Do not fail to apply RGS updates for removed channels

If we receive a Rapid Gossip Sync update for channels where we are
missing the existing channel data, we should ignore the missing
channel. This can happen in a number of cases, whether because we
received updated channel information via an onion error from an
HTLC failure or because we've partially synced the graph from a
peer over the standard lightning P2P protocol.

diff --git a/lightning-rapid-gossip-sync/src/processing.rs b/lightning-rapid-gossip-sync/src/processing.rs
index 4b6de04c6556a5ef302d4dced78f1b833f5e5380..f1072e26be1dc6c1c9078afc31bfa9f55d0f5707 100644 (file)
--- a/lightning-rapid-gossip-sync/src/processing.rs
+++ b/lightning-rapid-gossip-sync/src/processing.rs
@@ -169,23 +169,15 @@ impl<NG: Deref<Target=NetworkGraph<L>>, L: Deref> RapidGossipSync<NG, L> where L
                        if (channel_flags & 0b_1000_0000) != 0 {
                                // incremental update, field flags will indicate mutated values
                                let read_only_network_graph = network_graph.read_only();
-                               if let Some(channel) = read_only_network_graph
-                                       .channels()
-                                       .get(&short_channel_id) {
-
-                                       let directional_info = channel
-                                               .get_directional_info(channel_flags)
-                                               .ok_or(LightningError {
-                                                       err: "Couldn't find previous directional data for update".to_owned(),
-                                                       action: ErrorAction::IgnoreError,
-                                               })?;
-
+                               if let Some(directional_info) =
+                                       read_only_network_graph.channels().get(&short_channel_id)
+                                       .and_then(|channel| channel.get_directional_info(channel_flags))
+                               {
                                        synthetic_update.cltv_expiry_delta = directional_info.cltv_expiry_delta;
                                        synthetic_update.htlc_minimum_msat = directional_info.htlc_minimum_msat;
                                        synthetic_update.htlc_maximum_msat = directional_info.htlc_maximum_msat;
                                        synthetic_update.fee_base_msat = directional_info.fees.base_msat;
                                        synthetic_update.fee_proportional_millionths = directional_info.fees.proportional_millionths;
-
                                } else {
                                        skip_update_for_unknown_channel = true;
                                }
@@ -341,16 +333,7 @@ mod tests {
                assert_eq!(network_graph.read_only().channels().len(), 0);
 
                let rapid_sync = RapidGossipSync::new(&network_graph);
-               let update_result = rapid_sync.update_network_graph(&announced_update_input[..]);
-               assert!(update_result.is_err());
-               if let Err(GraphSyncError::LightningError(lightning_error)) = update_result {
-                       assert_eq!(
-                               lightning_error.err,
-                               "Couldn't find previous directional data for update"
-                       );
-               } else {
-                       panic!("Unexpected update result: {:?}", update_result)
-               }
+               rapid_sync.update_network_graph(&announced_update_input[..]).unwrap();
        }
 
        #[test]
@@ -405,16 +388,7 @@ mod tests {
                        0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 8, 153, 192, 0, 2, 27, 0, 0, 136, 0, 0, 0, 221, 255, 2,
                        68, 226, 0, 6, 11, 0, 1, 128,
                ];
-               let update_result = rapid_sync.update_network_graph(&opposite_direction_incremental_update_input[..]);
-               assert!(update_result.is_err());
-               if let Err(GraphSyncError::LightningError(lightning_error)) = update_result {
-                       assert_eq!(
-                               lightning_error.err,
-                               "Couldn't find previous directional data for update"
-                       );
-               } else {
-                       panic!("Unexpected update result: {:?}", update_result)
-               }
+               rapid_sync.update_network_graph(&opposite_direction_incremental_update_input[..]).unwrap();
        }
 
        #[test]