routing+htlcswitch: ProduceHtlcExtraData uses first hop pub key

htlcswitch/interfaces.go

@@ -14,6 +14,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
+	"github.com/lightningnetwork/lnd/routing/route"
 	"github.com/lightningnetwork/lnd/tlv"
 )
 
@@ -495,8 +496,9 @@ type AuxHtlcModifier interface {
 	// data blob of an HTLC, may produce a different blob or modify the
 	// amount of bitcoin this htlc should carry.
 	ProduceHtlcExtraData(totalAmount lnwire.MilliSatoshi,
-		htlcCustomRecords lnwire.CustomRecords) (lnwire.MilliSatoshi,
-		lnwire.CustomRecords, error)
+		htlcCustomRecords lnwire.CustomRecords,
+		peer route.Vertex) (lnwire.MilliSatoshi, lnwire.CustomRecords,
+		error)
 }
 
 // AuxTrafficShaper is an interface that allows the sender to determine if a

routing/bandwidth_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/routing/route"
 	"github.com/lightningnetwork/lnd/tlv"
 	"github.com/stretchr/testify/require"
 )
@@ -161,8 +162,8 @@ func (*mockTrafficShaper) PaymentBandwidth(_, _, _ fn.Option[tlv.Blob],
 // data blob of an HTLC, may produce a different blob or modify the
 // amount of bitcoin this htlc should carry.
 func (*mockTrafficShaper) ProduceHtlcExtraData(totalAmount lnwire.MilliSatoshi,
-	_ lnwire.CustomRecords) (lnwire.MilliSatoshi, lnwire.CustomRecords,
-	error) {
+	_ lnwire.CustomRecords, _ route.Vertex) (lnwire.MilliSatoshi,
+	lnwire.CustomRecords, error) {
 
 	return totalAmount, nil, nil
 }

routing/payment_lifecycle.go

@@ -724,6 +724,13 @@ func (p *paymentLifecycle) amendFirstHopData(rt *route.Route) error {
 	// value.
 	rt.FirstHopWireCustomRecords = p.firstHopCustomRecords
 
+	if len(rt.Hops) == 0 {
+		return fmt.Errorf("cannot amend first hop data, route length " +
+			"is zero")
+	}
+
+	firstHopPK := rt.Hops[0].PubKeyBytes
+
 	// extraDataRequest is a helper struct to pass the custom records and
 	// amount back from the traffic shaper.
 	type extraDataRequest struct {
@@ -740,6 +747,7 @@ func (p *paymentLifecycle) amendFirstHopData(rt *route.Route) error {
 		func(ts htlcswitch.AuxTrafficShaper) fn.Result[extraDataRequest] {
 			newAmt, newRecords, err := ts.ProduceHtlcExtraData(
 				rt.TotalAmount, p.firstHopCustomRecords,
+				firstHopPK,
 			)
 			if err != nil {
 				return fn.Err[extraDataRequest](err)

routing/payment_lifecycle_test.go

@@ -368,7 +368,11 @@ func TestRequestRouteSucceed(t *testing.T) {
 
 	// Create a mock payment session and a dummy route.
 	paySession := &mockPaymentSession{}
-	dummyRoute := &route.Route{}
+	dummyRoute := &route.Route{
+		Hops: []*route.Hop{
+			testHop,
+		},
+	}
 
 	// Mount the mocked payment session.
 	p.paySession = paySession