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