swap: add lasthop, outgoingchanids to swapinfo

interface.go

@@ -353,6 +353,15 @@ type SwapInfo struct {
 
 	// ExternalHtlc is set to true for external loop-in swaps.
 	ExternalHtlc bool
+
+	// LastHop optionally specifies the last hop to use for the loop in
+	// payment. On a loop out this field is nil.
+	LastHop *route.Vertex
+
+	// OutgoingChanSet optionally specifies the short channel ids of the
+	// channels that may be used to loop out. On a loop in this field
+	// is nil.
+	OutgoingChanSet loopdb.ChannelSet
 }
 
 // LastUpdate returns the last update time of the swap

loopin.go

@@ -431,6 +431,14 @@ func (s *loopInSwap) sendUpdate(ctx context.Context) error {
 	info.HtlcAddressNP2WSH = s.htlcNP2WSH.Address
 	info.ExternalHtlc = s.ExternalHtlc
 
+	// In order to avoid potentially dangerous ownership sharing
+	// we copy the last hop vertex.
+	if s.LastHop != nil {
+		lastHop := &route.Vertex{}
+		copy(lastHop[:], s.LastHop[:])
+		info.LastHop = lastHop
+	}
+
 	select {
 	case s.statusChan <- *info:
 	case <-ctx.Done():

loopin_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/lightninglabs/loop/test"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/routing/route"
 	"github.com/stretchr/testify/require"
 )
 
@@ -34,9 +35,14 @@ func TestLoopInSuccess(t *testing.T) {
 
 	cfg := newSwapConfig(&ctx.lnd.LndServices, ctx.store, ctx.server)
 
+	expectedLastHop := &route.Vertex{0x02}
+
+	req := &testLoopInRequest
+	req.LastHop = expectedLastHop
+
 	initResult, err := newLoopInSwap(
 		context.Background(), cfg,
-		height, &testLoopInRequest,
+		height, req,
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -54,7 +60,14 @@ func TestLoopInSuccess(t *testing.T) {
 		errChan <- err
 	}()
 
-	ctx.assertState(loopdb.StateInitiated)
+	swapInfo := <-ctx.statusChan
+	require.Equal(t, loopdb.StateInitiated, swapInfo.State)
+
+	// Check that the SwapInfo contains the provided last hop.
+	require.Equal(t, expectedLastHop, swapInfo.LastHop)
+
+	// Check that the SwapInfo does not contain an outgoing chan set.
+	require.Nil(t, swapInfo.OutgoingChanSet)
 
 	ctx.assertState(loopdb.StateHtlcPublished)
 	ctx.store.assertLoopInState(loopdb.StateHtlcPublished)

loopout.go

@@ -306,6 +306,15 @@ func (s *loopOutSwap) sendUpdate(ctx context.Context) error {
 
 	info.HtlcAddressP2WSH = s.htlc.Address
 
+	// In order to avoid potentially dangerous ownership sharing
+	// we copy the outgoing channel set.
+	if s.OutgoingChanSet != nil {
+		outgoingChanSet := make(loopdb.ChannelSet, len(s.OutgoingChanSet))
+		copy(outgoingChanSet[:], s.OutgoingChanSet[:])
+
+		info.OutgoingChanSet = outgoingChanSet
+	}
+
 	select {
 	case s.statusChan <- *info:
 	case <-ctx.Done():

loopout_test.go

@@ -52,9 +52,11 @@ func TestLoopOutPaymentParameters(t *testing.T) {
 
 	const maxParts = 5
 
+	chanSet := loopdb.ChannelSet{2, 3}
+
 	// Initiate the swap.
 	req := *testRequest
-	req.OutgoingChanSet = loopdb.ChannelSet{2, 3}
+	req.OutgoingChanSet = chanSet
 
 	initResult, err := newLoopOutSwap(
 		context.Background(), cfg, height, &req,
@@ -90,6 +92,12 @@ func TestLoopOutPaymentParameters(t *testing.T) {
 		t.Fatal("unexpected state")
 	}
 
+	// Check that the SwapInfo contains the outgoing chan set
+	require.Equal(t, chanSet, state.OutgoingChanSet)
+
+	// Check that the SwapInfo does not contain a last hop
+	require.Nil(t, state.LastHop)
+
 	// Intercept the swap and prepay payments. Order is undefined.
 	payments := []test.RouterPaymentChannelMessage{
 		<-ctx.Lnd.RouterSendPaymentChannel,