Merge pull request #7153 from carlaKC/7093-custommessage

multi: Add ability to handle protocol-range messages in Custom Message APIs

config.go

@@ -39,6 +39,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/signrpc"
 	"github.com/lightningnetwork/lnd/lnwallet"
+	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing"
 	"github.com/lightningnetwork/lnd/signal"
 	"github.com/lightningnetwork/lnd/sweep"
@@ -1656,6 +1657,17 @@ func ValidateConfig(cfg Config, interceptor signal.Interceptor, fileParser,
 			lncfg.DefaultIncomingBroadcastDelta)
 	}
 
+	// If the experimental protocol options specify any protocol messages
+	// that we want to handle as custom messages, set them now.
+	//nolint:lll
+	customMsg := cfg.ProtocolOptions.ExperimentalProtocol.CustomMessageOverrides()
+
+	// We can safely set our custom override values during startup because
+	// startup is blocked on config parsing.
+	if err := lnwire.SetCustomOverrides(customMsg); err != nil {
+		return nil, mkErr("custom-message: %v", err)
+	}
+
 	// Validate the subconfigs for workers, caches, and the tower client.
 	err = lncfg.Validate(
 		cfg.Workers,

docs/release-notes/release-notes-0.16.0.md

@@ -92,6 +92,11 @@ current gossip sync query status.
 * [Ensure that closing addresses match the node network for `OpenChannel` 
   requests](https://github.com/lightningnetwork/lnd/pull/7272)
 
+* The `SendCustomMessage` and `SubscribeCustomMessage` APIs can now be used to
+  send and receive custom messages below the custom range if lnd is built with
+  the `dev` tag, and configured to [opt into overriding a specific message 
+  type](https://github.com/lightningnetwork/lnd/pull/7153)
+
 ## Wallet
 
 * [Allows Taproot public keys and tap scripts to be imported as watch-only

lncfg/protocol_experimental_off.go

@@ -7,3 +7,9 @@ package lncfg
 // features that also require a build-tag to activate.
 type ExperimentalProtocol struct {
 }
+
+// CustomMessageOverrides returns the set of protocol messages that we override
+// to allow custom handling.
+func (p ExperimentalProtocol) CustomMessageOverrides() []uint16 {
+	return nil
+}

lncfg/protocol_experimental_on.go

@@ -5,5 +5,14 @@ package lncfg
 
 // ExperimentalProtocol is a sub-config that houses any experimental protocol
 // features that also require a build-tag to activate.
+//
+//nolint:lll
 type ExperimentalProtocol struct {
+	CustomMessage []uint16 `long:"custom-message" description:"allows the custom message apis to send and report messages with the protocol number provided that fall outside of the custom message number range."`
+}
+
+// CustomMessageOverrides returns the set of protocol messages that we override
+// to allow custom handling.
+func (p ExperimentalProtocol) CustomMessageOverrides() []uint16 {
+	return p.CustomMessage
 }

lnrpc/lightning.pb.go

@@ -1517,6 +1517,9 @@ type SendCustomMessageRequest struct {
 	// Peer to send the message to
 	Peer []byte `protobuf:"bytes,1,opt,name=peer,proto3" json:"peer,omitempty"`
 	// Message type. This value needs to be in the custom range (>= 32768).
+	// To send a type < custom range, lnd needs to be compiled with the `dev`
+	// build tag, and the message type to override should be specified in lnd's
+	// experimental protocol configuration.
 	Type uint32 `protobuf:"varint,2,opt,name=type,proto3" json:"type,omitempty"`
 	// Raw message data.
 	Data []byte `protobuf:"bytes,3,opt,name=data,proto3" json:"data,omitempty"`

lnrpc/lightning.proto

@@ -567,6 +567,10 @@ service Lightning {
     /* lncli: `subscribecustom`
     SubscribeCustomMessages subscribes to a stream of incoming custom peer
     messages.
+
+    To include messages with type outside of the custom range (>= 32768) lnd
+    needs to be compiled with  the `dev` build tag, and the message type to
+    override should be specified in lnd's experimental protocol configuration.
     */
     rpc SubscribeCustomMessages (SubscribeCustomMessagesRequest)
         returns (stream CustomMessage);
@@ -612,6 +616,9 @@ message SendCustomMessageRequest {
     bytes peer = 1;
 
     // Message type. This value needs to be in the custom range (>= 32768).
+    // To send a type < custom range, lnd needs to be compiled with the `dev`
+    // build tag, and the message type to override should be specified in lnd's
+    // experimental protocol configuration.
     uint32 type = 2;
 
