htlcswitch+lnwallet: persist UpdateFailHTLC extra data

When propagating a failure backwards along a route we want to persist
the received ExtraData of the downstream link so that any handling can
occur on our node before returning the updated ExtraData to our upstream
link.

Author: GeorgeTsagk

htlcswitch/link.go

@@ -3579,7 +3579,7 @@ func (l *channelLink) sendHTLCError(add lnwire.UpdateAddHTLC,
 		return
 	}
 
-	err = l.channel.FailHTLC(add.ID, reason, &sourceRef, nil, nil)
+	err = l.channel.FailHTLC(add.ID, reason, nil, &sourceRef, nil, nil)
 	if err != nil {
 		l.log.Errorf("unable cancel htlc: %v", err)
 		return
@@ -3588,7 +3588,7 @@ func (l *channelLink) sendHTLCError(add lnwire.UpdateAddHTLC,
 	// Send the appropriate failure message depending on whether we're
 	// in a blinded route or not.
 	if err := l.sendIncomingHTLCFailureMsg(
-		add.ID, e, reason,
+		add.ID, e, reason, nil,
 	); err != nil {
 		l.log.Errorf("unable to send HTLC failure: %v", err)
 		return
@@ -3632,8 +3632,8 @@ func (l *channelLink) sendHTLCError(add lnwire.UpdateAddHTLC,
 // used if we are the introduction node and need to present an error as if
 // we're the failing party.
 func (l *channelLink) sendIncomingHTLCFailureMsg(htlcIndex uint64,
-	e hop.ErrorEncrypter,
-	originalFailure lnwire.OpaqueReason) error {
+	e hop.ErrorEncrypter, originalFailure lnwire.OpaqueReason,
+	extraData lnwire.ExtraOpaqueData) error {
 
 	var msg lnwire.Message
 	switch {
@@ -3646,9 +3646,10 @@ func (l *channelLink) sendIncomingHTLCFailureMsg(htlcIndex uint64,
 	// code.
 	case e == nil:
 		msg = &lnwire.UpdateFailHTLC{
-			ChanID: l.ChanID(),
-			ID:     htlcIndex,
-			Reason: originalFailure,
+			ChanID:    l.ChanID(),
+			ID:        htlcIndex,
+			Reason:    originalFailure,
+			ExtraData: extraData,
 		}
 
 		l.log.Errorf("Unexpected blinded failure when "+
@@ -3659,9 +3660,10 @@ func (l *channelLink) sendIncomingHTLCFailureMsg(htlcIndex uint64,
 	// transformation on the error message and can just send the original.
 	case !e.Type().IsBlinded():
 		msg = &lnwire.UpdateFailHTLC{
-			ChanID: l.ChanID(),
-			ID:     htlcIndex,
-			Reason: originalFailure,
+			ChanID:    l.ChanID(),
+			ID:        htlcIndex,
+			Reason:    originalFailure,
+			ExtraData: extraData,
 		}
 
 	// When we're the introduction node, we need to convert the error to
@@ -4196,7 +4198,7 @@ func (l *channelLink) processRemoteUpdateFailMalformedHTLC(
 	// If remote side have been unable to parse the onion blob we have sent
 	// to it, than we should transform the malformed HTLC message to the
 	// usual HTLC fail message.
-	err := l.channel.ReceiveFailHTLC(msg.ID, b.Bytes())
+	err := l.channel.ReceiveFailHTLC(msg.ID, b.Bytes(), msg.ExtraData)
 	if err != nil {
 		l.failf(LinkFailureError{code: ErrInvalidUpdate},
 			"unable to handle upstream fail HTLC: %v", err)
@@ -4237,7 +4239,7 @@ func (l *channelLink) processRemoteUpdateFailHTLC(
 
