Merge pull request #5346 from joostjager/custom-messages

lnrpc+peer: custom peer messages

cmd/lncli/cmd_custom.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"encoding/hex"
+	"fmt"
+
+	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/urfave/cli"
+)
+
+var sendCustomCommand = cli.Command{
+	Name: "sendcustom",
+	Flags: []cli.Flag{
+		cli.StringFlag{
+			Name: "peer",
+		},
+		cli.Uint64Flag{
+			Name: "type",
+		},
+		cli.StringFlag{
+			Name: "data",
+		},
+	},
+	Action: actionDecorator(sendCustom),
+}
+
+func sendCustom(ctx *cli.Context) error {
+	ctxc := getContext()
+	client, cleanUp := getClient(ctx)
+	defer cleanUp()
+
+	peer, err := hex.DecodeString(ctx.String("peer"))
+	if err != nil {
+		return err
+	}
+
+	msgType := ctx.Uint64("type")
+
+	data, err := hex.DecodeString(ctx.String("data"))
+	if err != nil {
+		return err
+	}
+
+	_, err = client.SendCustomMessage(
+		ctxc,
+		&lnrpc.SendCustomMessageRequest{
+			Peer: peer,
+			Type: uint32(msgType),
+			Data: data,
+		},
+	)
+
+	return err
+}
+
+var subscribeCustomCommand = cli.Command{
+	Name:   "subscribecustom",
+	Action: actionDecorator(subscribeCustom),
+}
+
+func subscribeCustom(ctx *cli.Context) error {
+	ctxc := getContext()
+	client, cleanUp := getClient(ctx)
+	defer cleanUp()
+
+	stream, err := client.SubscribeCustomMessages(
+		ctxc,
+		&lnrpc.SubscribeCustomMessagesRequest{},
+	)
+	if err != nil {
+		return err
+	}
+
+	for {
+		msg, err := stream.Recv()
+		if err != nil {
+			return err
+		}
+
+		fmt.Printf("Received from peer %x: type=%d, data=%x\n",
+			msg.Peer, msg.Type, msg.Data)
+	}
+}

cmd/lncli/main.go

@@ -385,6 +385,8 @@ func main() {
 		profileSubCommand,
 		getStateCommand,
 		deletePaymentsCommand,
+		sendCustomCommand,
+		subscribeCustomCommand,
 	}
 
 	// Add any extra commands determined by build flags.

docs/release-notes/release-notes-0.14.0.md

@@ -212,7 +212,23 @@ If you use a strange system or changed group membership of the group running LND
 you may want to check your system to see if it introduces additional risk for
 you.
 
-## Safety
+## Custom peer messages
+
+Lightning nodes have a connection to each of their peers for exchanging
+messages. In regular operation, these messages coordinate processes such as
+channel opening and payment forwarding.
+
+The lightning spec however also defines a custom range (>= 32768) for
+experimental and application-specific peer messages.
+
+With this release, [custom peer message
+exchange](https://github.com/lightningnetwork/lnd/pull/5346) is added to open up
+a range of new possibilities. Custom peer messages allow the lightning protocol
+with its transport mechanisms (including tor) and public key authentication to
+be leveraged for application-level communication. Note that peers exchange these
+messages directly. There is no routing/path finding involved.
+
+# Safety
 
 * Locally force closed channels are now [kept in the channel.backup file until
   their time lock has fully matured](https://github.com/lightningnetwork/lnd/pull/5528).
@@ -511,6 +527,7 @@ change](https://github.com/lightningnetwork/lnd/pull/5613).
 * Hampus Sjöberg
 * Harsha Goli
 * Jesse de Wit
+* Joost Jager
 * Martin Habovstiak
 * Naveen Srinivasan
 * Oliver Gugger