itest: add testSendToRouteMultiPath

testSendToRouteMultiPath tests that we are able to successfully route a
payment using multiple shards across different paths, by using SendToRoute.

Co-authored-by: Joost Jager <joost.jager@gmail.com>

lntest/itest/lnd_mpp_test.go

@@ -0,0 +1,357 @@
+// +build rpctest
+
+package itest
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/btcsuite/btcd/wire"
+	"github.com/btcsuite/btcutil"
+	"github.com/lightningnetwork/lnd"
+	"github.com/lightningnetwork/lnd/lnrpc"
+	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
+	"github.com/lightningnetwork/lnd/lntest"
+	"github.com/lightningnetwork/lnd/routing/route"
+)
+
+// testSendToRouteMultiPath tests that we are able to successfully route a
+// payment using multiple shards across different paths, by using SendToRoute.
+func testSendToRouteMultiPath(net *lntest.NetworkHarness, t *harnessTest) {
+	ctxb := context.Background()
+
+	// To ensure the payment goes through seperate paths, we'll set a
+	// channel size that can only carry one shard at a time. We'll divide
+	// the payment into 3 shards.
+	const (
+		paymentAmt = btcutil.Amount(300000)
+		shardAmt   = paymentAmt / 3
+		chanAmt    = shardAmt * 3 / 2
+	)
+
+	// Set up a network with three different paths Alice <-> Bob.
+	//              _ Eve _
+	//             /       \
+	// Alice -- Carol ---- Bob
+	//      \              /
+	//       \__ Dave ____/
+	//
+	//
+	// Create the three nodes in addition to Alice and Bob.
+	alice := net.Alice
+	bob := net.Bob
+	carol, err := net.NewNode("carol", nil)
+	if err != nil {
+		t.Fatalf("unable to create carol: %v", err)
+	}
+	defer shutdownAndAssert(net, t, carol)
+
+	dave, err := net.NewNode("dave", nil)
+	if err != nil {
+		t.Fatalf("unable to create dave: %v", err)
+	}
+	defer shutdownAndAssert(net, t, dave)
+
+	eve, err := net.NewNode("eve", nil)
+	if err != nil {
+		t.Fatalf("unable to create eve: %v", err)
+	}
+	defer shutdownAndAssert(net, t, eve)
+
+	nodes := []*lntest.HarnessNode{alice, bob, carol, dave, eve}
+
+	// Connect nodes to ensure propagation of channels.
+	for i := 0; i < len(nodes); i++ {
+		for j := i + 1; j < len(nodes); j++ {
+			ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+			if err := net.EnsureConnected(ctxt, nodes[i], nodes[j]); err != nil {
+				t.Fatalf("unable to connect nodes: %v", err)
+			}
+		}
+	}
+
+	// We'll send shards along three routes from Alice.
+	sendRoutes := [][]*lntest.HarnessNode{
+		{carol, bob},
+		{dave, bob},
+		{carol, eve, bob},
+	}
+
+	// Keep a list of all our active channels.
+	var networkChans []*lnrpc.ChannelPoint
+	var closeChannelFuncs []func()
+
+	// openChannel is a helper to open a channel from->to.
+	openChannel := func(from, to *lntest.HarnessNode, chanSize btcutil.Amount) {
+		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+		err := net.SendCoins(ctxt, btcutil.SatoshiPerBitcoin, from)
+		if err != nil {
+			t.Fatalf("unable to send coins : %v", err)
+		}
+
+		ctxt, _ = context.WithTimeout(ctxb, channelOpenTimeout)
+		chanPoint := openChannelAndAssert(
+			ctxt, t, net, from, to,
+			lntest.OpenChannelParams{
+				Amt: chanSize,
+			},
+		)
+
+		closeChannelFuncs = append(closeChannelFuncs, func() {
+			ctxt, _ := context.WithTimeout(ctxb, channelCloseTimeout)
+			closeChannelAndAssert(
+				ctxt, t, net, from, chanPoint, false,
+			)
+		})
+
