routing: add cltv limit to payment session

routing/payment_session.go

@@ -138,6 +138,16 @@ func (p *paymentSession) RequestRoute(payment *LightningPayment,
 		"edges, %v vertexes", len(pruneView.edges),
 		len(pruneView.vertexes))
 
+	// If a route cltv limit was specified, we need to subtract the final
+	// delta before passing it into path finding. The optimal path is
+	// independent of the final cltv delta and the path finding algorithm is
+	// unaware of this value.
+	var cltvLimit *uint32
+	if payment.CltvLimit != nil {
+		limit := *payment.CltvLimit - uint32(finalCltvDelta)
+		cltvLimit = &limit
+	}
+
 	// TODO(roasbeef): sync logic amongst dist sys
 
 	// Taking into account this prune view, we'll attempt to locate a path
@@ -154,6 +164,7 @@ func (p *paymentSession) RequestRoute(payment *LightningPayment,
 			IgnoredEdges:      pruneView.edges,
 			FeeLimit:          payment.FeeLimit,
 			OutgoingChannelID: payment.OutgoingChannelID,
+			CltvLimit:         cltvLimit,
 		},
 		p.mc.selfNode.PubKeyBytes, payment.Target,
 		payment.Amount,

routing/payment_session_test.go

@@ -0,0 +1,60 @@
+package routing
+
+import (
+	"testing"
+
+	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+func TestRequestRoute(t *testing.T) {
+	const (
+		height = 10
+	)
+
+	findPath := func(g *graphParams, r *RestrictParams,
+		source, target Vertex, amt lnwire.MilliSatoshi) (
+		[]*channeldb.ChannelEdgePolicy, error) {
+
+		// We expect find path to receive a cltv limit excluding the
+		// final cltv delta.
+		if *r.CltvLimit != 22 {
+			t.Fatal("wrong cltv limit")
+		}
+
+		path := []*channeldb.ChannelEdgePolicy{
+			{
+				Node: &channeldb.LightningNode{},
+			},
+		}
+
+		return path, nil
+	}
+
+	session := &paymentSession{
+		mc: &missionControl{
+			selfNode: &channeldb.LightningNode{},
+		},
+		pruneViewSnapshot: graphPruneView{},
+		pathFinder:        findPath,
+	}
+
+	cltvLimit := uint32(30)
+	finalCltvDelta := uint16(8)
+
+	payment := &LightningPayment{
+		CltvLimit:      &cltvLimit,
+		FinalCLTVDelta: &finalCltvDelta,
+	}
+
+	route, err := session.RequestRoute(payment, height, finalCltvDelta)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// We expect an absolute route lock value of height + finalCltvDelta
+	if route.TotalTimeLock != 18 {
+		t.Fatalf("unexpected total time lock of %v",
+			route.TotalTimeLock)
+	}
+}

routing/router.go

@@ -1523,6 +1523,10 @@ type LightningPayment struct {
 	// if there isn't a route with lower fees than this limit.
 	FeeLimit lnwire.MilliSatoshi
 
+	// CltvLimit is the maximum time lock that is allowed for attempts to
+	// complete this payment.
+	CltvLimit *uint32
+
 	// PaymentHash is the r-hash value to use within the HTLC extended to
 	// the first hop.
 	PaymentHash [32]byte