EventHandler for applying NetworkUpdate
authorJeffrey Czyz <jkczyz@gmail.com>
Thu, 12 Aug 2021 21:02:42 +0000 (16:02 -0500)
committerJeffrey Czyz <jkczyz@gmail.com>
Wed, 15 Sep 2021 16:50:31 +0000 (11:50 -0500)
PaymentFailed events contain an optional NetworkUpdate describing
changes to the NetworkGraph as conveyed by a node along a failed payment
path according to BOLT 4. An EventHandler should apply the update to the
graph so that future routing decisions can account for it.

Implement EventHandler for NetGraphMsgHandler to update NetworkGraph.
Previously, NetGraphMsgHandler::handle_htlc_fail_channel_update
implemented this behavior.

fuzz/src/full_stack.rs
lightning/src/ln/functional_test_utils.rs
lightning/src/routing/network_graph.rs
lightning/src/routing/router.rs
lightning/src/util/events.rs

index ee7b2d18ae38f8feeed120ceec61ab76a6a37999..d82ff88d9c7d20acba55db6e8096a48b38015555 100644 (file)
@@ -38,7 +38,7 @@ use lightning::ln::peer_handler::{MessageHandler,PeerManager,SocketDescriptor,Ig
 use lightning::ln::msgs::DecodeError;
 use lightning::ln::script::ShutdownScript;
 use lightning::routing::router::get_route;
-use lightning::routing::network_graph::NetGraphMsgHandler;
+use lightning::routing::network_graph::{NetGraphMsgHandler, NetworkGraph};
 use lightning::util::config::UserConfig;
 use lightning::util::errors::APIError;
 use lightning::util::events::Event;
@@ -378,7 +378,8 @@ pub fn do_test(data: &[u8], logger: &Arc<dyn Logger>) {
        };
        let channelmanager = Arc::new(ChannelManager::new(fee_est.clone(), monitor.clone(), broadcast.clone(), Arc::clone(&logger), keys_manager.clone(), config, params));
        let our_id = PublicKey::from_secret_key(&Secp256k1::signing_only(), &keys_manager.get_node_secret());
-       let net_graph_msg_handler = Arc::new(NetGraphMsgHandler::new(genesis_block(network).block_hash(), None, Arc::clone(&logger)));
+       let network_graph = NetworkGraph::new(genesis_block(network).block_hash());
+       let net_graph_msg_handler = Arc::new(NetGraphMsgHandler::new(network_graph, None, Arc::clone(&logger)));
 
        let peers = RefCell::new([false; 256]);
        let mut loss_detector = MoneyLossDetector::new(&peers, channelmanager.clone(), monitor.clone(), PeerManager::new(MessageHandler {
index 96a6ae86d6d104d2c85c999bf1644d77eaafcbc7..6824fb043a9031725f65d256e2522fb73a47cbb3 100644 (file)
@@ -243,8 +243,8 @@ impl<'a, 'b, 'c> Drop for Node<'a, 'b, 'c> {
                                network_graph_ser.write(&mut w).unwrap();
                                let network_graph_deser = <NetworkGraph>::read(&mut io::Cursor::new(&w.0)).unwrap();
                                assert!(network_graph_deser == self.net_graph_msg_handler.network_graph);
-                               let net_graph_msg_handler = NetGraphMsgHandler::from_net_graph(
-                                       Some(self.chain_source), self.logger, network_graph_deser
+                               let net_graph_msg_handler = NetGraphMsgHandler::new(
+                                       network_graph_deser, Some(self.chain_source), self.logger
                                );
                                let mut chan_progress = 0;
                                loop {
@@ -1440,7 +1440,8 @@ pub fn create_network<'a, 'b: 'a, 'c: 'b>(node_count: usize, cfgs: &'b Vec<NodeC
        let connect_style = Rc::new(RefCell::new(ConnectStyle::FullBlockViaListen));
 
