From 0d0f22aacbda539fc0437ab1eb84cfd936edc613 Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Wed, 25 Nov 2020 15:06:46 -0800
Subject: [PATCH] link+peer: thread anchor tower client to link

---
 htlcswitch/link.go | 23 ++++++-----------------
 peer/brontide.go   | 20 ++++++++++++++++++--
 server.go          |  1 +
 3 files changed, 25 insertions(+), 19 deletions(-)

diff --git a/htlcswitch/link.go b/htlcswitch/link.go
index 3b0e923c..6a7c3128 100644
--- a/htlcswitch/link.go
+++ b/htlcswitch/link.go
@@ -256,7 +256,7 @@ type ChannelLinkConfig struct {
 
 	// TowerClient is an optional engine that manages the signing,
 	// encrypting, and uploading of justice transactions to the daemon's
-	// configured set of watchtowers.
+	// configured set of watchtowers for legacy channels.
 	TowerClient TowerClient
 
 	// MaxOutgoingCltvExpiry is the maximum outgoing timelock that the link
@@ -435,12 +435,7 @@ func (l *channelLink) Start() error {
 
 	// If the config supplied watchtower client, ensure the channel is
 	// registered before trying to use it during operation.
-	// TODO(halseth): support anchor types for watchtower.
-	state := l.channel.State()
-	if l.cfg.TowerClient != nil && state.ChanType.HasAnchors() {
-		l.log.Warnf("Skipping tower registration for anchor " +
-			"channel type")
-	} else if l.cfg.TowerClient != nil && !state.ChanType.HasAnchors() {
+	if l.cfg.TowerClient != nil {
 		err := l.cfg.TowerClient.RegisterChannel(l.ChanID())
 		if err != nil {
 			return err
@@ -1835,14 +1830,9 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 			return
 		}
 
-		// If we have a tower client, we'll proceed in backing up the
-		// state that was just revoked.
-		// TODO(halseth): support anchor types for watchtower.
-		state := l.channel.State()
-		if l.cfg.TowerClient != nil && state.ChanType.HasAnchors() {
-			l.log.Warnf("Skipping tower backup for anchor " +
-				"channel type")
-		} else if l.cfg.TowerClient != nil && !state.ChanType.HasAnchors() {
+		// If we have a tower client for this channel type, we'll
+		if l.cfg.TowerClient != nil {
+			state := l.channel.State()
 			breachInfo, err := lnwallet.NewBreachRetribution(
 				state, state.RemoteCommitment.CommitHeight-1, 0,
 			)
@@ -1852,10 +1842,9 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 				return
 			}
 
-			chanType := l.channel.State().ChanType
 			chanID := l.ChanID()
 			err = l.cfg.TowerClient.BackupState(
-				&chanID, breachInfo, chanType,
+				&chanID, breachInfo, state.ChanType,
 			)
 			if err != nil {
 				l.fail(LinkFailureError{code: ErrInternalError},
diff --git a/peer/brontide.go b/peer/brontide.go
index 164bbdf4..578d7133 100644
--- a/peer/brontide.go
+++ b/peer/brontide.go
@@ -248,9 +248,13 @@ type Config struct {
 	// HtlcNotifier is used when creating a ChannelLink.
 	HtlcNotifier *htlcswitch.HtlcNotifier
 
-	// TowerClient is used when creating a ChannelLink.
+	// TowerClient is used by legacy channels to backup revoked states.
 	TowerClient wtclient.Client
 
+	// AnchorTowerClient is used by anchor channels to backup revoked
+	// states.
+	AnchorTowerClient wtclient.Client
+
 	// DisconnectPeer is used to disconnect this peer if the cooperative close
 	// process fails.
 	DisconnectPeer func(*btcec.PublicKey) error
@@ -757,6 +761,18 @@ func (p *Brontide) addLink(chanPoint *wire.OutPoint,
 		return p.cfg.ChainArb.UpdateContractSignals(*chanPoint, signals)
 	}
 
+	chanType := lnChan.State().ChanType
+
+	// Select the appropriate tower client based on the channel type. It's
+	// okay if the clients are disabled altogether and these values are nil,
+	// as the link will check for nilness before using either.
+	var towerClient htlcswitch.TowerClient
+	if chanType.HasAnchors() {
+		towerClient = p.cfg.AnchorTowerClient
+	} else {
+		towerClient = p.cfg.TowerClient
+	}
+
 	linkCfg := htlcswitch.ChannelLinkConfig{
 		Peer:                    p,
 		DecodeHopIterators:      p.cfg.Sphinx.DecodeHopIterators,
@@ -782,7 +798,7 @@ func (p *Brontide) addLink(chanPoint *wire.OutPoint,
 		MinFeeUpdateTimeout:     htlcswitch.DefaultMinLinkFeeUpdateTimeout,
 		MaxFeeUpdateTimeout:     htlcswitch.DefaultMaxLinkFeeUpdateTimeout,
 		OutgoingCltvRejectDelta: p.cfg.OutgoingCltvRejectDelta,
-		TowerClient:             p.cfg.TowerClient,
+		TowerClient:             towerClient,
 		MaxOutgoingCltvExpiry:   p.cfg.MaxOutgoingCltvExpiry,
 		MaxFeeAllocation:        p.cfg.MaxChannelFeeAllocation,
 		NotifyActiveLink:        p.cfg.ChannelNotifier.NotifyActiveLinkEvent,
diff --git a/server.go b/server.go
index e725538a..c7d2f350 100644
--- a/server.go
+++ b/server.go
@@ -3077,6 +3077,7 @@ func (s *server) peerConnected(conn net.Conn, connReq *connmgr.ConnReq,
 		ChannelNotifier:         s.channelNotifier,
 		HtlcNotifier:            s.htlcNotifier,
 		TowerClient:             s.towerClient,
+		AnchorTowerClient:       s.anchorTowerClient,
 		DisconnectPeer:          s.DisconnectPeer,
 		GenNodeAnnouncement:     s.genNodeAnnouncement,