discovery/gossiper: ignore remote ChannelAnnouncement for own channel

To avoid learning about our own channel we have already closed and
removed from our graph, we ignore all ChannelAnns for channels we are
involved in.

discovery/gossiper.go

@@ -542,6 +542,22 @@ func (d *AuthenticatedGossiper) ProcessRemoteAnnouncement(msg lnwire.Message,
 
 		errChan <- nil
 		return errChan
+
+	// To avoid inserting edges in the graph for our own channels that we
+	// have already closed, we ignore such channel announcements coming
+	// from the remote.
+	case *lnwire.ChannelAnnouncement:
+		ownKey := d.selfKey.SerializeCompressed()
+		ownErr := fmt.Errorf("ignoring remote ChannelAnnouncement " +
+			"for own channel")
+
+		if bytes.Equal(m.NodeID1[:], ownKey) ||
+			bytes.Equal(m.NodeID2[:], ownKey) {
+
+			log.Warn(ownErr)
+			errChan <- ownErr
+			return errChan
+		}
 	}
 
 	nMsg := &networkMsg{