Add Experimental Endorsement Signalling

contractcourt/htlc_incoming_contest_resolver.go

@@ -103,7 +103,10 @@ func (h *htlcIncomingContestResolver) Resolve(
 	//
 	// TODO(roasbeef): Implement resolving HTLCs with custom records
 	// (follow-up PR).
-	if len(h.htlc.CustomRecords) != 0 {
+	if len(h.htlc.CustomRecords) != 0 && h.isTapscriptRoot {
+		log.Warnf("Not resolving HTLC with: %v custom records",
+			len(h.htlc.CustomRecords))
+
 		select { //nolint:gosimple
 		case <-h.quit:
 			return nil, errResolverShuttingDown

contractcourt/htlc_outgoing_contest_resolver.go

@@ -62,7 +62,10 @@ func (h *htlcOutgoingContestResolver) Resolve(
 	//
 	// TODO(roasbeef): Implement resolving HTLCs with custom records
 	// (follow-up PR).
-	if len(h.htlc.CustomRecords) != 0 {
+	if len(h.htlc.CustomRecords) != 0 && h.isTapscriptRoot {
+		log.Warnf("Not resolving HTLC with: %v custom records",
+			len(h.htlc.CustomRecords))
+
 		select { //nolint:gosimple
 		case <-h.quit:
 			return nil, errResolverShuttingDown

contractcourt/htlc_success_resolver.go

@@ -54,6 +54,12 @@ type htlcSuccessResolver struct {
 	// htlc contains information on the htlc that we are resolving on-chain.
 	htlc channeldb.HTLC
 
+	// isTapscriptRoot indicates whether the htlc is on a TapscriptRoot
+	// channel type.
+	// TODO: remove this when incoming HTLCs with custom records can be
+	// resolved for this channel type
+	isTapscriptRoot bool
+
 	// currentReport stores the current state of the resolver for reporting
 	// over the rpc interface. This should only be reported in case we have
 	// a non-nil SignDetails on the htlcResolution, otherwise the nursery
@@ -127,7 +133,10 @@ func (h *htlcSuccessResolver) Resolve(
 	//
 	// TODO(roasbeef): Implement resolving HTLCs with custom records
 	// (follow-up PR).
-	if len(h.htlc.CustomRecords) != 0 {
+	if len(h.htlc.CustomRecords) != 0 && h.isTapscriptRoot {
+		log.Warnf("Not resolving incoming htlc with %v custom records",
+			len(h.htlc.CustomRecords))
+
 		select { //nolint:gosimple
 		case <-h.quit:
 			return nil, errResolverShuttingDown
@@ -739,6 +748,17 @@ func (h *htlcSuccessResolver) HtlcPoint() wire.OutPoint {
 func (h *htlcSuccessResolver) SupplementDeadline(_ fn.Option[int32]) {
 }
 
+// SupplementState allows the user of a ContractResolver to supplement it with
+// state required for the proper resolution of a contract.
+//
+// NOTE: Part of the ContractResolver interface.
+func (h *htlcIncomingContestResolver) SupplementState(
+	state *channeldb.OpenChannel) {
+
+	h.isTapscriptRoot = state.ChanType.HasTapscriptRoot()
+	h.htlcLeaseResolver.SupplementState(state)
+}
+
 // A compile time assertion to ensure htlcSuccessResolver meets the
 // ContractResolver interface.
 var _ htlcContractResolver = (*htlcSuccessResolver)(nil)

contractcourt/htlc_timeout_resolver.go

@@ -50,6 +50,12 @@ type htlcTimeoutResolver struct {
 	// htlc contains information on the htlc that we are resolving on-chain.
 	htlc channeldb.HTLC
 
+	// isTapscriptRoot indicates whether the htlc is on a TapscriptRoot
+	// channel type.
+	// TODO: remove this when incoming HTLCs with custom records can be
+	// resolved for this channel type
+	isTapscriptRoot bool
+
 	// currentReport stores the current state of the resolver for reporting
 	// over the rpc interface. This should only be reported in case we have
 	// a non-nil SignDetails on the htlcResolution, otherwise the nursery
@@ -430,7 +436,10 @@ func (h *htlcTimeoutResolver) Resolve(
 	//
 	// TODO(roasbeef): Implement resolving HTLCs with custom records
 	// (follow-up PR).
-	if len(h.htlc.CustomRecords) != 0 {
+	if len(h.htlc.CustomRecords) != 0 && h.isTapscriptRoot {
+		log.Warnf("Not resolving incoming htlc with %v custom records",
+			len(h.htlc.CustomRecords))
+
 		select { //nolint:gosimple
 		case <-h.quit:
 			return nil, errResolverShuttingDown
@@ -1095,6 +1104,15 @@ func (h *htlcTimeoutResolver) SupplementDeadline(d fn.Option[int32]) {
 	h.incomingHTLCExpiryHeight = d
 }
 
+// SupplementState allows the user of a ContractResolver to supplement it with
+// state required for the proper resolution of a contract.
+//
+// NOTE: Part of the ContractResolver interface.
+func (h *htlcTimeoutResolver) SupplementState(state *channeldb.OpenChannel) {
+	h.isTapscriptRoot = state.ChanType.HasTapscriptRoot()
+	h.htlcLeaseResolver.SupplementState(state)
+}
+
 // A compile time assertion to ensure htlcTimeoutResolver meets the
 // ContractResolver interface.
 var _ htlcContractResolver = (*htlcTimeoutResolver)(nil)

docs/release-notes/release-notes-0.19.0.md

@@ -41,6 +41,12 @@
   cases.
 
