htlcswitch/link: fix UpdateShortChanID

htlcswitch/link.go

@@ -32,9 +32,14 @@ const (
 	expiryGraceDelta = 2
 )
 
-// ErrInternalLinkFailure is a generic error returned to the remote party so as
+var (
-// to obfuscate the true failure.
+	// ErrInternalLinkFailure is a generic error returned to the remote
-var ErrInternalLinkFailure = errors.New("internal link failure")
+	// party so as to obfuscate the true failure.
+	ErrInternalLinkFailure = errors.New("internal link failure")
+
+	// ErrLinkShuttingDown signals that the link is shutting down.
+	ErrLinkShuttingDown = errors.New("link shutting down")
+)
 
 // ForwardingPolicy describes the set of constraints that a given ChannelLink
 // is to adhere to when forwarding HTLC's. For each incoming HTLC, this set of
@@ -444,9 +449,11 @@ func (l *channelLink) Stop() {
 // EligibleToForward returns a bool indicating if the channel is able to
 // actively accept requests to forward HTLC's. We're able to forward HTLC's if
 // we know the remote party's next revocation point. Otherwise, we can't
-// initiate new channel state.
+// initiate new channel state. We also require that the short channel ID not be
+// the all-zero source ID, meaning that the channel has had its ID finalized.
 func (l *channelLink) EligibleToForward() bool {
-	return l.channel.RemoteNextRevocation() != nil
+	return l.channel.RemoteNextRevocation() != nil &&
+		l.ShortChanID() != sourceHop
 }
 
 // sampleNetworkFee samples the current fee rate on the network to get into the
@@ -603,7 +610,7 @@ func (l *channelLink) syncChanStates() error {
 		}
 
 	case <-l.quit:
-		return fmt.Errorf("shutting down")
+		return ErrLinkShuttingDown
 
 	case <-chanSyncDeadline:
 		return fmt.Errorf("didn't receive ChannelReestablish before " +
@@ -759,9 +766,12 @@ func (l *channelLink) htlcManager() {
 	// re-synchronize state with the remote peer. settledHtlcs is a map of
 	// HTLC's that we re-settled as part of the channel state sync.
 	if l.cfg.SyncStates {
-		if err := l.syncChanStates(); err != nil {
+		err := l.syncChanStates()
+		if err != nil {
 			l.errorf("unable to synchronize channel states: %v", err)
-			l.fail(err.Error())
+			if err != ErrLinkShuttingDown {
+				l.fail(err.Error())
+			}
 			return
 		}
 	}
@@ -1540,18 +1550,31 @@ func (l *channelLink) ShortChanID() lnwire.ShortChannelID {
 // within the chain.
 //
 // NOTE: Part of the ChannelLink interface.
-func (l *channelLink) UpdateShortChanID(sid lnwire.ShortChannelID) {
+func (l *channelLink) UpdateShortChanID() (lnwire.ShortChannelID, error) {
+	chanID := l.ChanID()
+
+	// Refresh the channel state's short channel ID by loading it from disk.
+	// This ensures that the channel state accurately reflects the updated
+	// short channel ID.
+	err := l.channel.State().RefreshShortChanID()
+	if err != nil {
+		l.errorf("unable to refresh short_chan_id for chan_id=%v: %v",
+			chanID, err)
+		return sourceHop, err
+	}
+
+	sid := l.channel.ShortChanID()
+
+	l.infof("Updating to short_chan_id=%v for chan_id=%v", sid, chanID)
+
 	l.Lock()
-	defer l.Unlock()
-
-	log.Infof("Updating short chan ID for ChannelPoint(%v)", l)
-
 	l.shortChanID = sid
+	l.Unlock()
 
 	go func() {
 		err := l.cfg.UpdateContractSignals(&contractcourt.ContractSignals{
 			HtlcUpdates: l.htlcUpdates,
-			ShortChanID: l.channel.ShortChanID(),
+			ShortChanID: sid,
 		})
 		if err != nil {
 			log.Errorf("Unable to update signals for "+
@@ -1559,7 +1582,7 @@ func (l *channelLink) UpdateShortChanID(sid lnwire.ShortChannelID) {
 		}
 	}()
 
-	return
+	return sid, nil
 }
 
 // ChanID returns the channel ID for the channel link. The channel ID is a more