Add a method to prune stale channels from `NetworkGraph`
[rust-lightning] / lightning / src / routing / network_graph.rs
index 7f9f5c3292d901ed235b843c3e0ef1a2e4493284..67dc302246325b7efa219e98acdde875e5be702c 100644 (file)
@@ -43,6 +43,13 @@ use sync::Mutex;
 use core::ops::Deref;
 use bitcoin::hashes::hex::ToHex;
 
+#[cfg(feature = "std")]
+use std::time::{SystemTime, UNIX_EPOCH};
+
+/// We remove stale channel directional info two weeks after the last update, per BOLT 7's
+/// suggestion.
+const STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS: u64 = 60 * 60 * 24 * 14;
+
 /// The maximum number of extra bytes which we do not understand in a gossip message before we will
 /// refuse to relay the message.
 const MAX_EXCESS_BYTES_FOR_RELAY: usize = 1024;
@@ -628,6 +635,10 @@ pub struct ChannelInfo {
        /// Everything else is useful only for sending out for initial routing sync.
        /// Not stored if contains excess data to prevent DoS.
        pub announcement_message: Option<ChannelAnnouncement>,
+       /// The timestamp when we received the announcement, if we are running with feature = "std"
+       /// (which we can probably assume we are - no-std environments probably won't have a full
+       /// network graph in memory!).
+       announcement_received_time: u64,
 }
 
 impl fmt::Display for ChannelInfo {
@@ -640,6 +651,7 @@ impl fmt::Display for ChannelInfo {
 
 impl_writeable_tlv_based!(ChannelInfo, {
        (0, features, required),
+       (1, announcement_received_time, (default_value, 0)),
        (2, node_one, required),
        (4, one_to_two, required),
        (6, node_two, required),
@@ -952,6 +964,13 @@ impl NetworkGraph {
                        },
                };
 
+               #[allow(unused_mut, unused_assignments)]
+               let mut announcement_received_time = 0;
+               #[cfg(feature = "std")]
+               {
+                       announcement_received_time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
+               }
+
                let chan_info = ChannelInfo {
                                features: msg.features.clone(),
                                node_one: NodeId::from_pubkey(&msg.node_id_1),
@@ -961,6 +980,7 @@ impl NetworkGraph {
                                capacity_sats: utxo_value,
                                announcement_message: if msg.excess_data.len() <= MAX_EXCESS_BYTES_FOR_RELAY
                                        { full_msg.cloned() } else { None },
+                               announcement_received_time,
                        };
 
                let mut channels = self.channels.write().unwrap();
@@ -1045,6 +1065,67 @@ impl NetworkGraph {
                }
        }
 
+       #[cfg(feature = "std")]
+       /// Removes information about channels that we haven't heard any updates about in some time.
+       /// This can be used regularly to prune the network graph of channels that likely no longer
+       /// exist.
+       ///
+       /// While there is no formal requirement that nodes regularly re-broadcast their channel
+       /// updates every two weeks, the non-normative section of BOLT 7 currently suggests that
+       /// pruning occur for updates which are at least two weeks old, which we implement here.
+       ///
+       ///
+       /// This method is only available with the `std` feature. See
+       /// [`NetworkGraph::remove_stale_channels_with_time`] for `no-std` use.
+       pub fn remove_stale_channels(&self) {
+               let time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
+               self.remove_stale_channels_with_time(time);
+       }
+
+       /// Removes information about channels that we haven't heard any updates about in some time.
+       /// This can be used regularly to prune the network graph of channels that likely no longer
+       /// exist.
+       ///
+       /// While there is no formal requirement that nodes regularly re-broadcast their channel
+       /// updates every two weeks, the non-normative section of BOLT 7 currently suggests that
+       /// pruning occur for updates which are at least two weeks old, which we implement here.
+       ///
+       /// This function takes the current unix time as an argument. For users with the `std` feature
+       /// enabled, [`NetworkGraph::remove_stale_channels`] may be preferable.
+       pub fn remove_stale_channels_with_time(&self, current_time_unix: u64) {
+               let mut channels = self.channels.write().unwrap();
+               // Time out if we haven't received an update in at least 14 days.
+               if current_time_unix > u32::max_value() as u64 { return; } // Remove by 2106
+               if current_time_unix < STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS { return; }
+               let min_time_unix: u32 = (current_time_unix - STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS) as u32;
+               // Sadly BTreeMap::retain was only stabilized in 1.53 so we can't switch to it for some
+               // time.
+               let mut scids_to_remove = Vec::new();
+               for (scid, info) in channels.iter_mut() {
+                       if info.one_to_two.is_some() && info.one_to_two.as_ref().unwrap().last_update < min_time_unix {
+                               info.one_to_two = None;
+                       }
+                       if info.two_to_one.is_some() && info.two_to_one.as_ref().unwrap().last_update < min_time_unix {
+                               info.two_to_one = None;
+                       }
+                       if info.one_to_two.is_none() && info.two_to_one.is_none() {
+                               // We check the announcement_received_time here to ensure we don't drop
+                               // announcements that we just received and are just waiting for our peer to send a
+                               // channel_update for.
+                               if info.announcement_received_time < min_time_unix as u64 {
+                                       scids_to_remove.push(*scid);
+                               }
+                       }
+               }
+               if !scids_to_remove.is_empty() {
+                       let mut nodes = self.nodes.write().unwrap();
+                       for scid in scids_to_remove {
+                               let info = channels.remove(&scid).expect("We just accessed this scid, it should be present");
+                               Self::remove_channel_in_nodes(&mut nodes, &info, scid);
+                       }
+               }
+       }
+
        /// For an already known (from announcement) channel, update info about one of the directions
        /// of the channel.
        ///
@@ -1250,6 +1331,8 @@ mod tests {
        use util::events::{Event, EventHandler, MessageSendEvent, MessageSendEventsProvider};
        use util::scid_utils::scid_from_parts;
 
