lnrpc+routing: convert amt pointer to fn.Option

Author: bitromortac

lnrpc/routerrpc/router_server.go

@@ -15,6 +15,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
 	"github.com/lightningnetwork/lnd/lntypes"
@@ -1411,10 +1412,10 @@ func (s *Server) BuildRoute(_ context.Context,
 	}
 
 	// Prepare BuildRoute call parameters from rpc request.
-	var amt *lnwire.MilliSatoshi
+	var amt fn.Option[lnwire.MilliSatoshi]
 	if req.AmtMsat != 0 {
 		rpcAmt := lnwire.MilliSatoshi(req.AmtMsat)
-		amt = &rpcAmt
+		amt = fn.Some(rpcAmt)
 	}
 
 	var outgoingChan *uint64

routing/router.go

@@ -1406,7 +1406,7 @@ func (e ErrNoChannel) Error() string {
 // BuildRoute returns a fully specified route based on a list of pubkeys. If
 // amount is nil, the minimum routable amount is used. To force a specific
 // outgoing channel, use the outgoingChan parameter.
-func (r *ChannelRouter) BuildRoute(amt *lnwire.MilliSatoshi,
+func (r *ChannelRouter) BuildRoute(amt fn.Option[lnwire.MilliSatoshi],
 	hops []route.Vertex, outgoingChan *uint64,
 	finalCltvDelta int32, payAddr *[32]byte) (*route.Route, error) {
 
@@ -1439,43 +1439,36 @@ func (r *ChannelRouter) BuildRoute(amt *lnwire.MilliSatoshi,
 		return nil, err
 	}
 
-	// If no amount is specified, we need to build a route for the minimum
-	// amount that this route can carry.
-	useMinAmt := amt == nil
-
 	var (
 		receiverAmt lnwire.MilliSatoshi
+		senderAmt   lnwire.MilliSatoshi
 		pathEdges   []*unifiedEdge
 	)
 
-	if useMinAmt {
-		// For minimum amount routes, aim to deliver at least 1 msat to
-		// the destination. There are nodes in the wild that have a
-		// min_htlc channel policy of zero, which could lead to a zero
-		// amount payment being made.
-		var senderAmt lnwire.MilliSatoshi
-		pathEdges, senderAmt, err = senderAmtBackwardPass(
-			unifiers, useMinAmt, 1, bandwidthHints,
-		)
-		if err != nil {
-			return nil, err
-		}
-
-		receiverAmt, err = receiverAmtForwardPass(senderAmt, pathEdges)
-		if err != nil {
-			return nil, err
-		}
-	} else {
-		// If an amount is specified, we need to build a route that
-		// delivers exactly this amount to the final destination.
-		pathEdges, _, err = senderAmtBackwardPass(
-			unifiers, useMinAmt, *amt, bandwidthHints,
-		)
-		if err != nil {
-			return nil, err
-		}
+	// We determine the edges compatible with the requested amount, as well
+	// as the amount to send, which can be used to determine the final
+	// receiver amount, if a minimal amount was requested.
+	pathEdges, senderAmt, err = senderAmtBackwardPass(
+		unifiers, amt, bandwidthHints,
+	)
+	if err != nil {
+		return nil, err
+	}
 
-		receiverAmt = *amt
+	// For the minimal amount search, we need to do a forward pass to find a
+	// larger receiver amount due to possible min HTLC bumps, otherwise we
+	// just use the requested amount.
+	receiverAmt, err = fn.ElimOption(
+		amt,
+		func() fn.Result[lnwire.MilliSatoshi] {
+			return fn.NewResult(
+				receiverAmtForwardPass(senderAmt, pathEdges),
+			)
+		},
+		fn.Ok[lnwire.MilliSatoshi],
+	).Unpack()
+	if err != nil {
+		return nil, err
 	}
 
 	// Fetch the current block height outside the routing transaction, to
@@ -1545,9 +1538,9 @@ func getEdgeUnifiers(source route.Vertex, hops []route.Vertex,
 
