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