     // Raw message data.

lnrpc/lightning.swagger.json

@@ -918,6 +918,7 @@
     "/v1/custommessage/subscribe": {
       "get": {
         "summary": "lncli: `subscribecustom`\nSubscribeCustomMessages subscribes to a stream of incoming custom peer\nmessages.",
+        "description": "To include messages with type outside of the custom range (\u003e= 32768) lnd\nneeds to be compiled with  the `dev` build tag, and the message type to\noverride should be specified in lnd's experimental protocol configuration.",
         "operationId": "Lightning_SubscribeCustomMessages",
         "responses": {
           "200": {
@@ -6616,7 +6617,7 @@
         "type": {
           "type": "integer",
           "format": "int64",
-          "description": "Message type. This value needs to be in the custom range (\u003e= 32768)."
+          "description": "Message type. This value needs to be in the custom range (\u003e= 32768).\nTo send a type \u003c custom range, lnd needs to be compiled with the `dev`\nbuild tag, and the message type to override should be specified in lnd's\nexperimental protocol configuration."
         },
         "data": {
           "type": "string",

lnrpc/lightning_grpc.pb.go

@@ -392,6 +392,10 @@ type LightningClient interface {
 	// lncli: `subscribecustom`
 	// SubscribeCustomMessages subscribes to a stream of incoming custom peer
 	// messages.
+	//
+	// To include messages with type outside of the custom range (>= 32768) lnd
+	// needs to be compiled with  the `dev` build tag, and the message type to
+	// override should be specified in lnd's experimental protocol configuration.
 	SubscribeCustomMessages(ctx context.Context, in *SubscribeCustomMessagesRequest, opts ...grpc.CallOption) (Lightning_SubscribeCustomMessagesClient, error)
 	// lncli: `listaliases`
 	// ListAliases returns the set of all aliases that have ever existed with
@@ -1687,6 +1691,10 @@ type LightningServer interface {
 	// lncli: `subscribecustom`
 	// SubscribeCustomMessages subscribes to a stream of incoming custom peer
 	// messages.
+	//
+	// To include messages with type outside of the custom range (>= 32768) lnd
+	// needs to be compiled with  the `dev` build tag, and the message type to
+	// override should be specified in lnd's experimental protocol configuration.
 	SubscribeCustomMessages(*SubscribeCustomMessagesRequest, Lightning_SubscribeCustomMessagesServer) error
 	// lncli: `listaliases`
 	// ListAliases returns the set of all aliases that have ever existed with

