routing: use first hop records on path finding

routing/pathfind.go

@@ -13,9 +13,11 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channeldb/models"
 	"github.com/lightningnetwork/lnd/feature"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
 	"github.com/lightningnetwork/lnd/routing/route"
+	"github.com/lightningnetwork/lnd/tlv"
 )
 
 const (
@@ -433,6 +435,10 @@ type RestrictParams struct {
 	// BlindedPayment is necessary to determine the hop size of the
 	// last/exit hop.
 	BlindedPayment *BlindedPayment
+
+	// FirstHopCustomRecords includes any records that should be included in
+	// the update_add_htlc message towards our peer.
+	FirstHopCustomRecords record.CustomSet
 }
 
 // PathFindingConfig defines global parameters that control the trade-off in
@@ -459,9 +465,10 @@ type PathFindingConfig struct {
 // available balance.
 func getOutgoingBalance(node route.Vertex, outgoingChans map[uint64]struct{},
 	bandwidthHints bandwidthHints,
-	g routingGraph) (lnwire.MilliSatoshi, lnwire.MilliSatoshi, error) {
+	g routingGraph, htlcBlob fn.Option[tlv.Blob]) (lnwire.MilliSatoshi, lnwire.MilliSatoshi, error) {
 
 	var max, total lnwire.MilliSatoshi
+
 	cb := func(channel *channeldb.DirectedChannel) error {
 		if !channel.OutPolicySet {
 			return nil
@@ -477,7 +484,7 @@ func getOutgoingBalance(node route.Vertex, outgoingChans map[uint64]struct{},
 		}
 
 		bandwidth, ok := bandwidthHints.availableChanBandwidth(
-			chanID, 0,
+			chanID, 0, htlcBlob,
 		)
 
 		// If the bandwidth is not available, use the channel capacity.
@@ -491,7 +498,9 @@ func getOutgoingBalance(node route.Vertex, outgoingChans map[uint64]struct{},
 			max = bandwidth
 		}
 
-		total += bandwidth
+		total = lnwire.MilliSatoshi(
+			safeAdd(uint64(total), uint64(bandwidth)),
+		)
 
 		return nil
 	}
@@ -599,8 +608,23 @@ func findPath(g *graphParams, r *RestrictParams, cfg *PathFindingConfig,
 	self := g.graph.sourceNode()
 
 	if source == self {
+
+		firstHopTLVs := tlv.MapToRecords(r.FirstHopCustomRecords)
+		wireRecords := fn.Map(func(r tlv.Record) tlv.RecordProducer {
+			return &r
+		}, firstHopTLVs)
+
+		firstHopData := lnwire.ExtraOpaqueData{}
+
+		err := firstHopData.PackRecords(wireRecords...)
+		if err != nil {
+			return nil, 0, err
+		}
+
+		tlvOption := fn.Some[tlv.Blob](firstHopData)
 		max, total, err := getOutgoingBalance(
 			self, outgoingChanMap, g.bandwidthHints, g.graph,
+			tlvOption,
 		)
 		if err != nil {
 			return nil, 0, err
@@ -1029,9 +1053,23 @@ func findPath(g *graphParams, r *RestrictParams, cfg *PathFindingConfig,
 				continue
 			}
 
+			firstHopTLVs := tlv.MapToRecords(r.FirstHopCustomRecords)
+			wireRecords := fn.Map(func(r tlv.Record) tlv.RecordProducer {
+				return &r
+			}, firstHopTLVs)
+
+			firstHopData := lnwire.ExtraOpaqueData{}
+
+			err := firstHopData.PackRecords(wireRecords...)
+			if err != nil {
+				return nil, 0, err
+			}
+
+			tlvOption := fn.Some[tlv.Blob](firstHopData)
+
 			edge := edgeUnifier.getEdge(
 				netAmountReceived, g.bandwidthHints,
-				partialPath.outboundFee,
+				partialPath.outboundFee, tlvOption,
 			)
 
 			if edge == nil {
@@ -1223,3 +1261,11 @@ func lastHopPayloadSize(r *RestrictParams, finalHtlcExpiry int32,
 	// The final hop does not have a short chanID set.
 	return finalHop.PayloadSize(0)
 }
+
+func safeAdd(x, y uint64) uint64 {
+	if y > math.MaxUint64-x {
+		// Overflow would occur, return maximum uint64 value
+		return math.MaxUint64
+	}
+	return x + y
+}

routing/payment_lifecycle.go

@@ -362,6 +362,7 @@ func (p *paymentLifecycle) requestRoute(
 	rt, err := p.paySession.RequestRoute(
 		ps.RemainingAmt, remainingFees,
 		uint32(ps.NumAttemptsInFlight), uint32(p.currentHeight),
+		p.firstHopTLVs,
 	)
 
 	// Exit early if there's no error.

routing/payment_session.go

@@ -10,6 +10,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channeldb/models"
 	"github.com/lightningnetwork/lnd/lnwire"
+	"github.com/lightningnetwork/lnd/record"
 	"github.com/lightningnetwork/lnd/routing/route"
 )
 
@@ -138,7 +139,8 @@ type PaymentSession interface {
 	// A noRouteError is returned if a non-critical error is encountered
 	// during path finding.
 	RequestRoute(maxAmt, feeLimit lnwire.MilliSatoshi,
-		activeShards, height uint32) (*route.Route, error)
+		activeShards, height uint32,
+		firstHopTLVs record.CustomSet) (*route.Route, error)
 
 	// UpdateAdditionalEdge takes an additional channel edge policy
 	// (private channels) and applies the update from the message. Returns
@@ -228,7 +230,8 @@ func newPaymentSession(p *LightningPayment,
 // NOTE: This function is safe for concurrent access.
 // NOTE: Part of the PaymentSession interface.
 func (p *paymentSession) RequestRoute(maxAmt, feeLimit lnwire.MilliSatoshi,
-	activeShards, height uint32) (*route.Route, error) {
+	activeShards, height uint32,
+	firstHopTLVs record.CustomSet) (*route.Route, error) {
 
 	if p.empty {
 		return nil, errEmptyPaySession
@@ -250,16 +253,17 @@ func (p *paymentSession) RequestRoute(maxAmt, feeLimit lnwire.MilliSatoshi,
 	// to our destination, respecting the recommendations from
 	// MissionControl.
 	restrictions := &RestrictParams{
-		ProbabilitySource:  p.missionControl.GetProbability,
-		FeeLimit:           feeLimit,
-		OutgoingChannelIDs: p.payment.OutgoingChannelIDs,
-		LastHop:            p.payment.LastHop,
-		CltvLimit:          cltvLimit,
-		DestCustomRecords:  p.payment.DestCustomRecords,
-		DestFeatures:       p.payment.DestFeatures,
-		PaymentAddr:        p.payment.PaymentAddr,
-		Amp:                p.payment.amp,
-		Metadata:           p.payment.Metadata,
+		ProbabilitySource:     p.missionControl.GetProbability,
+		FeeLimit:              feeLimit,
+		OutgoingChannelIDs:    p.payment.OutgoingChannelIDs,
+		LastHop:               p.payment.LastHop,
+		CltvLimit:             cltvLimit,
+		DestCustomRecords:     p.payment.DestCustomRecords,
+		DestFeatures:          p.payment.DestFeatures,
+		PaymentAddr:           p.payment.PaymentAddr,
+		Amp:                   p.payment.amp,
+		Metadata:              p.payment.Metadata,
+		FirstHopCustomRecords: firstHopTLVs,
 	}
 
 	finalHtlcExpiry := int32(height) + int32(finalCltvDelta)