, Eq)]
  65 pub struct Route {
  66         /// The list of routes taken for a single (potentially-)multi-part payment. The pubkey of the
  67         /// last RouteHop in each path must be the same.
  68         /// Each entry represents a list of hops, NOT INCLUDING our own, where the last hop is the
  69         /// destination. Thus, this must always be at least length one. While the maximum length of any
  70         /// given path is variable, keeping the length of any path to less than 20 should currently
  71         /// ensure it is viable.
  72         pub paths: Vec<Vec<RouteHop>>,
  73 }
  74
  75 impl Route {
  76         /// Returns the total amount of fees paid on this [`Route`].
  77         ///
  78         /// This doesn't include any extra payment made to the recipient, which can happen in excess of
  79         /// the amount passed to [`get_route`]'s `final_value_msat`.
  80         pub fn get_total_fees(&self) -> u64 {
  81                 // Do not count last hop of each path since that's the full value of the payment
  82                 return self.paths.iter()
  83                         .flat_map(|path| path.split_last().map(|(_, path_prefix)| path_prefix).unwrap_or(&[]))
  84                         .map(|hop| &hop.fee_msat)
  85                         .sum();
  86         }
  87
  88         /// Returns the total amount paid on this [`Route`], excluding the fees.
  89         pub fn get_total_amount(&self) -> u64 {
  90                 return self.paths.iter()
  91                         .map(|path| path.split_last().map(|(hop, _)| hop.fee_msat).unwrap_or(0))
  92                         .sum();
  93         }
  94 }
  95
  96 const SERIALIZATION_VERSION: u8 = 1;
  97 const MIN_SERIALIZATION_VERSION: u8 = 1;
  98
  99 impl Writeable for Route {
 100         fn write<W: ::util::ser::Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 101                 write_ver_prefix!(writer, SERIALIZATION_VERSION, MIN_SERIALIZATION_VERSION);
 102                 (self.paths.len() as u64).write(writer)?;
 103                 for hops in self.paths.iter() {
 104                         (hops.len() as u8).write(writer)?;
 105                         for hop in hops.iter() {
 106                                 hop.write(writer)?;
 107                         }
 108                 }
 109                 write_tlv_fields!(writer, {});
 110                 Ok(())
 111         }
 112 }
 113
 114 impl Readable for Route {
 115         fn read<R: io::Read>(reader: &mut R) -> Result<Route, DecodeError> {
 116                 let _ver = read_ver_prefix!(reader, SERIALIZATION_VERSION);
 117                 let path_count: u64 = Readable::read(reader)?;
 118                 let mut paths = Vec::with_capacity(cmp::min(path_count, 128) as usize);
 119                 for _ in 0..path_count {
 120                         let hop_count: u8 = Readable::read(reader)?;
 121                         let mut hops = Vec::with_capacity(hop_count as usize);
 122                         for _ in 0..hop_count {
 123                                 hops.push(Readable::read(reader)?);
 124                         }
 125                         paths.push(hops);
 126                 }
 127                 read_tlv_fields!(reader, {});
 128                 Ok(Route { paths })
 129         }
 130 }
 131
 132 /// Parameters needed to re-compute a [`Route`] for retrying a failed payment path.
 133 ///
 134 /// Provided in [`Event::PaymentPathFailed`] and passed to [`get_retry_route`].
 135 ///
 136 /// [`Event::PaymentPathFailed`]: crate::util::events::Event::PaymentPathFailed
 137 #[derive(Clone, Debug)]
 138 pub struct PaymentPathRetry {
 139         /// The recipient of the failed payment path.
 140         pub payee: Payee,
 141
 142         /// The amount in msats sent on the failed payment path.
 143         pub final_value_msat: u64,
 144
 145         /// The CLTV on the final hop of the failed payment path.
 146         pub final_cltv_expiry_delta: u32,
 147 }
 148
 149 impl_writeable_tlv_based!(PaymentPathRetry, {
 150         (0, payee, required),
 151         (2, final_value_msat, required),
 152         (4, final_cltv_expiry_delta, required),
 153 });
 154
 155 /// The recipient of a payment.
 156 #[derive(Clone, Debug)]
 157 pub struct Payee {
 158         /// The node id of the payee.
 159         pub pubkey: PublicKey,
 160
 161         /// Features supported by the payee.
 162         ///
 163         /// May be set from the payee's invoice or via [`for_keysend`]. May be `None` if the invoice
 164         /// does not contain any features.
 165         ///
 166         /// [`for_keysend`]: Self::for_keysend
 167         pub features: Option<InvoiceFeatures>,
 168
 169         /// Hints for routing to the payee, containing channels connecting the payee to public nodes.
 170         pub route_hints: Vec<RouteHint>,
 171 }
 172
 173 impl_writeable_tlv_based!(Payee, {
 174         (0, pubkey, required),
 175         (2, features, option),
 176         (4, route_hints, vec_type),
 177 });
 178
 179 impl Payee {
 180         /// Creates a payee with the node id of the given `pubkey`.
 181         pub fn new(pubkey: PublicKey) -> Self {
 182                 Self {
 183                         pubkey,
 184                         features: None,
 185                         route_hints: vec![],
 186                 }
 187         }
 188
 189         /// Creates a payee with the node id of the given `pubkey` to use for keysend payments.
 190         pub fn for_keysend(pubkey: PublicKey) -> Self {
 191                 Self::new(pubkey).with_features(InvoiceFeatures::for_keysend())
 192         }
 193
 194         /// Includes the payee's features.
 195         ///
 196         /// (C-not exported) since bindings don't support move semantics
 197         pub fn with_features(self, features: InvoiceFeatures) -> Self {
 198                 Self { features: Some(features), ..self }
 199         }
 200
 201         /// Includes hints for routing to the payee.
 202         ///
 203         /// (C-not exported) since bindings don't support move semantics
 204         pub fn with_route_hints(self, route_hints: Vec<RouteHint>) -> Self {
 205                 Self { route_hints, ..self }
 206         }
 207 }
 208
 209 /// A list of hops along a payment path terminating with a channel to the recipient.
 210 #[derive(Clone, Debug, Hash, Eq, PartialEq)]
 211 pub struct RouteHint(pub Vec<RouteHintHop>);
 212
 213
 214 impl Writeable for RouteHint {
 215         fn write<W: ::util::ser::Writer>(&self, writer: &mut W) -> Result<(), io::Error> {
 216                 (self.0.len() as u64).write(writer)?;
 217                 for hop in self.0.iter() {
 218                         hop.write(writer)?;
 219                 }
 220                 Ok(())
 221         }
 222 }
 223
 224 impl Readable for RouteHint {
 225         fn read<R: io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
 226                 let hop_count: u64 = Readable::read(reader)?;
 227                 let mut hops = Vec::with_capacity(cmp::min(hop_count, 16) as usize);
 228                 for _ in 0..hop_count {
 229                         hops.push(Readable::read(reader)?);
 230                 }
 231                 Ok(Self(hops))
 232         }
 233 }
 234
 235 /// A channel descriptor for a hop along a payment path.
 236 #[derive(Clone, Debug, Hash, Eq, PartialEq)]
 237 pub struct RouteHintHop {
 238         /// The node_id of the non-target end of the route
 239         pub src_node_id: PublicKey,
 240         /// The short_channel_id of this channel
 241         pub short_channel_id: u64,
 242         /// The fees which must be paid to use this channel
 243         pub fees: RoutingFees,
 244         /// The difference in CLTV values between this node and the next node.
 245         pub cltv_expiry_delta: u16,
 246         /// The minimum value, in msat, which must be relayed to the next hop.
 247         pub htlc_minimum_msat: Option<u64>,
 248         /// The maximum value in msat available for routing with a single HTLC.
 249         pub htlc_maximum_msat: Option<u64>,
 250 }
 251
 252 impl_writeable_tlv_based!(RouteHintHop, {
 253         (0, src_node_id, required),
 254         (1, htlc_minimum_msat, option),
 255         (2, short_channel_id, required),
 256         (3, htlc_maximum_msat, option),
 257         (4, fees, required),
 258         (6, cltv_expiry_delta, required),
 259 });
 260
 261 #[derive(Eq, PartialEq)]
 262 struct RouteGraphNode {
 263         node_id: NodeId,
 264         lowest_fee_to_peer_through_node: u64,
 265         lowest_fee_to_node: u64,
 266         // The maximum value a yet-to-be-constructed payment path might flow through this node.
 267         // This value is upper-bounded by us by:
 268         // - how much is needed for a path being constructed
 269         // - how much value can channels following this node (up to the destination) can contribute,
 270         //   considering their capacity and fees
 271         value_contribution_msat: u64,
 272         /// The effective htlc_minimum_msat at this hop. If a later hop on the path had a higher HTLC
 273         /// minimum, we use it, plus the fees required at each earlier hop to meet it.
 274         path_htlc_minimum_msat: u64,
 275         /// All penalties incurred from this hop on the way to the destination, as calculated using
 276         /// channel scoring.
 277         path_penalty_msat: u64,
 278 }
 279
 280 impl cmp::Ord for RouteGraphNode {
 281         fn cmp(&self, other: &RouteGraphNode) -> cmp::Ordering {
 282                 let other_score = cmp::max(other.lowest_fee_to_peer_through_node, other.path_htlc_minimum_msat)
 283                         .checked_add(other.path_penalty_msat)
 284                         .unwrap_or_else(|| u64::max_value());
 285                 let self_score = cmp::max(self.lowest_fee_to_peer_through_node, self.path_htlc_minimum_msat)
 286                         .checked_add(self.path_penalty_msat)
 287                         .unwrap_or_else(|| u64::max_value());
 288                 other_score.cmp(&self_score).then_with(|| other.node_id.cmp(&self.node_id))
 289         }
 290 }
 291
 292 impl cmp::PartialOrd for RouteGraphNode {
 293         fn partial_cmp(&self, other: &RouteGraphNode) -> Option<cmp::Ordering> {
 294                 Some(self.cmp(other))
 295         }
 296 }
 297
 298 struct DummyDirectionalChannelInfo {
 299         cltv_expiry_delta: u32,
 300         htlc_minimum_msat: u64,
 301         htlc_maximum_msat: Option<u64>,
 302         fees: RoutingFees,
 303 }
 304
 305 /// It's useful to keep track of the hops associated with the fees required to use them,
 306 /// so that we can choose cheaper paths (as per Dijkstra's algorithm).
 307 /// Fee values should be updated only in the context of the whole path, see update_value_and_recompute_fees.
 308 /// These fee values are useful to choose hops as we traverse the graph "payee-to-payer".
 309 #[derive(Clone, Debug)]
 310 struct PathBuildingHop<'a> {
 311         // The RouteHintHop fields which will eventually be used if this hop is used in a final Route.
 312         // Note that node_features is calculated separately after our initial graph walk.
 313         node_id: NodeId,
 314         short_channel_id: u64,
 315         channel_features: &'a ChannelFeatures,
 316         fee_msat: u64,
 317         cltv_expiry_delta: u32,
 318
 319         /// Minimal fees required to route to the source node of the current hop via any of its inbound channels.
 320         src_lowest_inbound_fees: RoutingFees,
 321         /// Fees of the channel used in this hop.
 322         channel_fees: RoutingFees,
 323         /// All the fees paid *after* this channel on the way to the destination
 324         next_hops_fee_msat: u64,
 325         /// Fee paid for the use of the current channel (see channel_fees).
 326         /// The value will be actually deducted from the counterparty balance on the previous link.
 327         hop_use_fee_msat: u64,
 328         /// Used to compare channels when choosing the for routing.
 329         /// Includes paying for the use of a hop and the following hops, as well as
 330         /// an estimated cost of reaching this hop.
 331         /// Might get stale when fees are recomputed. Primarily for internal use.
 332         total_fee_msat: u64,
 333         /// This is useful for update_value_and_recompute_fees to make sure
 334         /// we don't fall below the minimum. Should not be updated manually and
 335         /// generally should not be accessed.
 336         htlc_minimum_msat: u64,
 337         /// A mirror of the same field in RouteGraphNode. Note that this is only used during the graph
 338         /// walk and may be invalid thereafter.
 339         path_htlc_minimum_msat: u64,
 340         /// All penalties incurred from this channel on the way to the destination, as calculated using
 341         /// channel scoring.
 342         path_penalty_msat: u64,
 343         /// If we've already processed a node as the best node, we shouldn't process it again. Normally
 344         /// we'd just ignore it if we did as all channels would have a higher new fee, but because we
 345         /// may decrease the amounts in use as we walk the graph, the actual calculated fee may
 346         /// decrease as well. Thus, we have to explicitly track which nodes have been processed and
 347         /// avoid processing them again.
 348         was_processed: bool,
 349         #[cfg(any(test, feature = "fuzztarget"))]
 350         // In tests, we apply further sanity checks on cases where we skip nodes we already processed
 351         // to ensure it is specifically in cases where the fee has gone down because of a decrease in
 352         // value_contribution_msat, which requires tracking it here. See comments below where it is
 353         // used for more info.
 354         value_contribution_msat: u64,
 355 }
 356
 357 // Instantiated with a list of hops with correct data in them collected during path finding,
 358 // an instance of this struct should be further modified only via given methods.
 359 #[derive(Clone)]
 360 struct PaymentPath<'a> {
 361         hops: Vec<(PathBuildingHop<'a>, NodeFeatures)>,
 362 }
 363
 364 impl<'a> PaymentPath<'a> {
 365         // TODO: Add a value_msat field to PaymentPath and use it instead of this function.
 366         fn get_value_msat(&self) -> u64 {
 367                 self.hops.last().unwrap().0.fee_msat
 368         }
 369
 370         fn get_total_fee_paid_msat(&self) -> u64 {
 371                 if self.hops.len() < 1 {
 372                         return 0;
 373                 }
 374                 let mut result = 0;
 375                 // Can't use next_hops_fee_msat because it gets outdated.
 376                 for (i, (hop, _)) in self.hops.iter().enumerate() {
 377                         if i != self.hops.len() - 1 {
 378                                 result += hop.fee_msat;
 379                         }
 380                 }
 381                 return result;
 382         }
 383
 384         // If the amount transferred by the path is updated, the fees should be adjusted. Any other way
 385         // to change fees may result in an inconsistency.
 386         //
 387         // Sometimes we call this function right after constructing a path which is inconsistent in
 388         // that it the value being transferred has decreased while we were doing path finding, leading
 389         // to the fees being paid not lining up with the actual limits.
 390         //
 391         // Note that this function is not aware of the available_liquidity limit, and thus does not
 392         // support increasing the value being transferred.
 393         fn update_value_and_recompute_fees(&mut self, value_msat: u64) {
 394                 assert!(value_msat <= self.hops.last().unwrap().0.fee_msat);
 395
 396                 let mut total_fee_paid_msat = 0 as u64;
 397                 for i in (0..self.hops.len()).rev() {
 398                         let last_hop = i == self.hops.len() - 1;
 399
 400                         // For non-last-hop, this value will represent the fees paid on the current hop. It
 401                         // will consist of the fees for the use of the next hop, and extra fees to match
 402                         // htlc_minimum_msat of the current channel. Last hop is handled separately.
 403                         let mut cur_hop_fees_msat = 0;
 404                         if !last_hop {
 405                                 cur_hop_fees_msat = self.hops.get(i + 1).unwrap().0.hop_use_fee_msat;
 406                         }
 407
 408                         let mut cur_hop = &mut self.hops.get_mut(i).unwrap().0;
 409                         cur_hop.next_hops_fee_msat = total_fee_paid_msat;
 410                         // Overpay in fees if we can't save these funds due to htlc_minimum_msat.
 411                         // We try to account for htlc_minimum_msat in scoring (add_entry!), so that nodes don't
 412                         // set it too high just to maliciously take more fees by exploiting this
 413                         // match htlc_minimum_msat logic.
 414                         let mut cur_hop_transferred_amount_msat = total_fee_paid_msat + value_msat;
 415                         if let Some(extra_fees_msat) = cur_hop.htlc_minimum_msat.checked_sub(cur_hop_transferred_amount_msat) {
 416                                 // Note that there is a risk that *previous hops* (those closer to us, as we go
 417                                 // payee->our_node here) would exceed their htlc_maximum_msat or available balance.
 418                                 //
 419                                 // This might make us end up with a broken route, although this should be super-rare
 420                                 // in practice, both because of how healthy channels look like, and how we pick
 421                                 // channels in add_entry.
 422                                 // Also, this can't be exploited more heavily than *announce a free path and fail
 423                                 // all payments*.
 424                                 cur_hop_transferred_amount_msat += extra_fees_msat;
 425                                 total_fee_paid_msat += extra_fees_msat;
 426                                 cur_hop_fees_msat += extra_fees_msat;
 427                         }
 428
 429                         if last_hop {
 430                                 // Final hop is a special case: it usually has just value_msat (by design), but also
 431                                 // it still could overpay for the htlc_minimum_msat.
 432                                 cur_hop.fee_msat = cur_hop_transferred_amount_msat;
 433                         } else {
 434                                 // Propagate updated fees for the use of the channels to one hop back, where they
 435                                 // will be actually paid (fee_msat). The last hop is handled above separately.
 436                                 cur_hop.fee_msat = cur_hop_fees_msat;
 437                         }
 438
 439                         // Fee for the use of the current hop which will be deducted on the previous hop.
 440                         // Irrelevant for the first hop, as it doesn't have the previous hop, and the use of
 441                         // this channel is free for us.
 442                         if i != 0 {
 443                                 if let Some(new_fee) = compute_fees(cur_hop_transferred_amount_msat, cur_hop.channel_fees) {
 444                                         cur_hop.hop_use_fee_msat = new_fee;
 445                                         total_fee_paid_msat += new_fee;
 446                                 } else {
 447                                         // It should not be possible because this function is called only to reduce the
 448                                         // value. In that case, compute_fee was already called with the same fees for
 449                                         // larger amount and there was no overflow.
 450                                         unreachable!();
 451                                 }
 452                         }
 453                 }
 454         }
 455 }
 456
 457 fn compute_fees(amount_msat: u64, channel_fees: RoutingFees) -> Option<u64> {
 458         let proportional_fee_millions =
 459                 amount_msat.checked_mul(channel_fees.proportional_millionths as u64);
 460         if let Some(new_fee) = proportional_fee_millions.and_then(|part| {
 461                         (channel_fees.base_msat as u64).checked_add(part / 1_000_000) }) {
 462
 463                 Some(new_fee)
 464         } else {
 465                 // This function may be (indirectly) called without any verification,
 466                 // with channel_fees provided by a caller. We should handle it gracefully.
 467                 None
 468         }
 469 }
 470
 471 /// Gets a keysend route from us (payer) to the given target node (payee). This is needed because
 472 /// keysend payments do not have an invoice from which to pull the payee's supported features, which
 473 /// makes it tricky to otherwise supply the `payee` parameter of `get_route`.
 474 pub fn get_keysend_route<L: Deref, S: routing::Score>(
 475         our_node_pubkey: &PublicKey, network: &NetworkGraph, payee: &PublicKey,
 476         first_hops: Option<&[&ChannelDetails]>, last_hops: &[&RouteHint], final_value_msat: u64,
 477         final_cltv_expiry_delta: u32, logger: L, scorer: &S
 478 ) -> Result<Route, LightningError>
 479 where L::Target: Logger {
 480         let route_hints = last_hops.iter().map(|hint| (*hint).clone()).collect();
 481         let payee = Payee::for_keysend(*payee).with_route_hints(route_hints);
 482         get_route(
 483                 our_node_pubkey, &payee, network, first_hops, final_value_msat, final_cltv_expiry_delta,
 484                 logger, scorer
 485         )
 486 }
 487
 488 /// Gets a route suitable for retrying a failed payment path.
 489 ///
 490 /// Used to re-compute a [`Route`] when handling a [`Event::PaymentPathFailed`]. Any adjustments to
 491 /// the [`NetworkGraph`] and channel scores should be made prior to calling this function.
 492 ///
 493 /// [`Event::PaymentPathFailed`]: crate::util::events::Event::PaymentPathFailed
 494 pub fn get_retry_route<L: Deref, S: routing::Score>(
 495         our_node_pubkey: &PublicKey, retry: &PaymentPathRetry, network: &NetworkGraph,
 496         first_hops: Option<&[&ChannelDetails]>, logger: L, scorer: &S
 497 ) -> Result<Route, LightningError>
 498 where L::Target: Logger {
 499         get_route(
 500                 our_node_pubkey, &retry.payee, network, first_hops, retry.final_value_msat,
 501                 retry.final_cltv_expiry_delta, logger, scorer
 502         )
 503 }
 504
 505 /// Gets a route from us (payer) to the given target node (payee).
 506 ///
 507 /// If the payee provided features in their invoice, they should be provided via `payee`.  Without
 508 /// this, MPP will only be used if the payee's features are available in the network graph.
 509 ///
 510 /// Private routing paths between a public node and the target may be included in `payee`.
 511 ///
 512 /// If some channels aren't announced, it may be useful to fill in a first_hops with the
 513 /// results from a local ChannelManager::list_usable_channels() call. If it is filled in, our
 514 /// view of our local channels (from net_graph_msg_handler) will be ignored, and only those
 515 /// in first_hops will be used.
 516 ///
 517 /// Panics if first_hops contains channels without short_channel_ids
 518 /// (ChannelManager::list_usable_channels will never include such channels).
 519 ///
 520 /// The fees on channels from us to next-hops are ignored (as they are assumed to all be
 521 /// equal), however the enabled/disabled bit on such channels as well as the
 522 /// htlc_minimum_msat/htlc_maximum_msat *are* checked as they may change based on the receiving node.
 523 pub fn get_route<L: Deref, S: routing::Score>(
 524         our_node_pubkey: &PublicKey, payee: &Payee, network: &NetworkGraph,
 525         first_hops: Option<&[&ChannelDetails]>, final_value_msat: u64, final_cltv_expiry_delta: u32,
 526         logger: L, scorer: &S
 527 ) -> Result<Route, LightningError>
 528 where L::Target: Logger {
 529         let payee_node_id = NodeId::from_pubkey(&payee.pubkey);
 530         let our_node_id = NodeId::from_pubkey(&our_node_pubkey);
 531
 532         if payee_node_id == our_node_id {
 533                 return Err(LightningError{err: "Cannot generate a route to ourselves".to_owned(), action: ErrorAction::IgnoreError});
 534         }
 535
 536         if final_value_msat > MAX_VALUE_MSAT {
 537                 return Err(LightningError{err: "Cannot generate a route of more value than all existing satoshis".to_owned(), action: ErrorAction::IgnoreError});
 538         }
 539
 540         if final_value_msat == 0 {
 541                 return Err(LightningError{err: "Cannot send a payment of 0 msat".to_owned(), action: ErrorAction::IgnoreError});
 542         }
 543
 544         for route in payee.route_hints.iter() {
 545                 for hop in &route.0 {
 546                         if hop.src_node_id == payee.pubkey {
 547                                 return Err(LightningError{err: "Route hint cannot have the payee as the source.".to_owned(), action: ErrorAction::IgnoreError});
 548                         }
 549                 }
 550         }
 551
 552         // The general routing idea is the following:
 553         // 1. Fill first/last hops communicated by the caller.
 554         // 2. Attempt to construct a path from payer to payee for transferring
 555         //    any ~sufficient (described later) value.
 556         //    If succeed, remember which channels were used and how much liquidity they have available,
 557         //    so that future paths don't rely on the same liquidity.
 558         // 3. Prooceed to the next step if:
 559         //    - we hit the recommended target value;
 560         //    - OR if we could not construct a new path. Any next attempt will fail too.
 561         //    Otherwise, repeat step 2.
 562         // 4. See if we managed to collect paths which aggregately are able to transfer target value
 563         //    (not recommended value). If yes, proceed. If not, fail routing.
 564         // 5. Randomly combine paths into routes having enough to fulfill the payment. (TODO: knapsack)
 565         // 6. Of all the found paths, select only those with the lowest total fee.
 566         // 7. The last path in every selected route is likely to be more than we need.
 567         //    Reduce its value-to-transfer and recompute fees.
 568         // 8. Choose the best route by the lowest total fee.
 569
 570         // As for the actual search algorithm,
 571         // we do a payee-to-payer pseudo-Dijkstra's sorting by each node's distance from the payee
 572         // plus the minimum per-HTLC fee to get from it to another node (aka "shitty pseudo-A*").
 573         //
 574         // We are not a faithful Dijkstra's implementation because we can change values which impact
 575         // earlier nodes while processing later nodes. Specifically, if we reach a channel with a lower
 576         // liquidity limit (via htlc_maximum_msat, on-chain capacity or assumed liquidity limits) then
 577         // the value we are currently attempting to send over a path, we simply reduce the value being
 578         // sent along the path for any hops after that channel. This may imply that later fees (which
 579         // we've already tabulated) are lower because a smaller value is passing through the channels
 580         // (and the proportional fee is thus lower). There isn't a trivial way to recalculate the
 581         // channels which were selected earlier (and which may still be used for other paths without a
 582         // lower liquidity limit), so we simply accept that some liquidity-limited paths may be
 583         // de-preferenced.
 584         //
 585         // One potentially problematic case for this algorithm would be if there are many
 586         // liquidity-limited paths which are liquidity-limited near the destination (ie early in our
 587         // graph walking), we may never find a path which is not liquidity-limited and has lower
 588         // proportional fee (and only lower absolute fee when considering the ultimate value sent).
 589         // Because we only consider paths with at least 5% of the total value being sent, the damage
 590         // from such a case should be limited, however this could be further reduced in the future by
 591         // calculating fees on the amount we wish to route over a path, ie ignoring the liquidity
 592         // limits for the purposes of fee calculation.
 593         //
 594         // Alternatively, we could store more detailed path information in the heap (targets, below)
 595         // and index the best-path map (dist, below) by node *and* HTLC limits, however that would blow
 596         // up the runtime significantly both algorithmically (as we'd traverse nodes multiple times)
 597         // and practically (as we would need to store dynamically-allocated path information in heap
 598         // objects, increasing malloc traffic and indirect memory access significantly). Further, the
 599         // results of such an algorithm would likely be biased towards lower-value paths.
 600         //
 601         // Further, we could return to a faithful Dijkstra's algorithm by rejecting paths with limits
 602         // outside of our current search value, running a path search more times to gather candidate
 603         // paths at different values. While this may be acceptable, further path searches may increase
 604         // runtime for little gain. Specifically, the current algorithm rather efficiently explores the
 605         // graph for candidate paths, calculating the maximum value which can realistically be sent at
 606         // the same time, remaining generic across different payment values.
 607         //
 608         // TODO: There are a few tweaks we could do, including possibly pre-calculating more stuff
 609         // to use as the A* heuristic beyond just the cost to get one node further than the current
 610         // one.
 611
 612         let network_graph = network.read_only();
 613         let network_channels = network_graph.channels();
 614         let network_nodes = network_graph.nodes();
 615         let dummy_directional_info = DummyDirectionalChannelInfo { // used for first_hops routes
 616                 cltv_expiry_delta: 0,
 617                 htlc_minimum_msat: 0,
 618                 htlc_maximum_msat: None,
 619                 fees: RoutingFees {
 620                         base_msat: 0,
 621                         proportional_millionths: 0,
 622                 }
 623         };
 624
 625         // Allow MPP only if we have a features set from somewhere that indicates the payee supports
 626         // it. If the payee supports it they're supposed to include it in the invoice, so that should
 627         // work reliably.
 628         let allow_mpp = if let Some(features) = &payee.features {
 629                 features.supports_basic_mpp()
 630         } else if let Some(node) = network_nodes.get(&payee_node_id) {
 631                 if let Some(node_info) = node.announcement_info.as_ref() {
 632                         node_info.features.supports_basic_mpp()
 633                 } else { false }
 634         } else { false };
 635         log_trace!(logger, "Searching for a route from payer {} to payee {} {} MPP", our_node_pubkey,
 636                 payee.pubkey, if allow_mpp { "with" } else { "without" });
 637
 638         // Step (1).
