multi: optionally enable and signal anchor support

Defaults to disabled.

feature/default_sets.go

@@ -43,4 +43,8 @@ var defaultSetDesc = setDesc{
 		SetNodeAnn: {}, // N
 		SetInvoice: {}, // 9
 	},
+	lnwire.AnchorsOptional: {
+		SetInit:    {}, // I
+		SetNodeAnn: {}, // N
+	},
 }

feature/deps.go

@@ -55,6 +55,9 @@ var deps = depDesc{
 	lnwire.MPPOptional: {
 		lnwire.PaymentAddrOptional: {},
 	},
+	lnwire.AnchorsOptional: {
+		lnwire.StaticRemoteKeyOptional: {},
+	},
 }
 
 // ValidateDeps asserts that a feature vector sets all features and their

feature/manager.go

@@ -17,6 +17,9 @@ type Config struct {
 	// NoStaticRemoteKey unsets any optional or required StaticRemoteKey
 	// bits from all feature sets.
 	NoStaticRemoteKey bool
+
+	// NoAnchors unsets any bits signaling support for anchor outputs.
+	NoAnchors bool
 }
 
 // Manager is responsible for generating feature vectors for different requested
@@ -76,6 +79,10 @@ func newManager(cfg Config, desc setDesc) (*Manager, error) {
 			raw.Unset(lnwire.StaticRemoteKeyOptional)
 			raw.Unset(lnwire.StaticRemoteKeyRequired)
 		}
+		if cfg.NoAnchors {
+			raw.Unset(lnwire.AnchorsOptional)
+			raw.Unset(lnwire.AnchorsRequired)
+		}
 
 		// Ensure that all of our feature sets properly set any
 		// dependent features.

lncfg/protocol_legacy_off.go

@@ -15,8 +15,14 @@ func (l *ProtocolOptions) LegacyOnion() bool {
 	return false
 }
 
-// LegacyCommitment returns true if the old commitment format should be used
-// for new funded channels.
-func (l *ProtocolOptions) LegacyCommitment() bool {
+// NoStaticRemoteKey returns true if the old commitment format with a tweaked
+// remote key should be used for new funded channels.
+func (l *ProtocolOptions) NoStaticRemoteKey() bool {
+	return false
+}
+
+// AnchorCommitments returns true if support for the the anchor commitment type
+// should be signaled.
+func (l *ProtocolOptions) AnchorCommitments() bool {
 	return false
 }

lncfg/protocol_legacy_on.go

@@ -16,6 +16,10 @@ type ProtocolOptions struct {
 	// remote party's output in the commitment. If set to true, then we
 	// won't signal StaticRemoteKeyOptional.
 	CommitmentTweak bool `long:"committweak" description:"force node to not advertise the new commitment format"`
+
+	// Anchors should be set if we want to support opening or accepting
+	// channels having the anchor commitment type.
+	Anchors bool `long:"anchors" description:"EXPERIMENTAL: enable experimental support for anchor commitments. Won't work with watchtowers or static channel backups"`
 }
 
 // LegacyOnion returns true if the old legacy onion format should be used when
@@ -25,8 +29,14 @@ func (l *ProtocolOptions) LegacyOnion() bool {
 	return l.LegacyOnionFormat
 }
 
-// LegacyCommitment returns true if the old commitment format should be used
-// for new funded channels.
-func (l *ProtocolOptions) LegacyCommitment() bool {
+// NoStaticRemoteKey returns true if the old commitment format with a tweaked
+// remote key should be used for new funded channels.
+func (l *ProtocolOptions) NoStaticRemoteKey() bool {
 	return l.CommitmentTweak
 }
+
+// AnchorCommitments returns true if support for the the anchor commitment type
+// should be signaled.
+func (l *ProtocolOptions) AnchorCommitments() bool {
+	return l.Anchors
+}

lnwire/features.go

@@ -101,6 +101,16 @@ const (
 	// HTLC.
 	MPPOptional FeatureBit = 17
 
+	// AnchorsRequired is a required feature bit that signals that the node
+	// requires channels to be made using commitments having anchor
+	// outputs.
+	AnchorsRequired FeatureBit = 1336
+
+	// AnchorsRequired is an optional feature bit that signals that the
+	// node supports channels to be made using commitments having anchor
+	// outputs.
+	AnchorsOptional FeatureBit = 1337
+
 	// maxAllowedSize is a maximum allowed size of feature vector.
 	//
 	// NOTE: Within the protocol, the maximum allowed message size is 65535
@@ -138,6 +148,8 @@ var Features = map[FeatureBit]string{
 	PaymentAddrRequired:           "payment-addr",
 	MPPOptional:                   "multi-path-payments",
 	MPPRequired:                   "multi-path-payments",
+	AnchorsRequired:               "anchor-commitments",
+	AnchorsOptional:               "anchor-commitments",
 }
 
 // RawFeatureVector represents a set of feature bits as defined in BOLT-09.  A

server.go

@@ -340,12 +340,19 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 		globalFeatures.Set(lnwire.TLVOnionPayloadOptional)
 	}
 
-	// Similarly, we default to the new modern commitment format unless the
-	// legacy commitment config is set to true.
-	if !cfg.ProtocolOptions.LegacyCommitment() {
+	// Similarly, we default to supporting the new modern commitment format
+	// where the remote key is static unless the protocol config is set to
+	// keep using the older format.
+	if !cfg.ProtocolOptions.NoStaticRemoteKey() {
 		globalFeatures.Set(lnwire.StaticRemoteKeyOptional)
 	}
 
+	// We only signal that we support the experimental anchor commitments
+	// if explicitly enabled in the config.
+	if cfg.ProtocolOptions.AnchorCommitments() {
+		globalFeatures.Set(lnwire.AnchorsOptional)
+	}
+
 	var serializedPubKey [33]byte
 	copy(serializedPubKey[:], privKey.PubKey().SerializeCompressed())
 
@@ -376,7 +383,8 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 
 	featureMgr, err := feature.NewManager(feature.Config{
 		NoTLVOnion:        cfg.ProtocolOptions.LegacyOnion(),
-		NoStaticRemoteKey: cfg.ProtocolOptions.LegacyCommitment(),
+		NoStaticRemoteKey: cfg.ProtocolOptions.NoStaticRemoteKey(),
+		NoAnchors:         !cfg.ProtocolOptions.AnchorCommitments(),
 	})
 	if err != nil {
 		return nil, err