+		networkChans = append(networkChans, chanPoint)
+	}
+
+	// Open channels between the nodes.
+	openChannel(carol, bob, chanAmt)
+	openChannel(dave, bob, chanAmt)
+	openChannel(alice, dave, chanAmt)
+	openChannel(eve, bob, chanAmt)
+	openChannel(carol, eve, chanAmt)
+
+	// Since the channel Alice-> Carol will have to carry two
+	// shards, we make it larger.
+	openChannel(alice, carol, chanAmt+shardAmt)
+
+	for _, f := range closeChannelFuncs {
+		defer f()
+	}
+
+	// Wait for all nodes to have seen all channels.
+	for _, chanPoint := range networkChans {
+		for _, node := range nodes {
+			txid, err := lnd.GetChanPointFundingTxid(chanPoint)
+			if err != nil {
+				t.Fatalf("unable to get txid: %v", err)
+			}
+			point := wire.OutPoint{
+				Hash:  *txid,
+				Index: chanPoint.OutputIndex,
+			}
+
+			ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+			err = node.WaitForNetworkChannelOpen(ctxt, chanPoint)
+			if err != nil {
+				t.Fatalf("(%d): timeout waiting for "+
+					"channel(%s) open: %v",
+					node.NodeID, point, err)
+			}
+		}
+	}
+
+	// Make Bob create an invoice for Alice to pay.
+	payReqs, rHashes, invoices, err := createPayReqs(
+		net.Bob, paymentAmt, 1,
+	)
+	if err != nil {
+		t.Fatalf("unable to create pay reqs: %v", err)
+	}
+
+	rHash := rHashes[0]
+	payReq := payReqs[0]
+
+	ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+	decodeResp, err := net.Bob.DecodePayReq(
+		ctxt, &lnrpc.PayReqString{PayReq: payReq},
+	)
+	if err != nil {
+		t.Fatalf("decode pay req: %v", err)
+	}
+
+	payAddr := decodeResp.PaymentAddr
+
+	// Helper function for Alice to build a route from pubkeys.
+	buildRoute := func(amt btcutil.Amount, hops []*lntest.HarnessNode) (
+		*lnrpc.Route, error) {
+
+		rpcHops := make([][]byte, 0, len(hops))
+		for _, hop := range hops {
+			k := hop.PubKeyStr
+			pubkey, err := route.NewVertexFromStr(k)
+			if err != nil {
+				return nil, fmt.Errorf("error parsing %v: %v",
+					k, err)
+			}
+			rpcHops = append(rpcHops, pubkey[:])
+		}
+
+		req := &routerrpc.BuildRouteRequest{
+			AmtMsat:        int64(amt * 1000),
+			FinalCltvDelta: lnd.DefaultBitcoinTimeLockDelta,
+			HopPubkeys:     rpcHops,
+		}
+
+		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+		routeResp, err := net.Alice.RouterClient.BuildRoute(ctxt, req)
+		if err != nil {
+			return nil, err
+		}
+
+		return routeResp.Route, nil
+	}
+
+	responses := make(chan *routerrpc.SendToRouteResponse, len(sendRoutes))
+	for _, hops := range sendRoutes {
+		// Build a route for the specified hops.
+		r, err := buildRoute(shardAmt, hops)
+		if err != nil {
+			t.Fatalf("unable to build route: %v", err)
+		}
+
+		// Set the MPP records to indicate this is a payment shard.
+		hop := r.Hops[len(r.Hops)-1]
+		hop.TlvPayload = true
+		hop.MppRecord = &lnrpc.MPPRecord{
+			PaymentAddr:  payAddr,
+			TotalAmtMsat: int64(paymentAmt * 1000),
+		}
+
+		// Send the shard.
+		sendReq := &routerrpc.SendToRouteRequest{
+			PaymentHash: rHash,
+			Route:       r,
+		}
+
+		// We'll send all shards in their own goroutine, since SendToRoute will
+		// block as long as the payment is in flight.
+		go func() {
+			ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+			resp, err := net.Alice.RouterClient.SendToRoute(ctxt, sendReq)
+			if err != nil {
+				t.Fatalf("unable to send payment: %v", err)
+			}
+
+			responses <- resp
+		}()
