multi: add incoming htlc amount to interceptor

Author: guggero

htlcswitch/interceptable_switch.go

@@ -125,6 +125,10 @@ type FwdResolution struct {
 	// FwdActionSettle.
 	Preimage lntypes.Preimage
 
+	// IncomingAmountMsat is the amount that is to be used for validating if
+	// Action is FwdActionResumeModified.
+	IncomingAmountMsat fn.Option[lnwire.MilliSatoshi]
+
 	// OutgoingAmountMsat is the amount that is to be used for forwarding if
 	// Action is FwdActionResumeModified.
 	OutgoingAmountMsat fn.Option[lnwire.MilliSatoshi]
@@ -391,7 +395,8 @@ func (s *InterceptableSwitch) resolve(res *FwdResolution) error {
 
 	case FwdActionResumeModified:
 		return intercepted.ResumeModified(
-			res.OutgoingAmountMsat, res.CustomRecords,
+			res.IncomingAmountMsat, res.OutgoingAmountMsat,
+			res.CustomRecords,
 		)
 
 	case FwdActionSettle:
@@ -638,9 +643,15 @@ func (f *interceptedForward) Resume() error {
 
 // ResumeModified resumes the default behavior with field modifications.
 func (f *interceptedForward) ResumeModified(
+	incomingAmountMsat fn.Option[lnwire.MilliSatoshi],
 	outgoingAmountMsat fn.Option[lnwire.MilliSatoshi],
 	customRecords fn.Option[record.CustomSet]) error {
 
+	// Set the incoming amount, if it is provided, on the packet.
+	incomingAmountMsat.WhenSome(func(amount lnwire.MilliSatoshi) {
+		f.packet.incomingAmount = amount
+	})
+
 	// Modify the wire message contained in the packet.
 	switch htlc := f.packet.htlc.(type) {
 	case *lnwire.UpdateAddHTLC:

htlcswitch/interfaces.go

@@ -378,7 +378,8 @@ type InterceptedForward interface {
 
 	// ResumeModified notifies the intention to resume an existing hold
 	// forward with modified fields.
-	ResumeModified(outgoingAmountMsat fn.Option[lnwire.MilliSatoshi],
+	ResumeModified(incomingAmountMsat,
+		outgoingAmountMsat fn.Option[lnwire.MilliSatoshi],
 		customRecords fn.Option[record.CustomSet]) error
 
 	// Settle notifies the intention to settle an existing hold

intercepted_forward.go

@@ -55,7 +55,7 @@ func (f *interceptedForward) Resume() error {
 
 // ResumeModified notifies the intention to resume an existing hold forward with
 // a modified htlc.
-func (f *interceptedForward) ResumeModified(_ fn.Option[lnwire.MilliSatoshi],
+func (f *interceptedForward) ResumeModified(_, _ fn.Option[lnwire.MilliSatoshi],
 	_ fn.Option[record.CustomSet]) error {
 
 	return ErrCannotResume

lnrpc/routerrpc/forward_interceptor.go

@@ -123,6 +123,13 @@ func (r *forwardInterceptor) resolveFromClient(
 
 	case ResolveHoldForwardAction_RESUME_MODIFIED:
 		// Modify HTLC and resume forward.
+		incomingAmtMsat := fn.None[lnwire.MilliSatoshi]()
+		if in.IncomingAmountMsat > 0 {
+			incomingAmtMsat = fn.Some[lnwire.MilliSatoshi](
+				lnwire.MilliSatoshi(in.IncomingAmountMsat),
+			)
+		}
+
 		outgoingAmtMsat := fn.None[lnwire.MilliSatoshi]()
 		if in.OutgoingAmountMsat > 0 {
 			outgoingAmtMsat = fn.Some[lnwire.MilliSatoshi](
@@ -148,6 +155,7 @@ func (r *forwardInterceptor) resolveFromClient(
 		return r.htlcSwitch.Resolve(&htlcswitch.FwdResolution{
 			Key:                circuitKey,
 			Action:             htlcswitch.FwdActionResumeModified,
+			IncomingAmountMsat: incomingAmtMsat,
 			OutgoingAmountMsat: outgoingAmtMsat,
 			CustomRecords:      customRecords,
 		})

lnrpc/routerrpc/router.pb.go

@@ -993,13 +993,17 @@ message ForwardHtlcInterceptResponse {
     // default value for this field.
     lnrpc.Failure.FailureCode failure_code = 5;
 
+    // incoming_amount_msat is used to set the p2p message incoming amount field
+    // for validating an incoming HTLC.
+    uint64 incoming_amount_msat = 6;
+
     // outgoing_amount_msat is used to set the p2p message outgoing amount field
     // for resuming a HTLC.
-    uint64 outgoing_amount_msat = 6;
+    uint64 outgoing_amount_msat = 7;
 
     // custom_records is used to set the p2p message custom records field for
     // resuming a HTLC.
-    map<uint64, bytes> custom_records = 7;
+    map<uint64, bytes> custom_records = 8;
 }
 
 enum ResolveHoldForwardAction {

lnrpc/routerrpc/router.proto

@@ -1344,6 +1344,11 @@
           "$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."
         },
+        "incoming_amount_msat": {
+          "type": "string",
+          "format": "uint64",
+          "description": "incoming_amount_msat is used to set the p2p message incoming amount field\nfor validating an incoming HTLC."
+        },
         "outgoing_amount_msat": {
           "type": "string",
           "format": "uint64",