        for i in 0..node_count {
-               let net_graph_msg_handler = NetGraphMsgHandler::new(cfgs[i].chain_source.genesis_hash, None, cfgs[i].logger);
+               let network_graph = NetworkGraph::new(cfgs[i].chain_source.genesis_hash);
+               let net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, None, cfgs[i].logger);
                nodes.push(Node{ chain_source: cfgs[i].chain_source,
                                 tx_broadcaster: cfgs[i].tx_broadcaster, chain_monitor: &cfgs[i].chain_monitor,
                                 keys_manager: &cfgs[i].keys_manager, node: &chan_mgrs[i], net_graph_msg_handler,
index 1a149b3bd76cf580951c2cf2599da7c7924048d2..ca656039d122021fe500be7e7252d540160b591c 100644 (file)
@@ -29,7 +29,7 @@ use ln::msgs::{QueryChannelRange, ReplyChannelRange, QueryShortChannelIds, Reply
 use ln::msgs;
 use util::ser::{Writeable, Readable, Writer};
 use util::logger::{Logger, Level};
-use util::events::{MessageSendEvent, MessageSendEventsProvider};
+use util::events::{Event, EventHandler, MessageSendEvent, MessageSendEventsProvider};
 use util::scid_utils::{block_from_scid, scid_from_parts, MAX_SCID_BLOCK};
 
 use io;
@@ -110,12 +110,28 @@ impl_writeable_tlv_based_enum_upgradable!(NetworkUpdate,
        },
 );
 
+impl<C: Deref, L: Deref> EventHandler for NetGraphMsgHandler<C, L>
+where C::Target: chain::Access, L::Target: Logger {
+       fn handle_event(&self, event: &Event) {
+               if let Event::PaymentFailed { payment_hash: _, rejected_by_dest: _, network_update, .. } = event {
+                       if let Some(network_update) = network_update {
+                               self.handle_network_update(network_update);
+                       }
+               }
+       }
+}
+
 /// Receives and validates network updates from peers,
 /// stores authentic and relevant data as a network graph.
 /// This network graph is then used for routing payments.
 /// Provides interface to help with initial routing sync by
 /// serving historical announcements.
-pub struct NetGraphMsgHandler<C: Deref, L: Deref> where C::Target: chain::Access, L::Target: Logger {
+///
+/// Serves as an [`EventHandler`] for applying updates from [`Event::PaymentFailed`] to the
+/// [`NetworkGraph`].
+pub struct NetGraphMsgHandler<C: Deref, L: Deref>
+where C::Target: chain::Access, L::Target: Logger
+{
        secp_ctx: Secp256k1<secp256k1::VerifyOnly>,
        /// Representation of the payment channel network
        pub network_graph: NetworkGraph,
@@ -125,26 +141,15 @@ pub struct NetGraphMsgHandler<C: Deref, L: Deref> where C::Target: chain::Access
        logger: L,
 }
 