 # New Features
+
+* [Support](https://github.com/lightningnetwork/lnd/pull/8390) for 
+  [experimental endorsement](https://github.com/lightning/blips/pull/27) 
+  signal relay was added. This signal has *no impact* on routing, and
+  is deployed experimentally to assist ongoing channel jamming research.
+
 ## Functional Enhancements
 ## RPC Additions
 
@@ -173,6 +179,7 @@
 
 * Animesh Bilthare
 * Boris Nagaev
+* Carla Kirk-Cohen
 * CharlieZKSmith
 * Elle Mouton
 * George Tsagkarelis

feature/default_sets.go

@@ -96,4 +96,7 @@ var defaultSetDesc = setDesc{
 		SetInit:    {}, // I
 		SetNodeAnn: {}, // N
 	},
+	lnwire.ExperimentalEndorsementOptional: {
+		SetNodeAnn: {}, // N
+	},
 }

feature/manager.go

@@ -66,6 +66,10 @@ type Config struct {
 	// NoTaprootOverlay unsets the taproot overlay channel feature bits.
 	NoTaprootOverlay bool
 
+	// NoExperimentalEndorsement unsets any bits that signal support for
+	// forwarding experimental endorsement.
+	NoExperimentalEndorsement bool
+
 	// CustomFeatures is a set of custom features to advertise in each
 	// set.
 	CustomFeatures map[Set][]lnwire.FeatureBit
@@ -199,6 +203,12 @@ func newManager(cfg Config, desc setDesc) (*Manager, error) {
 			raw.Unset(lnwire.SimpleTaprootOverlayChansOptional)
 			raw.Unset(lnwire.SimpleTaprootOverlayChansRequired)
 		}
+
+		if cfg.NoExperimentalEndorsement {
+			raw.Unset(lnwire.ExperimentalEndorsementOptional)
+			raw.Unset(lnwire.ExperimentalEndorsementRequired)
+		}
+
 		for _, custom := range cfg.CustomFeatures[set] {
 			if custom > set.Maximum() {
 				return nil, fmt.Errorf("feature bit: %v "+

htlcswitch/interceptable_switch.go

@@ -715,9 +715,12 @@ func (f *interceptedForward) ResumeModified(
 			htlc.Amount = amount
 		})
 
-		if len(validatedRecords) > 0 {
-			htlc.CustomRecords = validatedRecords
-		}
+		// Merge custom records with any validated records that were
+		// added in the modify request, overwriting any existing values
+		// with those supplied in the modifier API.
+		htlc.CustomRecords = htlc.CustomRecords.MergedCopy(
+			validatedRecords,
+		)
 
 	case *lnwire.UpdateFulfillHTLC:
 		if len(validatedRecords) > 0 {

htlcswitch/link.go

@@ -30,6 +30,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/queue"
+	"github.com/lightningnetwork/lnd/record"
 	"github.com/lightningnetwork/lnd/ticker"
 	"github.com/lightningnetwork/lnd/tlv"
 )
@@ -285,6 +286,10 @@ type ChannelLinkConfig struct {
 	// MaxFeeExposure is the threshold in milli-satoshis after which we'll
 	// restrict the flow of HTLCs and fee updates.
 	MaxFeeExposure lnwire.MilliSatoshi
+
+	// ShouldFwdExpEndorsement is a closure that indicates whether the link
+	// should forward experimental endorsement signals.
+	ShouldFwdExpEndorsement func() bool
 }
 
 // channelLink is the service which drives a channel's commitment update
@@ -3624,6 +3629,13 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg) {
 				continue
 			}
 
+			endorseValue := l.experimentalEndorsement(
+				record.CustomSet(add.CustomRecords),
+			)
+			endorseType := uint64(
+				lnwire.ExperimentalEndorsementType,
+			)
+
 			switch fwdPkg.State {
 			case channeldb.FwdStateProcessed:
 				// This add was not forwarded on the previous
@@ -3645,6 +3657,14 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg) {
 					BlindingPoint: fwdInfo.NextBlinding,
 				}
 
+				endorseValue.WhenSome(func(e byte) {
+					custRecords := map[uint64][]byte{
+						endorseType: {e},
+					}
+
+					outgoingAdd.CustomRecords = custRecords
+				})
+
 				// Finally, we'll encode the onion packet for
 				// the _next_ hop using the hop iterator
 				// decoded for the current hop.
@@ -3695,6 +3715,12 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg) {
 				BlindingPoint: fwdInfo.NextBlinding,
 			}
 