 639         // Prepare the data we'll use for payee-to-payer search by
 640         // inserting first hops suggested by the caller as targets.
 641         // Our search will then attempt to reach them while traversing from the payee node.
 642         let mut first_hop_targets: HashMap<_, Vec<(_, ChannelFeatures, _, NodeFeatures)>> =
 643                 HashMap::with_capacity(if first_hops.is_some() { first_hops.as_ref().unwrap().len() } else { 0 });
 644         if let Some(hops) = first_hops {
 645                 for chan in hops {
 646                         let short_channel_id = chan.short_channel_id.expect("first_hops should be filled in with usable channels, not pending ones");
 647                         if chan.counterparty.node_id == *our_node_pubkey {
 648                                 return Err(LightningError{err: "First hop cannot have our_node_pubkey as a destination.".to_owned(), action: ErrorAction::IgnoreError});
 649                         }
 650                         first_hop_targets.entry(NodeId::from_pubkey(&chan.counterparty.node_id)).or_insert(Vec::new())
 651                                 .push((short_channel_id, chan.counterparty.features.to_context(), chan.outbound_capacity_msat, chan.counterparty.features.to_context()));
 652                 }
 653                 if first_hop_targets.is_empty() {
 654                         return Err(LightningError{err: "Cannot route when there are no outbound routes away from us".to_owned(), action: ErrorAction::IgnoreError});
 655                 }
 656         }
 657
 658         let empty_channel_features = ChannelFeatures::empty();
 659
 660         // The main heap containing all candidate next-hops sorted by their score (max(A* fee,
 661         // htlc_minimum)). Ideally this would be a heap which allowed cheap score reduction instead of
 662         // adding duplicate entries when we find a better path to a given node.
 663         let mut targets = BinaryHeap::new();
 664
 665         // Map from node_id to information about the best current path to that node, including feerate
 666         // information.
 667         let mut dist = HashMap::with_capacity(network_nodes.len());
 668
 669         // During routing, if we ignore a path due to an htlc_minimum_msat limit, we set this,
 670         // indicating that we may wish to try again with a higher value, potentially paying to meet an
 671         // htlc_minimum with extra fees while still finding a cheaper path.
 672         let mut hit_minimum_limit;
 673
 674         // When arranging a route, we select multiple paths so that we can make a multi-path payment.
 675         // We start with a path_value of the exact amount we want, and if that generates a route we may
 676         // return it immediately. Otherwise, we don't stop searching for paths until we have 3x the
 677         // amount we want in total across paths, selecting the best subset at the end.
 678         const ROUTE_CAPACITY_PROVISION_FACTOR: u64 = 3;
 679         let recommended_value_msat = final_value_msat * ROUTE_CAPACITY_PROVISION_FACTOR as u64;
 680         let mut path_value_msat = final_value_msat;
 681
 682         // We don't want multiple paths (as per MPP) share liquidity of the same channels.
 683         // This map allows paths to be aware of the channel use by other paths in the same call.
 684         // This would help to make a better path finding decisions and not "overbook" channels.
 685         // It is unaware of the directions (except for `outbound_capacity_msat` in `first_hops`).
 686         let mut bookkeeped_channels_liquidity_available_msat = HashMap::with_capacity(network_nodes.len());
 687
 688         // Keeping track of how much value we already collected across other paths. Helps to decide:
 689         // - how much a new path should be transferring (upper bound);
 690         // - whether a channel should be disregarded because
 691         //   it's available liquidity is too small comparing to how much more we need to collect;
 692         // - when we want to stop looking for new paths.
 693         let mut already_collected_value_msat = 0;
 694
 695         log_trace!(logger, "Building path from {} (payee) to {} (us/payer) for value {} msat.", payee.pubkey, our_node_pubkey, final_value_msat);
 696
 697         macro_rules! add_entry {
 698                 // Adds entry which goes from $src_node_id to $dest_node_id
 699                 // over the channel with id $chan_id with fees described in
 700                 // $directional_info.
 701                 // $next_hops_fee_msat represents the fees paid for using all the channel *after* this one,
 702                 // since that value has to be transferred over this channel.
 703                 // Returns whether this channel caused an update to `targets`.
 704                 ( $chan_id: expr, $src_node_id: expr, $dest_node_id: expr, $directional_info: expr, $capacity_sats: expr, $chan_features: expr, $next_hops_fee_msat: expr,
 705                    $next_hops_value_contribution: expr, $next_hops_path_htlc_minimum_msat: expr, $next_hops_path_penalty_msat: expr ) => { {
 706                         // We "return" whether we updated the path at the end, via this:
 707                         let mut did_add_update_path_to_src_node = false;
 708                         // Channels to self should not be used. This is more of belt-and-suspenders, because in
 709                         // practice these cases should be caught earlier:
 710                         // - for regular channels at channel announcement (TODO)
 711                         // - for first and last hops early in get_route
 712                         if $src_node_id != $dest_node_id.clone() {
 713                                 let available_liquidity_msat = bookkeeped_channels_liquidity_available_msat.entry($chan_id.clone()).or_insert_with(|| {
 714                                         let mut initial_liquidity_available_msat = None;
 715                                         if let Some(capacity_sats) = $capacity_sats {
 716                                                 initial_liquidity_available_msat = Some(capacity_sats * 1000);
 717                                         }
 718
 719                                         if let Some(htlc_maximum_msat) = $directional_info.htlc_maximum_msat {
 720                                                 if let Some(available_msat) = initial_liquidity_available_msat {
 721                                                         initial_liquidity_available_msat = Some(cmp::min(available_msat, htlc_maximum_msat));
 722                                                 } else {
 723                                                         initial_liquidity_available_msat = Some(htlc_maximum_msat);
 724                                                 }
 725                                         }
 726
 727                                         match initial_liquidity_available_msat {
 728                                                 Some(available_msat) => available_msat,
 729                                                 // We assume channels with unknown balance have
 730                                                 // a capacity of 0.0025 BTC (or 250_000 sats).
 731                                                 None => 250_000 * 1000
 732                                         }
 733                                 });
 734
 735                                 // It is tricky to substract $next_hops_fee_msat from available liquidity here.
 736                                 // It may be misleading because we might later choose to reduce the value transferred
 737                                 // over these channels, and the channel which was insufficient might become sufficient.
 738                                 // Worst case: we drop a good channel here because it can't cover the high following
 739                                 // fees caused by one expensive channel, but then this channel could have been used
 740                                 // if the amount being transferred over this path is lower.
 741                                 // We do this for now, but this is a subject for removal.
 742                                 if let Some(available_value_contribution_msat) = available_liquidity_msat.checked_sub($next_hops_fee_msat) {
 743
 744                                         // Routing Fragmentation Mitigation heuristic:
 745                                         //
 746                                         // Routing fragmentation across many payment paths increases the overall routing
 747                                         // fees as you have irreducible routing fees per-link used (`fee_base_msat`).
 748                                         // Taking too many smaller paths also increases the chance of payment failure.
 749                                         // Thus to avoid this effect, we require from our collected links to provide
 750                                         // at least a minimal contribution to the recommended value yet-to-be-fulfilled.
 751                                         //
 752                                         // This requirement is currently 5% of the remaining-to-be-collected value.
 753                                         // This means as we successfully advance in our collection,
 754                                         // the absolute liquidity contribution is lowered,
 755                                         // thus increasing the number of potential channels to be selected.
 756
 757                                         // Derive the minimal liquidity contribution with a ratio of 20 (5%, rounded up)
 758                                         // or 100% if we're not allowed to do multipath payments.
 759                                         let minimal_value_contribution_msat: u64 = if allow_mpp {
 760                                                 (recommended_value_msat - already_collected_value_msat + 19) / 20
 761                                         } else {
 762                                                 final_value_msat
 763                                         };
 764                                         // Verify the liquidity offered by this channel complies to the minimal contribution.
 765                                         let contributes_sufficient_value = available_value_contribution_msat >= minimal_value_contribution_msat;
 766
 767                                         let value_contribution_msat = cmp::min(available_value_contribution_msat, $next_hops_value_contribution);
 768                                         // Includes paying fees for the use of the following channels.
 769                                         let amount_to_transfer_over_msat: u64 = match value_contribution_msat.checked_add($next_hops_fee_msat) {
 770                                                 Some(result) => result,
 771                                                 // Can't overflow due to how the values were computed right above.
 772                                                 None => unreachable!(),
 773                                         };
 774                                         #[allow(unused_comparisons)] // $next_hops_path_htlc_minimum_msat is 0 in some calls so rustc complains
 775                                         let over_path_minimum_msat = amount_to_transfer_over_msat >= $directional_info.htlc_minimum_msat &&
 776                                                 amount_to_transfer_over_msat >= $next_hops_path_htlc_minimum_msat;
 777
 778                                         // If HTLC minimum is larger than the amount we're going to transfer, we shouldn't
 779                                         // bother considering this channel.
 780                                         // Since we're choosing amount_to_transfer_over_msat as maximum possible, it can
 781                                         // be only reduced later (not increased), so this channel should just be skipped
 782                                         // as not sufficient.
 783                                         if !over_path_minimum_msat {
 784                                                 hit_minimum_limit = true;
 785                                         } else if contributes_sufficient_value {
 786                                                 // Note that low contribution here (limited by available_liquidity_msat)
 787                                                 // might violate htlc_minimum_msat on the hops which are next along the
 788                                                 // payment path (upstream to the payee). To avoid that, we recompute path
 789                                                 // path fees knowing the final path contribution after constructing it.
 790                                                 let path_htlc_minimum_msat = compute_fees($next_hops_path_htlc_minimum_msat, $directional_info.fees)
 791                                                         .and_then(|fee_msat| fee_msat.checked_add($next_hops_path_htlc_minimum_msat))
 792                                                         .map(|fee_msat| cmp::max(fee_msat, $directional_info.htlc_minimum_msat))
 793                                                         .unwrap_or_else(|| u64::max_value());
 794                                                 let hm_entry = dist.entry($src_node_id);
 795                                                 let old_entry = hm_entry.or_insert_with(|| {
 796                                                         // If there was previously no known way to access
 797                                                         // the source node (recall it goes payee-to-payer) of $chan_id, first add
 798                                                         // a semi-dummy record just to compute the fees to reach the source node.
 799                                                         // This will affect our decision on selecting $chan_id
 800                                                         // as a way to reach the $dest_node_id.
 801                                                         let mut fee_base_msat = u32::max_value();
 802                                                         let mut fee_proportional_millionths = u32::max_value();
 803                                                         if let Some(Some(fees)) = network_nodes.get(&$src_node_id).map(|node| node.lowest_inbound_channel_fees) {
 804                                                                 fee_base_msat = fees.base_msat;
 805                                                                 fee_proportional_millionths = fees.proportional_millionths;
 806                                                         }
 807                                                         PathBuildingHop {
 808                                                                 node_id: $dest_node_id.clone(),
 809                                                                 short_channel_id: 0,
 810                                                                 channel_features: $chan_features,
 811                                                                 fee_msat: 0,
 812                                                                 cltv_expiry_delta: 0,
 813                                                                 src_lowest_inbound_fees: RoutingFees {
 814                                                                         base_msat: fee_base_msat,
 815                                                                         proportional_millionths: fee_proportional_millionths,
 816                                                                 },
 817                                                                 channel_fees: $directional_info.fees,
 818                                                                 next_hops_fee_msat: u64::max_value(),
 819                                                                 hop_use_fee_msat: u64::max_value(),
 820                                                                 total_fee_msat: u64::max_value(),
 821                                                                 htlc_minimum_msat: $directional_info.htlc_minimum_msat,
 822                                                                 path_htlc_minimum_msat,
 823                                                                 path_penalty_msat: u64::max_value(),
 824                                                                 was_processed: false,
 825                                                                 #[cfg(any(test, feature = "fuzztarget"))]
 826                                                                 value_contribution_msat,
 827                                                         }
 828                                                 });
 829
 830                                                 #[allow(unused_mut)] // We only use the mut in cfg(test)
 831                                                 let mut should_process = !old_entry.was_processed;
 832                                                 #[cfg(any(test, feature = "fuzztarget"))]
 833                                                 {
 834                                                         // In test/fuzzing builds, we do extra checks to make sure the skipping
 835                                                         // of already-seen nodes only happens in cases we expect (see below).
 836                                                         if !should_process { should_process = true; }
 837                                                 }
 838
 839                                                 if should_process {
 840                                                         let mut hop_use_fee_msat = 0;
 841                                                         let mut total_fee_msat = $next_hops_fee_msat;
 842
 843                                                         // Ignore hop_use_fee_msat for channel-from-us as we assume all channels-from-us
 844                                                         // will have the same effective-fee
 845                                                         if $src_node_id != our_node_id {
 846                                                                 match compute_fees(amount_to_transfer_over_msat, $directional_info.fees) {
 847                                                                         // max_value means we'll always fail
 848                                                                         // the old_entry.total_fee_msat > total_fee_msat check
 849                                                                         None => total_fee_msat = u64::max_value(),
 850                                                                         Some(fee_msat) => {
 851                                                                                 hop_use_fee_msat = fee_msat;
 852                                                                                 total_fee_msat += hop_use_fee_msat;
 853                                                                                 // When calculating the lowest inbound fees to a node, we
 854                                                                                 // calculate fees here not based on the actual value we think
 855                                                                                 // will flow over this channel, but on the minimum value that
 856                                                                                 // we'll accept flowing over it. The minimum accepted value
 857                                                                                 // is a constant through each path collection run, ensuring
 858                                                                                 // consistent basis. Otherwise we may later find a
 859                                                                                 // different path to the source node that is more expensive,
 860                                                                                 // but which we consider to be cheaper because we are capacity
 861                                                                                 // constrained and the relative fee becomes lower.
 862                                                                                 match compute_fees(minimal_value_contribution_msat, old_entry.src_lowest_inbound_fees)
 863                                                                                                 .map(|a| a.checked_add(total_fee_msat)) {
 864                                                                                         Some(Some(v)) => {
 865                                                                                                 total_fee_msat = v;
 866                                                                                         },
 867                                                                                         _ => {
 868                                                                                                 total_fee_msat = u64::max_value();
 869                                                                                         }
 870                                                                                 };
 871                                                                         }
 872                                                                 }
 873                                                         }
 874
 875                                                         let path_penalty_msat = $next_hops_path_penalty_msat
 876                                                                 .checked_add(scorer.channel_penalty_msat($chan_id.clone(), &$src_node_id, &$dest_node_id))
 877                                                                 .unwrap_or_else(|| u64::max_value());
 878                                                         let new_graph_node = RouteGraphNode {
 879                                                                 node_id: $src_node_id,
 880                                                                 lowest_fee_to_peer_through_node: total_fee_msat,
 881                                                                 lowest_fee_to_node: $next_hops_fee_msat as u64 + hop_use_fee_msat,
 882                                                                 value_contribution_msat: value_contribution_msat,
 883                                                                 path_htlc_minimum_msat,
 884                                                                 path_penalty_msat,
 885                                                         };
 886
 887                                                         // Update the way of reaching $src_node_id with the given $chan_id (from $dest_node_id),
 888                                                         // if this way is cheaper than the already known
 889                                                         // (considering the cost to "reach" this channel from the route destination,
 890                                                         // the cost of using this channel,
 891                                                         // and the cost of routing to the source node of this channel).
 892                                                         // Also, consider that htlc_minimum_msat_difference, because we might end up
 893                                                         // paying it. Consider the following exploit:
 894                                                         // we use 2 paths to transfer 1.5 BTC. One of them is 0-fee normal 1 BTC path,
 895                                                         // and for the other one we picked a 1sat-fee path with htlc_minimum_msat of
 896                                                         // 1 BTC. Now, since the latter is more expensive, we gonna try to cut it
 897                                                         // by 0.5 BTC, but then match htlc_minimum_msat by paying a fee of 0.5 BTC
 898                                                         // to this channel.
 899                                                         // Ideally the scoring could be smarter (e.g. 0.5*htlc_minimum_msat here),
 900                                                         // but it may require additional tracking - we don't want to double-count
 901                                                         // the fees included in $next_hops_path_htlc_minimum_msat, but also
 902                                                         // can't use something that may decrease on future hops.
 903                                                         let old_cost = cmp::max(old_entry.total_fee_msat, old_entry.path_htlc_minimum_msat)
 904                                                                 .checked_add(old_entry.path_penalty_msat)
 905                                                                 .unwrap_or_else(|| u64::max_value());
 906                                                         let new_cost = cmp::max(total_fee_msat, path_htlc_minimum_msat)
 907                                                                 .checked_add(path_penalty_msat)
 908                                                                 .unwrap_or_else(|| u64::max_value());
 909
 910                                                         if !old_entry.was_processed && new_cost < old_cost {
 911                                                                 targets.push(new_graph_node);
 912                                                                 old_entry.next_hops_fee_msat = $next_hops_fee_msat;
 913                                                                 old_entry.hop_use_fee_msat = hop_use_fee_msat;
 914                                                                 old_entry.total_fee_msat = total_fee_msat;
 915                                                                 old_entry.node_id = $dest_node_id.clone();
 916                                                                 old_entry.short_channel_id = $chan_id.clone();
 917                                                                 old_entry.channel_features = $chan_features;
 918                                                                 old_entry.fee_msat = 0; // This value will be later filled with hop_use_fee_msat of the following channel
 919                                                                 old_entry.cltv_expiry_delta = $directional_info.cltv_expiry_delta as u32;
 920                                                                 old_entry.channel_fees = $directional_info.fees;
 921                                                                 old_entry.htlc_minimum_msat = $directional_info.htlc_minimum_msat;
 922                                                                 old_entry.path_htlc_minimum_msat = path_htlc_minimum_msat;
 923                                                                 old_entry.path_penalty_msat = path_penalty_msat;
 924                                                                 #[cfg(any(test, feature = "fuzztarget"))]
 925                                                                 {
 926                                                                         old_entry.value_contribution_msat = value_contribution_msat;
 927                                                                 }
 928                                                                 did_add_update_path_to_src_node = true;
 929                                                         } else if old_entry.was_processed && new_cost < old_cost {
 930                                                                 #[cfg(any(test, feature = "fuzztarget"))]
 931                                                                 {
 932                                                                         // If we're skipping processing a node which was previously
 933                                                                         // processed even though we found another path to it with a
 934                                                                         // cheaper fee, check that it was because the second path we
 935                                                                         // found (which we are processing now) has a lower value
 936                                                                         // contribution due to an HTLC minimum limit.
 937                                                                         //
 938                                                                         // e.g. take a graph with two paths from node 1 to node 2, one
 939                                                                         // through channel A, and one through channel B. Channel A and
 940                                                                         // B are both in the to-process heap, with their scores set by
 941                                                                         // a higher htlc_minimum than fee.
 942                                                                         // Channel A is processed first, and the channels onwards from
 943                                                                         // node 1 are added to the to-process heap. Thereafter, we pop
 944                                                                         // Channel B off of the heap, note that it has a much more
 945                                                                         // restrictive htlc_maximum_msat, and recalculate the fees for
 946                                                                         // all of node 1's channels using the new, reduced, amount.
 947                                                                         //
 948                                                                         // This would be bogus - we'd be selecting a higher-fee path
 949                                                                         // with a lower htlc_maximum_msat instead of the one we'd
 950                                                                         // already decided to use.
 951                                                                         debug_assert!(path_htlc_minimum_msat < old_entry.path_htlc_minimum_msat);
 952                                                                         debug_assert!(
 953                                                                                 value_contribution_msat + path_penalty_msat <
 954                                                                                 old_entry.value_contribution_msat + old_entry.path_penalty_msat
 955                                                                         );
 956                                                                 }
 957                                                         }
 958                                                 }
 959                                         }
 960                                 }
 961                         }
 962                         did_add_update_path_to_src_node
 963                 } }
 964         }
 965
 966         let empty_node_features = NodeFeatures::empty();
 967         // Find ways (channels with destination) to reach a given node and store them
 968         // in the corresponding data structures (routing graph etc).
 969         // $fee_to_target_msat represents how much it costs to reach to this node from the payee,
 970         // meaning how much will be paid in fees after this node (to the best of our knowledge).
 971         // This data can later be helpful to optimize routing (pay lower fees).
 972         macro_rules! add_entries_to_cheapest_to_target_node {
 973                 ( $node: expr, $node_id: expr, $fee_to_target_msat: expr, $next_hops_value_contribution: expr, $next_hops_path_htlc_minimum_msat: expr, $next_hops_path_penalty_msat: expr ) => {
 974                         let skip_node = if let Some(elem) = dist.get_mut(&$node_id) {
 975                                 let was_processed = elem.was_processed;
 976                                 elem.was_processed = true;
 977                                 was_processed
 978                         } else {
 979                                 // Entries are added to dist in add_entry!() when there is a channel from a node.
 980                                 // Because there are no channels from payee, it will not have a dist entry at this point.
 981                                 // If we're processing any other node, it is always be the result of a channel from it.
 982                                 assert_eq!($node_id, payee_node_id);
 983                                 false
 984                         };
 985
 986                         if !skip_node {
 987                                 if let Some(first_channels) = first_hop_targets.get(&$node_id) {
 988                                         for (ref first_hop, ref features, ref outbound_capacity_msat, _) in first_channels {
 989                                                 add_entry!(first_hop, our_node_id, $node_id, dummy_directional_info, Some(outbound_capacity_msat / 1000), features, $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat, $next_hops_path_penalty_msat);
 990                                         }
 991                                 }
 992
 993                                 let features = if let Some(node_info) = $node.announcement_info.as_ref() {
 994                                         &node_info.features
 995                                 } else {
 996                                         &empty_node_features
 997                                 };
 998
 999                                 if !features.requires_unknown_bits() {
1000                                         for chan_id in $node.channels.iter() {
1001                                                 let chan = network_channels.get(chan_id).unwrap();
1002                                                 if !chan.features.requires_unknown_bits() {
1003                                                         if chan.node_one == $node_id {
1004                                                                 // ie $node is one, ie next hop in A* is two, via the two_to_one channel
1005                                                                 if first_hops.is_none() || chan.node_two != our_node_id {
1006                                                                         if let Some(two_to_one) = chan.two_to_one.as_ref() {
1007                                                                                 if two_to_one.enabled {
1008                                                                                         add_entry!(chan_id, chan.node_two, chan.node_one, two_to_one, chan.capacity_sats, &chan.features, $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat, $next_hops_path_penalty_msat);
1009                                                                                 }
1010                                                                         }
1011                                                                 }
1012                                                         } else {
1013                                                                 if first_hops.is_none() || chan.node_one != our_node_id{
1014                                                                         if let Some(one_to_two) = chan.one_to_two.as_ref() {
1015                                                                                 if one_to_two.enabled {
1016                                                                                         add_entry!(chan_id, chan.node_one, chan.node_two, one_to_two, chan.capacity_sats, &chan.features, $fee_to_target_msat, $next_hops_value_contribution, $next_hops_path_htlc_minimum_msat, $next_hops_path_penalty_msat);
1017                                                                                 }
1018                                                                         }
1019                                                                 }
1020                                                         }
1021                                                 }
1022                                         }
1023                                 }
1024                         }
1025                 };
1026         }
1027
1028         let mut payment_paths = Vec::<PaymentPath>::new();
1029
1030         // TODO: diversify by nodes (so that all paths aren't doomed if one node is offline).
1031         'paths_collection: loop {
1032                 // For every new path, start from scratch, except
1033                 // bookkeeped_channels_liquidity_available_msat, which will improve
1034                 // the further iterations of path finding. Also don't erase first_hop_targets.
1035                 targets.clear();
1036                 dist.clear();
1037                 hit_minimum_limit = false;
1038
1039                 // If first hop is a private channel and the only way to reach the payee, this is the only
1040                 // place where it could be added.
1041                 if let Some(first_channels) = first_hop_targets.get(&payee_node_id) {
1042                         for (ref first_hop, ref features, ref outbound_capacity_msat, _) in first_channels {
1043                                 let added = add_entry!(first_hop, our_node_id, payee_node_id, dummy_directional_info, Some(outbound_capacity_msat / 1000), features, 0, path_value_msat, 0, 0u64);
1044                                 log_trace!(logger, "{} direct route to payee via SCID {}", if added { "Added" } else { "Skipped" }, first_hop);
1045                         }
1046                 }
1047
1048                 // Add the payee as a target, so that the payee-to-payer
1049                 // search algorithm knows what to start with.
1050                 match network_nodes.get(&payee_node_id) {
1051                         // The payee is not in our network graph, so nothing to add here.
1052                         // There is still a chance of reaching them via last_hops though,
1053                         // so don't yet fail the payment here.
1054                         // If not, targets.pop() will not even let us enter the loop in step 2.
1055                         None => {},
1056                         Some(node) => {
1057                                 add_entries_to_cheapest_to_target_node!(node, payee_node_id, 0, path_value_msat, 0, 0u64);
1058                         },
1059                 }
1060
1061                 // Step (2).
1062                 // If a caller provided us with last hops, add them to routing targets. Since this happens
1063                 // earlier than general path finding, they will be somewhat prioritized, although currently
1064                 // it matters only if the fees are exactly the same.
1065                 for route in payee.route_hints.iter().filter(|route| !route.0.is_empty()) {
1066                         let first_hop_in_route = &(route.0)[0];
1067                         let have_hop_src_in_graph =
1068                                 // Only add the hops in this route to our candidate set if either
1069                                 // we have a direct channel to the first hop or the first hop is
1070                                 // in the regular network graph.
1071                                 first_hop_targets.get(&NodeId::from_pubkey(&first_hop_in_route.src_node_id)).is_some() ||
1072                                 network_nodes.get(&NodeId::from_pubkey(&first_hop_in_route.src_node_id)).is_some();
1073                         if have_hop_src_in_graph {
1074                                 // We start building the path from reverse, i.e., from payee
1075                                 // to the first RouteHintHop in the path.
1076                                 let hop_iter = route.0.iter().rev();
1077                                 let prev_hop_iter = core::iter::once(&payee.pubkey).chain(
1078                                         route.0.iter().skip(1).rev().map(|hop| &hop.src_node_id));
1079                                 let mut hop_used = true;
1080                                 let mut aggregate_next_hops_fee_msat: u64 = 0;
1081                                 let mut aggregate_next_hops_path_htlc_minimum_msat: u64 = 0;
1082                                 let mut aggregate_next_hops_path_penalty_msat: u64 = 0;
1083
1084                                 for (idx, (hop, prev_hop_id)) in hop_iter.zip(prev_hop_iter).enumerate() {
1085                                         // BOLT 11 doesn't allow inclusion of features for the last hop hints, which
1086                                         // really sucks, cause we're gonna need that eventually.
1087                                         let hop_htlc_minimum_msat: u64 = hop.htlc_minimum_msat.unwrap_or(0);
1088
1089                                         let directional_info = DummyDirectionalChannelInfo {
1090                                                 cltv_expiry_delta: hop.cltv_expiry_delta as u32,
1091                                                 htlc_minimum_msat: hop_htlc_minimum_msat,
1092                                                 htlc_maximum_msat: hop.htlc_maximum_msat,
1093                                                 fees: hop.fees,
1094                                         };
1095
1096                                         let reqd_channel_cap = if let Some (val) = final_value_msat.checked_add(match idx {
1097                                                 0 => 999,
1098                                                 _ => aggregate_next_hops_fee_msat.checked_add(999).unwrap_or(u64::max_value())
1099                                         }) { Some( val / 1000 ) } else { break; }; // converting from msat or breaking if max ~ infinity
1100
1101                                         let src_node_id = NodeId::from_pubkey(&hop.src_node_id);
1102                                         let dest_node_id = NodeId::from_pubkey(&prev_hop_id);
1103                                         aggregate_next_hops_path_penalty_msat = aggregate_next_hops_path_penalty_msat
1104                                                 .checked_add(scorer.channel_penalty_msat(hop.short_channel_id, &src_node_id, &dest_node_id))
1105                                                 .unwrap_or_else(|| u64::max_value());
1106
1107                                         // We assume that the recipient only included route hints for routes which had
1108                                         // sufficient value to route `final_value_msat`. Note that in the case of "0-value"
1109                                         // invoices where the invoice does not specify value this may not be the case, but
1110                                         // better to include the hints than not.
