link+peer: thread anchor tower client to link

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,