-impl<C: Deref, L: Deref> NetGraphMsgHandler<C, L> where C::Target: chain::Access, L::Target: Logger {
+impl<C: Deref, L: Deref> NetGraphMsgHandler<C, L>
+where C::Target: chain::Access, L::Target: Logger
+{
        /// Creates a new tracker of the actual state of the network of channels and nodes,
-       /// assuming a fresh network graph.
+       /// assuming an existing Network Graph.
        /// Chain monitor is used to make sure announced channels exist on-chain,
        /// channel data is correct, and that the announcement is signed with
        /// channel owners' keys.
-       pub fn new(genesis_hash: BlockHash, chain_access: Option<C>, logger: L) -> Self {
-               NetGraphMsgHandler {
-                       secp_ctx: Secp256k1::verification_only(),
-                       network_graph: NetworkGraph::new(genesis_hash),
-                       full_syncs_requested: AtomicUsize::new(0),
-                       chain_access,
-                       pending_events: Mutex::new(vec![]),
-                       logger,
-               }
-       }
-
-       /// Creates a new tracker of the actual state of the network of channels and nodes,
-       /// assuming an existing Network Graph.
-       pub fn from_net_graph(chain_access: Option<C>, logger: L, network_graph: NetworkGraph) -> Self {
+       pub fn new(network_graph: NetworkGraph, chain_access: Option<C>, logger: L) -> Self {
                NetGraphMsgHandler {
                        secp_ctx: Secp256k1::verification_only(),
                        network_graph,
@@ -173,6 +178,29 @@ impl<C: Deref, L: Deref> NetGraphMsgHandler<C, L> where C::Target: chain::Access
                        false
                }
        }
+
+       /// Applies changes to the [`NetworkGraph`] from the given update.
+       fn handle_network_update(&self, update: &NetworkUpdate) {
+               match *update {
+                       NetworkUpdate::ChannelUpdateMessage { ref msg } => {
+                               let short_channel_id = msg.contents.short_channel_id;
+                               let is_enabled = msg.contents.flags & (1 << 1) != (1 << 1);
+                               let status = if is_enabled { "enabled" } else { "disabled" };
+                               log_debug!(self.logger, "Updating channel with channel_update from a payment failure. Channel {} is {}.", short_channel_id, status);
+                               let _ = self.network_graph.update_channel(msg, &self.secp_ctx);
+                       },
+                       NetworkUpdate::ChannelClosed { short_channel_id, is_permanent } => {
+                               let action = if is_permanent { "Removing" } else { "Disabling" };
+                               log_debug!(self.logger, "{} channel graph entry for {} due to a payment failure.", action, short_channel_id);
+                               self.network_graph.close_channel_from_update(short_channel_id, is_permanent);
+                       },
+                       NetworkUpdate::NodeFailure { ref node_id, is_permanent } => {
+                               let action = if is_permanent { "Removing" } else { "Disabling" };
+                               log_debug!(self.logger, "{} node graph entry for {} due to a payment failure.", action, node_id);
+                               self.network_graph.fail_node(node_id, is_permanent);
+                       },
+               }
+       }
 }
 
 macro_rules! secp_verify_sig {
@@ -184,7 +212,9 @@ macro_rules! secp_verify_sig {
        };
 }
 
-impl<C: Deref , L: Deref > RoutingMessageHandler for NetGraphMsgHandler<C, L> where C::Target: chain::Access, L::Target: Logger {
+impl<C: Deref, L: Deref> RoutingMessageHandler for NetGraphMsgHandler<C, L>
+where C::Target: chain::Access, L::Target: Logger
+{
        fn handle_node_announcement(&self, msg: &msgs::NodeAnnouncement) -> Result<bool, LightningError> {
                self.network_graph.update_node_from_announcement(msg, &self.secp_ctx)?;
                Ok(msg.contents.excess_data.len() <=  MAX_EXCESS_BYTES_FOR_RELAY &&
@@ -1116,15 +1146,16 @@ impl ReadOnlyNetworkGraph<'_> {
 #[cfg(test)]
 mod tests {
        use chain;
+       use ln::PaymentHash;
        use ln::features::{ChannelFeatures, InitFeatures, NodeFeatures};
-       use routing::network_graph::{NetGraphMsgHandler, NetworkGraph, MAX_EXCESS_BYTES_FOR_RELAY};
+       use routing::network_graph::{NetGraphMsgHandler, NetworkGraph, NetworkUpdate, MAX_EXCESS_BYTES_FOR_RELAY};
        use ln::msgs::{Init, OptionalField, RoutingMessageHandler, UnsignedNodeAnnouncement, NodeAnnouncement,
                UnsignedChannelAnnouncement, ChannelAnnouncement, UnsignedChannelUpdate, ChannelUpdate, 
                ReplyChannelRange, ReplyShortChannelIdsEnd, QueryChannelRange, QueryShortChannelIds, MAX_VALUE_MSAT};
        use util::test_utils;
        use util::logger::Logger;
        use util::ser::{Readable, Writeable};
-       use util::events::{MessageSendEvent, MessageSendEventsProvider};
+       use util::events::{Event, EventHandler, MessageSendEvent, MessageSendEventsProvider};
        use util::scid_utils::scid_from_parts;
 
        use bitcoin::hashes::sha256d::Hash as Sha256dHash;
@@ -1148,7 +1179,8 @@ mod tests {
                let secp_ctx = Secp256k1::new();
                let logger = Arc::new(test_utils::TestLogger::new());
                let genesis_hash = genesis_block(Network::Testnet).header.block_hash();
-               let net_graph_msg_handler = NetGraphMsgHandler::new(genesis_hash, None, Arc::clone(&logger));
+               let network_graph = NetworkGraph::new(genesis_hash);
+               let net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, None, Arc::clone(&logger));
                (secp_ctx, net_graph_msg_handler)
        }
 