1111                                         if !add_entry!(hop.short_channel_id, src_node_id, dest_node_id, directional_info, reqd_channel_cap, &empty_channel_features, aggregate_next_hops_fee_msat, path_value_msat, aggregate_next_hops_path_htlc_minimum_msat, aggregate_next_hops_path_penalty_msat) {
1112                                                 // If this hop was not used then there is no use checking the preceding hops
1113                                                 // in the RouteHint. We can break by just searching for a direct channel between
1114                                                 // last checked hop and first_hop_targets
1115                                                 hop_used = false;
1116                                         }
1117
1118                                         // Searching for a direct channel between last checked hop and first_hop_targets
1119                                         if let Some(first_channels) = first_hop_targets.get(&NodeId::from_pubkey(&prev_hop_id)) {
1120                                                 for (ref first_hop, ref features, ref outbound_capacity_msat, _) in first_channels {
1121                                                         add_entry!(first_hop, our_node_id , NodeId::from_pubkey(&prev_hop_id), dummy_directional_info, Some(outbound_capacity_msat / 1000), features, aggregate_next_hops_fee_msat, path_value_msat, aggregate_next_hops_path_htlc_minimum_msat, aggregate_next_hops_path_penalty_msat);
1122                                                 }
1123                                         }
1124
1125                                         if !hop_used {
1126                                                 break;
1127                                         }
1128
1129                                         // In the next values of the iterator, the aggregate fees already reflects
1130                                         // the sum of value sent from payer (final_value_msat) and routing fees
1131                                         // for the last node in the RouteHint. We need to just add the fees to
1132                                         // route through the current node so that the preceeding node (next iteration)
1133                                         // can use it.
1134                                         let hops_fee = compute_fees(aggregate_next_hops_fee_msat + final_value_msat, hop.fees)
1135                                                 .map_or(None, |inc| inc.checked_add(aggregate_next_hops_fee_msat));
1136                                         aggregate_next_hops_fee_msat = if let Some(val) = hops_fee { val } else { break; };
1137
1138                                         let hop_htlc_minimum_msat_inc = if let Some(val) = compute_fees(aggregate_next_hops_path_htlc_minimum_msat, hop.fees) { val } else { break; };
1139                                         let hops_path_htlc_minimum = aggregate_next_hops_path_htlc_minimum_msat
1140                                                 .checked_add(hop_htlc_minimum_msat_inc);
1141                                         aggregate_next_hops_path_htlc_minimum_msat = if let Some(val) = hops_path_htlc_minimum { cmp::max(hop_htlc_minimum_msat, val) } else { break; };
1142
1143                                         if idx == route.0.len() - 1 {
1144                                                 // The last hop in this iterator is the first hop in
1145                                                 // overall RouteHint.
1146                                                 // If this hop connects to a node with which we have a direct channel,
1147                                                 // ignore the network graph and, if the last hop was added, add our
1148                                                 // direct channel to the candidate set.
1149                                                 //
1150                                                 // Note that we *must* check if the last hop was added as `add_entry`
1151                                                 // always assumes that the third argument is a node to which we have a
1152                                                 // path.
1153                                                 if let Some(first_channels) = first_hop_targets.get(&NodeId::from_pubkey(&hop.src_node_id)) {
1154                                                         for (ref first_hop, ref features, ref outbound_capacity_msat, _) in first_channels {
1155                                                                 add_entry!(first_hop, our_node_id , NodeId::from_pubkey(&hop.src_node_id), dummy_directional_info, Some(outbound_capacity_msat / 1000), features, aggregate_next_hops_fee_msat, path_value_msat, aggregate_next_hops_path_htlc_minimum_msat, aggregate_next_hops_path_penalty_msat);
1156                                                         }
1157                                                 }
1158                                         }
1159                                 }
1160                         }
1161                 }
1162
1163                 log_trace!(logger, "Starting main path collection loop with {} nodes pre-filled from first/last hops.", targets.len());
1164
1165                 // At this point, targets are filled with the data from first and
1166                 // last hops communicated by the caller, and the payment receiver.
1167                 let mut found_new_path = false;
1168
1169                 // Step (3).
1170                 // If this loop terminates due the exhaustion of targets, two situations are possible:
1171                 // - not enough outgoing liquidity:
1172                 //   0 < already_collected_value_msat < final_value_msat
1173                 // - enough outgoing liquidity:
1174                 //   final_value_msat <= already_collected_value_msat < recommended_value_msat
1175                 // Both these cases (and other cases except reaching recommended_value_msat) mean that
1176                 // paths_collection will be stopped because found_new_path==false.
1177                 // This is not necessarily a routing failure.
1178                 'path_construction: while let Some(RouteGraphNode { node_id, lowest_fee_to_node, value_contribution_msat, path_htlc_minimum_msat, path_penalty_msat, .. }) = targets.pop() {
1179
1180                         // Since we're going payee-to-payer, hitting our node as a target means we should stop
1181                         // traversing the graph and arrange the path out of what we found.
1182                         if node_id == our_node_id {
1183                                 let mut new_entry = dist.remove(&our_node_id).unwrap();
1184                                 let mut ordered_hops = vec!((new_entry.clone(), NodeFeatures::empty()));
1185
1186                                 'path_walk: loop {
1187                                         let mut features_set = false;
1188                                         if let Some(first_channels) = first_hop_targets.get(&ordered_hops.last().unwrap().0.node_id) {
1189                                                 for (scid, _, _, ref features) in first_channels {
1190                                                         if *scid == ordered_hops.last().unwrap().0.short_channel_id {
1191                                                                 ordered_hops.last_mut().unwrap().1 = features.clone();
1192                                                                 features_set = true;
1193                                                                 break;
1194                                                         }
1195                                                 }
1196                                         }
1197                                         if !features_set {
1198                                                 if let Some(node) = network_nodes.get(&ordered_hops.last().unwrap().0.node_id) {
1199                                                         if let Some(node_info) = node.announcement_info.as_ref() {
1200                                                                 ordered_hops.last_mut().unwrap().1 = node_info.features.clone();
1201                                                         } else {
1202                                                                 ordered_hops.last_mut().unwrap().1 = NodeFeatures::empty();
1203                                                         }
1204                                                 } else {
1205                                                         // We should be able to fill in features for everything except the last
1206                                                         // hop, if the last hop was provided via a BOLT 11 invoice (though we
1207                                                         // should be able to extend it further as BOLT 11 does have feature
1208                                                         // flags for the last hop node itself).
1209                                                         assert!(ordered_hops.last().unwrap().0.node_id == payee_node_id);
1210                                                 }
1211                                         }
1212
1213                                         // Means we succesfully traversed from the payer to the payee, now
1214                                         // save this path for the payment route. Also, update the liquidity
1215                                         // remaining on the used hops, so that we take them into account
1216                                         // while looking for more paths.
1217                                         if ordered_hops.last().unwrap().0.node_id == payee_node_id {
1218                                                 break 'path_walk;
1219                                         }
1220
1221                                         new_entry = match dist.remove(&ordered_hops.last().unwrap().0.node_id) {
1222                                                 Some(payment_hop) => payment_hop,
1223                                                 // We can't arrive at None because, if we ever add an entry to targets,
1224                                                 // we also fill in the entry in dist (see add_entry!).
1225                                                 None => unreachable!(),
1226                                         };
1227                                         // We "propagate" the fees one hop backward (topologically) here,
1228                                         // so that fees paid for a HTLC forwarding on the current channel are
1229                                         // associated with the previous channel (where they will be subtracted).
1230                                         ordered_hops.last_mut().unwrap().0.fee_msat = new_entry.hop_use_fee_msat;
1231                                         ordered_hops.last_mut().unwrap().0.cltv_expiry_delta = new_entry.cltv_expiry_delta;
1232                                         ordered_hops.push((new_entry.clone(), NodeFeatures::empty()));
1233                                 }
1234                                 ordered_hops.last_mut().unwrap().0.fee_msat = value_contribution_msat;
1235                                 ordered_hops.last_mut().unwrap().0.hop_use_fee_msat = 0;
1236                                 ordered_hops.last_mut().unwrap().0.cltv_expiry_delta = final_cltv_expiry_delta;
1237
1238                                 log_trace!(logger, "Found a path back to us from the target with {} hops contributing up to {} msat: {:?}",
1239                                         ordered_hops.len(), value_contribution_msat, ordered_hops);
1240
1241                                 let mut payment_path = PaymentPath {hops: ordered_hops};
1242
1243                                 // We could have possibly constructed a slightly inconsistent path: since we reduce
1244                                 // value being transferred along the way, we could have violated htlc_minimum_msat
1245                                 // on some channels we already passed (assuming dest->source direction). Here, we
1246                                 // recompute the fees again, so that if that's the case, we match the currently
1247                                 // underpaid htlc_minimum_msat with fees.
1248                                 payment_path.update_value_and_recompute_fees(cmp::min(value_contribution_msat, final_value_msat));
1249
1250                                 // Since a path allows to transfer as much value as
1251                                 // the smallest channel it has ("bottleneck"), we should recompute
1252                                 // the fees so sender HTLC don't overpay fees when traversing
1253                                 // larger channels than the bottleneck. This may happen because
1254                                 // when we were selecting those channels we were not aware how much value
1255                                 // this path will transfer, and the relative fee for them
1256                                 // might have been computed considering a larger value.
1257                                 // Remember that we used these channels so that we don't rely
1258                                 // on the same liquidity in future paths.
1259                                 let mut prevented_redundant_path_selection = false;
1260                                 for (payment_hop, _) in payment_path.hops.iter() {
1261                                         let channel_liquidity_available_msat = bookkeeped_channels_liquidity_available_msat.get_mut(&payment_hop.short_channel_id).unwrap();
1262                                         let mut spent_on_hop_msat = value_contribution_msat;
1263                                         let next_hops_fee_msat = payment_hop.next_hops_fee_msat;
1264                                         spent_on_hop_msat += next_hops_fee_msat;
1265                                         if spent_on_hop_msat == *channel_liquidity_available_msat {
1266                                                 // If this path used all of this channel's available liquidity, we know
1267                                                 // this path will not be selected again in the next loop iteration.
1268                                                 prevented_redundant_path_selection = true;
1269                                         }
1270                                         *channel_liquidity_available_msat -= spent_on_hop_msat;
1271                                 }
1272                                 if !prevented_redundant_path_selection {
1273                                         // If we weren't capped by hitting a liquidity limit on a channel in the path,
1274                                         // we'll probably end up picking the same path again on the next iteration.
1275                                         // Decrease the available liquidity of a hop in the middle of the path.
1276                                         let victim_scid = payment_path.hops[(payment_path.hops.len() - 1) / 2].0.short_channel_id;
1277                                         log_trace!(logger, "Disabling channel {} for future path building iterations to avoid duplicates.", victim_scid);
1278                                         let victim_liquidity = bookkeeped_channels_liquidity_available_msat.get_mut(&victim_scid).unwrap();
1279                                         *victim_liquidity = 0;
1280                                 }
1281
1282                                 // Track the total amount all our collected paths allow to send so that we:
1283                                 // - know when to stop looking for more paths
1284                                 // - know which of the hops are useless considering how much more sats we need
1285                                 //   (contributes_sufficient_value)
1286                                 already_collected_value_msat += value_contribution_msat;
1287
1288                                 payment_paths.push(payment_path);
1289                                 found_new_path = true;
1290                                 break 'path_construction;
1291                         }
1292
1293                         // If we found a path back to the payee, we shouldn't try to process it again. This is
1294                         // the equivalent of the `elem.was_processed` check in
1295                         // add_entries_to_cheapest_to_target_node!() (see comment there for more info).
1296                         if node_id == payee_node_id { continue 'path_construction; }
1297
1298                         // Otherwise, since the current target node is not us,
1299                         // keep "unrolling" the payment graph from payee to payer by
1300                         // finding a way to reach the current target from the payer side.
1301                         match network_nodes.get(&node_id) {
1302                                 None => {},
1303                                 Some(node) => {
1304                                         add_entries_to_cheapest_to_target_node!(node, node_id, lowest_fee_to_node, value_contribution_msat, path_htlc_minimum_msat, path_penalty_msat);
1305                                 },
1306                         }
1307                 }
1308
1309                 if !allow_mpp {
1310                         // If we don't support MPP, no use trying to gather more value ever.
1311                         break 'paths_collection;
1312                 }
1313
1314                 // Step (4).
1315                 // Stop either when the recommended value is reached or if no new path was found in this
1316                 // iteration.
1317                 // In the latter case, making another path finding attempt won't help,
1318                 // because we deterministically terminated the search due to low liquidity.
1319                 if already_collected_value_msat >= recommended_value_msat || !found_new_path {
1320                         log_trace!(logger, "Have now collected {} msat (seeking {} msat) in paths. Last path loop {} a new path.",
1321                                 already_collected_value_msat, recommended_value_msat, if found_new_path { "found" } else { "did not find" });
1322                         break 'paths_collection;
1323                 } else if found_new_path && already_collected_value_msat == final_value_msat && payment_paths.len() == 1 {
1324                         // Further, if this was our first walk of the graph, and we weren't limited by an
1325                         // htlc_minimum_msat, return immediately because this path should suffice. If we were
1326                         // limited by an htlc_minimum_msat value, find another path with a higher value,
1327                         // potentially allowing us to pay fees to meet the htlc_minimum on the new path while
1328                         // still keeping a lower total fee than this path.
1329                         if !hit_minimum_limit {
1330                                 log_trace!(logger, "Collected exactly our payment amount on the first pass, without hitting an htlc_minimum_msat limit, exiting.");
1331                                 break 'paths_collection;
1332                         }
1333                         log_trace!(logger, "Collected our payment amount on the first pass, but running again to collect extra paths with a potentially higher limit.");
1334                         path_value_msat = recommended_value_msat;
1335                 }
1336         }
1337
1338         // Step (5).
1339         if payment_paths.len() == 0 {
1340                 return Err(LightningError{err: "Failed to find a path to the given destination".to_owned(), action: ErrorAction::IgnoreError});
1341         }
1342
1343         if already_collected_value_msat < final_value_msat {
1344                 return Err(LightningError{err: "Failed to find a sufficient route to the given destination".to_owned(), action: ErrorAction::IgnoreError});
1345         }
1346
1347         // Sort by total fees and take the best paths.
1348         payment_paths.sort_by_key(|path| path.get_total_fee_paid_msat());
1349         if payment_paths.len() > 50 {
1350                 payment_paths.truncate(50);
1351         }
1352
1353         // Draw multiple sufficient routes by randomly combining the selected paths.
1354         let mut drawn_routes = Vec::new();
1355         for i in 0..payment_paths.len() {
1356                 let mut cur_route = Vec::<PaymentPath>::new();
1357                 let mut aggregate_route_value_msat = 0;
1358
1359                 // Step (6).
1360                 // TODO: real random shuffle
1361                 // Currently just starts with i_th and goes up to i-1_th in a looped way.
1362                 let cur_payment_paths = [&payment_paths[i..], &payment_paths[..i]].concat();
1363
1364                 // Step (7).
1365                 for payment_path in cur_payment_paths {
1366                         cur_route.push(payment_path.clone());
1367                         aggregate_route_value_msat += payment_path.get_value_msat();
1368                         if aggregate_route_value_msat > final_value_msat {
1369                                 // Last path likely overpaid. Substract it from the most expensive
1370                                 // (in terms of proportional fee) path in this route and recompute fees.
1371                                 // This might be not the most economically efficient way, but fewer paths
1372                                 // also makes routing more reliable.
1373                                 let mut overpaid_value_msat = aggregate_route_value_msat - final_value_msat;
1374
1375                                 // First, drop some expensive low-value paths entirely if possible.
1376                                 // Sort by value so that we drop many really-low values first, since
1377                                 // fewer paths is better: the payment is less likely to fail.
1378                                 // TODO: this could also be optimized by also sorting by feerate_per_sat_routed,
1379                                 // so that the sender pays less fees overall. And also htlc_minimum_msat.
1380                                 cur_route.sort_by_key(|path| path.get_value_msat());
1381                                 // We should make sure that at least 1 path left.
1382                                 let mut paths_left = cur_route.len();
1383                                 cur_route.retain(|path| {
1384                                         if paths_left == 1 {
1385                                                 return true
1386                                         }
1387                                         let mut keep = true;
1388                                         let path_value_msat = path.get_value_msat();
1389                                         if path_value_msat <= overpaid_value_msat {
1390                                                 keep = false;
1391                                                 overpaid_value_msat -= path_value_msat;
1392                                                 paths_left -= 1;
1393                                         }
1394                                         keep
1395                                 });
1396
1397                                 if overpaid_value_msat == 0 {
1398                                         break;
1399                                 }
1400
1401                                 assert!(cur_route.len() > 0);
1402
1403                                 // Step (8).
1404                                 // Now, substract the overpaid value from the most-expensive path.
1405                                 // TODO: this could also be optimized by also sorting by feerate_per_sat_routed,
1406                                 // so that the sender pays less fees overall. And also htlc_minimum_msat.
1407                                 cur_route.sort_by_key(|path| { path.hops.iter().map(|hop| hop.0.channel_fees.proportional_millionths as u64).sum::<u64>() });
1408                                 let expensive_payment_path = cur_route.first_mut().unwrap();
1409                                 // We already dropped all the small channels above, meaning all the
1410                                 // remaining channels are larger than remaining overpaid_value_msat.
1411                                 // Thus, this can't be negative.
1412                                 let expensive_path_new_value_msat = expensive_payment_path.get_value_msat() - overpaid_value_msat;
1413                                 expensive_payment_path.update_value_and_recompute_fees(expensive_path_new_value_msat);
1414                                 break;
1415                         }
1416                 }
1417                 drawn_routes.push(cur_route);
1418         }
1419
1420         // Step (9).
1421         // Select the best route by lowest total fee.
1422         drawn_routes.sort_by_key(|paths| paths.iter().map(|path| path.get_total_fee_paid_msat()).sum::<u64>());
1423         let mut selected_paths = Vec::<Vec<Result<RouteHop, LightningError>>>::new();
1424         for payment_path in drawn_routes.first().unwrap() {
1425                 selected_paths.push(payment_path.hops.iter().map(|(payment_hop, node_features)| {
1426                         Ok(RouteHop {
1427                                 pubkey: PublicKey::from_slice(payment_hop.node_id.as_slice()).map_err(|_| LightningError{err: format!("Public key {:?} is invalid", &payment_hop.node_id), action: ErrorAction::IgnoreAndLog(Level::Trace)})?,
1428                                 node_features: node_features.clone(),
1429                                 short_channel_id: payment_hop.short_channel_id,
1430                                 channel_features: payment_hop.channel_features.clone(),
1431                                 fee_msat: payment_hop.fee_msat,
1432                                 cltv_expiry_delta: payment_hop.cltv_expiry_delta,
1433                         })
1434                 }).collect());
1435         }
1436
1437         if let Some(features) = &payee.features {
1438                 for path in selected_paths.iter_mut() {
1439                         if let Ok(route_hop) = path.last_mut().unwrap() {
1440                                 route_hop.node_features = features.to_context();
1441                         }
1442                 }
1443         }
1444
1445         let route = Route { paths: selected_paths.into_iter().map(|path| path.into_iter().collect()).collect::<Result<Vec<_>, _>>()? };
1446         log_info!(logger, "Got route to {}: {}", payee.pubkey, log_route!(route));
1447         Ok(route)
1448 }
1449
1450 #[cfg(test)]
1451 mod tests {
1452         use routing;
1453         use routing::network_graph::{NetworkGraph, NetGraphMsgHandler, NodeId};
1454         use routing::router::{get_route, Payee, Route, RouteHint, RouteHintHop, RouteHop, RoutingFees};
1455         use routing::scorer::Scorer;
1456         use chain::transaction::OutPoint;
1457         use ln::features::{ChannelFeatures, InitFeatures, InvoiceFeatures, NodeFeatures};
1458         use ln::msgs::{ErrorAction, LightningError, OptionalField, UnsignedChannelAnnouncement, ChannelAnnouncement, RoutingMessageHandler,
1459            NodeAnnouncement, UnsignedNodeAnnouncement, ChannelUpdate, UnsignedChannelUpdate};
1460         use ln::channelmanager;
1461         use util::test_utils;
1462         use util::ser::Writeable;
1463
1464         use bitcoin::hashes::sha256d::Hash as Sha256dHash;
1465         use bitcoin::hashes::Hash;
1466         use bitcoin::network::constants::Network;
1467         use bitcoin::blockdata::constants::genesis_block;
1468         use bitcoin::blockdata::script::Builder;
1469         use bitcoin::blockdata::opcodes;
1470         use bitcoin::blockdata::transaction::TxOut;
1471
1472         use hex;
1473
1474         use bitcoin::secp256k1::key::{PublicKey,SecretKey};
1475         use bitcoin::secp256k1::{Secp256k1, All};
1476
1477         use prelude::*;
1478         use sync::{self, Arc};
1479
1480         fn get_channel_details(short_channel_id: Option<u64>, node_id: PublicKey,
1481                         features: InitFeatures, outbound_capacity_msat: u64) -> channelmanager::ChannelDetails {
1482                 channelmanager::ChannelDetails {
1483                         channel_id: [0; 32],
1484                         counterparty: channelmanager::ChannelCounterparty {
1485                                 features,
1486                                 node_id,
1487                                 unspendable_punishment_reserve: 0,
1488                                 forwarding_info: None,
1489                         },
1490                         funding_txo: Some(OutPoint { txid: bitcoin::Txid::from_slice(&[0; 32]).unwrap(), index: 0 }),
1491                         short_channel_id,
1492                         channel_value_satoshis: 0,
1493                         user_channel_id: 0,
1494                         outbound_capacity_msat,
1495                         inbound_capacity_msat: 42,
1496                         unspendable_punishment_reserve: None,
1497                         confirmations_required: None,
1498                         force_close_spend_delay: None,
1499                         is_outbound: true, is_funding_locked: true,
1500                         is_usable: true, is_public: true,
1501                 }
1502         }
1503
1504         // Using the same keys for LN and BTC ids
1505         fn add_channel(
1506                 net_graph_msg_handler: &NetGraphMsgHandler<Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>,
1507                 secp_ctx: &Secp256k1<All>, node_1_privkey: &SecretKey, node_2_privkey: &SecretKey, features: ChannelFeatures, short_channel_id: u64
1508         ) {
1509                 let node_id_1 = PublicKey::from_secret_key(&secp_ctx, node_1_privkey);
1510                 let node_id_2 = PublicKey::from_secret_key(&secp_ctx, node_2_privkey);
1511
1512                 let unsigned_announcement = UnsignedChannelAnnouncement {
1513                         features,
1514                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1515                         short_channel_id,
1516                         node_id_1,
1517                         node_id_2,
1518                         bitcoin_key_1: node_id_1,
1519                         bitcoin_key_2: node_id_2,
1520                         excess_data: Vec::new(),
1521                 };
1522
1523                 let msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_announcement.encode()[..])[..]);
1524                 let valid_announcement = ChannelAnnouncement {
1525                         node_signature_1: secp_ctx.sign(&msghash, node_1_privkey),
1526                         node_signature_2: secp_ctx.sign(&msghash, node_2_privkey),
1527                         bitcoin_signature_1: secp_ctx.sign(&msghash, node_1_privkey),
1528                         bitcoin_signature_2: secp_ctx.sign(&msghash, node_2_privkey),
1529                         contents: unsigned_announcement.clone(),
1530                 };
1531                 match net_graph_msg_handler.handle_channel_announcement(&valid_announcement) {
1532                         Ok(res) => assert!(res),
1533                         _ => panic!()
1534                 };
1535         }
1536
1537         fn update_channel(
1538                 net_graph_msg_handler: &NetGraphMsgHandler<Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>,
1539                 secp_ctx: &Secp256k1<All>, node_privkey: &SecretKey, update: UnsignedChannelUpdate
1540         ) {
1541                 let msghash = hash_to_message!(&Sha256dHash::hash(&update.encode()[..])[..]);
1542                 let valid_channel_update = ChannelUpdate {
1543                         signature: secp_ctx.sign(&msghash, node_privkey),
1544                         contents: update.clone()
1545                 };
1546
1547                 match net_graph_msg_handler.handle_channel_update(&valid_channel_update) {
1548                         Ok(res) => assert!(res),
1549                         Err(_) => panic!()
1550                 };
1551         }
1552
1553         fn add_or_update_node(
1554                 net_graph_msg_handler: &NetGraphMsgHandler<Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>,
1555                 secp_ctx: &Secp256k1<All>, node_privkey: &SecretKey, features: NodeFeatures, timestamp: u32
1556         ) {
1557                 let node_id = PublicKey::from_secret_key(&secp_ctx, node_privkey);
1558                 let unsigned_announcement = UnsignedNodeAnnouncement {
1559                         features,
1560                         timestamp,
1561                         node_id,
1562                         rgb: [0; 3],
1563                         alias: [0; 32],
1564                         addresses: Vec::new(),
1565                         excess_address_data: Vec::new(),
1566                         excess_data: Vec::new(),
1567                 };
1568                 let msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_announcement.encode()[..])[..]);
1569                 let valid_announcement = NodeAnnouncement {
1570                         signature: secp_ctx.sign(&msghash, node_privkey),
1571                         contents: unsigned_announcement.clone()
1572                 };
1573
1574                 match net_graph_msg_handler.handle_node_announcement(&valid_announcement) {
1575                         Ok(_) => (),
1576                         Err(_) => panic!()
1577                 };
1578         }
1579
1580         fn get_nodes(secp_ctx: &Secp256k1<All>) -> (SecretKey, PublicKey, Vec<SecretKey>, Vec<PublicKey>) {
1581                 let privkeys: Vec<SecretKey> = (2..10).map(|i| {
1582                         SecretKey::from_slice(&hex::decode(format!("{:02}", i).repeat(32)).unwrap()[..]).unwrap()
1583                 }).collect();
1584
1585                 let pubkeys = privkeys.iter().map(|secret| PublicKey::from_secret_key(&secp_ctx, secret)).collect();
1586
1587                 let our_privkey = SecretKey::from_slice(&hex::decode("01".repeat(32)).unwrap()[..]).unwrap();
1588                 let our_id = PublicKey::from_secret_key(&secp_ctx, &our_privkey);
1589
1590                 (our_privkey, our_id, privkeys, pubkeys)
1591         }
1592
1593         fn id_to_feature_flags(id: u8) -> Vec<u8> {
1594                 // Set the feature flags to the id'th odd (ie non-required) feature bit so that we can
1595                 // test for it later.
1596                 let idx = (id - 1) * 2 + 1;
1597                 if idx > 8*3 {
1598                         vec![1 << (idx - 8*3), 0, 0, 0]
1599                 } else if idx > 8*2 {
1600                         vec![1 << (idx - 8*2), 0, 0]
1601                 } else if idx > 8*1 {
1602                         vec![1 << (idx - 8*1), 0]
1603                 } else {
1604                         vec![1 << idx]
1605                 }
1606         }
1607
1608         fn build_graph() -> (Secp256k1<All>, NetGraphMsgHandler<sync::Arc<test_utils::TestChainSource>, sync::Arc<crate::util::test_utils::TestLogger>>, sync::Arc<test_utils::TestChainSource>, sync::Arc<test_utils::TestLogger>) {
1609                 let secp_ctx = Secp256k1::new();
1610                 let logger = Arc::new(test_utils::TestLogger::new());
1611                 let chain_monitor = Arc::new(test_utils::TestChainSource::new(Network::Testnet));
1612                 let network_graph = NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash());
1613                 let net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, None, Arc::clone(&logger));
1614                 // Build network from our_id to node6:
1615                 //
1616                 //        -1(1)2-  node0  -1(3)2-
1617                 //       /                       \
1618                 // our_id -1(12)2- node7 -1(13)2--- node2
1619                 //       \                       /
1620                 //        -1(2)2-  node1  -1(4)2-
1621                 //
1622                 //
1623                 // chan1  1-to-2: disabled
1624                 // chan1  2-to-1: enabled, 0 fee
1625                 //
1626                 // chan2  1-to-2: enabled, ignored fee
1627                 // chan2  2-to-1: enabled, 0 fee
1628                 //
1629                 // chan3  1-to-2: enabled, 0 fee
1630                 // chan3  2-to-1: enabled, 100 msat fee
1631                 //
1632                 // chan4  1-to-2: enabled, 100% fee
1633                 // chan4  2-to-1: enabled, 0 fee
1634                 //
1635                 // chan12 1-to-2: enabled, ignored fee
1636                 // chan12 2-to-1: enabled, 0 fee
1637                 //
1638                 // chan13 1-to-2: enabled, 200% fee
1639                 // chan13 2-to-1: enabled, 0 fee
1640                 //
1641                 //
1642                 //       -1(5)2- node3 -1(8)2--
1643                 //       |         2          |
1644                 //       |       (11)         |
1645                 //      /          1           \
1646                 // node2--1(6)2- node4 -1(9)2--- node6 (not in global route map)
1647                 //      \                      /
1648                 //       -1(7)2- node5 -1(10)2-
1649                 //
1650                 // Channels 5, 8, 9 and 10 are private channels.