 	// Add fail to the update log.
 	idx := msg.ID
-	err := l.channel.ReceiveFailHTLC(idx, msg.Reason[:])
+	err := l.channel.ReceiveFailHTLC(idx, msg.Reason[:], msg.ExtraData)
 	if err != nil {
 		l.failf(LinkFailureError{code: ErrInvalidUpdate},
 			"unable to handle upstream fail HTLC: %v", err)
@@ -4677,8 +4679,8 @@ func (l *channelLink) processLocalUpdateFailHTLC(ctx context.Context,
 	// remove then HTLC from our local state machine.
 	inKey := pkt.inKey()
 	err := l.channel.FailHTLC(
-		pkt.incomingHTLCID, htlc.Reason, pkt.sourceRef, pkt.destRef,
-		&inKey,
+		pkt.incomingHTLCID, htlc.Reason, htlc.ExtraData, pkt.sourceRef,
+		pkt.destRef, &inKey,
 	)
 	if err != nil {
 		l.log.Errorf("unable to cancel incoming HTLC for "+
@@ -4714,7 +4716,9 @@ func (l *channelLink) processLocalUpdateFailHTLC(ctx context.Context,
 	// HTLC. If the incoming blinding point is non-nil, we know that we are
 	// a relaying node in a blinded path. Otherwise, we're either an
 	// introduction node or not part of a blinded path at all.
-	err = l.sendIncomingHTLCFailureMsg(htlc.ID, pkt.obfuscator, htlc.Reason)
+	err = l.sendIncomingHTLCFailureMsg(
+		htlc.ID, pkt.obfuscator, htlc.Reason, htlc.ExtraData,
+	)
 	if err != nil {
 		l.log.Errorf("unable to send HTLC failure: %v", err)
 

lnwallet/channel.go

@@ -1152,13 +1152,14 @@ func (lc *LightningChannel) logUpdateToPayDesc(logUpdate *channeldb.LogUpdate,
 		ogHTLC := remoteUpdateLog.lookupHtlc(wireMsg.ID)
 
 		pd = &paymentDescriptor{
-			ChanID:      wireMsg.ChanID,
-			Amount:      ogHTLC.Amount,
-			RHash:       ogHTLC.RHash,
-			ParentIndex: ogHTLC.HtlcIndex,
-			LogIndex:    logUpdate.LogIndex,
-			EntryType:   Fail,
-			FailReason:  wireMsg.Reason[:],
+			ChanID:        wireMsg.ChanID,
+			Amount:        ogHTLC.Amount,
+			RHash:         ogHTLC.RHash,
+			ParentIndex:   ogHTLC.HtlcIndex,
+			LogIndex:      logUpdate.LogIndex,
+			EntryType:     Fail,
+			FailReason:    wireMsg.Reason[:],
+			FailExtraData: wireMsg.ExtraData,
 			removeCommitHeights: lntypes.Dual[uint64]{
 				Remote: commitHeight,
 			},
@@ -1252,13 +1253,14 @@ func (lc *LightningChannel) localLogUpdateToPayDesc(logUpdate *channeldb.LogUpda
 		ogHTLC := remoteUpdateLog.lookupHtlc(wireMsg.ID)
 
 		return &paymentDescriptor{
-			ChanID:      wireMsg.ChanID,
-			Amount:      ogHTLC.Amount,
-			RHash:       ogHTLC.RHash,
-			ParentIndex: ogHTLC.HtlcIndex,
-			LogIndex:    logUpdate.LogIndex,
-			EntryType:   Fail,
-			FailReason:  wireMsg.Reason[:],
+			ChanID:        wireMsg.ChanID,
+			Amount:        ogHTLC.Amount,
+			RHash:         ogHTLC.RHash,
+			ParentIndex:   ogHTLC.HtlcIndex,
+			LogIndex:      logUpdate.LogIndex,
+			EntryType:     Fail,
+			FailReason:    wireMsg.Reason[:],
+			FailExtraData: wireMsg.ExtraData,
 			removeCommitHeights: lntypes.Dual[uint64]{
 				Remote: commitHeight,
 			},
@@ -1367,13 +1369,14 @@ func (lc *LightningChannel) remoteLogUpdateToPayDesc(logUpdate *channeldb.LogUpd
 		ogHTLC := localUpdateLog.lookupHtlc(wireMsg.ID)
 