 // senderAmtBackwardPass returns a list of unified edges for the given route and
 // determines the amount that should be sent to fulfill min HTLC requirements.
-// The minimal sender amount can be searched for by activating useMinAmt.
-func senderAmtBackwardPass(unifiers []*edgeUnifier, useMinAmt bool,
-	receiverAmt lnwire.MilliSatoshi,
+// The minimal sender amount can be searched for by using amt=None.
+func senderAmtBackwardPass(unifiers []*edgeUnifier,
+	amt fn.Option[lnwire.MilliSatoshi],
 	bandwidthHints bandwidthHints) ([]*unifiedEdge, lnwire.MilliSatoshi,
 	error) {
 
@@ -1563,11 +1556,15 @@ func senderAmtBackwardPass(unifiers []*edgeUnifier, useMinAmt bool,
 	// incomingAmt tracks the amount that is forwarded on the edges of a
 	// route. The last hop only forwards the amount that the receiver should
 	// receive, as there are no fees paid to the last node.
-	incomingAmt := receiverAmt
+	// For minimum amount routes, aim to deliver at least 1 msat to
+	// the destination. There are nodes in the wild that have a
+	// min_htlc channel policy of zero, which could lead to a zero
+	// amount payment being made.
+	incomingAmt := amt.UnwrapOr(1)
 
 	// If using min amt, increase the amount if needed to fulfill min HTLC
 	// requirements.
-	if useMinAmt {
+	if amt.IsNone() {
 		min := edgeUnifier.minAmt()
 		if min > incomingAmt {
 			incomingAmt = min
@@ -1591,7 +1588,7 @@ func senderAmtBackwardPass(unifiers []*edgeUnifier, useMinAmt bool,
 
 		// If using min amt, increase the amount if needed to fulfill
 		// min HTLC requirements.
-		if useMinAmt {
+		if amt.IsNone() {
 			min := edgeUnifier.minAmt()
 			if min > incomingAmt {
 				incomingAmt = min

routing/router_test.go

@@ -24,6 +24,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channeldb/models"
 	"github.com/lightningnetwork/lnd/clock"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/graph"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/input"
@@ -1641,14 +1642,16 @@ func TestBuildRoute(t *testing.T) {
 	_, err = rand.Read(payAddr[:])
 	require.NoError(t, err)
 
+	noAmt := fn.None[lnwire.MilliSatoshi]()
+
 	// Test that we can't build a route when no hops are given.
 	hops = []route.Vertex{}
-	_, err = ctx.router.BuildRoute(nil, hops, nil, 40, nil)
+	_, err = ctx.router.BuildRoute(noAmt, hops, nil, 40, nil)
 	require.Error(t, err)
 
 	// Create hop list for an unknown destination.
 	hops := []route.Vertex{ctx.aliases["b"], ctx.aliases["y"]}
-	_, err = ctx.router.BuildRoute(nil, hops, nil, 40, &payAddr)
+	_, err = ctx.router.BuildRoute(noAmt, hops, nil, 40, &payAddr)
 	noChanErr := ErrNoChannel{}
 	require.ErrorAs(t, err, &noChanErr)
 	require.Equal(t, 1, noChanErr.position)
@@ -1658,7 +1661,7 @@ func TestBuildRoute(t *testing.T) {
 	amt := lnwire.NewMSatFromSatoshis(100)
 
 	// Build the route for the given amount.
-	rt, err := ctx.router.BuildRoute(&amt, hops, nil, 40, &payAddr)
+	rt, err := ctx.router.BuildRoute(fn.Some(amt), hops, nil, 40, &payAddr)
 	require.NoError(t, err)
 
 	// Check that we get the expected route back. The total amount should be
@@ -1668,7 +1671,7 @@ func TestBuildRoute(t *testing.T) {
 	require.Equal(t, lnwire.MilliSatoshi(106000), rt.TotalAmount)
 
 	// Build the route for the minimum amount.
-	rt, err = ctx.router.BuildRoute(nil, hops, nil, 40, &payAddr)
+	rt, err = ctx.router.BuildRoute(noAmt, hops, nil, 40, &payAddr)
 	require.NoError(t, err)
 