1651                 //
1652                 // chan5  1-to-2: enabled, 100 msat fee
1653                 // chan5  2-to-1: enabled, 0 fee
1654                 //
1655                 // chan6  1-to-2: enabled, 0 fee
1656                 // chan6  2-to-1: enabled, 0 fee
1657                 //
1658                 // chan7  1-to-2: enabled, 100% fee
1659                 // chan7  2-to-1: enabled, 0 fee
1660                 //
1661                 // chan8  1-to-2: enabled, variable fee (0 then 1000 msat)
1662                 // chan8  2-to-1: enabled, 0 fee
1663                 //
1664                 // chan9  1-to-2: enabled, 1001 msat fee
1665                 // chan9  2-to-1: enabled, 0 fee
1666                 //
1667                 // chan10 1-to-2: enabled, 0 fee
1668                 // chan10 2-to-1: enabled, 0 fee
1669                 //
1670                 // chan11 1-to-2: enabled, 0 fee
1671                 // chan11 2-to-1: enabled, 0 fee
1672
1673                 let (our_privkey, _, privkeys, _) = get_nodes(&secp_ctx);
1674
1675                 add_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, &privkeys[0], ChannelFeatures::from_le_bytes(id_to_feature_flags(1)), 1);
1676                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
1677                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1678                         short_channel_id: 1,
1679                         timestamp: 1,
1680                         flags: 1,
1681                         cltv_expiry_delta: 0,
1682                         htlc_minimum_msat: 0,
1683                         htlc_maximum_msat: OptionalField::Absent,
1684                         fee_base_msat: 0,
1685                         fee_proportional_millionths: 0,
1686                         excess_data: Vec::new()
1687                 });
1688
1689                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[0], NodeFeatures::from_le_bytes(id_to_feature_flags(1)), 0);
1690
1691                 add_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, &privkeys[1], ChannelFeatures::from_le_bytes(id_to_feature_flags(2)), 2);
1692                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
1693                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1694                         short_channel_id: 2,
1695                         timestamp: 1,
1696                         flags: 0,
1697                         cltv_expiry_delta: u16::max_value(),
1698                         htlc_minimum_msat: 0,
1699                         htlc_maximum_msat: OptionalField::Absent,
1700                         fee_base_msat: u32::max_value(),
1701                         fee_proportional_millionths: u32::max_value(),
1702                         excess_data: Vec::new()
1703                 });
1704                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
1705                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1706                         short_channel_id: 2,
1707                         timestamp: 1,
1708                         flags: 1,
1709                         cltv_expiry_delta: 0,
1710                         htlc_minimum_msat: 0,
1711                         htlc_maximum_msat: OptionalField::Absent,
1712                         fee_base_msat: 0,
1713                         fee_proportional_millionths: 0,
1714                         excess_data: Vec::new()
1715                 });
1716
1717                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[1], NodeFeatures::from_le_bytes(id_to_feature_flags(2)), 0);
1718
1719                 add_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, &privkeys[7], ChannelFeatures::from_le_bytes(id_to_feature_flags(12)), 12);
1720                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
1721                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1722                         short_channel_id: 12,
1723                         timestamp: 1,
1724                         flags: 0,
1725                         cltv_expiry_delta: u16::max_value(),
1726                         htlc_minimum_msat: 0,
1727                         htlc_maximum_msat: OptionalField::Absent,
1728                         fee_base_msat: u32::max_value(),
1729                         fee_proportional_millionths: u32::max_value(),
1730                         excess_data: Vec::new()
1731                 });
1732                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
1733                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1734                         short_channel_id: 12,
1735                         timestamp: 1,
1736                         flags: 1,
1737                         cltv_expiry_delta: 0,
1738                         htlc_minimum_msat: 0,
1739                         htlc_maximum_msat: OptionalField::Absent,
1740                         fee_base_msat: 0,
1741                         fee_proportional_millionths: 0,
1742                         excess_data: Vec::new()
1743                 });
1744
1745                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[7], NodeFeatures::from_le_bytes(id_to_feature_flags(8)), 0);
1746
1747                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], &privkeys[2], ChannelFeatures::from_le_bytes(id_to_feature_flags(3)), 3);
1748                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
1749                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1750                         short_channel_id: 3,
1751                         timestamp: 1,
1752                         flags: 0,
1753                         cltv_expiry_delta: (3 << 8) | 1,
1754                         htlc_minimum_msat: 0,
1755                         htlc_maximum_msat: OptionalField::Absent,
1756                         fee_base_msat: 0,
1757                         fee_proportional_millionths: 0,
1758                         excess_data: Vec::new()
1759                 });
1760                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
1761                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1762                         short_channel_id: 3,
1763                         timestamp: 1,
1764                         flags: 1,
1765                         cltv_expiry_delta: (3 << 8) | 2,
1766                         htlc_minimum_msat: 0,
1767                         htlc_maximum_msat: OptionalField::Absent,
1768                         fee_base_msat: 100,
1769                         fee_proportional_millionths: 0,
1770                         excess_data: Vec::new()
1771                 });
1772
1773                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], &privkeys[2], ChannelFeatures::from_le_bytes(id_to_feature_flags(4)), 4);
1774                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
1775                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1776                         short_channel_id: 4,
1777                         timestamp: 1,
1778                         flags: 0,
1779                         cltv_expiry_delta: (4 << 8) | 1,
1780                         htlc_minimum_msat: 0,
1781                         htlc_maximum_msat: OptionalField::Absent,
1782                         fee_base_msat: 0,
1783                         fee_proportional_millionths: 1000000,
1784                         excess_data: Vec::new()
1785                 });
1786                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
1787                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1788                         short_channel_id: 4,
1789                         timestamp: 1,
1790                         flags: 1,
1791                         cltv_expiry_delta: (4 << 8) | 2,
1792                         htlc_minimum_msat: 0,
1793                         htlc_maximum_msat: OptionalField::Absent,
1794                         fee_base_msat: 0,
1795                         fee_proportional_millionths: 0,
1796                         excess_data: Vec::new()
1797                 });
1798
1799                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], &privkeys[2], ChannelFeatures::from_le_bytes(id_to_feature_flags(13)), 13);
1800                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
1801                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1802                         short_channel_id: 13,
1803                         timestamp: 1,
1804                         flags: 0,
1805                         cltv_expiry_delta: (13 << 8) | 1,
1806                         htlc_minimum_msat: 0,
1807                         htlc_maximum_msat: OptionalField::Absent,
1808                         fee_base_msat: 0,
1809                         fee_proportional_millionths: 2000000,
1810                         excess_data: Vec::new()
1811                 });
1812                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
1813                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1814                         short_channel_id: 13,
1815                         timestamp: 1,
1816                         flags: 1,
1817                         cltv_expiry_delta: (13 << 8) | 2,
1818                         htlc_minimum_msat: 0,
1819                         htlc_maximum_msat: OptionalField::Absent,
1820                         fee_base_msat: 0,
1821                         fee_proportional_millionths: 0,
1822                         excess_data: Vec::new()
1823                 });
1824
1825                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[2], NodeFeatures::from_le_bytes(id_to_feature_flags(3)), 0);
1826
1827                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], &privkeys[4], ChannelFeatures::from_le_bytes(id_to_feature_flags(6)), 6);
1828                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
1829                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1830                         short_channel_id: 6,
1831                         timestamp: 1,
1832                         flags: 0,
1833                         cltv_expiry_delta: (6 << 8) | 1,
1834                         htlc_minimum_msat: 0,
1835                         htlc_maximum_msat: OptionalField::Absent,
1836                         fee_base_msat: 0,
1837                         fee_proportional_millionths: 0,
1838                         excess_data: Vec::new()
1839                 });
1840                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
1841                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1842                         short_channel_id: 6,
1843                         timestamp: 1,
1844                         flags: 1,
1845                         cltv_expiry_delta: (6 << 8) | 2,
1846                         htlc_minimum_msat: 0,
1847                         htlc_maximum_msat: OptionalField::Absent,
1848                         fee_base_msat: 0,
1849                         fee_proportional_millionths: 0,
1850                         excess_data: Vec::new(),
1851                 });
1852
1853                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], &privkeys[3], ChannelFeatures::from_le_bytes(id_to_feature_flags(11)), 11);
1854                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
1855                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1856                         short_channel_id: 11,
1857                         timestamp: 1,
1858                         flags: 0,
1859                         cltv_expiry_delta: (11 << 8) | 1,
1860                         htlc_minimum_msat: 0,
1861                         htlc_maximum_msat: OptionalField::Absent,
1862                         fee_base_msat: 0,
1863                         fee_proportional_millionths: 0,
1864                         excess_data: Vec::new()
1865                 });
1866                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[3], UnsignedChannelUpdate {
1867                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1868                         short_channel_id: 11,
1869                         timestamp: 1,
1870                         flags: 1,
1871                         cltv_expiry_delta: (11 << 8) | 2,
1872                         htlc_minimum_msat: 0,
1873                         htlc_maximum_msat: OptionalField::Absent,
1874                         fee_base_msat: 0,
1875                         fee_proportional_millionths: 0,
1876                         excess_data: Vec::new()
1877                 });
1878
1879                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[4], NodeFeatures::from_le_bytes(id_to_feature_flags(5)), 0);
1880
1881                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[3], NodeFeatures::from_le_bytes(id_to_feature_flags(4)), 0);
1882
1883                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], &privkeys[5], ChannelFeatures::from_le_bytes(id_to_feature_flags(7)), 7);
1884                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
1885                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1886                         short_channel_id: 7,
1887                         timestamp: 1,
1888                         flags: 0,
1889                         cltv_expiry_delta: (7 << 8) | 1,
1890                         htlc_minimum_msat: 0,
1891                         htlc_maximum_msat: OptionalField::Absent,
1892                         fee_base_msat: 0,
1893                         fee_proportional_millionths: 1000000,
1894                         excess_data: Vec::new()
1895                 });
1896                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[5], UnsignedChannelUpdate {
1897                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1898                         short_channel_id: 7,
1899                         timestamp: 1,
1900                         flags: 1,
1901                         cltv_expiry_delta: (7 << 8) | 2,
1902                         htlc_minimum_msat: 0,
1903                         htlc_maximum_msat: OptionalField::Absent,
1904                         fee_base_msat: 0,
1905                         fee_proportional_millionths: 0,
1906                         excess_data: Vec::new()
1907                 });
1908
1909                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[5], NodeFeatures::from_le_bytes(id_to_feature_flags(6)), 0);
1910
1911                 (secp_ctx, net_graph_msg_handler, chain_monitor, logger)
1912         }
1913
1914         #[test]
1915         fn simple_route_test() {
1916                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
1917                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
1918                 let payee = Payee::new(nodes[2]);
1919                 let scorer = Scorer::new(0);
1920
1921                 // Simple route to 2 via 1
1922
1923                 if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 0, 42, Arc::clone(&logger), &scorer) {
1924                         assert_eq!(err, "Cannot send a payment of 0 msat");
1925                 } else { panic!(); }
1926
1927                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer).unwrap();
1928                 assert_eq!(route.paths[0].len(), 2);
1929
1930                 assert_eq!(route.paths[0][0].pubkey, nodes[1]);
1931                 assert_eq!(route.paths[0][0].short_channel_id, 2);
1932                 assert_eq!(route.paths[0][0].fee_msat, 100);
1933                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (4 << 8) | 1);
1934                 assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(2));
1935                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(2));
1936
1937                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
1938                 assert_eq!(route.paths[0][1].short_channel_id, 4);
1939                 assert_eq!(route.paths[0][1].fee_msat, 100);
1940                 assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
1941                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
1942                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(4));
1943         }
1944
1945         #[test]
1946         fn invalid_first_hop_test() {
1947                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
1948                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
1949                 let payee = Payee::new(nodes[2]);
1950                 let scorer = Scorer::new(0);
1951
1952                 // Simple route to 2 via 1
1953
1954                 let our_chans = vec![get_channel_details(Some(2), our_id, InitFeatures::from_le_bytes(vec![0b11]), 100000)];
1955
1956                 if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, Some(&our_chans.iter().collect::<Vec<_>>()), 100, 42, Arc::clone(&logger), &scorer) {
1957                         assert_eq!(err, "First hop cannot have our_node_pubkey as a destination.");
1958                 } else { panic!(); }
1959
1960                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer).unwrap();
1961                 assert_eq!(route.paths[0].len(), 2);
1962         }
1963
1964         #[test]
1965         fn htlc_minimum_test() {
1966                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
1967                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
1968                 let payee = Payee::new(nodes[2]);
1969                 let scorer = Scorer::new(0);
1970
1971                 // Simple route to 2 via 1
1972
1973                 // Disable other paths
1974                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
1975                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1976                         short_channel_id: 12,
1977                         timestamp: 2,
1978                         flags: 2, // to disable
1979                         cltv_expiry_delta: 0,
1980                         htlc_minimum_msat: 0,
1981                         htlc_maximum_msat: OptionalField::Absent,
1982                         fee_base_msat: 0,
1983                         fee_proportional_millionths: 0,
1984                         excess_data: Vec::new()
1985                 });
1986                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
1987                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
1988                         short_channel_id: 3,
1989                         timestamp: 2,
1990                         flags: 2, // to disable
1991                         cltv_expiry_delta: 0,
1992                         htlc_minimum_msat: 0,
1993                         htlc_maximum_msat: OptionalField::Absent,
1994                         fee_base_msat: 0,
1995                         fee_proportional_millionths: 0,
1996                         excess_data: Vec::new()
1997                 });
1998                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
1999                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2000                         short_channel_id: 13,
2001                         timestamp: 2,
2002                         flags: 2, // to disable
2003                         cltv_expiry_delta: 0,
2004                         htlc_minimum_msat: 0,
2005                         htlc_maximum_msat: OptionalField::Absent,
2006                         fee_base_msat: 0,
2007                         fee_proportional_millionths: 0,
2008                         excess_data: Vec::new()
2009                 });
2010                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
2011                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2012                         short_channel_id: 6,
2013                         timestamp: 2,
2014                         flags: 2, // to disable
2015                         cltv_expiry_delta: 0,
2016                         htlc_minimum_msat: 0,
2017                         htlc_maximum_msat: OptionalField::Absent,
2018                         fee_base_msat: 0,
2019                         fee_proportional_millionths: 0,
2020                         excess_data: Vec::new()
2021                 });
2022                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
2023                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2024                         short_channel_id: 7,
2025                         timestamp: 2,
2026                         flags: 2, // to disable
2027                         cltv_expiry_delta: 0,
2028                         htlc_minimum_msat: 0,
2029                         htlc_maximum_msat: OptionalField::Absent,
2030                         fee_base_msat: 0,
2031                         fee_proportional_millionths: 0,
2032                         excess_data: Vec::new()
2033                 });
2034
2035                 // Check against amount_to_transfer_over_msat.
2036                 // Set minimal HTLC of 200_000_000 msat.
2037                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2038                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2039                         short_channel_id: 2,
2040                         timestamp: 3,
2041                         flags: 0,
2042                         cltv_expiry_delta: 0,
2043                         htlc_minimum_msat: 200_000_000,
2044                         htlc_maximum_msat: OptionalField::Absent,
2045                         fee_base_msat: 0,
2046                         fee_proportional_millionths: 0,
2047                         excess_data: Vec::new()
2048                 });
2049
2050                 // Second hop only allows to forward 199_999_999 at most, thus not allowing the first hop to
2051                 // be used.
2052                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
2053                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2054                         short_channel_id: 4,
2055                         timestamp: 3,
2056                         flags: 0,
2057                         cltv_expiry_delta: 0,
2058                         htlc_minimum_msat: 0,
2059                         htlc_maximum_msat: OptionalField::Present(199_999_999),
2060                         fee_base_msat: 0,
2061                         fee_proportional_millionths: 0,
2062                         excess_data: Vec::new()
2063                 });
2064
2065                 // Not possible to send 199_999_999, because the minimum on channel=2 is 200_000_000.
2066                 if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 199_999_999, 42, Arc::clone(&logger), &scorer) {
2067                         assert_eq!(err, "Failed to find a path to the given destination");
2068                 } else { panic!(); }
2069
2070                 // Lift the restriction on the first hop.
2071                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2072                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2073                         short_channel_id: 2,
2074                         timestamp: 4,
2075                         flags: 0,
2076                         cltv_expiry_delta: 0,
2077                         htlc_minimum_msat: 0,
2078                         htlc_maximum_msat: OptionalField::Absent,
2079                         fee_base_msat: 0,
2080                         fee_proportional_millionths: 0,
2081                         excess_data: Vec::new()
2082                 });
2083
2084                 // A payment above the minimum should pass
2085                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 199_999_999, 42, Arc::clone(&logger), &scorer).unwrap();
2086                 assert_eq!(route.paths[0].len(), 2);
2087         }
2088
2089         #[test]
2090         fn htlc_minimum_overpay_test() {
2091                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2092                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
2093                 let payee = Payee::new(nodes[2]).with_features(InvoiceFeatures::known());
2094                 let scorer = Scorer::new(0);
2095
2096                 // A route to node#2 via two paths.
2097                 // One path allows transferring 35-40 sats, another one also allows 35-40 sats.
2098                 // Thus, they can't send 60 without overpaying.
2099                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2100                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2101                         short_channel_id: 2,
2102                         timestamp: 2,
2103                         flags: 0,
2104                         cltv_expiry_delta: 0,
2105                         htlc_minimum_msat: 35_000,
2106                         htlc_maximum_msat: OptionalField::Present(40_000),
2107                         fee_base_msat: 0,
2108                         fee_proportional_millionths: 0,
2109                         excess_data: Vec::new()
2110                 });
2111                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2112                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2113                         short_channel_id: 12,
2114                         timestamp: 3,
2115                         flags: 0,
2116                         cltv_expiry_delta: 0,
2117                         htlc_minimum_msat: 35_000,
2118                         htlc_maximum_msat: OptionalField::Present(40_000),
2119                         fee_base_msat: 0,
2120                         fee_proportional_millionths: 0,
2121                         excess_data: Vec::new()
2122                 });
2123
2124                 // Make 0 fee.
2125                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
2126                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2127                         short_channel_id: 13,
2128                         timestamp: 2,
2129                         flags: 0,
2130                         cltv_expiry_delta: 0,
2131                         htlc_minimum_msat: 0,
2132                         htlc_maximum_msat: OptionalField::Absent,
2133                         fee_base_msat: 0,
2134                         fee_proportional_millionths: 0,
2135                         excess_data: Vec::new()
2136                 });
2137                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
2138                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2139                         short_channel_id: 4,
2140                         timestamp: 2,
2141                         flags: 0,
2142                         cltv_expiry_delta: 0,
2143                         htlc_minimum_msat: 0,
2144                         htlc_maximum_msat: OptionalField::Absent,
2145                         fee_base_msat: 0,
2146                         fee_proportional_millionths: 0,
2147                         excess_data: Vec::new()
2148                 });
2149
2150                 // Disable other paths
2151                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2152                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2153                         short_channel_id: 1,
2154                         timestamp: 3,
2155                         flags: 2, // to disable
2156                         cltv_expiry_delta: 0,
2157                         htlc_minimum_msat: 0,
2158                         htlc_maximum_msat: OptionalField::Absent,
2159                         fee_base_msat: 0,
2160                         fee_proportional_millionths: 0,
2161                         excess_data: Vec::new()
2162                 });
2163
2164                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 60_000, 42, Arc::clone(&logger), &scorer).unwrap();
2165                 // Overpay fees to hit htlc_minimum_msat.
2166                 let overpaid_fees = route.paths[0][0].fee_msat + route.paths[1][0].fee_msat;
2167                 // TODO: this could be better balanced to overpay 10k and not 15k.
2168                 assert_eq!(overpaid_fees, 15_000);
2169
2170                 // Now, test that if there are 2 paths, a "cheaper" by fee path wouldn't be prioritized
2171                 // while taking even more fee to match htlc_minimum_msat.
2172                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2173                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2174                         short_channel_id: 12,
2175                         timestamp: 4,
2176                         flags: 0,
2177                         cltv_expiry_delta: 0,
2178                         htlc_minimum_msat: 65_000,
2179                         htlc_maximum_msat: OptionalField::Present(80_000),
2180                         fee_base_msat: 0,
2181                         fee_proportional_millionths: 0,
2182                         excess_data: Vec::new()
2183                 });
2184                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2185                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2186                         short_channel_id: 2,
2187                         timestamp: 3,
2188                         flags: 0,
2189                         cltv_expiry_delta: 0,
2190                         htlc_minimum_msat: 0,
2191                         htlc_maximum_msat: OptionalField::Absent,
2192                         fee_base_msat: 0,
2193                         fee_proportional_millionths: 0,
2194                         excess_data: Vec::new()
2195                 });
2196                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
2197                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2198                         short_channel_id: 4,
2199                         timestamp: 4,
2200                         flags: 0,
2201                         cltv_expiry_delta: 0,
2202                         htlc_minimum_msat: 0,
2203                         htlc_maximum_msat: OptionalField::Absent,
2204                         fee_base_msat: 0,
2205                         fee_proportional_millionths: 100_000,
2206                         excess_data: Vec::new()
2207                 });
2208
2209                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 60_000, 42, Arc::clone(&logger), &scorer).unwrap();
2210                 // Fine to overpay for htlc_minimum_msat if it allows us to save fee.
2211                 assert_eq!(route.paths.len(), 1);
2212                 assert_eq!(route.paths[0][0].short_channel_id, 12);
2213                 let fees = route.paths[0][0].fee_msat;
2214                 assert_eq!(fees, 5_000);
2215
2216                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 50_000, 42, Arc::clone(&logger), &scorer).unwrap();
2217                 // Not fine to overpay for htlc_minimum_msat if it requires paying more than fee on
2218                 // the other channel.
2219                 assert_eq!(route.paths.len(), 1);
2220                 assert_eq!(route.paths[0][0].short_channel_id, 2);
2221                 let fees = route.paths[0][0].fee_msat;
2222                 assert_eq!(fees, 5_000);
2223         }
2224
2225         #[test]
2226         fn disable_channels_test() {
2227                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2228                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
2229                 let payee = Payee::new(nodes[2]);
2230                 let scorer = Scorer::new(0);
2231
2232                 // // Disable channels 4 and 12 by flags=2
2233                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
2234                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2235                         short_channel_id: 4,
2236                         timestamp: 2,
2237                         flags: 2, // to disable
2238                         cltv_expiry_delta: 0,
2239                         htlc_minimum_msat: 0,
2240                         htlc_maximum_msat: OptionalField::Absent,
2241                         fee_base_msat: 0,
2242                         fee_proportional_millionths: 0,
2243                         excess_data: Vec::new()
2244                 });
2245                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2246                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2247                         short_channel_id: 12,
2248                         timestamp: 2,
2249                         flags: 2, // to disable
2250                         cltv_expiry_delta: 0,
2251                         htlc_minimum_msat: 0,
2252                         htlc_maximum_msat: OptionalField::Absent,
2253                         fee_base_msat: 0,
2254                         fee_proportional_millionths: 0,
2255                         excess_data: Vec::new()
2256                 });
2257
2258                 // If all the channels require some features we don't understand, route should fail
2259                 if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer) {
2260                         assert_eq!(err, "Failed to find a path to the given destination");
2261                 } else { panic!(); }
2262
2263                 // If we specify a channel to node7, that overrides our local channel view and that gets used
2264                 let our_chans = vec![get_channel_details(Some(42), nodes[7].clone(), InitFeatures::from_le_bytes(vec![0b11]), 250_000_000)];
2265                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, Some(&our_chans.iter().collect::<Vec<_>>()), 100, 42, Arc::clone(&logger), &scorer).unwrap();
2266                 assert_eq!(route.paths[0].len(), 2);
2267
2268                 assert_eq!(route.paths[0][0].pubkey, nodes[7]);
2269                 assert_eq!(route.paths[0][0].short_channel_id, 42);
2270                 assert_eq!(route.paths[0][0].fee_msat, 200);
2271                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (13 << 8) | 1);
2272                 assert_eq!(route.paths[0][0].node_features.le_flags(), &vec![0b11]); // it should also override our view of their features
2273                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &Vec::<u8>::new()); // No feature flags will meet the relevant-to-channel conversion
2274
2275                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2276                 assert_eq!(route.paths[0][1].short_channel_id, 13);
2277                 assert_eq!(route.paths[0][1].fee_msat, 100);
2278                 assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
2279                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2280                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(13));
2281         }
2282
2283         #[test]
2284         fn disable_node_test() {
2285                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2286                 let (_, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
2287                 let payee = Payee::new(nodes[2]);
2288                 let scorer = Scorer::new(0);
2289
2290                 // Disable nodes 1, 2, and 8 by requiring unknown feature bits
2291                 let unknown_features = NodeFeatures::known().set_unknown_feature_required();
2292                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[0], unknown_features.clone(), 1);
2293                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[1], unknown_features.clone(), 1);
2294                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[7], unknown_features.clone(), 1);
2295
2296                 // If all nodes require some features we don't understand, route should fail
2297                 if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer) {
2298                         assert_eq!(err, "Failed to find a path to the given destination");
2299                 } else { panic!(); }
2300
2301                 // If we specify a channel to node7, that overrides our local channel view and that gets used
2302                 let our_chans = vec![get_channel_details(Some(42), nodes[7].clone(), InitFeatures::from_le_bytes(vec![0b11]), 250_000_000)];
2303                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, Some(&our_chans.iter().collect::<Vec<_>>()), 100, 42, Arc::clone(&logger), &scorer).unwrap();
2304                 assert_eq!(route.paths[0].len(), 2);
2305
2306                 assert_eq!(route.paths[0][0].pubkey, nodes[7]);
2307                 assert_eq!(route.paths[0][0].short_channel_id, 42);
2308                 assert_eq!(route.paths[0][0].fee_msat, 200);
2309                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (13 << 8) | 1);
2310                 assert_eq!(route.paths[0][0].node_features.le_flags(), &vec![0b11]); // it should also override our view of their features
2311                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &Vec::<u8>::new()); // No feature flags will meet the relevant-to-channel conversion
2312
2313                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2314                 assert_eq!(route.paths[0][1].short_channel_id, 13);
2315                 assert_eq!(route.paths[0][1].fee_msat, 100);
2316                 assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
2317                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2318                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(13));
2319
2320                 // Note that we don't test disabling node 3 and failing to route to it, as we (somewhat
2321                 // naively) assume that the user checked the feature bits on the invoice, which override
2322                 // the node_announcement.