 		return &paymentDescriptor{
-			ChanID:      wireMsg.ChanID,
-			Amount:      ogHTLC.Amount,
-			RHash:       ogHTLC.RHash,
-			ParentIndex: ogHTLC.HtlcIndex,
-			LogIndex:    logUpdate.LogIndex,
-			EntryType:   Fail,
-			FailReason:  wireMsg.Reason[:],
+			ChanID:        wireMsg.ChanID,
+			Amount:        ogHTLC.Amount,
+			RHash:         ogHTLC.RHash,
+			ParentIndex:   ogHTLC.HtlcIndex,
+			LogIndex:      logUpdate.LogIndex,
+			EntryType:     Fail,
+			FailReason:    wireMsg.Reason[:],
+			FailExtraData: wireMsg.ExtraData,
 			removeCommitHeights: lntypes.Dual[uint64]{
 				Local: commitHeight,
 			},
@@ -6298,7 +6301,8 @@ func (lc *LightningChannel) ReceiveHTLCSettle(preimage [32]byte, htlcIndex uint6
 // NOTE: It is okay for sourceRef, destRef, and closeKey to be nil when unit
 // testing the wallet.
 func (lc *LightningChannel) FailHTLC(htlcIndex uint64, reason []byte,
-	sourceRef *channeldb.AddRef, destRef *channeldb.SettleFailRef,
+	extraData lnwire.ExtraOpaqueData, sourceRef *channeldb.AddRef,
+	destRef *channeldb.SettleFailRef,
 	closeKey *models.CircuitKey) error {
 
 	lc.Lock()
@@ -6326,6 +6330,7 @@ func (lc *LightningChannel) FailHTLC(htlcIndex uint64, reason []byte,
 		SourceRef:        sourceRef,
 		DestRef:          destRef,
 		ClosedCircuitKey: closeKey,
+		FailExtraData:    extraData,
 	}
 
 	lc.updateLogs.Local.appendUpdate(pd)
@@ -6393,7 +6398,7 @@ func (lc *LightningChannel) MalformedFailHTLC(htlcIndex uint64,
 // commitment update. This method should be called in response to the upstream
 // party cancelling an outgoing HTLC.
 func (lc *LightningChannel) ReceiveFailHTLC(htlcIndex uint64, reason []byte,
-) error {
+	extraData lnwire.ExtraOpaqueData) error {
 
 	lc.Lock()
 	defer lc.Unlock()
@@ -6410,13 +6415,14 @@ func (lc *LightningChannel) ReceiveFailHTLC(htlcIndex uint64, reason []byte,
 	}
 
 	pd := &paymentDescriptor{
-		ChanID:      lc.ChannelID(),
-		Amount:      htlc.Amount,
-		RHash:       htlc.RHash,
-		ParentIndex: htlc.HtlcIndex,
-		LogIndex:    lc.updateLogs.Remote.logIndex,
-		EntryType:   Fail,
-		FailReason:  reason,
+		ChanID:        lc.ChannelID(),
+		Amount:        htlc.Amount,
+		RHash:         htlc.RHash,
+		ParentIndex:   htlc.HtlcIndex,
+		LogIndex:      lc.updateLogs.Remote.logIndex,
+		EntryType:     Fail,
+		FailReason:    reason,
+		FailExtraData: extraData,
 	}
 
 	lc.updateLogs.Remote.appendUpdate(pd)

lnwallet/payment_descriptor.go

@@ -229,6 +229,10 @@ type paymentDescriptor struct {
 	// CustomRecords also stores the set of optional custom records that
 	// may have been attached to a sent HTLC.
 	CustomRecords lnwire.CustomRecords
+
+	// FailExtraData stores any extra opaque data that may have been present
+	// when receiving an UpdateFailHTLC message.
+	FailExtraData lnwire.ExtraOpaqueData
 }
 
 // toLogUpdate recovers the underlying LogUpdate from the paymentDescriptor.
@@ -257,9 +261,10 @@ func (pd *paymentDescriptor) toLogUpdate() channeldb.LogUpdate {
 		}
 	case Fail:
 		msg = &lnwire.UpdateFailHTLC{
-			ChanID: pd.ChanID,
-			ID:     pd.ParentIndex,
-			Reason: pd.FailReason,
+			ChanID:    pd.ChanID,
+			ID:        pd.ParentIndex,
+			Reason:    pd.FailReason,
+			ExtraData: pd.FailExtraData,
 		}
 	case MalformedFail:
 		msg = &lnwire.UpdateFailMalformedHTLC{