multi: skip range check in pathfinder and switch for custom htlc payments

routing/bandwidth.go

@@ -24,9 +24,9 @@ type bandwidthHints interface {
 	availableChanBandwidth(channelID uint64,
 		amount lnwire.MilliSatoshi) (lnwire.MilliSatoshi, bool)
 
-	// firstHopCustomBlob returns the custom blob for the first hop of the
-	// payment, if available.
-	firstHopCustomBlob() fn.Option[tlv.Blob]
+	// isCustomHTLCPayment returns true if this payment is a custom payment.
+	// For custom payments policy checks might not be needed.
+	isCustomHTLCPayment() bool
 }
 
 // getLinkQuery is the function signature used to lookup a link.
@@ -205,8 +205,27 @@ func (b *bandwidthManager) availableChanBandwidth(channelID uint64,
 	return bandwidth, true
 }
 
-// firstHopCustomBlob returns the custom blob for the first hop of the payment,
-// if available.
-func (b *bandwidthManager) firstHopCustomBlob() fn.Option[tlv.Blob] {
-	return b.firstHopBlob
+// isCustomHTLCPayment returns true if this payment is a custom payment.
+// For custom payments policy checks might not be needed.
+func (b *bandwidthManager) isCustomHTLCPayment() bool {
+	var isCustomHTLCPayment bool
+
+	b.firstHopBlob.WhenSome(func(blob tlv.Blob) {
+		customRecords, err := lnwire.ParseCustomRecords(blob)
+		if err != nil {
+			log.Warnf("failed to parse custom records when "+
+				"checking if payment is custom: %v", err)
+
+			return
+		}
+
+		isCustomHTLCPayment = fn.MapOptionZ(
+			b.trafficShaper,
+			func(s htlcswitch.AuxTrafficShaper) bool {
+				return s.IsCustomHTLC(customRecords)
+			},
+		)
+	})
+
+	return isCustomHTLCPayment
 }

routing/integrated_routing_context_test.go

@@ -11,7 +11,6 @@ import (
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/routing/route"
-	"github.com/lightningnetwork/lnd/tlv"
 	"github.com/lightningnetwork/lnd/zpay32"
 	"github.com/stretchr/testify/require"
 )
@@ -36,8 +35,8 @@ func (m *mockBandwidthHints) availableChanBandwidth(channelID uint64,
 	return balance, ok
 }
 
-func (m *mockBandwidthHints) firstHopCustomBlob() fn.Option[tlv.Blob] {
-	return fn.None[tlv.Blob]()
+func (m *mockBandwidthHints) isCustomHTLCPayment() bool {
+	return false
 }
 
 // integratedRoutingContext defines the context in which integrated routing

routing/unified_edges.go

@@ -251,12 +251,13 @@ func (u *edgeUnifier) getEdgeLocal(netAmtReceived lnwire.MilliSatoshi,
 		// Add inbound fee to get to the amount that is sent over the
 		// local channel.
 		amt := netAmtReceived + lnwire.MilliSatoshi(inboundFee)
-
 		// Check valid amount range for the channel. We skip this test
-		// for payments with custom HTLC data, as the amount sent on
-		// the BTC layer may differ from the amount that is actually
-		// forwarded in custom channels.
-		if bandwidthHints.firstHopCustomBlob().IsNone() &&
+
+		// for payments with custom htlc data we skip the amount range
+		// check because the amt of the payment does not relate to the
+		// actual amount carried by the HTLC but instead in encoded in
+		// the blob data.
+		if !bandwidthHints.isCustomHTLCPayment() &&
 			!edge.amtInRange(amt) {
 
 			log.Debugf("Amount %v not in range for edge %v",