2323         }
2324
2325         #[test]
2326         fn our_chans_test() {
2327                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2328                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
2329                 let scorer = Scorer::new(0);
2330
2331                 // Route to 1 via 2 and 3 because our channel to 1 is disabled
2332                 let payee = Payee::new(nodes[0]);
2333                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer).unwrap();
2334                 assert_eq!(route.paths[0].len(), 3);
2335
2336                 assert_eq!(route.paths[0][0].pubkey, nodes[1]);
2337                 assert_eq!(route.paths[0][0].short_channel_id, 2);
2338                 assert_eq!(route.paths[0][0].fee_msat, 200);
2339                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (4 << 8) | 1);
2340                 assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(2));
2341                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(2));
2342
2343                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2344                 assert_eq!(route.paths[0][1].short_channel_id, 4);
2345                 assert_eq!(route.paths[0][1].fee_msat, 100);
2346                 assert_eq!(route.paths[0][1].cltv_expiry_delta, (3 << 8) | 2);
2347                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2348                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(4));
2349
2350                 assert_eq!(route.paths[0][2].pubkey, nodes[0]);
2351                 assert_eq!(route.paths[0][2].short_channel_id, 3);
2352                 assert_eq!(route.paths[0][2].fee_msat, 100);
2353                 assert_eq!(route.paths[0][2].cltv_expiry_delta, 42);
2354                 assert_eq!(route.paths[0][2].node_features.le_flags(), &id_to_feature_flags(1));
2355                 assert_eq!(route.paths[0][2].channel_features.le_flags(), &id_to_feature_flags(3));
2356
2357                 // If we specify a channel to node7, that overrides our local channel view and that gets used
2358                 let payee = Payee::new(nodes[2]);
2359                 let our_chans = vec![get_channel_details(Some(42), nodes[7].clone(), InitFeatures::from_le_bytes(vec![0b11]), 250_000_000)];
2360                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, Some(&our_chans.iter().collect::<Vec<_>>()), 100, 42, Arc::clone(&logger), &scorer).unwrap();
2361                 assert_eq!(route.paths[0].len(), 2);
2362
2363                 assert_eq!(route.paths[0][0].pubkey, nodes[7]);
2364                 assert_eq!(route.paths[0][0].short_channel_id, 42);
2365                 assert_eq!(route.paths[0][0].fee_msat, 200);
2366                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (13 << 8) | 1);
2367                 assert_eq!(route.paths[0][0].node_features.le_flags(), &vec![0b11]);
2368                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &Vec::<u8>::new()); // No feature flags will meet the relevant-to-channel conversion
2369
2370                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2371                 assert_eq!(route.paths[0][1].short_channel_id, 13);
2372                 assert_eq!(route.paths[0][1].fee_msat, 100);
2373                 assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
2374                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2375                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(13));
2376         }
2377
2378         fn last_hops(nodes: &Vec<PublicKey>) -> Vec<RouteHint> {
2379                 let zero_fees = RoutingFees {
2380                         base_msat: 0,
2381                         proportional_millionths: 0,
2382                 };
2383                 vec![RouteHint(vec![RouteHintHop {
2384                         src_node_id: nodes[3],
2385                         short_channel_id: 8,
2386                         fees: zero_fees,
2387                         cltv_expiry_delta: (8 << 8) | 1,
2388                         htlc_minimum_msat: None,
2389                         htlc_maximum_msat: None,
2390                 }
2391                 ]), RouteHint(vec![RouteHintHop {
2392                         src_node_id: nodes[4],
2393                         short_channel_id: 9,
2394                         fees: RoutingFees {
2395                                 base_msat: 1001,
2396                                 proportional_millionths: 0,
2397                         },
2398                         cltv_expiry_delta: (9 << 8) | 1,
2399                         htlc_minimum_msat: None,
2400                         htlc_maximum_msat: None,
2401                 }]), RouteHint(vec![RouteHintHop {
2402                         src_node_id: nodes[5],
2403                         short_channel_id: 10,
2404                         fees: zero_fees,
2405                         cltv_expiry_delta: (10 << 8) | 1,
2406                         htlc_minimum_msat: None,
2407                         htlc_maximum_msat: None,
2408                 }])]
2409         }
2410
2411         fn last_hops_multi_private_channels(nodes: &Vec<PublicKey>) -> Vec<RouteHint> {
2412                 let zero_fees = RoutingFees {
2413                         base_msat: 0,
2414                         proportional_millionths: 0,
2415                 };
2416                 vec![RouteHint(vec![RouteHintHop {
2417                         src_node_id: nodes[2],
2418                         short_channel_id: 5,
2419                         fees: RoutingFees {
2420                                 base_msat: 100,
2421                                 proportional_millionths: 0,
2422                         },
2423                         cltv_expiry_delta: (5 << 8) | 1,
2424                         htlc_minimum_msat: None,
2425                         htlc_maximum_msat: None,
2426                 }, RouteHintHop {
2427                         src_node_id: nodes[3],
2428                         short_channel_id: 8,
2429                         fees: zero_fees,
2430                         cltv_expiry_delta: (8 << 8) | 1,
2431                         htlc_minimum_msat: None,
2432                         htlc_maximum_msat: None,
2433                 }
2434                 ]), RouteHint(vec![RouteHintHop {
2435                         src_node_id: nodes[4],
2436                         short_channel_id: 9,
2437                         fees: RoutingFees {
2438                                 base_msat: 1001,
2439                                 proportional_millionths: 0,
2440                         },
2441                         cltv_expiry_delta: (9 << 8) | 1,
2442                         htlc_minimum_msat: None,
2443                         htlc_maximum_msat: None,
2444                 }]), RouteHint(vec![RouteHintHop {
2445                         src_node_id: nodes[5],
2446                         short_channel_id: 10,
2447                         fees: zero_fees,
2448                         cltv_expiry_delta: (10 << 8) | 1,
2449                         htlc_minimum_msat: None,
2450                         htlc_maximum_msat: None,
2451                 }])]
2452         }
2453
2454         #[test]
2455         fn partial_route_hint_test() {
2456                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2457                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
2458                 let scorer = Scorer::new(0);
2459
2460                 // Simple test across 2, 3, 5, and 4 via a last_hop channel
2461                 // Tests the behaviour when the RouteHint contains a suboptimal hop.
2462                 // RouteHint may be partially used by the algo to build the best path.
2463
2464                 // First check that last hop can't have its source as the payee.
2465                 let invalid_last_hop = RouteHint(vec![RouteHintHop {
2466                         src_node_id: nodes[6],
2467                         short_channel_id: 8,
2468                         fees: RoutingFees {
2469                                 base_msat: 1000,
2470                                 proportional_millionths: 0,
2471                         },
2472                         cltv_expiry_delta: (8 << 8) | 1,
2473                         htlc_minimum_msat: None,
2474                         htlc_maximum_msat: None,
2475                 }]);
2476
2477                 let mut invalid_last_hops = last_hops_multi_private_channels(&nodes);
2478                 invalid_last_hops.push(invalid_last_hop);
2479                 {
2480                         let payee = Payee::new(nodes[6]).with_route_hints(invalid_last_hops);
2481                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer) {
2482                                 assert_eq!(err, "Route hint cannot have the payee as the source.");
2483                         } else { panic!(); }
2484                 }
2485
2486                 let payee = Payee::new(nodes[6]).with_route_hints(last_hops_multi_private_channels(&nodes));
2487                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer).unwrap();
2488                 assert_eq!(route.paths[0].len(), 5);
2489
2490                 assert_eq!(route.paths[0][0].pubkey, nodes[1]);
2491                 assert_eq!(route.paths[0][0].short_channel_id, 2);
2492                 assert_eq!(route.paths[0][0].fee_msat, 100);
2493                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (4 << 8) | 1);
2494                 assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(2));
2495                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(2));
2496
2497                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2498                 assert_eq!(route.paths[0][1].short_channel_id, 4);
2499                 assert_eq!(route.paths[0][1].fee_msat, 0);
2500                 assert_eq!(route.paths[0][1].cltv_expiry_delta, (6 << 8) | 1);
2501                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2502                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(4));
2503
2504                 assert_eq!(route.paths[0][2].pubkey, nodes[4]);
2505                 assert_eq!(route.paths[0][2].short_channel_id, 6);
2506                 assert_eq!(route.paths[0][2].fee_msat, 0);
2507                 assert_eq!(route.paths[0][2].cltv_expiry_delta, (11 << 8) | 1);
2508                 assert_eq!(route.paths[0][2].node_features.le_flags(), &id_to_feature_flags(5));
2509                 assert_eq!(route.paths[0][2].channel_features.le_flags(), &id_to_feature_flags(6));
2510
2511                 assert_eq!(route.paths[0][3].pubkey, nodes[3]);
2512                 assert_eq!(route.paths[0][3].short_channel_id, 11);
2513                 assert_eq!(route.paths[0][3].fee_msat, 0);
2514                 assert_eq!(route.paths[0][3].cltv_expiry_delta, (8 << 8) | 1);
2515                 // If we have a peer in the node map, we'll use their features here since we don't have
2516                 // a way of figuring out their features from the invoice:
2517                 assert_eq!(route.paths[0][3].node_features.le_flags(), &id_to_feature_flags(4));
2518                 assert_eq!(route.paths[0][3].channel_features.le_flags(), &id_to_feature_flags(11));
2519
2520                 assert_eq!(route.paths[0][4].pubkey, nodes[6]);
2521                 assert_eq!(route.paths[0][4].short_channel_id, 8);
2522                 assert_eq!(route.paths[0][4].fee_msat, 100);
2523                 assert_eq!(route.paths[0][4].cltv_expiry_delta, 42);
2524                 assert_eq!(route.paths[0][4].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
2525                 assert_eq!(route.paths[0][4].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
2526         }
2527
2528         fn empty_last_hop(nodes: &Vec<PublicKey>) -> Vec<RouteHint> {
2529                 let zero_fees = RoutingFees {
2530                         base_msat: 0,
2531                         proportional_millionths: 0,
2532                 };
2533                 vec![RouteHint(vec![RouteHintHop {
2534                         src_node_id: nodes[3],
2535                         short_channel_id: 8,
2536                         fees: zero_fees,
2537                         cltv_expiry_delta: (8 << 8) | 1,
2538                         htlc_minimum_msat: None,
2539                         htlc_maximum_msat: None,
2540                 }]), RouteHint(vec![
2541
2542                 ]), RouteHint(vec![RouteHintHop {
2543                         src_node_id: nodes[5],
2544                         short_channel_id: 10,
2545                         fees: zero_fees,
2546                         cltv_expiry_delta: (10 << 8) | 1,
2547                         htlc_minimum_msat: None,
2548                         htlc_maximum_msat: None,
2549                 }])]
2550         }
2551
2552         #[test]
2553         fn ignores_empty_last_hops_test() {
2554                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2555                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
2556                 let payee = Payee::new(nodes[6]).with_route_hints(empty_last_hop(&nodes));
2557                 let scorer = Scorer::new(0);
2558
2559                 // Test handling of an empty RouteHint passed in Invoice.
2560
2561                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer).unwrap();
2562                 assert_eq!(route.paths[0].len(), 5);
2563
2564                 assert_eq!(route.paths[0][0].pubkey, nodes[1]);
2565                 assert_eq!(route.paths[0][0].short_channel_id, 2);
2566                 assert_eq!(route.paths[0][0].fee_msat, 100);
2567                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (4 << 8) | 1);
2568                 assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(2));
2569                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(2));
2570
2571                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2572                 assert_eq!(route.paths[0][1].short_channel_id, 4);
2573                 assert_eq!(route.paths[0][1].fee_msat, 0);
2574                 assert_eq!(route.paths[0][1].cltv_expiry_delta, (6 << 8) | 1);
2575                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2576                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(4));
2577
2578                 assert_eq!(route.paths[0][2].pubkey, nodes[4]);
2579                 assert_eq!(route.paths[0][2].short_channel_id, 6);
2580                 assert_eq!(route.paths[0][2].fee_msat, 0);
2581                 assert_eq!(route.paths[0][2].cltv_expiry_delta, (11 << 8) | 1);
2582                 assert_eq!(route.paths[0][2].node_features.le_flags(), &id_to_feature_flags(5));
2583                 assert_eq!(route.paths[0][2].channel_features.le_flags(), &id_to_feature_flags(6));
2584
2585                 assert_eq!(route.paths[0][3].pubkey, nodes[3]);
2586                 assert_eq!(route.paths[0][3].short_channel_id, 11);
2587                 assert_eq!(route.paths[0][3].fee_msat, 0);
2588                 assert_eq!(route.paths[0][3].cltv_expiry_delta, (8 << 8) | 1);
2589                 // If we have a peer in the node map, we'll use their features here since we don't have
2590                 // a way of figuring out their features from the invoice:
2591                 assert_eq!(route.paths[0][3].node_features.le_flags(), &id_to_feature_flags(4));
2592                 assert_eq!(route.paths[0][3].channel_features.le_flags(), &id_to_feature_flags(11));
2593
2594                 assert_eq!(route.paths[0][4].pubkey, nodes[6]);
2595                 assert_eq!(route.paths[0][4].short_channel_id, 8);
2596                 assert_eq!(route.paths[0][4].fee_msat, 100);
2597                 assert_eq!(route.paths[0][4].cltv_expiry_delta, 42);
2598                 assert_eq!(route.paths[0][4].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
2599                 assert_eq!(route.paths[0][4].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
2600         }
2601
2602         fn multi_hint_last_hops(nodes: &Vec<PublicKey>) -> Vec<RouteHint> {
2603                 let zero_fees = RoutingFees {
2604                         base_msat: 0,
2605                         proportional_millionths: 0,
2606                 };
2607                 vec![RouteHint(vec![RouteHintHop {
2608                         src_node_id: nodes[2],
2609                         short_channel_id: 5,
2610                         fees: RoutingFees {
2611                                 base_msat: 100,
2612                                 proportional_millionths: 0,
2613                         },
2614                         cltv_expiry_delta: (5 << 8) | 1,
2615                         htlc_minimum_msat: None,
2616                         htlc_maximum_msat: None,
2617                 }, RouteHintHop {
2618                         src_node_id: nodes[3],
2619                         short_channel_id: 8,
2620                         fees: zero_fees,
2621                         cltv_expiry_delta: (8 << 8) | 1,
2622                         htlc_minimum_msat: None,
2623                         htlc_maximum_msat: None,
2624                 }]), RouteHint(vec![RouteHintHop {
2625                         src_node_id: nodes[5],
2626                         short_channel_id: 10,
2627                         fees: zero_fees,
2628                         cltv_expiry_delta: (10 << 8) | 1,
2629                         htlc_minimum_msat: None,
2630                         htlc_maximum_msat: None,
2631                 }])]
2632         }
2633
2634         #[test]
2635         fn multi_hint_last_hops_test() {
2636                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2637                 let (_, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
2638                 let payee = Payee::new(nodes[6]).with_route_hints(multi_hint_last_hops(&nodes));
2639                 let scorer = Scorer::new(0);
2640                 // Test through channels 2, 3, 5, 8.
2641                 // Test shows that multiple hop hints are considered.
2642
2643                 // Disabling channels 6 & 7 by flags=2
2644                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
2645                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2646                         short_channel_id: 6,
2647                         timestamp: 2,
2648                         flags: 2, // to disable
2649                         cltv_expiry_delta: 0,
2650                         htlc_minimum_msat: 0,
2651                         htlc_maximum_msat: OptionalField::Absent,
2652                         fee_base_msat: 0,
2653                         fee_proportional_millionths: 0,
2654                         excess_data: Vec::new()
2655                 });
2656                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
2657                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2658                         short_channel_id: 7,
2659                         timestamp: 2,
2660                         flags: 2, // to disable
2661                         cltv_expiry_delta: 0,
2662                         htlc_minimum_msat: 0,
2663                         htlc_maximum_msat: OptionalField::Absent,
2664                         fee_base_msat: 0,
2665                         fee_proportional_millionths: 0,
2666                         excess_data: Vec::new()
2667                 });
2668
2669                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer).unwrap();
2670                 assert_eq!(route.paths[0].len(), 4);
2671
2672                 assert_eq!(route.paths[0][0].pubkey, nodes[1]);
2673                 assert_eq!(route.paths[0][0].short_channel_id, 2);
2674                 assert_eq!(route.paths[0][0].fee_msat, 200);
2675                 assert_eq!(route.paths[0][0].cltv_expiry_delta, 1025);
2676                 assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(2));
2677                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(2));
2678
2679                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2680                 assert_eq!(route.paths[0][1].short_channel_id, 4);
2681                 assert_eq!(route.paths[0][1].fee_msat, 100);
2682                 assert_eq!(route.paths[0][1].cltv_expiry_delta, 1281);
2683                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2684                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(4));
2685
2686                 assert_eq!(route.paths[0][2].pubkey, nodes[3]);
2687                 assert_eq!(route.paths[0][2].short_channel_id, 5);
2688                 assert_eq!(route.paths[0][2].fee_msat, 0);
2689                 assert_eq!(route.paths[0][2].cltv_expiry_delta, 2049);
2690                 assert_eq!(route.paths[0][2].node_features.le_flags(), &id_to_feature_flags(4));
2691                 assert_eq!(route.paths[0][2].channel_features.le_flags(), &Vec::<u8>::new());
2692
2693                 assert_eq!(route.paths[0][3].pubkey, nodes[6]);
2694                 assert_eq!(route.paths[0][3].short_channel_id, 8);
2695                 assert_eq!(route.paths[0][3].fee_msat, 100);
2696                 assert_eq!(route.paths[0][3].cltv_expiry_delta, 42);
2697                 assert_eq!(route.paths[0][3].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
2698                 assert_eq!(route.paths[0][3].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
2699         }
2700
2701         fn last_hops_with_public_channel(nodes: &Vec<PublicKey>) -> Vec<RouteHint> {
2702                 let zero_fees = RoutingFees {
2703                         base_msat: 0,
2704                         proportional_millionths: 0,
2705                 };
2706                 vec![RouteHint(vec![RouteHintHop {
2707                         src_node_id: nodes[4],
2708                         short_channel_id: 11,
2709                         fees: zero_fees,
2710                         cltv_expiry_delta: (11 << 8) | 1,
2711                         htlc_minimum_msat: None,
2712                         htlc_maximum_msat: None,
2713                 }, RouteHintHop {
2714                         src_node_id: nodes[3],
2715                         short_channel_id: 8,
2716                         fees: zero_fees,
2717                         cltv_expiry_delta: (8 << 8) | 1,
2718                         htlc_minimum_msat: None,
2719                         htlc_maximum_msat: None,
2720                 }]), RouteHint(vec![RouteHintHop {
2721                         src_node_id: nodes[4],
2722                         short_channel_id: 9,
2723                         fees: RoutingFees {
2724                                 base_msat: 1001,
2725                                 proportional_millionths: 0,
2726                         },
2727                         cltv_expiry_delta: (9 << 8) | 1,
2728                         htlc_minimum_msat: None,
2729                         htlc_maximum_msat: None,
2730                 }]), RouteHint(vec![RouteHintHop {
2731                         src_node_id: nodes[5],
2732                         short_channel_id: 10,
2733                         fees: zero_fees,
2734                         cltv_expiry_delta: (10 << 8) | 1,
2735                         htlc_minimum_msat: None,
2736                         htlc_maximum_msat: None,
2737                 }])]
2738         }
2739
2740         #[test]
2741         fn last_hops_with_public_channel_test() {
2742                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2743                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
2744                 let payee = Payee::new(nodes[6]).with_route_hints(last_hops_with_public_channel(&nodes));
2745                 let scorer = Scorer::new(0);
2746                 // This test shows that public routes can be present in the invoice
2747                 // which would be handled in the same manner.
2748
2749                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer).unwrap();
2750                 assert_eq!(route.paths[0].len(), 5);
2751
2752                 assert_eq!(route.paths[0][0].pubkey, nodes[1]);
2753                 assert_eq!(route.paths[0][0].short_channel_id, 2);
2754                 assert_eq!(route.paths[0][0].fee_msat, 100);
2755                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (4 << 8) | 1);
2756                 assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(2));
2757                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(2));
2758
2759                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2760                 assert_eq!(route.paths[0][1].short_channel_id, 4);
2761                 assert_eq!(route.paths[0][1].fee_msat, 0);
2762                 assert_eq!(route.paths[0][1].cltv_expiry_delta, (6 << 8) | 1);
2763                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2764                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(4));
2765
2766                 assert_eq!(route.paths[0][2].pubkey, nodes[4]);
2767                 assert_eq!(route.paths[0][2].short_channel_id, 6);
2768                 assert_eq!(route.paths[0][2].fee_msat, 0);
2769                 assert_eq!(route.paths[0][2].cltv_expiry_delta, (11 << 8) | 1);
2770                 assert_eq!(route.paths[0][2].node_features.le_flags(), &id_to_feature_flags(5));
2771                 assert_eq!(route.paths[0][2].channel_features.le_flags(), &id_to_feature_flags(6));
2772
2773                 assert_eq!(route.paths[0][3].pubkey, nodes[3]);
2774                 assert_eq!(route.paths[0][3].short_channel_id, 11);
2775                 assert_eq!(route.paths[0][3].fee_msat, 0);
2776                 assert_eq!(route.paths[0][3].cltv_expiry_delta, (8 << 8) | 1);
2777                 // If we have a peer in the node map, we'll use their features here since we don't have
2778                 // a way of figuring out their features from the invoice:
2779                 assert_eq!(route.paths[0][3].node_features.le_flags(), &id_to_feature_flags(4));
2780                 assert_eq!(route.paths[0][3].channel_features.le_flags(), &Vec::<u8>::new());
2781
2782                 assert_eq!(route.paths[0][4].pubkey, nodes[6]);
2783                 assert_eq!(route.paths[0][4].short_channel_id, 8);
2784                 assert_eq!(route.paths[0][4].fee_msat, 100);
2785                 assert_eq!(route.paths[0][4].cltv_expiry_delta, 42);
2786                 assert_eq!(route.paths[0][4].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
2787                 assert_eq!(route.paths[0][4].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
2788         }
2789
2790         #[test]
2791         fn our_chans_last_hop_connect_test() {
2792                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
2793                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
2794                 let scorer = Scorer::new(0);
2795
2796                 // Simple test with outbound channel to 4 to test that last_hops and first_hops connect
2797                 let our_chans = vec![get_channel_details(Some(42), nodes[3].clone(), InitFeatures::from_le_bytes(vec![0b11]), 250_000_000)];
2798                 let mut last_hops = last_hops(&nodes);
2799                 let payee = Payee::new(nodes[6]).with_route_hints(last_hops.clone());
2800                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, Some(&our_chans.iter().collect::<Vec<_>>()), 100, 42, Arc::clone(&logger), &scorer).unwrap();
2801                 assert_eq!(route.paths[0].len(), 2);
2802
2803                 assert_eq!(route.paths[0][0].pubkey, nodes[3]);
2804                 assert_eq!(route.paths[0][0].short_channel_id, 42);
2805                 assert_eq!(route.paths[0][0].fee_msat, 0);
2806                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (8 << 8) | 1);
2807                 assert_eq!(route.paths[0][0].node_features.le_flags(), &vec![0b11]);
2808                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &Vec::<u8>::new()); // No feature flags will meet the relevant-to-channel conversion
2809
2810                 assert_eq!(route.paths[0][1].pubkey, nodes[6]);
2811                 assert_eq!(route.paths[0][1].short_channel_id, 8);
2812                 assert_eq!(route.paths[0][1].fee_msat, 100);
2813                 assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
2814                 assert_eq!(route.paths[0][1].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
2815                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
2816
2817                 last_hops[0].0[0].fees.base_msat = 1000;
2818
2819                 // Revert to via 6 as the fee on 8 goes up
2820                 let payee = Payee::new(nodes[6]).with_route_hints(last_hops);
2821                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42, Arc::clone(&logger), &scorer).unwrap();
2822                 assert_eq!(route.paths[0].len(), 4);
2823
2824                 assert_eq!(route.paths[0][0].pubkey, nodes[1]);
2825                 assert_eq!(route.paths[0][0].short_channel_id, 2);
2826                 assert_eq!(route.paths[0][0].fee_msat, 200); // fee increased as its % of value transferred across node
2827                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (4 << 8) | 1);
2828                 assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(2));
2829                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(2));
2830
2831                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2832                 assert_eq!(route.paths[0][1].short_channel_id, 4);
2833                 assert_eq!(route.paths[0][1].fee_msat, 100);
2834                 assert_eq!(route.paths[0][1].cltv_expiry_delta, (7 << 8) | 1);
2835                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2836                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(4));
2837
2838                 assert_eq!(route.paths[0][2].pubkey, nodes[5]);
2839                 assert_eq!(route.paths[0][2].short_channel_id, 7);
2840                 assert_eq!(route.paths[0][2].fee_msat, 0);
2841                 assert_eq!(route.paths[0][2].cltv_expiry_delta, (10 << 8) | 1);
2842                 // If we have a peer in the node map, we'll use their features here since we don't have
2843                 // a way of figuring out their features from the invoice:
2844                 assert_eq!(route.paths[0][2].node_features.le_flags(), &id_to_feature_flags(6));
2845                 assert_eq!(route.paths[0][2].channel_features.le_flags(), &id_to_feature_flags(7));
2846
2847                 assert_eq!(route.paths[0][3].pubkey, nodes[6]);
2848                 assert_eq!(route.paths[0][3].short_channel_id, 10);
2849                 assert_eq!(route.paths[0][3].fee_msat, 100);
2850                 assert_eq!(route.paths[0][3].cltv_expiry_delta, 42);
2851                 assert_eq!(route.paths[0][3].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
2852                 assert_eq!(route.paths[0][3].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
2853
2854                 // ...but still use 8 for larger payments as 6 has a variable feerate
2855                 let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 2000, 42, Arc::clone(&logger), &scorer).unwrap();
2856                 assert_eq!(route.paths[0].len(), 5);
2857
2858                 assert_eq!(route.paths[0][0].pubkey, nodes[1]);
2859                 assert_eq!(route.paths[0][0].short_channel_id, 2);
2860                 assert_eq!(route.paths[0][0].fee_msat, 3000);
2861                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (4 << 8) | 1);
2862                 assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(2));
2863                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(2));
2864
2865                 assert_eq!(route.paths[0][1].pubkey, nodes[2]);
2866                 assert_eq!(route.paths[0][1].short_channel_id, 4);
2867                 assert_eq!(route.paths[0][1].fee_msat, 0);
2868                 assert_eq!(route.paths[0][1].cltv_expiry_delta, (6 << 8) | 1);
2869                 assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
2870                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(4));
2871
2872                 assert_eq!(route.paths[0][2].pubkey, nodes[4]);
2873                 assert_eq!(route.paths[0][2].short_channel_id, 6);
2874                 assert_eq!(route.paths[0][2].fee_msat, 0);
2875                 assert_eq!(route.paths[0][2].cltv_expiry_delta, (11 << 8) | 1);
2876                 assert_eq!(route.paths[0][2].node_features.le_flags(), &id_to_feature_flags(5));
2877                 assert_eq!(route.paths[0][2].channel_features.le_flags(), &id_to_feature_flags(6));
2878
2879                 assert_eq!(route.paths[0][3].pubkey, nodes[3]);
2880                 assert_eq!(route.paths[0][3].short_channel_id, 11);
2881                 assert_eq!(route.paths[0][3].fee_msat, 1000);
2882                 assert_eq!(route.paths[0][3].cltv_expiry_delta, (8 << 8) | 1);
2883                 // If we have a peer in the node map, we'll use their features here since we don't have
2884                 // a way of figuring out their features from the invoice:
2885                 assert_eq!(route.paths[0][3].node_features.le_flags(), &id_to_feature_flags(4));
2886                 assert_eq!(route.paths[0][3].channel_features.le_flags(), &id_to_feature_flags(11));
2887
2888                 assert_eq!(route.paths[0][4].pubkey, nodes[6]);
2889                 assert_eq!(route.paths[0][4].short_channel_id, 8);
2890                 assert_eq!(route.paths[0][4].fee_msat, 2000);
2891                 assert_eq!(route.paths[0][4].cltv_expiry_delta, 42);
2892                 assert_eq!(route.paths[0][4].node_features.le_flags(), &Vec::<u8>::new()); // We dont pass flags in from invoices yet
2893                 assert_eq!(route.paths[0][4].channel_features.le_flags(), &Vec::<u8>::new()); // We can't learn any flags from invoices, sadly
2894         }
2895
2896         fn do_unannounced_path_test(last_hop_htlc_max: Option<u64>, last_hop_fee_prop: u32, outbound_capacity_msat: u64, route_val: u64) -> Result<Route, LightningError> {
2897                 let source_node_id = PublicKey::from_secret_key(&Secp256k1::new(), &SecretKey::from_slice(&hex::decode(format!("{:02}", 41).repeat(32)).unwrap()[..]).unwrap());
2898                 let middle_node_id = PublicKey::from_secret_key(&Secp256k1::new(), &SecretKey::from_slice(&hex::decode(format!("{:02}", 42).repeat(32)).unwrap()[..]).unwrap());
2899                 let target_node_id = PublicKey::from_secret_key(&Secp256k1::new(), &SecretKey::from_slice(&hex::decode(format!("{:02}", 43).repeat(32)).unwrap()[..]).unwrap());
2900
2901                 // If we specify a channel to a middle hop, that overrides our local channel view and that gets used
2902                 let last_hops = RouteHint(vec![RouteHintHop {
2903                         src_node_id: middle_node_id,
2904                         short_channel_id: 8,
2905                         fees: RoutingFees {
2906                                 base_msat: 1000,
2907                                 proportional_millionths: last_hop_fee_prop,
2908                         },
2909                         cltv_expiry_delta: (8 << 8) | 1,
2910                         htlc_minimum_msat: None,
2911                         htlc_maximum_msat: last_hop_htlc_max,
2912                 }]);
2913                 let payee = Payee::new(target_node_id).with_route_hints(vec![last_hops]);
2914                 let our_chans = vec![get_channel_details(Some(42), middle_node_id, InitFeatures::from_le_bytes(vec![0b11]), outbound_capacity_msat)];
2915                 let scorer = Scorer::new(0);
2916                 get_route(&source_node_id, &payee, &NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash()), Some(&our_chans.iter().collect::<Vec<_>>()), route_val, 42, &test_utils::TestLogger::new(), &scorer)
2917         }
2918
2919         #[test]
2920         fn unannounced_path_test() {
2921                 // We should be able to send a payment to a destination without any help of a routing graph
2922                 // if we have a channel with a common counterparty that appears in the first and last hop
2923                 // hints.
