watchtower/wtwire/features: add watchtower feature bits

watchtower/wtwire/features.go

@@ -0,0 +1,26 @@
+package wtwire
+
+import "github.com/lightningnetwork/lnd/lnwire"
+
+// GlobalFeatures holds the globally advertised feature bits understood by
+// watchtower implementations.
+var GlobalFeatures map[lnwire.FeatureBit]string
+
+// LocalFeatures holds the locally advertised feature bits understood by
+// watchtower implementations.
+var LocalFeatures = map[lnwire.FeatureBit]string{
+	WtSessionsRequired: "wt-sessions-required",
+	WtSessionsOptional: "wt-sessions-optional",
+}
+
+const (
+	// WtSessionsRequired specifies that the advertising node requires the
+	// remote party to understand the protocol for creating and updating
+	// watchtower sessions.
+	WtSessionsRequired lnwire.FeatureBit = 8
+
+	// WtSessionsOptional specifies that the advertising node can support
+	// a remote party who understand the protocol for creating and updating
+	// watchtower sessions.
+	WtSessionsOptional lnwire.FeatureBit = 9
+)