@@ -1309,7 +1341,8 @@ mod tests {
                };
 
                // Test if the UTXO lookups were not supported
-               let mut net_graph_msg_handler = NetGraphMsgHandler::new(genesis_block(Network::Testnet).header.block_hash(), None, Arc::clone(&logger));
+               let network_graph = NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash());
+               let mut net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, None, Arc::clone(&logger));
                match net_graph_msg_handler.handle_channel_announcement(&valid_announcement) {
                        Ok(res) => assert!(res),
                        _ => panic!()
@@ -1333,7 +1366,8 @@ mod tests {
                // Test if an associated transaction were not on-chain (or not confirmed).
                let chain_source = Arc::new(test_utils::TestChainSource::new(Network::Testnet));
                *chain_source.utxo_ret.lock().unwrap() = Err(chain::AccessError::UnknownTx);
-               net_graph_msg_handler = NetGraphMsgHandler::new(chain_source.clone().genesis_hash, Some(chain_source.clone()), Arc::clone(&logger));
+               let network_graph = NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash());
+               net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, Some(chain_source.clone()), Arc::clone(&logger));
                unsigned_announcement.short_channel_id += 1;
 
                msghash = hash_to_message!(&Sha256dHash::hash(&unsigned_announcement.encode()[..])[..]);
@@ -1457,7 +1491,8 @@ mod tests {
                let secp_ctx = Secp256k1::new();
                let logger: Arc<Logger> = Arc::new(test_utils::TestLogger::new());
                let chain_source = Arc::new(test_utils::TestChainSource::new(Network::Testnet));
-               let net_graph_msg_handler = NetGraphMsgHandler::new(genesis_block(Network::Testnet).header.block_hash(), Some(chain_source.clone()), Arc::clone(&logger));
+               let network_graph = NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash());
+               let net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, Some(chain_source.clone()), Arc::clone(&logger));
 
                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
@@ -1621,8 +1656,14 @@ mod tests {
        }
 
        #[test]
-       fn handling_htlc_fail_channel_update() {
-               let (secp_ctx, net_graph_msg_handler) = create_net_graph_msg_handler();
+       fn handling_network_update() {
+               let logger = test_utils::TestLogger::new();
+               let chain_source = Arc::new(test_utils::TestChainSource::new(Network::Testnet));
+               let genesis_hash = genesis_block(Network::Testnet).header.block_hash();
+               let network_graph = NetworkGraph::new(genesis_hash);
+               let net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, Some(chain_source.clone()), &logger);
+               let secp_ctx = Secp256k1::new();
+
                let node_1_privkey = &SecretKey::from_slice(&[42; 32]).unwrap();
                let node_2_privkey = &SecretKey::from_slice(&[41; 32]).unwrap();
                let node_id_1 = PublicKey::from_secret_key(&secp_ctx, node_1_privkey);
@@ -1632,11 +1673,11 @@ mod tests {
 
                let short_channel_id = 0;
                let chain_hash = genesis_block(Network::Testnet).header.block_hash();
+               let network_graph = &net_graph_msg_handler.network_graph;
 
                {
                        // There is no nodes in the table at the beginning.
-                       let network = &net_graph_msg_handler.network_graph;
-                       assert_eq!(network.read_only().nodes().len(), 0);
+                       assert_eq!(network_graph.read_only().nodes().len(), 0);
                }
 