2924                 let route = do_unannounced_path_test(None, 1, 2000000, 1000000).unwrap();
2925
2926                 let middle_node_id = PublicKey::from_secret_key(&Secp256k1::new(), &SecretKey::from_slice(&hex::decode(format!("{:02}", 42).repeat(32)).unwrap()[..]).unwrap());
2927                 let target_node_id = PublicKey::from_secret_key(&Secp256k1::new(), &SecretKey::from_slice(&hex::decode(format!("{:02}", 43).repeat(32)).unwrap()[..]).unwrap());
2928                 assert_eq!(route.paths[0].len(), 2);
2929
2930                 assert_eq!(route.paths[0][0].pubkey, middle_node_id);
2931                 assert_eq!(route.paths[0][0].short_channel_id, 42);
2932                 assert_eq!(route.paths[0][0].fee_msat, 1001);
2933                 assert_eq!(route.paths[0][0].cltv_expiry_delta, (8 << 8) | 1);
2934                 assert_eq!(route.paths[0][0].node_features.le_flags(), &[0b11]);
2935                 assert_eq!(route.paths[0][0].channel_features.le_flags(), &[0; 0]); // We can't learn any flags from invoices, sadly
2936
2937                 assert_eq!(route.paths[0][1].pubkey, target_node_id);
2938                 assert_eq!(route.paths[0][1].short_channel_id, 8);
2939                 assert_eq!(route.paths[0][1].fee_msat, 1000000);
2940                 assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
2941                 assert_eq!(route.paths[0][1].node_features.le_flags(), &[0; 0]); // We dont pass flags in from invoices yet
2942                 assert_eq!(route.paths[0][1].channel_features.le_flags(), &[0; 0]); // We can't learn any flags from invoices, sadly
2943         }
2944
2945         #[test]
2946         fn overflow_unannounced_path_test_liquidity_underflow() {
2947                 // Previously, when we had a last-hop hint connected directly to a first-hop channel, where
2948                 // the last-hop had a fee which overflowed a u64, we'd panic.
2949                 // This was due to us adding the first-hop from us unconditionally, causing us to think
2950                 // we'd built a path (as our node is in the "best candidate" set), when we had not.
2951                 // In this test, we previously hit a subtraction underflow due to having less available
2952                 // liquidity at the last hop than 0.
2953                 assert!(do_unannounced_path_test(Some(21_000_000_0000_0000_000), 0, 21_000_000_0000_0000_000, 21_000_000_0000_0000_000).is_err());
2954         }
2955
2956         #[test]
2957         fn overflow_unannounced_path_test_feerate_overflow() {
2958                 // This tests for the same case as above, except instead of hitting a subtraction
2959                 // underflow, we hit a case where the fee charged at a hop overflowed.
2960                 assert!(do_unannounced_path_test(Some(21_000_000_0000_0000_000), 50000, 21_000_000_0000_0000_000, 21_000_000_0000_0000_000).is_err());
2961         }
2962
2963         #[test]
2964         fn available_amount_while_routing_test() {
2965                 // Tests whether we choose the correct available channel amount while routing.
2966
2967                 let (secp_ctx, mut net_graph_msg_handler, chain_monitor, logger) = build_graph();
2968                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
2969                 let scorer = Scorer::new(0);
2970                 let payee = Payee::new(nodes[2]).with_features(InvoiceFeatures::known());
2971
2972                 // We will use a simple single-path route from
2973                 // our node to node2 via node0: channels {1, 3}.
2974
2975                 // First disable all other paths.
2976                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2977                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2978                         short_channel_id: 2,
2979                         timestamp: 2,
2980                         flags: 2,
2981                         cltv_expiry_delta: 0,
2982                         htlc_minimum_msat: 0,
2983                         htlc_maximum_msat: OptionalField::Present(100_000),
2984                         fee_base_msat: 0,
2985                         fee_proportional_millionths: 0,
2986                         excess_data: Vec::new()
2987                 });
2988                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
2989                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
2990                         short_channel_id: 12,
2991                         timestamp: 2,
2992                         flags: 2,
2993                         cltv_expiry_delta: 0,
2994                         htlc_minimum_msat: 0,
2995                         htlc_maximum_msat: OptionalField::Present(100_000),
2996                         fee_base_msat: 0,
2997                         fee_proportional_millionths: 0,
2998                         excess_data: Vec::new()
2999                 });
3000
3001                 // Make the first channel (#1) very permissive,
3002                 // and we will be testing all limits on the second channel.
3003                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3004                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3005                         short_channel_id: 1,
3006                         timestamp: 2,
3007                         flags: 0,
3008                         cltv_expiry_delta: 0,
3009                         htlc_minimum_msat: 0,
3010                         htlc_maximum_msat: OptionalField::Present(1_000_000_000),
3011                         fee_base_msat: 0,
3012                         fee_proportional_millionths: 0,
3013                         excess_data: Vec::new()
3014                 });
3015
3016                 // First, let's see if routing works if we have absolutely no idea about the available amount.
3017                 // In this case, it should be set to 250_000 sats.
3018                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3019                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3020                         short_channel_id: 3,
3021                         timestamp: 2,
3022                         flags: 0,
3023                         cltv_expiry_delta: 0,
3024                         htlc_minimum_msat: 0,
3025                         htlc_maximum_msat: OptionalField::Absent,
3026                         fee_base_msat: 0,
3027                         fee_proportional_millionths: 0,
3028                         excess_data: Vec::new()
3029                 });
3030
3031                 {
3032                         // Attempt to route more than available results in a failure.
3033                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
3034                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 250_000_001, 42, Arc::clone(&logger), &scorer) {
3035                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
3036                         } else { panic!(); }
3037                 }
3038
3039                 {
3040                         // Now, attempt to route an exact amount we have should be fine.
3041                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 250_000_000, 42, Arc::clone(&logger), &scorer).unwrap();
3042                         assert_eq!(route.paths.len(), 1);
3043                         let path = route.paths.last().unwrap();
3044                         assert_eq!(path.len(), 2);
3045                         assert_eq!(path.last().unwrap().pubkey, nodes[2]);
3046                         assert_eq!(path.last().unwrap().fee_msat, 250_000_000);
3047                 }
3048
3049                 // Check that setting outbound_capacity_msat in first_hops limits the channels.
3050                 // Disable channel #1 and use another first hop.
3051                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3052                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3053                         short_channel_id: 1,
3054                         timestamp: 3,
3055                         flags: 2,
3056                         cltv_expiry_delta: 0,
3057                         htlc_minimum_msat: 0,
3058                         htlc_maximum_msat: OptionalField::Present(1_000_000_000),
3059                         fee_base_msat: 0,
3060                         fee_proportional_millionths: 0,
3061                         excess_data: Vec::new()
3062                 });
3063
3064                 // Now, limit the first_hop by the outbound_capacity_msat of 200_000 sats.
3065                 let our_chans = vec![get_channel_details(Some(42), nodes[0].clone(), InitFeatures::from_le_bytes(vec![0b11]), 200_000_000)];
3066
3067                 {
3068                         // Attempt to route more than available results in a failure.
3069                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
3070                                         &our_id, &payee, &net_graph_msg_handler.network_graph, Some(&our_chans.iter().collect::<Vec<_>>()), 200_000_001, 42, Arc::clone(&logger), &scorer) {
3071                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
3072                         } else { panic!(); }
3073                 }
3074
3075                 {
3076                         // Now, attempt to route an exact amount we have should be fine.
3077                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, Some(&our_chans.iter().collect::<Vec<_>>()), 200_000_000, 42, Arc::clone(&logger), &scorer).unwrap();
3078                         assert_eq!(route.paths.len(), 1);
3079                         let path = route.paths.last().unwrap();
3080                         assert_eq!(path.len(), 2);
3081                         assert_eq!(path.last().unwrap().pubkey, nodes[2]);
3082                         assert_eq!(path.last().unwrap().fee_msat, 200_000_000);
3083                 }
3084
3085                 // Enable channel #1 back.
3086                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3087                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3088                         short_channel_id: 1,
3089                         timestamp: 4,
3090                         flags: 0,
3091                         cltv_expiry_delta: 0,
3092                         htlc_minimum_msat: 0,
3093                         htlc_maximum_msat: OptionalField::Present(1_000_000_000),
3094                         fee_base_msat: 0,
3095                         fee_proportional_millionths: 0,
3096                         excess_data: Vec::new()
3097                 });
3098
3099
3100                 // Now let's see if routing works if we know only htlc_maximum_msat.
3101                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3102                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3103                         short_channel_id: 3,
3104                         timestamp: 3,
3105                         flags: 0,
3106                         cltv_expiry_delta: 0,
3107                         htlc_minimum_msat: 0,
3108                         htlc_maximum_msat: OptionalField::Present(15_000),
3109                         fee_base_msat: 0,
3110                         fee_proportional_millionths: 0,
3111                         excess_data: Vec::new()
3112                 });
3113
3114                 {
3115                         // Attempt to route more than available results in a failure.
3116                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
3117                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 15_001, 42, Arc::clone(&logger), &scorer) {
3118                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
3119                         } else { panic!(); }
3120                 }
3121
3122                 {
3123                         // Now, attempt to route an exact amount we have should be fine.
3124                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 15_000, 42, Arc::clone(&logger), &scorer).unwrap();
3125                         assert_eq!(route.paths.len(), 1);
3126                         let path = route.paths.last().unwrap();
3127                         assert_eq!(path.len(), 2);
3128                         assert_eq!(path.last().unwrap().pubkey, nodes[2]);
3129                         assert_eq!(path.last().unwrap().fee_msat, 15_000);
3130                 }
3131
3132                 // Now let's see if routing works if we know only capacity from the UTXO.
3133
3134                 // We can't change UTXO capacity on the fly, so we'll disable
3135                 // the existing channel and add another one with the capacity we need.
3136                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3137                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3138                         short_channel_id: 3,
3139                         timestamp: 4,
3140                         flags: 2,
3141                         cltv_expiry_delta: 0,
3142                         htlc_minimum_msat: 0,
3143                         htlc_maximum_msat: OptionalField::Absent,
3144                         fee_base_msat: 0,
3145                         fee_proportional_millionths: 0,
3146                         excess_data: Vec::new()
3147                 });
3148
3149                 let good_script = Builder::new().push_opcode(opcodes::all::OP_PUSHNUM_2)
3150                 .push_slice(&PublicKey::from_secret_key(&secp_ctx, &privkeys[0]).serialize())
3151                 .push_slice(&PublicKey::from_secret_key(&secp_ctx, &privkeys[2]).serialize())
3152                 .push_opcode(opcodes::all::OP_PUSHNUM_2)
3153                 .push_opcode(opcodes::all::OP_CHECKMULTISIG).into_script().to_v0_p2wsh();
3154
3155                 *chain_monitor.utxo_ret.lock().unwrap() = Ok(TxOut { value: 15, script_pubkey: good_script.clone() });
3156                 net_graph_msg_handler.add_chain_access(Some(chain_monitor));
3157
3158                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], &privkeys[2], ChannelFeatures::from_le_bytes(id_to_feature_flags(3)), 333);
3159                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3160                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3161                         short_channel_id: 333,
3162                         timestamp: 1,
3163                         flags: 0,
3164                         cltv_expiry_delta: (3 << 8) | 1,
3165                         htlc_minimum_msat: 0,
3166                         htlc_maximum_msat: OptionalField::Absent,
3167                         fee_base_msat: 0,
3168                         fee_proportional_millionths: 0,
3169                         excess_data: Vec::new()
3170                 });
3171                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3172                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3173                         short_channel_id: 333,
3174                         timestamp: 1,
3175                         flags: 1,
3176                         cltv_expiry_delta: (3 << 8) | 2,
3177                         htlc_minimum_msat: 0,
3178                         htlc_maximum_msat: OptionalField::Absent,
3179                         fee_base_msat: 100,
3180                         fee_proportional_millionths: 0,
3181                         excess_data: Vec::new()
3182                 });
3183
3184                 {
3185                         // Attempt to route more than available results in a failure.
3186                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
3187                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 15_001, 42, Arc::clone(&logger), &scorer) {
3188                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
3189                         } else { panic!(); }
3190                 }
3191
3192                 {
3193                         // Now, attempt to route an exact amount we have should be fine.
3194                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 15_000, 42, Arc::clone(&logger), &scorer).unwrap();
3195                         assert_eq!(route.paths.len(), 1);
3196                         let path = route.paths.last().unwrap();
3197                         assert_eq!(path.len(), 2);
3198                         assert_eq!(path.last().unwrap().pubkey, nodes[2]);
3199                         assert_eq!(path.last().unwrap().fee_msat, 15_000);
3200                 }
3201
3202                 // Now let's see if routing chooses htlc_maximum_msat over UTXO capacity.
3203                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3204                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3205                         short_channel_id: 333,
3206                         timestamp: 6,
3207                         flags: 0,
3208                         cltv_expiry_delta: 0,
3209                         htlc_minimum_msat: 0,
3210                         htlc_maximum_msat: OptionalField::Present(10_000),
3211                         fee_base_msat: 0,
3212                         fee_proportional_millionths: 0,
3213                         excess_data: Vec::new()
3214                 });
3215
3216                 {
3217                         // Attempt to route more than available results in a failure.
3218                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
3219                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 10_001, 42, Arc::clone(&logger), &scorer) {
3220                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
3221                         } else { panic!(); }
3222                 }
3223
3224                 {
3225                         // Now, attempt to route an exact amount we have should be fine.
3226                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 10_000, 42, Arc::clone(&logger), &scorer).unwrap();
3227                         assert_eq!(route.paths.len(), 1);
3228                         let path = route.paths.last().unwrap();
3229                         assert_eq!(path.len(), 2);
3230                         assert_eq!(path.last().unwrap().pubkey, nodes[2]);
3231                         assert_eq!(path.last().unwrap().fee_msat, 10_000);
3232                 }
3233         }
3234
3235         #[test]
3236         fn available_liquidity_last_hop_test() {
3237                 // Check that available liquidity properly limits the path even when only
3238                 // one of the latter hops is limited.
3239                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
3240                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
3241                 let scorer = Scorer::new(0);
3242                 let payee = Payee::new(nodes[3]).with_features(InvoiceFeatures::known());
3243
3244                 // Path via {node7, node2, node4} is channels {12, 13, 6, 11}.
3245                 // {12, 13, 11} have the capacities of 100, {6} has a capacity of 50.
3246                 // Total capacity: 50 sats.
3247
3248                 // Disable other potential paths.
3249                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3250                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3251                         short_channel_id: 2,
3252                         timestamp: 2,
3253                         flags: 2,
3254                         cltv_expiry_delta: 0,
3255                         htlc_minimum_msat: 0,
3256                         htlc_maximum_msat: OptionalField::Present(100_000),
3257                         fee_base_msat: 0,
3258                         fee_proportional_millionths: 0,
3259                         excess_data: Vec::new()
3260                 });
3261                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3262                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3263                         short_channel_id: 7,
3264                         timestamp: 2,
3265                         flags: 2,
3266                         cltv_expiry_delta: 0,
3267                         htlc_minimum_msat: 0,
3268                         htlc_maximum_msat: OptionalField::Present(100_000),
3269                         fee_base_msat: 0,
3270                         fee_proportional_millionths: 0,
3271                         excess_data: Vec::new()
3272                 });
3273
3274                 // Limit capacities
3275
3276                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3277                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3278                         short_channel_id: 12,
3279                         timestamp: 2,
3280                         flags: 0,
3281                         cltv_expiry_delta: 0,
3282                         htlc_minimum_msat: 0,
3283                         htlc_maximum_msat: OptionalField::Present(100_000),
3284                         fee_base_msat: 0,
3285                         fee_proportional_millionths: 0,
3286                         excess_data: Vec::new()
3287                 });
3288                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
3289                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3290                         short_channel_id: 13,
3291                         timestamp: 2,
3292                         flags: 0,
3293                         cltv_expiry_delta: 0,
3294                         htlc_minimum_msat: 0,
3295                         htlc_maximum_msat: OptionalField::Present(100_000),
3296                         fee_base_msat: 0,
3297                         fee_proportional_millionths: 0,
3298                         excess_data: Vec::new()
3299                 });
3300
3301                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3302                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3303                         short_channel_id: 6,
3304                         timestamp: 2,
3305                         flags: 0,
3306                         cltv_expiry_delta: 0,
3307                         htlc_minimum_msat: 0,
3308                         htlc_maximum_msat: OptionalField::Present(50_000),
3309                         fee_base_msat: 0,
3310                         fee_proportional_millionths: 0,
3311                         excess_data: Vec::new()
3312                 });
3313                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
3314                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3315                         short_channel_id: 11,
3316                         timestamp: 2,
3317                         flags: 0,
3318                         cltv_expiry_delta: 0,
3319                         htlc_minimum_msat: 0,
3320                         htlc_maximum_msat: OptionalField::Present(100_000),
3321                         fee_base_msat: 0,
3322                         fee_proportional_millionths: 0,
3323                         excess_data: Vec::new()
3324                 });
3325                 {
3326                         // Attempt to route more than available results in a failure.
3327                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
3328                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 60_000, 42, Arc::clone(&logger), &scorer) {
3329                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
3330                         } else { panic!(); }
3331                 }
3332
3333                 {
3334                         // Now, attempt to route 49 sats (just a bit below the capacity).
3335                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 49_000, 42, Arc::clone(&logger), &scorer).unwrap();
3336                         assert_eq!(route.paths.len(), 1);
3337                         let mut total_amount_paid_msat = 0;
3338                         for path in &route.paths {
3339                                 assert_eq!(path.len(), 4);
3340                                 assert_eq!(path.last().unwrap().pubkey, nodes[3]);
3341                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
3342                         }
3343                         assert_eq!(total_amount_paid_msat, 49_000);
3344                 }
3345
3346                 {
3347                         // Attempt to route an exact amount is also fine
3348                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 50_000, 42, Arc::clone(&logger), &scorer).unwrap();
3349                         assert_eq!(route.paths.len(), 1);
3350                         let mut total_amount_paid_msat = 0;
3351                         for path in &route.paths {
3352                                 assert_eq!(path.len(), 4);
3353                                 assert_eq!(path.last().unwrap().pubkey, nodes[3]);
3354                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
3355                         }
3356                         assert_eq!(total_amount_paid_msat, 50_000);
3357                 }
3358         }
3359
3360         #[test]
3361         fn ignore_fee_first_hop_test() {
3362                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
3363                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
3364                 let scorer = Scorer::new(0);
3365                 let payee = Payee::new(nodes[2]);
3366
3367                 // Path via node0 is channels {1, 3}. Limit them to 100 and 50 sats (total limit 50).
3368                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3369                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3370                         short_channel_id: 1,
3371                         timestamp: 2,
3372                         flags: 0,
3373                         cltv_expiry_delta: 0,
3374                         htlc_minimum_msat: 0,
3375                         htlc_maximum_msat: OptionalField::Present(100_000),
3376                         fee_base_msat: 1_000_000,
3377                         fee_proportional_millionths: 0,
3378                         excess_data: Vec::new()
3379                 });
3380                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3381                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3382                         short_channel_id: 3,
3383                         timestamp: 2,
3384                         flags: 0,
3385                         cltv_expiry_delta: 0,
3386                         htlc_minimum_msat: 0,
3387                         htlc_maximum_msat: OptionalField::Present(50_000),
3388                         fee_base_msat: 0,
3389                         fee_proportional_millionths: 0,
3390                         excess_data: Vec::new()
3391                 });
3392
3393                 {
3394                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 50_000, 42, Arc::clone(&logger), &scorer).unwrap();
3395                         assert_eq!(route.paths.len(), 1);
3396                         let mut total_amount_paid_msat = 0;
3397                         for path in &route.paths {
3398                                 assert_eq!(path.len(), 2);
3399                                 assert_eq!(path.last().unwrap().pubkey, nodes[2]);
3400                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
3401                         }
3402                         assert_eq!(total_amount_paid_msat, 50_000);
3403                 }
3404         }
3405
3406         #[test]
3407         fn simple_mpp_route_test() {
3408                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
3409                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
3410                 let scorer = Scorer::new(0);
3411                 let payee = Payee::new(nodes[2]).with_features(InvoiceFeatures::known());
3412
3413                 // We need a route consisting of 3 paths:
3414                 // From our node to node2 via node0, node7, node1 (three paths one hop each).
3415                 // To achieve this, the amount being transferred should be around
3416                 // the total capacity of these 3 paths.
3417
3418                 // First, we set limits on these (previously unlimited) channels.
3419                 // Their aggregate capacity will be 50 + 60 + 180 = 290 sats.
3420
3421                 // Path via node0 is channels {1, 3}. Limit them to 100 and 50 sats (total limit 50).
3422                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3423                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3424                         short_channel_id: 1,
3425                         timestamp: 2,
3426                         flags: 0,
3427                         cltv_expiry_delta: 0,
3428                         htlc_minimum_msat: 0,
3429                         htlc_maximum_msat: OptionalField::Present(100_000),
3430                         fee_base_msat: 0,
3431                         fee_proportional_millionths: 0,
3432                         excess_data: Vec::new()
3433                 });
3434                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3435                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3436                         short_channel_id: 3,
3437                         timestamp: 2,
3438                         flags: 0,
3439                         cltv_expiry_delta: 0,
3440                         htlc_minimum_msat: 0,
3441                         htlc_maximum_msat: OptionalField::Present(50_000),
3442                         fee_base_msat: 0,
3443                         fee_proportional_millionths: 0,
3444                         excess_data: Vec::new()
3445                 });
3446
3447                 // Path via node7 is channels {12, 13}. Limit them to 60 and 60 sats
3448                 // (total limit 60).
3449                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3450                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3451                         short_channel_id: 12,
3452                         timestamp: 2,
3453                         flags: 0,
3454                         cltv_expiry_delta: 0,
3455                         htlc_minimum_msat: 0,
3456                         htlc_maximum_msat: OptionalField::Present(60_000),
3457                         fee_base_msat: 0,
3458                         fee_proportional_millionths: 0,
3459                         excess_data: Vec::new()
3460                 });
3461                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
3462                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3463                         short_channel_id: 13,
3464                         timestamp: 2,
3465                         flags: 0,
3466                         cltv_expiry_delta: 0,
3467                         htlc_minimum_msat: 0,
3468                         htlc_maximum_msat: OptionalField::Present(60_000),
3469                         fee_base_msat: 0,
3470                         fee_proportional_millionths: 0,
3471                         excess_data: Vec::new()
3472                 });
3473
3474                 // Path via node1 is channels {2, 4}. Limit them to 200 and 180 sats
3475                 // (total capacity 180 sats).
3476                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3477                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3478                         short_channel_id: 2,
3479                         timestamp: 2,
3480                         flags: 0,
3481                         cltv_expiry_delta: 0,
3482                         htlc_minimum_msat: 0,
3483                         htlc_maximum_msat: OptionalField::Present(200_000),
3484                         fee_base_msat: 0,
3485                         fee_proportional_millionths: 0,
3486                         excess_data: Vec::new()
3487                 });
3488                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
3489                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3490                         short_channel_id: 4,
3491                         timestamp: 2,
3492                         flags: 0,
3493                         cltv_expiry_delta: 0,
3494                         htlc_minimum_msat: 0,
3495                         htlc_maximum_msat: OptionalField::Present(180_000),
3496                         fee_base_msat: 0,
3497                         fee_proportional_millionths: 0,
3498                         excess_data: Vec::new()
3499                 });
3500
3501                 {
3502                         // Attempt to route more than available results in a failure.
3503                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
3504                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 300_000, 42, Arc::clone(&logger), &scorer) {
3505                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
3506                         } else { panic!(); }
3507                 }
3508
3509                 {
3510                         // Now, attempt to route 250 sats (just a bit below the capacity).
3511                         // Our algorithm should provide us with these 3 paths.
3512                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 250_000, 42, Arc::clone(&logger), &scorer).unwrap();
3513                         assert_eq!(route.paths.len(), 3);
3514                         let mut total_amount_paid_msat = 0;
3515                         for path in &route.paths {
3516                                 assert_eq!(path.len(), 2);
3517                                 assert_eq!(path.last().unwrap().pubkey, nodes[2]);
3518                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
3519                         }
3520                         assert_eq!(total_amount_paid_msat, 250_000);
3521                 }
3522
3523                 {
3524                         // Attempt to route an exact amount is also fine
3525                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 290_000, 42, Arc::clone(&logger), &scorer).unwrap();
3526                         assert_eq!(route.paths.len(), 3);
3527                         let mut total_amount_paid_msat = 0;
3528                         for path in &route.paths {
3529                                 assert_eq!(path.len(), 2);
3530                                 assert_eq!(path.last().unwrap().pubkey, nodes[2]);
3531                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
3532                         }
3533                         assert_eq!(total_amount_paid_msat, 290_000);
3534                 }
3535         }
3536
3537         #[test]
3538         fn long_mpp_route_test() {
3539                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
3540                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
3541                 let scorer = Scorer::new(0);
3542                 let payee = Payee::new(nodes[3]).with_features(InvoiceFeatures::known());
3543
3544                 // We need a route consisting of 3 paths:
3545                 // From our node to node3 via {node0, node2}, {node7, node2, node4} and {node7, node2}.
3546                 // Note that these paths overlap (channels 5, 12, 13).
3547                 // We will route 300 sats.
3548                 // Each path will have 100 sats capacity, those channels which
3549                 // are used twice will have 200 sats capacity.
3550
3551                 // Disable other potential paths.