+	}
+
+	// Wait for all responses to be back, and check that they all
+	// succeeded.
+	for range sendRoutes {
+		var resp *routerrpc.SendToRouteResponse
+		select {
+		case resp = <-responses:
+		case <-time.After(defaultTimeout):
+			t.Fatalf("response not received")
+		}
+
+		if resp.Failure != nil {
+			t.Fatalf("received payment failure : %v", resp.Failure)
+		}
+
+		// All shards should come back with the preimage.
+		if !bytes.Equal(resp.Preimage, invoices[0].RPreimage) {
+			t.Fatalf("preimage doesn't match")
+		}
+	}
+
+	// assertNumHtlcs is a helper that checks the node's latest payment,
+	// and asserts it was split into num shards.
+	assertNumHtlcs := func(node *lntest.HarnessNode, num int) {
+		req := &lnrpc.ListPaymentsRequest{
+			IncludeIncomplete: true,
+		}
+		ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+		paymentsResp, err := node.ListPayments(ctxt, req)
+		if err != nil {
+			t.Fatalf("error when obtaining payments: %v",
+				err)
+		}
+
+		payments := paymentsResp.Payments
+		if len(payments) == 0 {
+			t.Fatalf("no payments found")
+		}
+
+		payment := payments[len(payments)-1]
+		htlcs := payment.Htlcs
+		if len(htlcs) == 0 {
+			t.Fatalf("no htlcs")
+		}
+
+		succeeded := 0
+		for _, htlc := range htlcs {
+			if htlc.Status == lnrpc.HTLCAttempt_SUCCEEDED {
+				succeeded++
+			}
+		}
+
+		if succeeded != num {
+			t.Fatalf("expected %v succussful HTLCs, got %v", num,
+				succeeded)
+		}
+	}
+
+	// assertSettledInvoice checks that the invoice for the given payment
+	// hash is settled, and has been paid using num HTLCs.
+	assertSettledInvoice := func(node *lntest.HarnessNode, rhash []byte,
+		num int) {
+
+		found := false
+		offset := uint64(0)
+		for !found {
+			ctxt, _ := context.WithTimeout(ctxb, defaultTimeout)
+			invoicesResp, err := node.ListInvoices(
+				ctxt, &lnrpc.ListInvoiceRequest{
+					IndexOffset: offset,
+				},
+			)
+			if err != nil {
+				t.Fatalf("error when obtaining payments: %v",
+					err)
+			}
+
+			if len(invoicesResp.Invoices) == 0 {
+				break
+			}
+
+			for _, inv := range invoicesResp.Invoices {
+				if !bytes.Equal(inv.RHash, rhash) {
+					continue
+				}
+
+				// Assert that the amount paid to the invoice is
+				// correct.
+				if inv.AmtPaidSat != int64(paymentAmt) {
+					t.Fatalf("incorrect payment amt for "+
+						"invoicewant: %d, got %d",
+						paymentAmt, inv.AmtPaidSat)
+				}
+
+				if inv.State != lnrpc.Invoice_SETTLED {
+					t.Fatalf("Invoice not settled: %v",
+						inv.State)
+				}
+
+				if len(inv.Htlcs) != num {
+					t.Fatalf("expected invoice to be "+
+						"settled with %v HTLCs, had %v",
+						num, len(inv.Htlcs))
+				}
+
+				found = true
+				break
+			}
+
+			offset = invoicesResp.LastIndexOffset
+		}
+
+		if !found {
+			t.Fatalf("invoice not found")
+		}
+	}
+
+	// Finally check that the payment shows up with three settled HTLCs in
+	// Alice's list of payments...
+	assertNumHtlcs(net.Alice, 3)
+
+	// ...and in Bob's list of paid invoices.
+	assertSettledInvoice(net.Bob, rHash, 3)
+}

lntest/itest/lnd_test.go

@@ -14908,6 +14908,10 @@ var testsCases = []*testCase{
 		name: "psbt channel funding",
 		test: testPsbtChanFunding,
 	},
+	{
+		name: "sendtoroute multi path payment",
+		test: testSendToRouteMultiPath,
+	},
 }
 
 // TestLightningNetworkDaemon performs a series of integration tests amongst a