Merge pull request #1491 from tnull/2022-05-build-route-from-pubkeys
authorMatt Corallo <649246+TheBlueMatt@users.noreply.github.com>
Fri, 27 May 2022 02:05:52 +0000 (19:05 -0700)
committerGitHub <noreply@github.com>
Fri, 27 May 2022 02:05:52 +0000 (19:05 -0700)
Build route from hop pubkey list.

lightning/src/routing/router.rs

index d85485fe82600b351e927db598889ea96a81ce1a..5bb81a033eb697193cde37776c8f9a9dadde04c8 100644 (file)
@@ -19,7 +19,7 @@ use ln::features::{ChannelFeatures, InvoiceFeatures, NodeFeatures};
 use ln::msgs::{DecodeError, ErrorAction, LightningError, MAX_VALUE_MSAT};
 use routing::scoring::{ChannelUsage, Score};
 use routing::network_graph::{DirectedChannelInfoWithUpdate, EffectiveCapacity, NetworkGraph, ReadOnlyNetworkGraph, NodeId, RoutingFees};
-use util::ser::{Writeable, Readable};
+use util::ser::{Writeable, Readable, Writer};
 use util::logger::{Level, Logger};
 use util::chacha20::ChaCha20;
 
@@ -151,8 +151,8 @@ impl Readable for Route {
 
 /// Parameters needed to find a [`Route`].
 ///
-/// Passed to [`find_route`] and also provided in [`Event::PaymentPathFailed`] for retrying a failed
-/// payment path.
+/// Passed to [`find_route`] and [`build_route_from_hops`], but also provided in
+/// [`Event::PaymentPathFailed`] for retrying a failed payment path.
 ///
 /// [`Event::PaymentPathFailed`]: crate::util::events::Event::PaymentPathFailed
 #[derive(Clone, Debug)]
@@ -676,16 +676,11 @@ pub fn find_route<L: Deref, S: Score>(
 ) -> Result<Route, LightningError>
 where L::Target: Logger {
        let network_graph = network.read_only();
-       match get_route(
-               our_node_pubkey, &route_params.payment_params, &network_graph, first_hops, route_params.final_value_msat,
-               route_params.final_cltv_expiry_delta, logger, scorer, random_seed_bytes
-       ) {
-               Ok(mut route) => {
-                       add_random_cltv_offset(&mut route, &route_params.payment_params, &network_graph, random_seed_bytes);
-                       Ok(route)
-               },
-               Err(err) => Err(err),
-       }
+       let mut route = get_route(our_node_pubkey, &route_params.payment_params, &network_graph, first_hops,
+               route_params.final_value_msat, route_params.final_cltv_expiry_delta, logger, scorer,
+               random_seed_bytes)?;
+       add_random_cltv_offset(&mut route, &route_params.payment_params, &network_graph, random_seed_bytes);
+       Ok(route)
 }
 
 pub(crate) fn get_route<L: Deref, S: Score>(
@@ -1703,7 +1698,9 @@ where L::Target: Logger {
 // destination, if the remaining CLTV expiry delta exactly matches a feasible path in the network
 // graph. In order to improve privacy, this method obfuscates the CLTV expiry deltas along the
 // payment path by adding a randomized 'shadow route' offset to the final hop.
-fn add_random_cltv_offset(route: &mut Route, payment_params: &PaymentParameters, network_graph: &ReadOnlyNetworkGraph, random_seed_bytes: &[u8; 32]) {
+fn add_random_cltv_offset(route: &mut Route, payment_params: &PaymentParameters,
+       network_graph: &ReadOnlyNetworkGraph, random_seed_bytes: &[u8; 32]
+) {
        let network_channels = network_graph.channels();
        let network_nodes = network_graph.nodes();
 
@@ -1785,10 +1782,84 @@ fn add_random_cltv_offset(route: &mut Route, payment_params: &PaymentParameters,
        }
 }
 