3552                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3553                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3554                         short_channel_id: 2,
3555                         timestamp: 2,
3556                         flags: 2,
3557                         cltv_expiry_delta: 0,
3558                         htlc_minimum_msat: 0,
3559                         htlc_maximum_msat: OptionalField::Present(100_000),
3560                         fee_base_msat: 0,
3561                         fee_proportional_millionths: 0,
3562                         excess_data: Vec::new()
3563                 });
3564                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3565                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3566                         short_channel_id: 7,
3567                         timestamp: 2,
3568                         flags: 2,
3569                         cltv_expiry_delta: 0,
3570                         htlc_minimum_msat: 0,
3571                         htlc_maximum_msat: OptionalField::Present(100_000),
3572                         fee_base_msat: 0,
3573                         fee_proportional_millionths: 0,
3574                         excess_data: Vec::new()
3575                 });
3576
3577                 // Path via {node0, node2} is channels {1, 3, 5}.
3578                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3579                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3580                         short_channel_id: 1,
3581                         timestamp: 2,
3582                         flags: 0,
3583                         cltv_expiry_delta: 0,
3584                         htlc_minimum_msat: 0,
3585                         htlc_maximum_msat: OptionalField::Present(100_000),
3586                         fee_base_msat: 0,
3587                         fee_proportional_millionths: 0,
3588                         excess_data: Vec::new()
3589                 });
3590                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3591                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3592                         short_channel_id: 3,
3593                         timestamp: 2,
3594                         flags: 0,
3595                         cltv_expiry_delta: 0,
3596                         htlc_minimum_msat: 0,
3597                         htlc_maximum_msat: OptionalField::Present(100_000),
3598                         fee_base_msat: 0,
3599                         fee_proportional_millionths: 0,
3600                         excess_data: Vec::new()
3601                 });
3602
3603                 // Capacity of 200 sats because this channel will be used by 3rd path as well.
3604                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], &privkeys[3], ChannelFeatures::from_le_bytes(id_to_feature_flags(5)), 5);
3605                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3606                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3607                         short_channel_id: 5,
3608                         timestamp: 2,
3609                         flags: 0,
3610                         cltv_expiry_delta: 0,
3611                         htlc_minimum_msat: 0,
3612                         htlc_maximum_msat: OptionalField::Present(200_000),
3613                         fee_base_msat: 0,
3614                         fee_proportional_millionths: 0,
3615                         excess_data: Vec::new()
3616                 });
3617
3618                 // Path via {node7, node2, node4} is channels {12, 13, 6, 11}.
3619                 // Add 100 sats to the capacities of {12, 13}, because these channels
3620                 // are also used for 3rd path. 100 sats for the rest. Total capacity: 100 sats.
3621                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3622                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3623                         short_channel_id: 12,
3624                         timestamp: 2,
3625                         flags: 0,
3626                         cltv_expiry_delta: 0,
3627                         htlc_minimum_msat: 0,
3628                         htlc_maximum_msat: OptionalField::Present(200_000),
3629                         fee_base_msat: 0,
3630                         fee_proportional_millionths: 0,
3631                         excess_data: Vec::new()
3632                 });
3633                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
3634                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3635                         short_channel_id: 13,
3636                         timestamp: 2,
3637                         flags: 0,
3638                         cltv_expiry_delta: 0,
3639                         htlc_minimum_msat: 0,
3640                         htlc_maximum_msat: OptionalField::Present(200_000),
3641                         fee_base_msat: 0,
3642                         fee_proportional_millionths: 0,
3643                         excess_data: Vec::new()
3644                 });
3645
3646                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3647                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3648                         short_channel_id: 6,
3649                         timestamp: 2,
3650                         flags: 0,
3651                         cltv_expiry_delta: 0,
3652                         htlc_minimum_msat: 0,
3653                         htlc_maximum_msat: OptionalField::Present(100_000),
3654                         fee_base_msat: 0,
3655                         fee_proportional_millionths: 0,
3656                         excess_data: Vec::new()
3657                 });
3658                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
3659                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3660                         short_channel_id: 11,
3661                         timestamp: 2,
3662                         flags: 0,
3663                         cltv_expiry_delta: 0,
3664                         htlc_minimum_msat: 0,
3665                         htlc_maximum_msat: OptionalField::Present(100_000),
3666                         fee_base_msat: 0,
3667                         fee_proportional_millionths: 0,
3668                         excess_data: Vec::new()
3669                 });
3670
3671                 // Path via {node7, node2} is channels {12, 13, 5}.
3672                 // We already limited them to 200 sats (they are used twice for 100 sats).
3673                 // Nothing to do here.
3674
3675                 {
3676                         // Attempt to route more than available results in a failure.
3677                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
3678                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 350_000, 42, Arc::clone(&logger), &scorer) {
3679                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
3680                         } else { panic!(); }
3681                 }
3682
3683                 {
3684                         // Now, attempt to route 300 sats (exact amount we can route).
3685                         // Our algorithm should provide us with these 3 paths, 100 sats each.
3686                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 300_000, 42, Arc::clone(&logger), &scorer).unwrap();
3687                         assert_eq!(route.paths.len(), 3);
3688
3689                         let mut total_amount_paid_msat = 0;
3690                         for path in &route.paths {
3691                                 assert_eq!(path.last().unwrap().pubkey, nodes[3]);
3692                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
3693                         }
3694                         assert_eq!(total_amount_paid_msat, 300_000);
3695                 }
3696
3697         }
3698
3699         #[test]
3700         fn mpp_cheaper_route_test() {
3701                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
3702                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
3703                 let scorer = Scorer::new(0);
3704                 let payee = Payee::new(nodes[3]).with_features(InvoiceFeatures::known());
3705
3706                 // This test checks that if we have two cheaper paths and one more expensive path,
3707                 // so that liquidity-wise any 2 of 3 combination is sufficient,
3708                 // two cheaper paths will be taken.
3709                 // These paths have equal available liquidity.
3710
3711                 // We need a combination of 3 paths:
3712                 // From our node to node3 via {node0, node2}, {node7, node2, node4} and {node7, node2}.
3713                 // Note that these paths overlap (channels 5, 12, 13).
3714                 // Each path will have 100 sats capacity, those channels which
3715                 // are used twice will have 200 sats capacity.
3716
3717                 // Disable other potential paths.
3718                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3719                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3720                         short_channel_id: 2,
3721                         timestamp: 2,
3722                         flags: 2,
3723                         cltv_expiry_delta: 0,
3724                         htlc_minimum_msat: 0,
3725                         htlc_maximum_msat: OptionalField::Present(100_000),
3726                         fee_base_msat: 0,
3727                         fee_proportional_millionths: 0,
3728                         excess_data: Vec::new()
3729                 });
3730                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3731                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3732                         short_channel_id: 7,
3733                         timestamp: 2,
3734                         flags: 2,
3735                         cltv_expiry_delta: 0,
3736                         htlc_minimum_msat: 0,
3737                         htlc_maximum_msat: OptionalField::Present(100_000),
3738                         fee_base_msat: 0,
3739                         fee_proportional_millionths: 0,
3740                         excess_data: Vec::new()
3741                 });
3742
3743                 // Path via {node0, node2} is channels {1, 3, 5}.
3744                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3745                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3746                         short_channel_id: 1,
3747                         timestamp: 2,
3748                         flags: 0,
3749                         cltv_expiry_delta: 0,
3750                         htlc_minimum_msat: 0,
3751                         htlc_maximum_msat: OptionalField::Present(100_000),
3752                         fee_base_msat: 0,
3753                         fee_proportional_millionths: 0,
3754                         excess_data: Vec::new()
3755                 });
3756                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3757                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3758                         short_channel_id: 3,
3759                         timestamp: 2,
3760                         flags: 0,
3761                         cltv_expiry_delta: 0,
3762                         htlc_minimum_msat: 0,
3763                         htlc_maximum_msat: OptionalField::Present(100_000),
3764                         fee_base_msat: 0,
3765                         fee_proportional_millionths: 0,
3766                         excess_data: Vec::new()
3767                 });
3768
3769                 // Capacity of 200 sats because this channel will be used by 3rd path as well.
3770                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], &privkeys[3], ChannelFeatures::from_le_bytes(id_to_feature_flags(5)), 5);
3771                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3772                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3773                         short_channel_id: 5,
3774                         timestamp: 2,
3775                         flags: 0,
3776                         cltv_expiry_delta: 0,
3777                         htlc_minimum_msat: 0,
3778                         htlc_maximum_msat: OptionalField::Present(200_000),
3779                         fee_base_msat: 0,
3780                         fee_proportional_millionths: 0,
3781                         excess_data: Vec::new()
3782                 });
3783
3784                 // Path via {node7, node2, node4} is channels {12, 13, 6, 11}.
3785                 // Add 100 sats to the capacities of {12, 13}, because these channels
3786                 // are also used for 3rd path. 100 sats for the rest. Total capacity: 100 sats.
3787                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3788                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3789                         short_channel_id: 12,
3790                         timestamp: 2,
3791                         flags: 0,
3792                         cltv_expiry_delta: 0,
3793                         htlc_minimum_msat: 0,
3794                         htlc_maximum_msat: OptionalField::Present(200_000),
3795                         fee_base_msat: 0,
3796                         fee_proportional_millionths: 0,
3797                         excess_data: Vec::new()
3798                 });
3799                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
3800                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3801                         short_channel_id: 13,
3802                         timestamp: 2,
3803                         flags: 0,
3804                         cltv_expiry_delta: 0,
3805                         htlc_minimum_msat: 0,
3806                         htlc_maximum_msat: OptionalField::Present(200_000),
3807                         fee_base_msat: 0,
3808                         fee_proportional_millionths: 0,
3809                         excess_data: Vec::new()
3810                 });
3811
3812                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3813                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3814                         short_channel_id: 6,
3815                         timestamp: 2,
3816                         flags: 0,
3817                         cltv_expiry_delta: 0,
3818                         htlc_minimum_msat: 0,
3819                         htlc_maximum_msat: OptionalField::Present(100_000),
3820                         fee_base_msat: 1_000,
3821                         fee_proportional_millionths: 0,
3822                         excess_data: Vec::new()
3823                 });
3824                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
3825                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3826                         short_channel_id: 11,
3827                         timestamp: 2,
3828                         flags: 0,
3829                         cltv_expiry_delta: 0,
3830                         htlc_minimum_msat: 0,
3831                         htlc_maximum_msat: OptionalField::Present(100_000),
3832                         fee_base_msat: 0,
3833                         fee_proportional_millionths: 0,
3834                         excess_data: Vec::new()
3835                 });
3836
3837                 // Path via {node7, node2} is channels {12, 13, 5}.
3838                 // We already limited them to 200 sats (they are used twice for 100 sats).
3839                 // Nothing to do here.
3840
3841                 {
3842                         // Now, attempt to route 180 sats.
3843                         // Our algorithm should provide us with these 2 paths.
3844                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 180_000, 42, Arc::clone(&logger), &scorer).unwrap();
3845                         assert_eq!(route.paths.len(), 2);
3846
3847                         let mut total_value_transferred_msat = 0;
3848                         let mut total_paid_msat = 0;
3849                         for path in &route.paths {
3850                                 assert_eq!(path.last().unwrap().pubkey, nodes[3]);
3851                                 total_value_transferred_msat += path.last().unwrap().fee_msat;
3852                                 for hop in path {
3853                                         total_paid_msat += hop.fee_msat;
3854                                 }
3855                         }
3856                         // If we paid fee, this would be higher.
3857                         assert_eq!(total_value_transferred_msat, 180_000);
3858                         let total_fees_paid = total_paid_msat - total_value_transferred_msat;
3859                         assert_eq!(total_fees_paid, 0);
3860                 }
3861         }
3862
3863         #[test]
3864         fn fees_on_mpp_route_test() {
3865                 // This test makes sure that MPP algorithm properly takes into account
3866                 // fees charged on the channels, by making the fees impactful:
3867                 // if the fee is not properly accounted for, the behavior is different.
3868                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
3869                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
3870                 let scorer = Scorer::new(0);
3871                 let payee = Payee::new(nodes[3]).with_features(InvoiceFeatures::known());
3872
3873                 // We need a route consisting of 2 paths:
3874                 // From our node to node3 via {node0, node2} and {node7, node2, node4}.
3875                 // We will route 200 sats, Each path will have 100 sats capacity.
3876
3877                 // This test is not particularly stable: e.g.,
3878                 // there's a way to route via {node0, node2, node4}.
3879                 // It works while pathfinding is deterministic, but can be broken otherwise.
3880                 // It's fine to ignore this concern for now.
3881
3882                 // Disable other potential paths.
3883                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3884                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3885                         short_channel_id: 2,
3886                         timestamp: 2,
3887                         flags: 2,
3888                         cltv_expiry_delta: 0,
3889                         htlc_minimum_msat: 0,
3890                         htlc_maximum_msat: OptionalField::Present(100_000),
3891                         fee_base_msat: 0,
3892                         fee_proportional_millionths: 0,
3893                         excess_data: Vec::new()
3894                 });
3895
3896                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3897                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3898                         short_channel_id: 7,
3899                         timestamp: 2,
3900                         flags: 2,
3901                         cltv_expiry_delta: 0,
3902                         htlc_minimum_msat: 0,
3903                         htlc_maximum_msat: OptionalField::Present(100_000),
3904                         fee_base_msat: 0,
3905                         fee_proportional_millionths: 0,
3906                         excess_data: Vec::new()
3907                 });
3908
3909                 // Path via {node0, node2} is channels {1, 3, 5}.
3910                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3911                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3912                         short_channel_id: 1,
3913                         timestamp: 2,
3914                         flags: 0,
3915                         cltv_expiry_delta: 0,
3916                         htlc_minimum_msat: 0,
3917                         htlc_maximum_msat: OptionalField::Present(100_000),
3918                         fee_base_msat: 0,
3919                         fee_proportional_millionths: 0,
3920                         excess_data: Vec::new()
3921                 });
3922                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
3923                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3924                         short_channel_id: 3,
3925                         timestamp: 2,
3926                         flags: 0,
3927                         cltv_expiry_delta: 0,
3928                         htlc_minimum_msat: 0,
3929                         htlc_maximum_msat: OptionalField::Present(100_000),
3930                         fee_base_msat: 0,
3931                         fee_proportional_millionths: 0,
3932                         excess_data: Vec::new()
3933                 });
3934
3935                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], &privkeys[3], ChannelFeatures::from_le_bytes(id_to_feature_flags(5)), 5);
3936                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3937                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3938                         short_channel_id: 5,
3939                         timestamp: 2,
3940                         flags: 0,
3941                         cltv_expiry_delta: 0,
3942                         htlc_minimum_msat: 0,
3943                         htlc_maximum_msat: OptionalField::Present(100_000),
3944                         fee_base_msat: 0,
3945                         fee_proportional_millionths: 0,
3946                         excess_data: Vec::new()
3947                 });
3948
3949                 // Path via {node7, node2, node4} is channels {12, 13, 6, 11}.
3950                 // All channels should be 100 sats capacity. But for the fee experiment,
3951                 // we'll add absolute fee of 150 sats paid for the use channel 6 (paid to node2 on channel 13).
3952                 // Since channel 12 allows to deliver only 250 sats to channel 13, channel 13 can transfer only
3953                 // 100 sats (and pay 150 sats in fees for the use of channel 6),
3954                 // so no matter how large are other channels,
3955                 // the whole path will be limited by 100 sats with just these 2 conditions:
3956                 // - channel 12 capacity is 250 sats
3957                 // - fee for channel 6 is 150 sats
3958                 // Let's test this by enforcing these 2 conditions and removing other limits.
3959                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
3960                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3961                         short_channel_id: 12,
3962                         timestamp: 2,
3963                         flags: 0,
3964                         cltv_expiry_delta: 0,
3965                         htlc_minimum_msat: 0,
3966                         htlc_maximum_msat: OptionalField::Present(250_000),
3967                         fee_base_msat: 0,
3968                         fee_proportional_millionths: 0,
3969                         excess_data: Vec::new()
3970                 });
3971                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
3972                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3973                         short_channel_id: 13,
3974                         timestamp: 2,
3975                         flags: 0,
3976                         cltv_expiry_delta: 0,
3977                         htlc_minimum_msat: 0,
3978                         htlc_maximum_msat: OptionalField::Absent,
3979                         fee_base_msat: 0,
3980                         fee_proportional_millionths: 0,
3981                         excess_data: Vec::new()
3982                 });
3983
3984                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
3985                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3986                         short_channel_id: 6,
3987                         timestamp: 2,
3988                         flags: 0,
3989                         cltv_expiry_delta: 0,
3990                         htlc_minimum_msat: 0,
3991                         htlc_maximum_msat: OptionalField::Absent,
3992                         fee_base_msat: 150_000,
3993                         fee_proportional_millionths: 0,
3994                         excess_data: Vec::new()
3995                 });
3996                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
3997                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
3998                         short_channel_id: 11,
3999                         timestamp: 2,
4000                         flags: 0,
4001                         cltv_expiry_delta: 0,
4002                         htlc_minimum_msat: 0,
4003                         htlc_maximum_msat: OptionalField::Absent,
4004                         fee_base_msat: 0,
4005                         fee_proportional_millionths: 0,
4006                         excess_data: Vec::new()
4007                 });
4008
4009                 {
4010                         // Attempt to route more than available results in a failure.
4011                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
4012                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 210_000, 42, Arc::clone(&logger), &scorer) {
4013                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
4014                         } else { panic!(); }
4015                 }
4016
4017                 {
4018                         // Now, attempt to route 200 sats (exact amount we can route).
4019                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 200_000, 42, Arc::clone(&logger), &scorer).unwrap();
4020                         assert_eq!(route.paths.len(), 2);
4021
4022                         let mut total_amount_paid_msat = 0;
4023                         for path in &route.paths {
4024                                 assert_eq!(path.last().unwrap().pubkey, nodes[3]);
4025                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
4026                         }
4027                         assert_eq!(total_amount_paid_msat, 200_000);
4028                         assert_eq!(route.get_total_fees(), 150_000);
4029                 }
4030
4031         }
4032
4033         #[test]
4034         fn drop_lowest_channel_mpp_route_test() {
4035                 // This test checks that low-capacity channel is dropped when after
4036                 // path finding we realize that we found more capacity than we need.
4037                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
4038                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
4039                 let scorer = Scorer::new(0);
4040                 let payee = Payee::new(nodes[2]).with_features(InvoiceFeatures::known());
4041
4042                 // We need a route consisting of 3 paths:
4043                 // From our node to node2 via node0, node7, node1 (three paths one hop each).
4044
4045                 // The first and the second paths should be sufficient, but the third should be
4046                 // cheaper, so that we select it but drop later.
4047
4048                 // First, we set limits on these (previously unlimited) channels.
4049                 // Their aggregate capacity will be 50 + 60 + 20 = 130 sats.
4050
4051                 // Path via node0 is channels {1, 3}. Limit them to 100 and 50 sats (total limit 50);
4052                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
4053                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4054                         short_channel_id: 1,
4055                         timestamp: 2,
4056                         flags: 0,
4057                         cltv_expiry_delta: 0,
4058                         htlc_minimum_msat: 0,
4059                         htlc_maximum_msat: OptionalField::Present(100_000),
4060                         fee_base_msat: 0,
4061                         fee_proportional_millionths: 0,
4062                         excess_data: Vec::new()
4063                 });
4064                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[0], UnsignedChannelUpdate {
4065                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4066                         short_channel_id: 3,
4067                         timestamp: 2,
4068                         flags: 0,
4069                         cltv_expiry_delta: 0,
4070                         htlc_minimum_msat: 0,
4071                         htlc_maximum_msat: OptionalField::Present(50_000),
4072                         fee_base_msat: 100,
4073                         fee_proportional_millionths: 0,
4074                         excess_data: Vec::new()
4075                 });
4076
4077                 // Path via node7 is channels {12, 13}. Limit them to 60 and 60 sats (total limit 60);
4078                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
4079                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4080                         short_channel_id: 12,
4081                         timestamp: 2,
4082                         flags: 0,
4083                         cltv_expiry_delta: 0,
4084                         htlc_minimum_msat: 0,
4085                         htlc_maximum_msat: OptionalField::Present(60_000),
4086                         fee_base_msat: 100,
4087                         fee_proportional_millionths: 0,
4088                         excess_data: Vec::new()
4089                 });
4090                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[7], UnsignedChannelUpdate {
4091                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4092                         short_channel_id: 13,
4093                         timestamp: 2,
4094                         flags: 0,
4095                         cltv_expiry_delta: 0,
4096                         htlc_minimum_msat: 0,
4097                         htlc_maximum_msat: OptionalField::Present(60_000),
4098                         fee_base_msat: 0,
4099                         fee_proportional_millionths: 0,
4100                         excess_data: Vec::new()
4101                 });
4102
4103                 // Path via node1 is channels {2, 4}. Limit them to 20 and 20 sats (total capacity 20 sats).
4104                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
4105                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4106                         short_channel_id: 2,
4107                         timestamp: 2,
4108                         flags: 0,
4109                         cltv_expiry_delta: 0,
4110                         htlc_minimum_msat: 0,
4111                         htlc_maximum_msat: OptionalField::Present(20_000),
4112                         fee_base_msat: 0,
4113                         fee_proportional_millionths: 0,
4114                         excess_data: Vec::new()
4115                 });
4116                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
4117                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4118                         short_channel_id: 4,
4119                         timestamp: 2,
4120                         flags: 0,
4121                         cltv_expiry_delta: 0,
4122                         htlc_minimum_msat: 0,
4123                         htlc_maximum_msat: OptionalField::Present(20_000),
4124                         fee_base_msat: 0,
4125                         fee_proportional_millionths: 0,
4126                         excess_data: Vec::new()
4127                 });
4128
4129                 {
4130                         // Attempt to route more than available results in a failure.
4131                         if let Err(LightningError{err, action: ErrorAction::IgnoreError}) = get_route(
4132                                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 150_000, 42, Arc::clone(&logger), &scorer) {
4133                                 assert_eq!(err, "Failed to find a sufficient route to the given destination");
4134                         } else { panic!(); }
4135                 }
4136
4137                 {
4138                         // Now, attempt to route 125 sats (just a bit below the capacity of 3 channels).
4139                         // Our algorithm should provide us with these 3 paths.
4140                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 125_000, 42, Arc::clone(&logger), &scorer).unwrap();
4141                         assert_eq!(route.paths.len(), 3);
4142                         let mut total_amount_paid_msat = 0;
4143                         for path in &route.paths {
4144                                 assert_eq!(path.len(), 2);
4145                                 assert_eq!(path.last().unwrap().pubkey, nodes[2]);
4146                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
4147                         }
4148                         assert_eq!(total_amount_paid_msat, 125_000);
4149                 }
4150
4151                 {
4152                         // Attempt to route without the last small cheap channel
4153                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 90_000, 42, Arc::clone(&logger), &scorer).unwrap();
4154                         assert_eq!(route.paths.len(), 2);
4155                         let mut total_amount_paid_msat = 0;
4156                         for path in &route.paths {
4157                                 assert_eq!(path.len(), 2);
4158                                 assert_eq!(path.last().unwrap().pubkey, nodes[2]);
4159                                 total_amount_paid_msat += path.last().unwrap().fee_msat;
4160                         }
4161                         assert_eq!(total_amount_paid_msat, 90_000);
4162                 }
4163         }
4164
4165         #[test]
4166         fn min_criteria_consistency() {
4167                 // Test that we don't use an inconsistent metric between updating and walking nodes during
4168                 // our Dijkstra's pass. In the initial version of MPP, the "best source" for a given node
4169                 // was updated with a different criterion from the heap sorting, resulting in loops in
4170                 // calculated paths. We test for that specific case here.
4171
4172                 // We construct a network that looks like this:
4173                 //
4174                 //            node2 -1(3)2- node3
4175                 //              2          2
4176                 //               (2)     (4)
4177                 //                  1   1
4178                 //    node1 -1(5)2- node4 -1(1)2- node6
4179                 //    2
4180                 //   (6)
4181                 //        1
4182                 // our_node
4183                 //
4184                 // We create a loop on the side of our real path - our destination is node 6, with a
4185                 // previous hop of node 4. From 4, the cheapest previous path is channel 2 from node 2,
4186                 // followed by node 3 over channel 3. Thereafter, the cheapest next-hop is back to node 4
4187                 // (this time over channel 4). Channel 4 has 0 htlc_minimum_msat whereas channel 1 (the
4188                 // other channel with a previous-hop of node 4) has a high (but irrelevant to the overall
4189                 // payment) htlc_minimum_msat. In the original algorithm, this resulted in node4's
4190                 // "previous hop" being set to node 3, creating a loop in the path.
4191                 let secp_ctx = Secp256k1::new();
4192                 let logger = Arc::new(test_utils::TestLogger::new());
4193                 let network_graph = NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash());
4194                 let net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, None, Arc::clone(&logger));
4195                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
4196                 let scorer = Scorer::new(0);
4197                 let payee = Payee::new(nodes[6]);
4198
4199                 add_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, &privkeys[1], ChannelFeatures::from_le_bytes(id_to_feature_flags(6)), 6);
4200                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
4201                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4202                         short_channel_id: 6,
4203                         timestamp: 1,
4204                         flags: 0,
4205                         cltv_expiry_delta: (6 << 8) | 0,
4206                         htlc_minimum_msat: 0,
4207                         htlc_maximum_msat: OptionalField::Absent,
4208                         fee_base_msat: 0,
4209                         fee_proportional_millionths: 0,
4210                         excess_data: Vec::new()
4211                 });
4212                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[1], NodeFeatures::from_le_bytes(id_to_feature_flags(1)), 0);
4213
4214                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], &privkeys[4], ChannelFeatures::from_le_bytes(id_to_feature_flags(5)), 5);
4215                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
4216                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4217                         short_channel_id: 5,
4218                         timestamp: 1,
4219                         flags: 0,
4220                         cltv_expiry_delta: (5 << 8) | 0,
4221                         htlc_minimum_msat: 0,
4222                         htlc_maximum_msat: OptionalField::Absent,
4223                         fee_base_msat: 100,
4224                         fee_proportional_millionths: 0,
4225                         excess_data: Vec::new()
4226                 });
4227                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[4], NodeFeatures::from_le_bytes(id_to_feature_flags(4)), 0);
4228
4229                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], &privkeys[3], ChannelFeatures::from_le_bytes(id_to_feature_flags(4)), 4);
4230                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
4231                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4232                         short_channel_id: 4,
4233                         timestamp: 1,
4234                         flags: 0,
4235                         cltv_expiry_delta: (4 << 8) | 0,
4236                         htlc_minimum_msat: 0,
4237                         htlc_maximum_msat: OptionalField::Absent,
4238                         fee_base_msat: 0,
4239                         fee_proportional_millionths: 0,
4240                         excess_data: Vec::new()
4241                 });
4242                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[3], NodeFeatures::from_le_bytes(id_to_feature_flags(3)), 0);
4243
4244                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[3], &privkeys[2], ChannelFeatures::from_le_bytes(id_to_feature_flags(3)), 3);
4245                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[3], UnsignedChannelUpdate {
4246                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4247                         short_channel_id: 3,
4248                         timestamp: 1,
4249                         flags: 0,
4250                         cltv_expiry_delta: (3 << 8) | 0,
4251                         htlc_minimum_msat: 0,
4252                         htlc_maximum_msat: OptionalField::Absent,
4253                         fee_base_msat: 0,
4254                         fee_proportional_millionths: 0,
4255                         excess_data: Vec::new()
4256                 });
4257                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[2], NodeFeatures::from_le_bytes(id_to_feature_flags(2)), 0);
4258
4259                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], &privkeys[4], ChannelFeatures::from_le_bytes(id_to_feature_flags(2)), 2);
4260                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[2], UnsignedChannelUpdate {
4261                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4262                         short_channel_id: 2,
4263                         timestamp: 1,
4264                         flags: 0,
4265                         cltv_expiry_delta: (2 << 8) | 0,
4266                         htlc_minimum_msat: 0,
4267                         htlc_maximum_msat: OptionalField::Absent,
4268                         fee_base_msat: 0,
4269                         fee_proportional_millionths: 0,
4270                         excess_data: Vec::new()
4271                 });
4272
4273                 add_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], &privkeys[6], ChannelFeatures::from_le_bytes(id_to_feature_flags(1)), 1);
4274                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[4], UnsignedChannelUpdate {
4275                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4276                         short_channel_id: 1,
4277                         timestamp: 1,
4278                         flags: 0,
4279                         cltv_expiry_delta: (1 << 8) | 0,
4280                         htlc_minimum_msat: 100,
4281                         htlc_maximum_msat: OptionalField::Absent,
4282                         fee_base_msat: 0,
4283                         fee_proportional_millionths: 0,
4284                         excess_data: Vec::new()
4285                 });
4286                 add_or_update_node(&net_graph_msg_handler, &secp_ctx, &privkeys[6], NodeFeatures::from_le_bytes(id_to_feature_flags(6)), 0);
4287
4288                 {
4289                         // Now ensure the route flows simply over nodes 1 and 4 to 6.