lntest/itest/lnd_custom_message.go

@@ -0,0 +1,188 @@
+package itest
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/stretchr/testify/require"
+)
+
+// testCustomMessage tests sending and receiving of overridden custom message
+// types (within the message type range usually reserved for protocol messages)
+// via the send and subscribe custom message APIs.
+func testCustomMessage(net *lntest.NetworkHarness, t *harnessTest) {
+	ctx, cancel := context.WithCancel(context.Background())
+	var wg sync.WaitGroup
+
+	// At the end of our test, cancel our context and wait for all
+	// goroutines to exit.
+	defer func() {
+		cancel()
+		wg.Wait()
+	}()
+
+	var (
+		overrideType1  uint32 = 554
+		overrideType2  uint32 = 555
+		msgOverrideArg        = "--protocol.custom-message=%v"
+	)
+
+	// Update Alice to accept custom protocol messages with type 1 but do
+	// not allow Bob to handle them yet.
+	net.Alice.Cfg.ExtraArgs = append(
+		net.Alice.Cfg.ExtraArgs,
+		fmt.Sprintf(msgOverrideArg, overrideType1),
+	)
+	require.NoError(t.t, net.RestartNode(net.Alice, nil, nil))
+
+	// Wait for Alice's server to be active after the restart before we
+	// try to subscribe to our message stream.
+	require.NoError(t.t, net.Alice.WaitUntilServerActive())
+
+	// Subscribe Alice to custom messages before we send any, so that we
+	// don't miss any.
+	msgClient, err := net.Alice.LightningClient.SubscribeCustomMessages(
+		ctx, &lnrpc.SubscribeCustomMessagesRequest{},
+	)
+	require.NoError(t.t, err, "alice could not subscribe")
+
+	// Create a channel to receive custom messages on.
+	messages := make(chan *lnrpc.CustomMessage)
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			// If we fail to receive, just exit. The test should
+			// fail elsewhere if it doesn't get a message that it
+			// was expecting.
+			msg, err := msgClient.Recv()
+			if err != nil {
+				return
+			}
+
+			// Deliver the message into our channel or exit if the
+			// test is shutting down.
+			select {
+			case messages <- msg:
+			case <-ctx.Done():
+				return
+			}
+		}
+	}()
+
+	// Connect alice and bob so that they can exchange messages.
+	net.EnsureConnected(t.t, net.Alice, net.Bob)
+
+	// Create a custom message that is within our allowed range.
+	msgType := uint32(lnwire.CustomTypeStart + 1)
+	msgData := []byte{1, 2, 3}
+
+	// Send it from Bob to Alice.
+	ctxt, _ := context.WithTimeout(ctx, defaultTimeout)
+	_, err = net.Bob.LightningClient.SendCustomMessage(
+		ctxt, &lnrpc.SendCustomMessageRequest{
+			Peer: net.Alice.PubKey[:],
+			Type: msgType,
+			Data: msgData,
+		},
+	)
+	require.NoError(t.t, err, "bob could not send")
+
+	// Wait for Alice to receive the message. It should come through because
+	// it is within our allowed range.
+	select {
+	case msg := <-messages:
+		// Check our type and data and (sanity) check the peer we got it
+		// from.
+		require.Equal(t.t, msgType, msg.Type, "first msg type wrong")
+		require.Equal(t.t, msgData, msg.Data, "first msg data wrong")
+		require.Equal(t.t, net.Bob.PubKey[:], msg.Peer, "first msg "+
+			"peer wrong")
+
+	case <-time.After(defaultTimeout):
+		t.t.Fatalf("alice did not receive first custom message: %v",
+			msgType)
+	}
+
+	// Try to send a message from Bob to Alice which has a message type
+	// outside of the custom type range and assert that it fails.
+	ctxt, _ = context.WithTimeout(ctx, defaultTimeout)
+	_, err = net.Bob.LightningClient.SendCustomMessage(
+		ctxt, &lnrpc.SendCustomMessageRequest{
+			Peer: net.Alice.PubKey[:],
+			Type: overrideType1,
+			Data: msgData,
+		},
+	)
+	require.Error(t.t, err, "bob should not be able to send type 1")
+
+	// Now, restart Bob with the ability to send two different custom
+	// protocol messages.
+	net.Bob.Cfg.ExtraArgs = append(
+		net.Bob.Cfg.ExtraArgs,
+		fmt.Sprintf(msgOverrideArg, overrideType1),
+		fmt.Sprintf(msgOverrideArg, overrideType2),
+	)
+	require.NoError(t.t, net.RestartNode(net.Bob, nil, nil))
+
+	// Make sure Bob and Alice are connected after his restart.
+	net.EnsureConnected(t.t, net.Alice, net.Bob)
+
+	// Send a message from Bob to Alice with a type that Bob is allowed to
+	// send, but Alice will not handle as a custom message.
+	ctxt, _ = context.WithTimeout(ctx, defaultTimeout)
+	_, err = net.Bob.LightningClient.SendCustomMessage(
+		ctxt, &lnrpc.SendCustomMessageRequest{
+			Peer: net.Alice.PubKey[:],
+			Type: overrideType2,
+			Data: msgData,
+		},
+	)
+	require.NoError(t.t, err, "bob should be able to send type 2")
+
+	// Do a quick check that Alice did not receive this message in her
+	// stream. Note that this is an instant check, so could miss the message
+	// being received. We'll also check below that she didn't get it, this
+	// is just a sanity check.
+	select {
+	case msg := <-messages:
+		t.t.Fatalf("unexpected message: %v", msg)
+	default:
+	}
+
+	// Finally, send a custom message with a type that Bob is allowed to
+	// send and Alice is configured to receive.
+	ctxt, _ = context.WithTimeout(ctx, defaultTimeout)
+	_, err = net.Bob.LightningClient.SendCustomMessage(
+		ctxt, &lnrpc.SendCustomMessageRequest{
+			Peer: net.Alice.PubKey[:],
+			Type: overrideType1,
+			Data: msgData,
+		},
+	)
+	require.NoError(t.t, err, "bob should be able to send type 1")
+
+	// Wait to receive a message from Bob. This check serves to ensure that
+	// our message type 1 was delivered, and assert that the preceding one
+	// was not (we could have missed it in our check above). When we receive
+	// the second message, we know that the first one did not go through,
+	// because we expect our messages to deliver in order.
+	select {
+	case msg := <-messages:
+		// Check our type and data and (sanity) check the peer we got it
+		// from.
+		require.Equal(t.t, overrideType1, msg.Type, "second message "+
+			"type")
+		require.Equal(t.t, msgData, msg.Data, "second message data")
+		require.Equal(t.t, net.Bob.PubKey[:], msg.Peer, "second "+
+			"message peer")
+
+	case <-time.After(defaultTimeout):
+		t.t.Fatalf("alice did not receive second custom message")
+	}
+}

