lnwallet: handle nonce init in ProcessChanSyncMsg

In this commit, we update the logic to handle nonce init in
ProcessChanSyncMsg. Once a channel is already open, this is where we'll
get the new nonce data from the remote party we'll use to gain the nonce
we need to sign for their next state.

htlcswitch/link.go

@@ -660,7 +660,6 @@ func (l *channelLink) syncChanStates() error {
 		return fmt.Errorf("unable to generate chan sync message for "+
 			"ChannelPoint(%v)", l.channel.ChannelPoint())
 	}
-
 	if err := l.cfg.Peer.SendMessage(true, localChanSyncMsg); err != nil {
 		return fmt.Errorf("unable to send chan sync message for "+
 			"ChannelPoint(%v): %v", l.channel.ChannelPoint(), err)
@@ -703,6 +702,13 @@ func (l *channelLink) syncChanStates() error {
 				l.ChanID(), nextRevocation,
 			)
 
+			// If this is a taproot channel, then we'll send the
+			// very same nonce that we sent above, as they should
+			// take the latest verification nonce we send.
+			if chanState.ChanType.IsTaproot() {
+				fundingLockedMsg.NextLocalNonce = localChanSyncMsg.LocalNonce
+			}
+
 			// For channels that negotiated the option-scid-alias
 			// feature bit, ensure that we send over the alias in
 			// the channel_ready message. We'll send the first
@@ -1900,8 +1906,8 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 		// chain, validate this new commitment, closing the link if
 		// invalid.
 		err = l.channel.ReceiveNewCommitment(&lnwallet.CommitSigs{
-			CommitSig:  msg.CommitSig,
-			HtlcSigs:   msg.HtlcSigs,
+			CommitSig: msg.CommitSig,
+			HtlcSigs:  msg.HtlcSigs,
 		})
 		if err != nil {
 			// If we were unable to reconstruct their proposed
@@ -2265,9 +2271,9 @@ func (l *channelLink) updateCommitTx() error {
 	}
 
 	commitSig := &lnwire.CommitSig{
-		ChanID:     l.ChanID(),
-		CommitSig:  newCommit.CommitSig,
-		HtlcSigs:   newCommit.HtlcSigs,
+		ChanID:    l.ChanID(),
+		CommitSig: newCommit.CommitSig,
+		HtlcSigs:  newCommit.HtlcSigs,
 	}
 	l.cfg.Peer.SendMessage(false, commitSig)