+			endorseValue.WhenSome(func(e byte) {
+				addMsg.CustomRecords = map[uint64][]byte{
+					endorseType: {e},
+				}
+			})
+
 			// Finally, we'll encode the onion packet for the
 			// _next_ hop using the hop iterator decoded for the
 			// current hop.
@@ -3782,6 +3808,46 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg) {
 	l.forwardBatch(replay, switchPackets...)
 }
 
+// experimentalEndorsement returns the value to set for our outgoing
+// experimental endorsement field, and a boolean indicating whether it should
+// be populated on the outgoing htlc.
+func (l *channelLink) experimentalEndorsement(
+	customUpdateAdd record.CustomSet) fn.Option[byte] {
+
+	// Only relay experimental signal if we are within the experiment
+	// period.
+	if !l.cfg.ShouldFwdExpEndorsement() {
+		return fn.None[byte]()
+	}
+
+	// If we don't have any custom records or the experimental field is
+	// not set, just forward a zero value.
+	if len(customUpdateAdd) == 0 {
+		return fn.Some[byte](lnwire.ExperimentalUnendorsed)
+	}
+
+	t := uint64(lnwire.ExperimentalEndorsementType)
+	value, set := customUpdateAdd[t]
+	if !set {
+		return fn.Some[byte](lnwire.ExperimentalUnendorsed)
+	}
+
+	// We expect at least one byte for this field, consider it invalid if
+	// it has no data and just forward a zero value.
+	if len(value) == 0 {
+		return fn.Some[byte](lnwire.ExperimentalUnendorsed)
+	}
+
+	// Only forward endorsed if the incoming link is endorsed.
+	if value[0] == lnwire.ExperimentalEndorsed {
+		return fn.Some[byte](lnwire.ExperimentalEndorsed)
+	}
+
+	// Forward as unendorsed otherwise, including cases where we've
+	// received an invalid value that uses more than 3 bits of information.
+	return fn.Some[byte](lnwire.ExperimentalUnendorsed)
+}
+
 // processExitHop handles an htlc for which this link is the exit hop. It
 // returns a boolean indicating whether the commitment tx needs an update.
 func (l *channelLink) processExitHop(add lnwire.UpdateAddHTLC,

htlcswitch/link_test.go

@@ -2245,6 +2245,7 @@ func newSingleLinkTestHarness(t *testing.T, chanAmt,
 		NotifyInactiveLinkEvent: func(wire.OutPoint) {},
 		HtlcNotifier:            aliceSwitch.cfg.HtlcNotifier,
 		GetAliases:              getAliases,
+		ShouldFwdExpEndorsement: func() bool { return true },
 	}
 
 	aliceLink := NewChannelLink(aliceCfg, aliceLc.channel)
@@ -4888,6 +4889,8 @@ func (h *persistentLinkHarness) restartLink(
 	// Instantiate with a long interval, so that we can precisely control
 	// the firing via force feeding.
 	bticker := ticker.NewForce(time.Hour)
+
+	//nolint:lll
 	aliceCfg := ChannelLinkConfig{
 		FwrdingPolicy:      globalPolicy,
 		Peer:               alicePeer,
@@ -4932,6 +4935,7 @@ func (h *persistentLinkHarness) restartLink(
 		HtlcNotifier:            h.hSwitch.cfg.HtlcNotifier,
 		SyncStates:              syncStates,
 		GetAliases:              getAliases,
+		ShouldFwdExpEndorsement: func() bool { return true },
 	}
 
 	aliceLink := NewChannelLink(aliceCfg, aliceChannel)

htlcswitch/test_utils.go

@@ -1154,6 +1154,7 @@ func (h *hopNetwork) createChannelLink(server, peer *mockServer,
 		return server.htlcSwitch.ForwardPackets(linkQuit, packets...)
 	}
 
+	//nolint:lll
 	link := NewChannelLink(
 		ChannelLinkConfig{
 			BestHeight:         server.htlcSwitch.BestHeight,
@@ -1193,6 +1194,7 @@ func (h *hopNetwork) createChannelLink(server, peer *mockServer,
 			NotifyInactiveLinkEvent: func(wire.OutPoint) {},
 			HtlcNotifier:            server.htlcSwitch.cfg.HtlcNotifier,
 			GetAliases:              getAliases,
+			ShouldFwdExpEndorsement: func() bool { return true },
 		},
 		channel,
 	)

itest/list_on_test.go

@@ -702,4 +702,8 @@ var allTestCases = []*lntest.TestCase{
 		Name:     "send to route failed htlc timeout",
 		TestFunc: testSendToRouteFailHTLCTimeout,
 	},
+	{
+		Name:     "experimental endorsement",
+		TestFunc: testExperimentalEndorsement,
+	},
 }