+       use super::STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS;
+
        use bitcoin::hashes::sha256d::Hash as Sha256dHash;
        use bitcoin::hashes::Hash;
        use bitcoin::network::constants::Network;
@@ -1733,28 +1816,73 @@ mod tests {
                }
 
                // Permanent closing deletes a channel
+               net_graph_msg_handler.handle_event(&Event::PaymentPathFailed {
+                       payment_id: None,
+                       payment_hash: PaymentHash([0; 32]),
+                       rejected_by_dest: false,
+                       all_paths_failed: true,
+                       path: vec![],
+                       network_update: Some(NetworkUpdate::ChannelClosed {
+                               short_channel_id,
+                               is_permanent: true,
+                       }),
+                       short_channel_id: None,
+                       retry: None,
+                       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_graph.read_only().nodes().len(), 0);
+               // TODO: Test NetworkUpdate::NodeFailure, which is not implemented yet.
+       }
+
+       #[test]
+       fn test_channel_timeouts() {
+               // Test the removal of channels with `remove_stale_channels`.
+               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 valid_channel_announcement = get_signed_channel_announcement(|_| {}, node_1_privkey, node_2_privkey, &secp_ctx);
+               let short_channel_id = valid_channel_announcement.contents.short_channel_id;
+               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 valid_channel_update = get_signed_channel_update(|_| {}, node_1_privkey, &secp_ctx);
+               assert!(net_graph_msg_handler.handle_channel_update(&valid_channel_update).is_ok());
+               assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_some());
+
+               network_graph.remove_stale_channels_with_time(100 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS);
+               assert_eq!(network_graph.read_only().channels().len(), 1);
+               assert_eq!(network_graph.read_only().nodes().len(), 2);
+
+               network_graph.remove_stale_channels_with_time(101 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS);
+               #[cfg(feature = "std")]
                {
-                       net_graph_msg_handler.handle_event(&Event::PaymentPathFailed {
-                               payment_id: None,
-                               payment_hash: PaymentHash([0; 32]),
-                               rejected_by_dest: false,
-                               all_paths_failed: true,
-                               path: vec![],
-                               network_update: Some(NetworkUpdate::ChannelClosed {
-                                       short_channel_id,
-                                       is_permanent: true,
-                               }),
-                               short_channel_id: None,
-                               retry: None,
-                               error_code: None,
-                               error_data: None,
-                       });
+                       // In std mode, a further check is performed before fully removing the channel -
+                       // the channel_announcement must have been received at least two weeks ago. We
+                       // fudge that here by indicating the time has jumped two weeks. Note that the
+                       // directional channel information will have been removed already..
+                       assert_eq!(network_graph.read_only().channels().len(), 1);
+                       assert_eq!(network_graph.read_only().nodes().len(), 2);
+                       assert!(network_graph.read_only().channels().get(&short_channel_id).unwrap().one_to_two.is_none());
 
-                       assert_eq!(network_graph.read_only().channels().len(), 0);
-                       // Nodes are also deleted because there are no associated channels anymore
-                       assert_eq!(network_graph.read_only().nodes().len(), 0);
+                       use std::time::{SystemTime, UNIX_EPOCH};
+                       let announcement_time = SystemTime::now().duration_since(UNIX_EPOCH).expect("Time must be > 1970").as_secs();
+                       network_graph.remove_stale_channels_with_time(announcement_time + 1 + STALE_CHANNEL_UPDATE_AGE_LIMIT_SECS);
                }
-               // TODO: Test NetworkUpdate::NodeFailure, which is not implemented yet.
+
+               assert_eq!(network_graph.read_only().channels().len(), 0);
+               assert_eq!(network_graph.read_only().nodes().len(), 0);
        }
 
        #[test]