lntest/itest/lnd_test_list_on_test.go

@@ -274,4 +274,8 @@ var allTestCases = []*testCase{
 		name: "open channel fee policy",
 		test: testOpenChannelUpdateFeePolicy,
 	},
+	{
+		name: "custom messaging",
+		test: testCustomMessage,
+	},
 }

lnwire/custom.go

@@ -2,13 +2,66 @@ package lnwire
 
 import (
 	"bytes"
-	"errors"
+	"fmt"
 	"io"
+	"sync"
 )
 
 // CustomTypeStart is the start of the custom type range for peer messages as
 // defined in BOLT 01.
-var CustomTypeStart MessageType = 32768
+const CustomTypeStart MessageType = 32768
+
+var (
+	// customTypeOverride contains a set of message types < CustomTypeStart
+	// that lnd allows to be treated as custom messages. This allows us to
+	// override messages reserved for the protocol level and treat them as
+	// custom messages. This set of message types is stored as a global so
+	// that we do not need to pass around state when accounting for this
+	// set of messages in message creation.
+	//
+	// Note: This global is protected by the customTypeOverride mutex.
+	customTypeOverride map[MessageType]struct{}
+
+	// customTypeOverrideMtx manages concurrent access to
+	// customTypeOverride.
+	customTypeOverrideMtx sync.RWMutex
+)
+
+// SetCustomOverrides validates that the set of override types are outside of
+// the custom message range (there's no reason to override messages that are
+// already within the range), and updates the customTypeOverride global to hold
+// this set of message types. Note that this function will completely overwrite
+// the set of overrides, so should be called with the full set of types.
+func SetCustomOverrides(overrideTypes []uint16) error {
+	customTypeOverrideMtx.Lock()
+	defer customTypeOverrideMtx.Unlock()
+
+	customTypeOverride = make(map[MessageType]struct{}, len(overrideTypes))
+
+	for _, t := range overrideTypes {
+		msgType := MessageType(t)
+
+		if msgType >= CustomTypeStart {
+			return fmt.Errorf("can't override type: %v, already "+
+				"in custom range", t)
+		}
+
+		customTypeOverride[msgType] = struct{}{}
+	}
+
+	return nil
+}
+
+// IsCustomOverride returns a bool indicating whether the message type is one
+// of the protocol messages that we override for custom use.
+func IsCustomOverride(t MessageType) bool {
+	customTypeOverrideMtx.RLock()
+	defer customTypeOverrideMtx.RUnlock()
+
+	_, ok := customTypeOverride[t]
+
+	return ok
+}
 
 // Custom represents an application-defined wire message.
 type Custom struct {
@@ -20,10 +73,11 @@ type Custom struct {
 // interface.
 var _ Message = (*Custom)(nil)
 
-// NewCustom instanties a new custom message.
+// NewCustom instantiates a new custom message.
 func NewCustom(msgType MessageType, data []byte) (*Custom, error) {
-	if msgType < CustomTypeStart {
-		return nil, errors.New("msg type not in custom range")
+	if msgType < CustomTypeStart && !IsCustomOverride(msgType) {
+		return nil, fmt.Errorf("msg type: %d not in custom range: %v "+
+			"and not overridden", msgType, CustomTypeStart)
 	}
 
 	return &Custom{

lnwire/message.go

@@ -237,9 +237,16 @@ func makeEmptyMessage(msgType MessageType) (Message, error) {
 	case MsgGossipTimestampRange:
 		msg = &GossipTimestampRange{}
 	default:
-		if msgType < CustomTypeStart {
+		// If the message is not within our custom range and has not
+		// specifically been overridden, return an unknown message.
+		//
+		// Note that we do not allow custom message overrides to replace
+		// known message types, only protocol messages that are not yet
+		// known to lnd.
+		if msgType < CustomTypeStart && !IsCustomOverride(msgType) {
 			return nil, &UnknownMessage{msgType}
 		}
+
 		msg = &Custom{
 			Type: msgType,
 		}