4290                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 10_000, 42, Arc::clone(&logger), &scorer).unwrap();
4291                         assert_eq!(route.paths.len(), 1);
4292                         assert_eq!(route.paths[0].len(), 3);
4293
4294                         assert_eq!(route.paths[0][0].pubkey, nodes[1]);
4295                         assert_eq!(route.paths[0][0].short_channel_id, 6);
4296                         assert_eq!(route.paths[0][0].fee_msat, 100);
4297                         assert_eq!(route.paths[0][0].cltv_expiry_delta, (5 << 8) | 0);
4298                         assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(1));
4299                         assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(6));
4300
4301                         assert_eq!(route.paths[0][1].pubkey, nodes[4]);
4302                         assert_eq!(route.paths[0][1].short_channel_id, 5);
4303                         assert_eq!(route.paths[0][1].fee_msat, 0);
4304                         assert_eq!(route.paths[0][1].cltv_expiry_delta, (1 << 8) | 0);
4305                         assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(4));
4306                         assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(5));
4307
4308                         assert_eq!(route.paths[0][2].pubkey, nodes[6]);
4309                         assert_eq!(route.paths[0][2].short_channel_id, 1);
4310                         assert_eq!(route.paths[0][2].fee_msat, 10_000);
4311                         assert_eq!(route.paths[0][2].cltv_expiry_delta, 42);
4312                         assert_eq!(route.paths[0][2].node_features.le_flags(), &id_to_feature_flags(6));
4313                         assert_eq!(route.paths[0][2].channel_features.le_flags(), &id_to_feature_flags(1));
4314                 }
4315         }
4316
4317
4318         #[test]
4319         fn exact_fee_liquidity_limit() {
4320                 // Test that if, while walking the graph, we find a hop that has exactly enough liquidity
4321                 // for us, including later hop fees, we take it. In the first version of our MPP algorithm
4322                 // we calculated fees on a higher value, resulting in us ignoring such paths.
4323                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
4324                 let (our_privkey, our_id, _, nodes) = get_nodes(&secp_ctx);
4325                 let scorer = Scorer::new(0);
4326                 let payee = Payee::new(nodes[2]);
4327
4328                 // We modify the graph to set the htlc_maximum of channel 2 to below the value we wish to
4329                 // send.
4330                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
4331                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4332                         short_channel_id: 2,
4333                         timestamp: 2,
4334                         flags: 0,
4335                         cltv_expiry_delta: 0,
4336                         htlc_minimum_msat: 0,
4337                         htlc_maximum_msat: OptionalField::Present(85_000),
4338                         fee_base_msat: 0,
4339                         fee_proportional_millionths: 0,
4340                         excess_data: Vec::new()
4341                 });
4342
4343                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
4344                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4345                         short_channel_id: 12,
4346                         timestamp: 2,
4347                         flags: 0,
4348                         cltv_expiry_delta: (4 << 8) | 1,
4349                         htlc_minimum_msat: 0,
4350                         htlc_maximum_msat: OptionalField::Present(270_000),
4351                         fee_base_msat: 0,
4352                         fee_proportional_millionths: 1000000,
4353                         excess_data: Vec::new()
4354                 });
4355
4356                 {
4357                         // Now, attempt to route 90 sats, which is exactly 90 sats at the last hop, plus the
4358                         // 200% fee charged channel 13 in the 1-to-2 direction.
4359                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 90_000, 42, Arc::clone(&logger), &scorer).unwrap();
4360                         assert_eq!(route.paths.len(), 1);
4361                         assert_eq!(route.paths[0].len(), 2);
4362
4363                         assert_eq!(route.paths[0][0].pubkey, nodes[7]);
4364                         assert_eq!(route.paths[0][0].short_channel_id, 12);
4365                         assert_eq!(route.paths[0][0].fee_msat, 90_000*2);
4366                         assert_eq!(route.paths[0][0].cltv_expiry_delta, (13 << 8) | 1);
4367                         assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(8));
4368                         assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(12));
4369
4370                         assert_eq!(route.paths[0][1].pubkey, nodes[2]);
4371                         assert_eq!(route.paths[0][1].short_channel_id, 13);
4372                         assert_eq!(route.paths[0][1].fee_msat, 90_000);
4373                         assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
4374                         assert_eq!(route.paths[0][1].node_features.le_flags(), &id_to_feature_flags(3));
4375                         assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(13));
4376                 }
4377         }
4378
4379         #[test]
4380         fn htlc_max_reduction_below_min() {
4381                 // Test that if, while walking the graph, we reduce the value being sent to meet an
4382                 // htlc_maximum_msat, we don't end up undershooting a later htlc_minimum_msat. In the
4383                 // initial version of MPP we'd accept such routes but reject them while recalculating fees,
4384                 // resulting in us thinking there is no possible path, even if other paths exist.
4385                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
4386                 let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
4387                 let scorer = Scorer::new(0);
4388                 let payee = Payee::new(nodes[2]).with_features(InvoiceFeatures::known());
4389
4390                 // We modify the graph to set the htlc_minimum of channel 2 and 4 as needed - channel 2
4391                 // gets an htlc_maximum_msat of 80_000 and channel 4 an htlc_minimum_msat of 90_000. We
4392                 // then try to send 90_000.
4393                 update_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, UnsignedChannelUpdate {
4394                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4395                         short_channel_id: 2,
4396                         timestamp: 2,
4397                         flags: 0,
4398                         cltv_expiry_delta: 0,
4399                         htlc_minimum_msat: 0,
4400                         htlc_maximum_msat: OptionalField::Present(80_000),
4401                         fee_base_msat: 0,
4402                         fee_proportional_millionths: 0,
4403                         excess_data: Vec::new()
4404                 });
4405                 update_channel(&net_graph_msg_handler, &secp_ctx, &privkeys[1], UnsignedChannelUpdate {
4406                         chain_hash: genesis_block(Network::Testnet).header.block_hash(),
4407                         short_channel_id: 4,
4408                         timestamp: 2,
4409                         flags: 0,
4410                         cltv_expiry_delta: (4 << 8) | 1,
4411                         htlc_minimum_msat: 90_000,
4412                         htlc_maximum_msat: OptionalField::Absent,
4413                         fee_base_msat: 0,
4414                         fee_proportional_millionths: 0,
4415                         excess_data: Vec::new()
4416                 });
4417
4418                 {
4419                         // Now, attempt to route 90 sats, hitting the htlc_minimum on channel 4, but
4420                         // overshooting the htlc_maximum on channel 2. Thus, we should pick the (absurdly
4421                         // expensive) channels 12-13 path.
4422                         let route = get_route(&our_id, &payee, &net_graph_msg_handler.network_graph, None, 90_000, 42, Arc::clone(&logger), &scorer).unwrap();
4423                         assert_eq!(route.paths.len(), 1);
4424                         assert_eq!(route.paths[0].len(), 2);
4425
4426                         assert_eq!(route.paths[0][0].pubkey, nodes[7]);
4427                         assert_eq!(route.paths[0][0].short_channel_id, 12);
4428                         assert_eq!(route.paths[0][0].fee_msat, 90_000*2);
4429                         assert_eq!(route.paths[0][0].cltv_expiry_delta, (13 << 8) | 1);
4430                         assert_eq!(route.paths[0][0].node_features.le_flags(), &id_to_feature_flags(8));
4431                         assert_eq!(route.paths[0][0].channel_features.le_flags(), &id_to_feature_flags(12));
4432
4433                         assert_eq!(route.paths[0][1].pubkey, nodes[2]);
4434                         assert_eq!(route.paths[0][1].short_channel_id, 13);
4435                         assert_eq!(route.paths[0][1].fee_msat, 90_000);
4436                         assert_eq!(route.paths[0][1].cltv_expiry_delta, 42);
4437                         assert_eq!(route.paths[0][1].node_features.le_flags(), InvoiceFeatures::known().le_flags());
4438                         assert_eq!(route.paths[0][1].channel_features.le_flags(), &id_to_feature_flags(13));
4439                 }
4440         }
4441
4442         #[test]
4443         fn multiple_direct_first_hops() {
4444                 // Previously we'd only ever considered one first hop path per counterparty.
4445                 // However, as we don't restrict users to one channel per peer, we really need to support
4446                 // looking at all first hop paths.
4447                 // Here we test that we do not ignore all-but-the-last first hop paths per counterparty (as
4448                 // we used to do by overwriting the `first_hop_targets` hashmap entry) and that we can MPP
4449                 // route over multiple channels with the same first hop.
4450                 let secp_ctx = Secp256k1::new();
4451                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
4452                 let logger = Arc::new(test_utils::TestLogger::new());
4453                 let network_graph = NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash());
4454                 let scorer = Scorer::new(0);
4455                 let payee = Payee::new(nodes[0]).with_features(InvoiceFeatures::known());
4456
4457                 {
4458                         let route = get_route(&our_id, &payee, &network_graph, Some(&[
4459                                 &get_channel_details(Some(3), nodes[0], InitFeatures::known(), 200_000),
4460                                 &get_channel_details(Some(2), nodes[0], InitFeatures::known(), 10_000),
4461                         ]), 100_000, 42, Arc::clone(&logger), &scorer).unwrap();
4462                         assert_eq!(route.paths.len(), 1);
4463                         assert_eq!(route.paths[0].len(), 1);
4464
4465                         assert_eq!(route.paths[0][0].pubkey, nodes[0]);
4466                         assert_eq!(route.paths[0][0].short_channel_id, 3);
4467                         assert_eq!(route.paths[0][0].fee_msat, 100_000);
4468                 }
4469                 {
4470                         let route = get_route(&our_id, &payee, &network_graph, Some(&[
4471                                 &get_channel_details(Some(3), nodes[0], InitFeatures::known(), 50_000),
4472                                 &get_channel_details(Some(2), nodes[0], InitFeatures::known(), 50_000),
4473                         ]), 100_000, 42, Arc::clone(&logger), &scorer).unwrap();
4474                         assert_eq!(route.paths.len(), 2);
4475                         assert_eq!(route.paths[0].len(), 1);
4476                         assert_eq!(route.paths[1].len(), 1);
4477
4478                         assert_eq!(route.paths[0][0].pubkey, nodes[0]);
4479                         assert_eq!(route.paths[0][0].short_channel_id, 3);
4480                         assert_eq!(route.paths[0][0].fee_msat, 50_000);
4481
4482                         assert_eq!(route.paths[1][0].pubkey, nodes[0]);
4483                         assert_eq!(route.paths[1][0].short_channel_id, 2);
4484                         assert_eq!(route.paths[1][0].fee_msat, 50_000);
4485                 }
4486         }
4487
4488         #[test]
4489         fn prefers_shorter_route_with_higher_fees() {
4490                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
4491                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
4492                 let payee = Payee::new(nodes[6]).with_route_hints(last_hops(&nodes));
4493
4494                 // Without penalizing each hop 100 msats, a longer path with lower fees is chosen.
4495                 let scorer = Scorer::new(0);
4496                 let route = get_route(
4497                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42,
4498                         Arc::clone(&logger), &scorer
4499                 ).unwrap();
4500                 let path = route.paths[0].iter().map(|hop| hop.short_channel_id).collect::<Vec<_>>();
4501
4502                 assert_eq!(route.get_total_fees(), 100);
4503                 assert_eq!(route.get_total_amount(), 100);
4504                 assert_eq!(path, vec![2, 4, 6, 11, 8]);
4505
4506                 // Applying a 100 msat penalty to each hop results in taking channels 7 and 10 to nodes[6]
4507                 // from nodes[2] rather than channel 6, 11, and 8, even though the longer path is cheaper.
4508                 let scorer = Scorer::new(100);
4509                 let route = get_route(
4510                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42,
4511                         Arc::clone(&logger), &scorer
4512                 ).unwrap();
4513                 let path = route.paths[0].iter().map(|hop| hop.short_channel_id).collect::<Vec<_>>();
4514
4515                 assert_eq!(route.get_total_fees(), 300);
4516                 assert_eq!(route.get_total_amount(), 100);
4517                 assert_eq!(path, vec![2, 4, 7, 10]);
4518         }
4519
4520         struct BadChannelScorer {
4521                 short_channel_id: u64,
4522         }
4523
4524         impl routing::Score for BadChannelScorer {
4525                 fn channel_penalty_msat(&self, short_channel_id: u64, _source: &NodeId, _target: &NodeId) -> u64 {
4526                         if short_channel_id == self.short_channel_id { u64::max_value() } else { 0 }
4527                 }
4528         }
4529
4530         struct BadNodeScorer {
4531                 node_id: NodeId,
4532         }
4533
4534         impl routing::Score for BadNodeScorer {
4535                 fn channel_penalty_msat(&self, _short_channel_id: u64, _source: &NodeId, target: &NodeId) -> u64 {
4536                         if *target == self.node_id { u64::max_value() } else { 0 }
4537                 }
4538         }
4539
4540         #[test]
4541         fn avoids_routing_through_bad_channels_and_nodes() {
4542                 let (secp_ctx, net_graph_msg_handler, _, logger) = build_graph();
4543                 let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
4544                 let payee = Payee::new(nodes[6]).with_route_hints(last_hops(&nodes));
4545
4546                 // A path to nodes[6] exists when no penalties are applied to any channel.
4547                 let scorer = Scorer::new(0);
4548                 let route = get_route(
4549                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42,
4550                         Arc::clone(&logger), &scorer
4551                 ).unwrap();
4552                 let path = route.paths[0].iter().map(|hop| hop.short_channel_id).collect::<Vec<_>>();
4553
4554                 assert_eq!(route.get_total_fees(), 100);
4555                 assert_eq!(route.get_total_amount(), 100);
4556                 assert_eq!(path, vec![2, 4, 6, 11, 8]);
4557
4558                 // A different path to nodes[6] exists if channel 6 cannot be routed over.
4559                 let scorer = BadChannelScorer { short_channel_id: 6 };
4560                 let route = get_route(
4561                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42,
4562                         Arc::clone(&logger), &scorer
4563                 ).unwrap();
4564                 let path = route.paths[0].iter().map(|hop| hop.short_channel_id).collect::<Vec<_>>();
4565
4566                 assert_eq!(route.get_total_fees(), 300);
4567                 assert_eq!(route.get_total_amount(), 100);
4568                 assert_eq!(path, vec![2, 4, 7, 10]);
4569
4570                 // A path to nodes[6] does not exist if nodes[2] cannot be routed through.
4571                 let scorer = BadNodeScorer { node_id: NodeId::from_pubkey(&nodes[2]) };
4572                 match get_route(
4573                         &our_id, &payee, &net_graph_msg_handler.network_graph, None, 100, 42,
4574                         Arc::clone(&logger), &scorer
4575                 ) {
4576                         Err(LightningError { err, .. } ) => {
4577                                 assert_eq!(err, "Failed to find a path to the given destination");
4578                         },
4579                         Ok(_) => panic!("Expected error"),
4580                 }
4581         }
4582
4583         #[test]
4584         fn total_fees_single_path() {
4585                 let route = Route {
4586                         paths: vec![vec![
4587                                 RouteHop {
4588                                         pubkey: PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap(),
4589                                         channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
4590                                         short_channel_id: 0, fee_msat: 100, cltv_expiry_delta: 0
4591                                 },
4592                                 RouteHop {
4593                                         pubkey: PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap(),
4594                                         channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
4595                                         short_channel_id: 0, fee_msat: 150, cltv_expiry_delta: 0
4596                                 },
4597                                 RouteHop {
4598                                         pubkey: PublicKey::from_slice(&hex::decode("027f31ebc5462c1fdce1b737ecff52d37d75dea43ce11c74d25aa297165faa2007").unwrap()[..]).unwrap(),
4599                                         channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
4600                                         short_channel_id: 0, fee_msat: 225, cltv_expiry_delta: 0
4601                                 },
4602                         ]],
4603                 };
4604
4605                 assert_eq!(route.get_total_fees(), 250);
4606                 assert_eq!(route.get_total_amount(), 225);
4607         }
4608
4609         #[test]
4610         fn total_fees_multi_path() {
4611                 let route = Route {
4612                         paths: vec![vec![
4613                                 RouteHop {
4614                                         pubkey: PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap(),
4615                                         channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
4616                                         short_channel_id: 0, fee_msat: 100, cltv_expiry_delta: 0
4617                                 },
4618                                 RouteHop {
4619                                         pubkey: PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap(),
4620                                         channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
4621                                         short_channel_id: 0, fee_msat: 150, cltv_expiry_delta: 0
4622                                 },
4623                         ],vec![
4624                                 RouteHop {
4625                                         pubkey: PublicKey::from_slice(&hex::decode("02eec7245d6b7d2ccb30380bfbe2a3648cd7a942653f5aa340edcea1f283686619").unwrap()[..]).unwrap(),
4626                                         channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
4627                                         short_channel_id: 0, fee_msat: 100, cltv_expiry_delta: 0
4628                                 },
4629                                 RouteHop {
4630                                         pubkey: PublicKey::from_slice(&hex::decode("0324653eac434488002cc06bbfb7f10fe18991e35f9fe4302dbea6d2353dc0ab1c").unwrap()[..]).unwrap(),
4631                                         channel_features: ChannelFeatures::empty(), node_features: NodeFeatures::empty(),
4632                                         short_channel_id: 0, fee_msat: 150, cltv_expiry_delta: 0
4633                                 },
4634                         ]],
4635                 };
4636
4637                 assert_eq!(route.get_total_fees(), 200);
4638                 assert_eq!(route.get_total_amount(), 300);
4639         }
4640
4641         #[test]
4642         fn total_empty_route_no_panic() {
4643                 // In an earlier version of `Route::get_total_fees` and `Route::get_total_amount`, they
4644                 // would both panic if the route was completely empty. We test to ensure they return 0
4645                 // here, even though its somewhat nonsensical as a route.
4646                 let route = Route { paths: Vec::new() };
4647
4648                 assert_eq!(route.get_total_fees(), 0);
4649                 assert_eq!(route.get_total_amount(), 0);
4650         }
4651
4652         #[cfg(not(feature = "no-std"))]
4653         pub(super) fn random_init_seed() -> u64 {
4654                 // Because the default HashMap in std pulls OS randomness, we can use it as a (bad) RNG.
4655                 use core::hash::{BuildHasher, Hasher};
4656                 let seed = std::collections::hash_map::RandomState::new().build_hasher().finish();
4657                 println!("Using seed of {}", seed);
4658                 seed
4659         }
4660         #[cfg(not(feature = "no-std"))]
4661         use util::ser::Readable;
4662
4663         #[test]
4664         #[cfg(not(feature = "no-std"))]
4665         fn generate_routes() {
4666                 let mut d = match super::test_utils::get_route_file() {
4667                         Ok(f) => f,
4668                         Err(e) => {
4669                                 eprintln!("{}", e);
4670                                 return;
4671                         },
4672                 };
4673                 let graph = NetworkGraph::read(&mut d).unwrap();
4674                 let scorer = Scorer::new(0);
4675
4676                 // First, get 100 (source, destination) pairs for which route-getting actually succeeds...
4677                 let mut seed = random_init_seed() as usize;
4678                 let nodes = graph.read_only().nodes().clone();
4679                 'load_endpoints: for _ in 0..10 {
4680                         loop {
4681                                 seed = seed.overflowing_mul(0xdeadbeef).0;
4682                                 let src = &PublicKey::from_slice(nodes.keys().skip(seed % nodes.len()).next().unwrap().as_slice()).unwrap();
4683                                 seed = seed.overflowing_mul(0xdeadbeef).0;
4684                                 let dst = PublicKey::from_slice(nodes.keys().skip(seed % nodes.len()).next().unwrap().as_slice()).unwrap();
4685                                 let payee = Payee::new(dst);
4686                                 let amt = seed as u64 % 200_000_000;
4687                                 if get_route(src, &payee, &graph, None, amt, 42, &test_utils::TestLogger::new(), &scorer).is_ok() {
4688                                         continue 'load_endpoints;
4689                                 }
4690                         }
4691                 }
4692         }
4693
4694         #[test]
4695         #[cfg(not(feature = "no-std"))]
4696         fn generate_routes_mpp() {
4697                 let mut d = match super::test_utils::get_route_file() {
4698                         Ok(f) => f,
4699                         Err(e) => {
4700                                 eprintln!("{}", e);
4701                                 return;
4702                         },
4703                 };
4704                 let graph = NetworkGraph::read(&mut d).unwrap();
4705                 let scorer = Scorer::new(0);
4706
4707                 // First, get 100 (source, destination) pairs for which route-getting actually succeeds...
4708                 let mut seed = random_init_seed() as usize;
4709                 let nodes = graph.read_only().nodes().clone();
4710                 'load_endpoints: for _ in 0..10 {
4711                         loop {
4712                                 seed = seed.overflowing_mul(0xdeadbeef).0;
4713                                 let src = &PublicKey::from_slice(nodes.keys().skip(seed % nodes.len()).next().unwrap().as_slice()).unwrap();
4714                                 seed = seed.overflowing_mul(0xdeadbeef).0;
4715                                 let dst = PublicKey::from_slice(nodes.keys().skip(seed % nodes.len()).next().unwrap().as_slice()).unwrap();
4716                                 let payee = Payee::new(dst).with_features(InvoiceFeatures::known());
4717                                 let amt = seed as u64 % 200_000_000;
4718                                 if get_route(src, &payee, &graph, None, amt, 42, &test_utils::TestLogger::new(), &scorer).is_ok() {
4719                                         continue 'load_endpoints;
4720                                 }
4721                         }
4722                 }
4723         }
4724 }
4725
4726 #[cfg(all(test, not(feature = "no-std")))]
4727 pub(crate) mod test_utils {
4728         use std::fs::File;
4729         /// Tries to open a network graph file, or panics with a URL to fetch it.
4730         pub(crate) fn get_route_file() -> Result<std::fs::File, &'static str> {
4731                 let res = File::open("net_graph-2021-05-31.bin") // By default we're run in RL/lightning
4732                         .or_else(|_| File::open("lightning/net_graph-2021-05-31.bin")) // We may be run manually in RL/
4733                         .or_else(|_| { // Fall back to guessing based on the binary location
4734                                 // path is likely something like .../rust-lightning/target/debug/deps/lightning-...
4735                                 let mut path = std::env::current_exe().unwrap();
4736                                 path.pop(); // lightning-...
4737                                 path.pop(); // deps
4738                                 path.pop(); // debug
4739                                 path.pop(); // target
4740                                 path.push("lightning");
4741                                 path.push("net_graph-2021-05-31.bin");
4742                                 eprintln!("{}", path.to_str().unwrap());
4743                                 File::open(path)
4744                         })
4745                 .map_err(|_| "Please fetch https://bitcoin.ninja/ldk-net_graph-v0.0.15-2021-05-31.bin and place it at lightning/net_graph-2021-05-31.bin");
4746                 #[cfg(require_route_graph_test)]
4747                 return Ok(res.unwrap());
4748                 #[cfg(not(require_route_graph_test))]
4749                 return res;
4750         }
4751 }
4752
4753 #[cfg(all(test, feature = "unstable", not(feature = "no-std")))]
4754 mod benches {
4755         use super::*;
4756         use routing::scorer::Scorer;
4757         use util::logger::{Logger, Record};
4758
4759         use test::Bencher;
4760
4761         struct DummyLogger {}
4762         impl Logger for DummyLogger {
4763                 fn log(&self, _record: &Record) {}
4764         }
4765
4766         #[bench]
4767         fn generate_routes(bench: &mut Bencher) {
4768                 let mut d = test_utils::get_route_file().unwrap();
4769                 let graph = NetworkGraph::read(&mut d).unwrap();
4770                 let nodes = graph.read_only().nodes().clone();
4771                 let scorer = Scorer::new(0);
4772
4773                 // First, get 100 (source, destination) pairs for which route-getting actually succeeds...
4774                 let mut path_endpoints = Vec::new();
4775                 let mut seed: usize = 0xdeadbeef;
4776                 'load_endpoints: for _ in 0..100 {
4777                         loop {
4778                                 seed *= 0xdeadbeef;
4779                                 let src = PublicKey::from_slice(nodes.keys().skip(seed % nodes.len()).next().unwrap().as_slice()).unwrap();
4780                                 seed *= 0xdeadbeef;
4781                                 let dst = PublicKey::from_slice(nodes.keys().skip(seed % nodes.len()).next().unwrap().as_slice()).unwrap();
4782                                 let payee = Payee::new(dst);
4783                                 let amt = seed as u64 % 1_000_000;
4784                                 if get_route(&src, &payee, &graph, None, amt, 42, &DummyLogger{}, &scorer).is_ok() {
4785                                         path_endpoints.push((src, dst, amt));
4786                                         continue 'load_endpoints;
4787                                 }
4788                         }
4789                 }
4790
4791                 // ...then benchmark finding paths between the nodes we learned.
4792                 let mut idx = 0;
4793                 bench.iter(|| {
4794                         let (src, dst, amt) = path_endpoints[idx % path_endpoints.len()];
4795                         let payee = Payee::new(dst);
4796                         assert!(get_route(&src, &payee, &graph, None, amt, 42, &DummyLogger{}, &scorer).is_ok());
4797                         idx += 1;
4798                 });
4799         }
4800
4801         #[bench]
4802         fn generate_mpp_routes(bench: &mut Bencher) {
4803                 let mut d = test_utils::get_route_file().unwrap();
4804                 let graph = NetworkGraph::read(&mut d).unwrap();
4805                 let nodes = graph.read_only().nodes().clone();
4806                 let scorer = Scorer::new(0);
4807
4808                 // First, get 100 (source, destination) pairs for which route-getting actually succeeds...
4809                 let mut path_endpoints = Vec::new();
4810                 let mut seed: usize = 0xdeadbeef;
4811                 'load_endpoints: for _ in 0..100 {
4812                         loop {
4813                                 seed *= 0xdeadbeef;
4814                                 let src = PublicKey::from_slice(nodes.keys().skip(seed % nodes.len()).next().unwrap().as_slice()).unwrap();
4815                                 seed *= 0xdeadbeef;
4816                                 let dst = PublicKey::from_slice(nodes.keys().skip(seed % nodes.len()).next().unwrap().as_slice()).unwrap();
4817                                 let payee = Payee::new(dst).with_features(InvoiceFeatures::known());
4818                                 let amt = seed as u64 % 1_000_000;
4819                                 if get_route(&src, &payee, &graph, None, amt, 42, &DummyLogger{}, &scorer).is_ok() {
4820                                         path_endpoints.push((src, dst, amt));
4821                                         continue 'load_endpoints;
4822                                 }
4823                         }
4824                 }
4825
4826                 // ...then benchmark finding paths between the nodes we learned.
4827                 let mut idx = 0;
4828                 bench.iter(|| {
4829                         let (src, dst, amt) = path_endpoints[idx % path_endpoints.len()];
4830                         let payee = Payee::new(dst).with_features(InvoiceFeatures::known());
4831                         assert!(get_route(&src, &payee, &graph, None, amt, 42, &DummyLogger{}, &scorer).is_ok());
4832                         idx += 1;
4833                 });
4834         }
4835 }