+/// Construct a route from us (payer) to the target node (payee) via the given hops (which should
+/// exclude the payer, but include the payee). This may be useful, e.g., for probing the chosen path.
+///
+/// Re-uses logic from `find_route`, so the restrictions described there also apply here.
+pub fn build_route_from_hops<L: Deref>(
+       our_node_pubkey: &PublicKey, hops: &[PublicKey], route_params: &RouteParameters, network: &NetworkGraph,
+       logger: L, random_seed_bytes: &[u8; 32]
+) -> Result<Route, LightningError>
+where L::Target: Logger {
+       let network_graph = network.read_only();
+       let mut route = build_route_from_hops_internal(
+               our_node_pubkey, hops, &route_params.payment_params, &network_graph,
+               route_params.final_value_msat, route_params.final_cltv_expiry_delta, logger, random_seed_bytes)?;
+       add_random_cltv_offset(&mut route, &route_params.payment_params, &network_graph, random_seed_bytes);
+       Ok(route)
+}
+
+fn build_route_from_hops_internal<L: Deref>(
+       our_node_pubkey: &PublicKey, hops: &[PublicKey], payment_params: &PaymentParameters,
+       network_graph: &ReadOnlyNetworkGraph, final_value_msat: u64, final_cltv_expiry_delta: u32,
+       logger: L, random_seed_bytes: &[u8; 32]
+) -> Result<Route, LightningError> where L::Target: Logger {
+
+       struct HopScorer {
+               our_node_id: NodeId,
+               hop_ids: [Option<NodeId>; MAX_PATH_LENGTH_ESTIMATE as usize],
+       }
+
+       impl Score for HopScorer {
+               fn channel_penalty_msat(&self, _short_channel_id: u64, source: &NodeId, target: &NodeId,
+                       _usage: ChannelUsage) -> u64
+               {
+                       let mut cur_id = self.our_node_id;
+                       for i in 0..self.hop_ids.len() {
+                               if let Some(next_id) = self.hop_ids[i] {
+                                       if cur_id == *source && next_id == *target {
+                                               return 0;
+                                       }
+                                       cur_id = next_id;
+                               } else {
+                                       break;
+                               }
+                       }
+                       u64::max_value()
+               }
+
+               fn payment_path_failed(&mut self, _path: &[&RouteHop], _short_channel_id: u64) {}
+
+               fn payment_path_successful(&mut self, _path: &[&RouteHop]) {}
+       }
+
+       impl<'a> Writeable for HopScorer {
+               #[inline]
+               fn write<W: Writer>(&self, _w: &mut W) -> Result<(), io::Error> {
+                       unreachable!();
+               }
+       }
+
+       if hops.len() > MAX_PATH_LENGTH_ESTIMATE.into() {
+               return Err(LightningError{err: "Cannot build a route exceeding the maximum path length.".to_owned(), action: ErrorAction::IgnoreError});
+       }
+
+       let our_node_id = NodeId::from_pubkey(our_node_pubkey);
+       let mut hop_ids = [None; MAX_PATH_LENGTH_ESTIMATE as usize];
+       for i in 0..hops.len() {
+               hop_ids[i] = Some(NodeId::from_pubkey(&hops[i]));
+       }
+
+       let scorer = HopScorer { our_node_id, hop_ids };
+
+       get_route(our_node_pubkey, payment_params, network_graph, None, final_value_msat,
+               final_cltv_expiry_delta, logger, &scorer, random_seed_bytes)
+}
+
 #[cfg(test)]
 mod tests {
        use routing::network_graph::{NetworkGraph, NetGraphMsgHandler, NodeId};
-       use routing::router::{get_route, add_random_cltv_offset, default_node_features,
+       use routing::router::{get_route, build_route_from_hops_internal, add_random_cltv_offset, default_node_features,
                PaymentParameters, Route, RouteHint, RouteHintHop, RouteHop, RoutingFees,
                DEFAULT_MAX_TOTAL_CLTV_EXPIRY_DELTA, MAX_PATH_LENGTH_ESTIMATE};
        use routing::scoring::{ChannelUsage, Score};
@@ -5486,6 +5557,26 @@ mod tests {
                assert!(path_plausibility.iter().all(|x| *x));
        }
 
+       #[test]
+       fn builds_correct_path_from_hops() {
+               let (secp_ctx, network, _, _, logger) = build_graph();
+               let (_, our_id, _, nodes) = get_nodes(&secp_ctx);
+               let network_graph = network.read_only();
+
+               let keys_manager = test_utils::TestKeysInterface::new(&[0u8; 32], Network::Testnet);
+               let random_seed_bytes = keys_manager.get_secure_random_bytes();
+
+               let payment_params = PaymentParameters::from_node_id(nodes[3]);
+               let hops = [nodes[1], nodes[2], nodes[4], nodes[3]];
+               let route = build_route_from_hops_internal(&our_id, &hops, &payment_params,
+                        &network_graph, 100, 0, Arc::clone(&logger), &random_seed_bytes).unwrap();
+               let route_hop_pubkeys = route.paths[0].iter().map(|hop| hop.pubkey).collect::<Vec<_>>();
+               assert_eq!(hops.len(), route.paths[0].len());
+               for (idx, hop_pubkey) in hops.iter().enumerate() {
+                       assert!(*hop_pubkey == route_hop_pubkeys[idx]);
+               }
+       }
+
        #[cfg(not(feature = "no-std"))]
        pub(super) fn random_init_seed() -> u64 {
                // Because the default HashMap in std pulls OS randomness, we can use it as a (bad) RNG.