Interceptor improvements

* Add OnionBlob and OutgoingAmount parameters
* Add OutgoingRequestedChanId when resuming a forward htlc

htlcswitch/interceptable_switch.go

@@ -119,6 +119,10 @@ type FwdResolution struct {
 	// FwdActionSettle.
 	Preimage lntypes.Preimage
 
+	OutgoingAmount lnwire.MilliSatoshi
+	OutgoingChanID lnwire.ShortChannelID
+	OnionBlob      [lnwire.OnionPacketSize]byte
+
 	// FailureMessage is the encrypted failure message that is to be passed
 	// back to the sender if action is FwdActionFail.
 	FailureMessage []byte
@@ -356,7 +360,10 @@ func (s *InterceptableSwitch) setInterceptor(interceptor ForwardInterceptor) {
 	log.Infof("Interceptor disconnected, resolving held packets")
 
 	s.heldHtlcSet.popAll(func(fwd InterceptedForward) {
-		err := fwd.Resume()
+		err := fwd.Resume(
+			fwd.Packet().OutgoingAmount,
+			fwd.Packet().OutgoingChanID,
+			fwd.Packet().OnionBlob)
 		if err != nil {
 			log.Errorf("Failed to resume hold forward %v", err)
 		}
@@ -371,7 +378,7 @@ func (s *InterceptableSwitch) resolve(res *FwdResolution) error {
 
 	switch res.Action {
 	case FwdActionResume:
-		return intercepted.Resume()
+		return intercepted.Resume(res.OutgoingAmount, res.OutgoingChanID, res.OnionBlob)
 
 	case FwdActionSettle:
 		return intercepted.Settle(res.Preimage)
@@ -609,7 +616,12 @@ func (f *interceptedForward) Packet() InterceptedPacket {
 }
 
 // Resume resumes the default behavior as if the packet was not intercepted.
-func (f *interceptedForward) Resume() error {
+func (f *interceptedForward) Resume(outgoingAmount lnwire.MilliSatoshi, outgoingChanID lnwire.ShortChannelID, onionBlob [lnwire.OnionPacketSize]byte) error {
+	f.htlc.OnionBlob = onionBlob
+	f.htlc.Amount = outgoingAmount
+	f.packet.htlc = f.htlc
+	f.packet.amount = outgoingAmount
+	f.packet.outgoingChanID = outgoingChanID
 	// Forward to the switch. A link quit channel isn't needed, because we
 	// are on a different thread now.
 	return f.htlcSwitch.ForwardPackets(nil, f.packet)

htlcswitch/interfaces.go

@@ -326,7 +326,7 @@ type InterceptedForward interface {
 	// Resume notifies the intention to resume an existing hold forward. This
 	// basically means the caller wants to resume with the default behavior for
 	// this htlc which usually means forward it.
-	Resume() error
+	Resume(lnwire.MilliSatoshi, lnwire.ShortChannelID, [lnwire.OnionPacketSize]byte) error
 
 	// Settle notifies the intention to settle an existing hold
 	// forward with a given preimage.

intercepted_forward.go

@@ -47,7 +47,7 @@ func (f *interceptedForward) Packet() htlcswitch.InterceptedPacket {
 // Resume notifies the intention to resume an existing hold forward. This
 // basically means the caller wants to resume with the default behavior for this
 // htlc which usually means forward it.
-func (f *interceptedForward) Resume() error {
+func (f *interceptedForward) Resume(lnwire.MilliSatoshi, lnwire.ShortChannelID, [lnwire.OnionPacketSize]byte) error {
 	return ErrCannotResume
 }
 

lnrpc/routerrpc/forward_interceptor.go

@@ -114,9 +114,14 @@ func (r *forwardInterceptor) resolveFromClient(
 
 	switch in.Action {
 	case ResolveHoldForwardAction_RESUME:
+		var onionBlob [lnwire.OnionPacketSize]byte
+		copy(onionBlob[:], in.OnionBlob)
 		return r.htlcSwitch.Resolve(&htlcswitch.FwdResolution{
-			Key:    circuitKey,
-			Action: htlcswitch.FwdActionResume,
+			Key:            circuitKey,
+			Action:         htlcswitch.FwdActionResume,
+			OutgoingAmount: lnwire.MilliSatoshi(in.OutgoingAmountMsat),
+			OutgoingChanID: lnwire.NewShortChanIDFromInt(in.OutgoingRequestedChanId),
+			OnionBlob:      onionBlob,
 		})
 
 	case ResolveHoldForwardAction_FAIL:

lnrpc/routerrpc/router.proto

@@ -928,6 +928,16 @@ message ForwardHtlcInterceptResponse {
     // For backwards-compatibility reasons, TEMPORARY_CHANNEL_FAILURE is the
     // default value for this field.
     lnrpc.Failure.FailureCode failure_code = 5;
+
+    uint64 outgoing_amount_msat = 6;
+
+    // The requested outgoing channel id for this forwarded htlc. Because of
+    // non-strict forwarding, this isn't necessarily the channel over which the
+    // packet will be forwarded eventually. A different channel to the same peer
+    // may be selected as well.
+    uint64 outgoing_requested_chan_id = 7;
+
+    bytes onion_blob = 8;
 }
 
 enum ResolveHoldForwardAction {

lnrpc/routerrpc/router.swagger.json

@@ -1325,6 +1325,19 @@
         "failure_code": {
           "$ref": "#/definitions/FailureFailureCode",
           "description": "Return the specified failure code in case the resolve action is Fail. The\nmessage data fields are populated automatically.\n\nIf a non-zero failure_code is specified, failure_message must not be set.\n\nFor backwards-compatibility reasons, TEMPORARY_CHANNEL_FAILURE is the\ndefault value for this field."
+        },
+        "outgoing_amount_msat": {
+          "type": "string",
+          "format": "uint64"
+        },
+        "outgoing_requested_chan_id": {
+          "type": "string",
+          "format": "uint64",
+          "description": "The requested outgoing channel id for this forwarded htlc. Because of\nnon-strict forwarding, this isn't necessarily the channel over which the\npacket will be forwarded eventually. A different channel to the same peer\nmay be selected as well."
+        },
+        "onion_blob": {
+          "type": "string",
+          "format": "byte"
         }
       },
       "description": "*\nForwardHtlcInterceptResponse enables the caller to resolve a previously hold\nforward. The caller can choose either to:\n- `Resume`: Execute the default behavior (usually forward).\n- `Reject`: Fail the htlc backwards.\n- `Settle`: Settle this htlc with a given preimage."