multi: add a new func which reports all htlcs

Instead of just reporting the htlcs which are active on both
commitment transactions we introduce a function which reports
all htlcs which are either on both or on either of them.
We then use this function to decide whether we have a clean state.

channeldb/channel.go

@@ -2510,6 +2510,52 @@ func (c *OpenChannel) ActiveHtlcs() []HTLC {
 	return activeHtlcs
 }
 
+// LocalAndRemoteHtlcs returns a slice of HTLC's which are currently active on
+// both or on either commitment transactions.
+func (c *OpenChannel) LocalAndRemoteHtlcs() []HTLC {
+	c.RLock()
+	defer c.RUnlock()
+
+	activeHtlcs := make([]HTLC, 0, len(c.RemoteCommitment.Htlcs))
+
+	// We'll only return HTLC's that are locked into *both* commitment
+	// transactions. So we'll iterate through their set of HTLC's to note
+	// which ones are present on their commitment. We combine the RHash and
+	// the HTLC index to create a unique key.
+	remoteHtlcs := make(map[[32 + 8]byte]struct{})
+	var htlcKey [32 + 8]byte
+	for _, htlc := range c.RemoteCommitment.Htlcs {
+		log.Tracef("RemoteCommitment has htlc: id=%v, update=%v "+
+			"incoming=%v", htlc.HtlcIndex, htlc.LogIndex,
+			htlc.Incoming)
+
+		copy(htlcKey[:32], htlc.RHash[:])
+		binary.BigEndian.PutUint64(htlcKey[32:], htlc.HtlcIndex)
+		remoteHtlcs[htlcKey] = struct{}{}
+		activeHtlcs = append(activeHtlcs, htlc)
+	}
+
+	// Now that we know which HTLC's they have, we'll only mark the HTLC's
+	// as active if *we* know them as well.
+	for _, htlc := range c.LocalCommitment.Htlcs {
+		log.Tracef("LocalCommitment has htlc: id=%v, update=%v "+
+			"incoming=%v", htlc.HtlcIndex, htlc.LogIndex,
+			htlc.Incoming)
+
+		copy(htlcKey[:32], htlc.RHash[:])
+		binary.BigEndian.PutUint64(htlcKey[32:], htlc.HtlcIndex)
+		// We skip the htlcs which are already part of the remote set to
+		// not have duplicates.
+		if _, ok := remoteHtlcs[htlcKey]; ok {
+			continue
+		}
+
+		activeHtlcs = append(activeHtlcs, htlc)
+	}
+
+	return activeHtlcs
+}
+
 // HTLC is the on-disk representation of a hash time-locked contract. HTLCs are
 // contained within ChannelDeltas which encode the current state of the
 // commitment between state updates.

lnwallet/channel.go

@@ -5403,7 +5403,7 @@ func (lc *LightningChannel) IsChannelClean() bool {
 
 	// We call ActiveHtlcs to ensure there are no HTLCs on either
 	// commitment.
-	if len(lc.channelState.ActiveHtlcs()) != 0 {
+	if len(lc.channelState.LocalAndRemoteHtlcs()) != 0 {
 		return false
 	}
 

rpcserver.go

@@ -2811,7 +2811,7 @@ func (r *rpcServer) CloseChannel(in *lnrpc.CloseChannelRequest,
 		// If the user hasn't specified NoWait, then before we attempt
 		// to close the channel we ensure there are no active HTLCs on
 		// the link.
-		if !in.NoWait && len(channel.ActiveHtlcs()) != 0 {
+		if !in.NoWait && len(channel.LocalAndRemoteHtlcs()) != 0 {
 			return fmt.Errorf("cannot co-op close channel " +
 				"with active htlcs")
 		}