watchtower/multi: send connection features + chain hash in Init

watchtower/wtwire/init.go

@@ -1,23 +1,59 @@
 package wtwire
 
-import "github.com/lightningnetwork/lnd/lnwire"
+import (
+	"io"
+
+	"github.com/btcsuite/btcd/chaincfg/chainhash"
+	"github.com/lightningnetwork/lnd/lnwire"
+)
 
 // Init is the first message sent over the watchtower wire protocol, and
-// specifies features and level of requiredness maintained by the sending node.
-// The watchtower Init message is identical to the LN Init message, except it
-// uses a different message type to ensure the two are not conflated.
+// specifies connection features bits and level of requiredness maintained by
+// the sending node. The Init message also sends the chain hash identifying the
+// network that the sender is on.
 type Init struct {
-	*lnwire.Init
+	// ConnFeatures are the feature bits being advertised for the duration
+	// of a single connection with a peer.
+	ConnFeatures *lnwire.RawFeatureVector
+
+	// ChainHash is the genesis hash of the chain that the advertiser claims
+	// to be on.
+	ChainHash chainhash.Hash
 }
 
-// NewInitMessage generates a new Init message from raw global and local feature
-// vectors.
-func NewInitMessage(gf, lf *lnwire.RawFeatureVector) *Init {
+// NewInitMessage generates a new Init message from a raw connection feature
+// vector and chain hash.
+func NewInitMessage(connFeatures *lnwire.RawFeatureVector,
+	chainHash chainhash.Hash) *Init {
+
 	return &Init{
-		Init: lnwire.NewInitMessage(gf, lf),
+		ConnFeatures: connFeatures,
+		ChainHash:    chainHash,
 	}
 }
 
+// Encode serializes the target Init into the passed io.Writer observing the
+// protocol version specified.
+//
+// This is part of the wtwire.Message interface.
+func (msg *Init) Encode(w io.Writer, pver uint32) error {
+	return WriteElements(w,
+		msg.ConnFeatures,
+		msg.ChainHash,
+	)
+}
+
+// Decode deserializes a serialized Init message stored in the passed io.Reader
+// observing the specified protocol version.
+//
+// This is part of the wtwire.Message interface.
+func (msg *Init) Decode(r io.Reader, pver uint32) error {
+	return ReadElements(r,
+		&msg.ConnFeatures,
+		&msg.ChainHash,
+	)
+}
+
 // MsgType returns the integer uniquely identifying this message type on the
 // wire.
 //
@@ -26,5 +62,13 @@ func (msg *Init) MsgType() MessageType {
 	return MsgInit
 }
 
+// MaxPayloadLength returns the maximum allowed payload size for an Init
+// complete message observing the specified protocol version.
+//
+// This is part of the wtwire.Message interface.
+func (msg *Init) MaxPayloadLength(uint32) uint32 {
+	return MaxMessagePayload
+}
+
 // A compile-time constraint to ensure Init implements the Message interface.
 var _ Message = (*Init)(nil)