                {
@@ -1660,10 +1701,9 @@ mod tests {
                                bitcoin_signature_2: secp_ctx.sign(&msghash, node_2_btckey),
                                contents: unsigned_announcement.clone(),
                        };
-                       match net_graph_msg_handler.handle_channel_announcement(&valid_channel_announcement) {
-                               Ok(_) => (),
-                               Err(_) => panic!()
-                       };
+                       let chain_source: Option<&test_utils::TestChainSource> = None;
+                       assert!(network_graph.update_channel_from_announcement(&valid_channel_announcement, &chain_source, &secp_ctx).is_ok());
+                       assert!(network_graph.read_only().channels().get(&short_channel_id).is_some());
 
                        let unsigned_channel_update = UnsignedChannelUpdate {
                                chain_hash,
@@ -1683,29 +1723,42 @@ mod tests {
                                contents: unsigned_channel_update.clone()
                        };
 
-                       match net_graph_msg_handler.handle_channel_update(&valid_channel_update) {
-                               Ok(res) => assert!(res),
-                               _ => panic!()
-                       };
+                       assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_none());
+
+                       net_graph_msg_handler.handle_event(&Event::PaymentFailed {
+                               payment_hash: PaymentHash([0; 32]),
+                               rejected_by_dest: false,
+                               network_update: Some(NetworkUpdate::ChannelUpdateMessage {
+                                       msg: valid_channel_update,
+                               }),
+                               error_code: None,
+                               error_data: None,
+                       });
+
+                       assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_some());
                }
 
                // Non-permanent closing just disables a channel
                {
-                       let network = &net_graph_msg_handler.network_graph;
-                       match network.read_only().channels().get(&short_channel_id) {
+                       match network_graph.read_only().channels().get(&short_channel_id) {
                                None => panic!(),
                                Some(channel_info) => {
-                                       assert!(channel_info.one_to_two.is_some());
+                                       assert!(channel_info.one_to_two.as_ref().unwrap().enabled);
                                }
                        };
-               }
 
-               net_graph_msg_handler.network_graph.close_channel_from_update(short_channel_id, false);
+                       net_graph_msg_handler.handle_event(&Event::PaymentFailed {
+                               payment_hash: PaymentHash([0; 32]),
+                               rejected_by_dest: false,
+                               network_update: Some(NetworkUpdate::ChannelClosed {
+                                       short_channel_id,
+                                       is_permanent: false,
+                               }),
+                               error_code: None,
+                               error_data: None,
+                       });
 
-               // Non-permanent closing just disables a channel
-               {
-                       let network = &net_graph_msg_handler.network_graph;
-                       match network.read_only().channels().get(&short_channel_id) {
+                       match network_graph.read_only().channels().get(&short_channel_id) {
                                None => panic!(),
                                Some(channel_info) => {
                                        assert!(!channel_info.one_to_two.as_ref().unwrap().enabled);
@@ -1713,14 +1766,22 @@ mod tests {
                        };
                }
 
-               net_graph_msg_handler.network_graph.close_channel_from_update(short_channel_id, true);
-
                // Permanent closing deletes a channel
                {
-                       let network = &net_graph_msg_handler.network_graph;
-                       assert_eq!(network.read_only().channels().len(), 0);
+                       net_graph_msg_handler.handle_event(&Event::PaymentFailed {
+                               payment_hash: PaymentHash([0; 32]),
+                               rejected_by_dest: false,
+                               network_update: Some(NetworkUpdate::ChannelClosed {
+                                       short_channel_id,
+                                       is_permanent: true,
+                               }),
+                               error_code: None,
+                               error_data: None,
+                       });
+
+                       assert_eq!(network_graph.read_only().channels().len(), 0);
                        // Nodes are also deleted because there are no associated channels anymore
-                       assert_eq!(network.read_only().nodes().len(), 0);
+                       assert_eq!(network_graph.read_only().nodes().len(), 0);
                }
                // TODO: Test NetworkUpdate::NodeFailure, which is not implemented yet.
        }
index 770b62d9cd2e1e9598cd312dd8137def71eab1bb..97c2c7623ea77c2642ab2ec0874ea47ab9d7073d 100644 (file)
@@ -1296,8 +1296,10 @@ mod tests {
        }
 