 	// Check that we get the expected route back. The minimum that we can
@@ -1684,7 +1687,7 @@ func TestBuildRoute(t *testing.T) {
 	// Test a route that contains incompatible channel htlc constraints.
 	// There is no amount that can pass through both channel 5 and 4.
 	hops = []route.Vertex{ctx.aliases["e"], ctx.aliases["c"]}
-	_, err = ctx.router.BuildRoute(nil, hops, nil, 40, nil)
+	_, err = ctx.router.BuildRoute(noAmt, hops, nil, 40, nil)
 	require.Error(t, err)
 	noChanErr = ErrNoChannel{}
 	require.ErrorAs(t, err, &noChanErr)
@@ -1702,7 +1705,7 @@ func TestBuildRoute(t *testing.T) {
 	// amount that could be delivered to the receiver of 21819 msat, using
 	// policy of channel 3.
 	hops = []route.Vertex{ctx.aliases["b"], ctx.aliases["z"]}
-	rt, err = ctx.router.BuildRoute(nil, hops, nil, 40, &payAddr)
+	rt, err = ctx.router.BuildRoute(noAmt, hops, nil, 40, &payAddr)
 	require.NoError(t, err)
 	checkHops(rt, []uint64{1, 8}, payAddr)
 	require.Equal(t, lnwire.MilliSatoshi(21200), rt.TotalAmount)
@@ -1714,7 +1717,7 @@ func TestBuildRoute(t *testing.T) {
 	// We get 106000 - 1000 (base in) - 0.001 * 106000 (rate in) = 104894.
 	hops = []route.Vertex{ctx.aliases["d"], ctx.aliases["f"]}
 	amt = lnwire.NewMSatFromSatoshis(100)
-	rt, err = ctx.router.BuildRoute(&amt, hops, nil, 40, &payAddr)
+	rt, err = ctx.router.BuildRoute(fn.Some(amt), hops, nil, 40, &payAddr)
 	require.NoError(t, err)
 	checkHops(rt, []uint64{9, 10}, payAddr)
 	require.EqualValues(t, 104894, rt.TotalAmount)
@@ -1728,7 +1731,7 @@ func TestBuildRoute(t *testing.T) {
 	// of 20179 msat, which results in underpayment of 1 msat in fee. There
 	// is a third pass through newRoute in which this gets corrected to end
 	hops = []route.Vertex{ctx.aliases["d"], ctx.aliases["f"]}
-	rt, err = ctx.router.BuildRoute(nil, hops, nil, 40, &payAddr)
+	rt, err = ctx.router.BuildRoute(noAmt, hops, nil, 40, &payAddr)
 	require.NoError(t, err)
 	checkHops(rt, []uint64{9, 10}, payAddr)
 	require.EqualValues(t, 20180, rt.TotalAmount, "%v", rt.TotalAmount)
@@ -1919,20 +1922,20 @@ func TestSenderAmtBackwardPass(t *testing.T) {
 	// A search for an amount that is below the minimum HTLC amount should
 	// fail.
 	_, _, err := senderAmtBackwardPass(
-		edgeUnifiers, false, minHTLC-1, &bandwidthHints,
+		edgeUnifiers, fn.Some(minHTLC-1), &bandwidthHints,
 	)
 	require.Error(t, err)
 
 	// Do a min amount search.
-	unifiedEdges, senderAmount, err := senderAmtBackwardPass(
-		edgeUnifiers, true, 1, &bandwidthHints,
+	_, senderAmount, err := senderAmtBackwardPass(
+		edgeUnifiers, fn.None[lnwire.MilliSatoshi](), &bandwidthHints,
 	)
 	require.NoError(t, err)
 	require.Equal(t, minHTLC+333+222+222+111, senderAmount)
 
 	// Do a search for a specific amount.
-	unifiedEdges, senderAmount, err = senderAmtBackwardPass(
-		edgeUnifiers, false, testReceiverAmt, &bandwidthHints,
+	unifiedEdges, senderAmount, err := senderAmtBackwardPass(
+		edgeUnifiers, fn.Some(testReceiverAmt), &bandwidthHints,
 	)
 	require.NoError(t, err)
 	require.Equal(t, testReceiverAmt+333+222+222+111, senderAmount)
@@ -1961,7 +1964,7 @@ func TestSenderAmtBackwardPass(t *testing.T) {
 	}
 
 	unifiedEdges, senderAmount, err = senderAmtBackwardPass(
-		edgeUnifiers, false, testReceiverAmt, &bandwidthHints,
+		edgeUnifiers, fn.Some(testReceiverAmt), &bandwidthHints,
 	)
 	require.NoError(t, err)