        // Using the same keys for LN and BTC ids
-       fn add_channel(net_graph_msg_handler: &NetGraphMsgHandler<Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>, secp_ctx: &Secp256k1<All>, node_1_privkey: &SecretKey,
-          node_2_privkey: &SecretKey, features: ChannelFeatures, short_channel_id: u64) {
+       fn add_channel(
+               net_graph_msg_handler: &NetGraphMsgHandler<Arc<test_utils::TestChainSource>, Arc<test_utils::TestLogger>>,
+               secp_ctx: &Secp256k1<All>, node_1_privkey: &SecretKey, node_2_privkey: &SecretKey, features: ChannelFeatures, short_channel_id: u64
+       ) {
                let node_id_1 = PublicKey::from_secret_key(&secp_ctx, node_1_privkey);
                let node_id_2 = PublicKey::from_secret_key(&secp_ctx, node_2_privkey);
 
@@ -1326,7 +1328,10 @@ mod tests {
                };
        }
 
-       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) {
+       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
+       ) {
                let msghash = hash_to_message!(&Sha256dHash::hash(&update.encode()[..])[..]);
                let valid_channel_update = ChannelUpdate {
                        signature: secp_ctx.sign(&msghash, node_privkey),
@@ -1339,8 +1344,10 @@ mod tests {
                };
        }
 
-       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,
-          features: NodeFeatures, timestamp: u32) {
+       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, features: NodeFeatures, timestamp: u32
+       ) {
                let node_id = PublicKey::from_secret_key(&secp_ctx, node_privkey);
                let unsigned_announcement = UnsignedNodeAnnouncement {
                        features,
@@ -1396,7 +1403,8 @@ mod tests {
                let secp_ctx = Secp256k1::new();
                let logger = Arc::new(test_utils::TestLogger::new());
                let chain_monitor = Arc::new(test_utils::TestChainSource::new(Network::Testnet));
-               let net_graph_msg_handler = NetGraphMsgHandler::new(genesis_block(Network::Testnet).header.block_hash(), None, Arc::clone(&logger));
+               let network_graph = NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash());
+               let net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, None, Arc::clone(&logger));
                // Build network from our_id to node6:
                //
                //        -1(1)2-  node0  -1(3)2-
@@ -3947,7 +3955,8 @@ mod tests {
                // "previous hop" being set to node 3, creating a loop in the path.
                let secp_ctx = Secp256k1::new();
                let logger = Arc::new(test_utils::TestLogger::new());
-               let net_graph_msg_handler = NetGraphMsgHandler::new(genesis_block(Network::Testnet).header.block_hash(), None, Arc::clone(&logger));
+               let network_graph = NetworkGraph::new(genesis_block(Network::Testnet).header.block_hash());
+               let net_graph_msg_handler = NetGraphMsgHandler::new(network_graph, None, Arc::clone(&logger));
                let (our_privkey, our_id, privkeys, nodes) = get_nodes(&secp_ctx);
 
                add_channel(&net_graph_msg_handler, &secp_ctx, &our_privkey, &privkeys[1], ChannelFeatures::from_le_bytes(id_to_feature_flags(6)), 6);
index bde7d8c441301251cd8d2278c3837348ce2e3cbc..d63dd88b76163c86fd16410e468eb03f7d95fcc6 100644 (file)
@@ -130,10 +130,13 @@ pub enum Event {
                /// retry the payment via a different route.
                rejected_by_dest: bool,
                /// Any failure information conveyed via the Onion return packet by a node along the failed
-               /// payment route. Should be applied to the [`NetworkGraph`] so that routing decisions can
-               /// take into account the update.
+               /// payment route.
+               ///
+               /// Should be applied to the [`NetworkGraph`] so that routing decisions can take into
+               /// account the update. [`NetGraphMsgHandler`] is capable of doing this.
                ///
                /// [`NetworkGraph`]: crate::routing::network_graph::NetworkGraph
+               /// [`NetGraphMsgHandler`]: crate::routing::network_graph::NetGraphMsgHandler
                network_update: Option<NetworkUpdate>,
 #[cfg(test)]
                error_code: Option<u16>,