Merge pull request #5236 from offerm/preimage-to-settleevent

feature: expose preimage in forward+settle event

htlcswitch/htlcnotifier.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/htlcswitch/hop"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/subscribe"
 )
@@ -281,6 +282,9 @@ type SettleEvent struct {
 	// forwards with their corresponding forwarding event.
 	HtlcKey
 
+	// Preimage that was released for settling the htlc.
+	Preimage lntypes.Preimage
+
 	// HtlcEventType classifies the event as part of a local send or
 	// receive, or as part of a forward.
 	HtlcEventType
@@ -360,9 +364,12 @@ func (h *HtlcNotifier) NotifyForwardingFailEvent(key HtlcKey,
 // to as part of a forward or a receive to our node has been settled.
 //
 // Note this is part of the htlcNotifier interface.
-func (h *HtlcNotifier) NotifySettleEvent(key HtlcKey, eventType HtlcEventType) {
+func (h *HtlcNotifier) NotifySettleEvent(key HtlcKey,
+	preimage lntypes.Preimage, eventType HtlcEventType) {
+
 	event := &SettleEvent{
 		HtlcKey:       key,
+		Preimage:      preimage,
 		HtlcEventType: eventType,
 		Timestamp:     h.now(),
 	}

htlcswitch/interfaces.go

@@ -286,5 +286,6 @@ type htlcNotifier interface {
 	// NotifySettleEvent notifies the HtlcNotifier that a htlc that we
 	// committed to as part of a forward or a receive to our node has been
 	// settled.
-	NotifySettleEvent(key HtlcKey, eventType HtlcEventType)
+	NotifySettleEvent(key HtlcKey, preimage lntypes.Preimage,
+		eventType HtlcEventType)
 }

htlcswitch/link.go

@@ -1449,6 +1449,7 @@ func (l *channelLink) handleDownstreamPkt(pkt *htlcPacket) {
 		// Send a settle event notification to htlcNotifier.
 		l.cfg.HtlcNotifier.NotifySettleEvent(
 			newHtlcKey(pkt),
+			htlc.PaymentPreimage,
 			getEventType(pkt),
 		)
 
@@ -2990,6 +2991,7 @@ func (l *channelLink) settleHTLC(preimage lntypes.Preimage,
 				HtlcID: pd.HtlcIndex,
 			},
 		},
+		preimage,
 		HtlcEventTypeReceive,
 	)
 

htlcswitch/mock.go

@@ -968,5 +968,6 @@ func (h *mockHTLCNotifier) NotifyForwardingFailEvent(key HtlcKey,
 	eventType HtlcEventType) {
 }
 
-func (h *mockHTLCNotifier) NotifySettleEvent(key HtlcKey, eventType HtlcEventType) {
+func (h *mockHTLCNotifier) NotifySettleEvent(key HtlcKey,
+	preimage lntypes.Preimage, eventType HtlcEventType) {
 }

htlcswitch/switch.go

@@ -848,9 +848,10 @@ func (s *Switch) handleLocalResponse(pkt *htlcPacket) {
 	key := newHtlcKey(pkt)
 	eventType := getEventType(pkt)
 
-	switch pkt.htlc.(type) {
+	switch htlc := pkt.htlc.(type) {
 	case *lnwire.UpdateFulfillHTLC:
-		s.cfg.HtlcNotifier.NotifySettleEvent(key, eventType)
+		s.cfg.HtlcNotifier.NotifySettleEvent(key, htlc.PaymentPreimage,
+			eventType)
 
 	case *lnwire.UpdateFailHTLC:
 		s.cfg.HtlcNotifier.NotifyForwardingFailEvent(key, eventType)

htlcswitch/switch_test.go

@@ -2762,7 +2762,8 @@ func TestInvalidFailure(t *testing.T) {
 // these tests.
 type htlcNotifierEvents func(channels *clusterChannels, htlcID uint64,
 	ts time.Time, htlc *lnwire.UpdateAddHTLC,
-	hops []*hop.Payload) ([]interface{}, []interface{}, []interface{})
+	hops []*hop.Payload,
+	preimage *lntypes.Preimage) ([]interface{}, []interface{}, []interface{})
 
 // TestHtlcNotifier tests the notifying of htlc events that are routed over a
 // three hop network. It sets up an Alice -> Bob -> Carol network and routes
@@ -2793,11 +2794,12 @@ func TestHtlcNotifier(t *testing.T) {
 			expectedEvents: func(channels *clusterChannels,
 				htlcID uint64, ts time.Time,
 				htlc *lnwire.UpdateAddHTLC,
-				hops []*hop.Payload) ([]interface{},
+				hops []*hop.Payload,
+				preimage *lntypes.Preimage) ([]interface{},
 				[]interface{}, []interface{}) {
 
 				return getThreeHopEvents(
-					channels, htlcID, ts, htlc, hops, nil,
+					channels, htlcID, ts, htlc, hops, nil, preimage,
 				)
 			},
 			iterations: 2,
@@ -2812,7 +2814,8 @@ func TestHtlcNotifier(t *testing.T) {
 			expectedEvents: func(channels *clusterChannels,
 				htlcID uint64, ts time.Time,
 				htlc *lnwire.UpdateAddHTLC,
-				hops []*hop.Payload) ([]interface{},
+				hops []*hop.Payload,
+				preimage *lntypes.Preimage) ([]interface{},
 				[]interface{}, []interface{}) {
 
 				return getThreeHopEvents(
@@ -2821,6 +2824,7 @@ func TestHtlcNotifier(t *testing.T) {
 						msg:           &lnwire.FailChannelDisabled{},
 						FailureDetail: OutgoingFailureForwardsDisabled,
 					},
+					preimage,
 				)
 			},
 			iterations: 1,
@@ -2942,11 +2946,12 @@ func testHtcNotifier(t *testing.T, testOpts []serverOption, iterations int,
 	// of htlc ids.
 	for i := 0; i < iterations; i++ {
 		// We'll start off by making a payment from
-		// Alice -> Bob -> Carol.
-		htlc, hops := n.sendThreeHopPayment(t)
+		// Alice -> Bob -> Carol. The preimage, generated
+		// by Carol's Invoice is expected in the Settle events
+		htlc, hops, preimage := n.sendThreeHopPayment(t)
 
 		alice, bob, carol := getEvents(
-			channels, uint64(i), now, htlc, hops,
+			channels, uint64(i), now, htlc, hops, preimage,
 		)
 
 		checkHtlcEvents(t, aliceEvents.Updates(), alice)
@@ -2981,7 +2986,7 @@ func checkHtlcEvents(t *testing.T, events <-chan interface{},
 // Alice -> Bob -> Carol in a three hop network and returns Alice's first htlc
 // and the remainder of the hops.
 func (n *threeHopNetwork) sendThreeHopPayment(t *testing.T) (*lnwire.UpdateAddHTLC,
-	[]*hop.Payload) {
+	[]*hop.Payload, *lntypes.Preimage) {
 
 	amount := lnwire.NewMSatFromSatoshis(btcutil.SatoshiPerBitcoin)
 
@@ -3009,7 +3014,7 @@ func (n *threeHopNetwork) sendThreeHopPayment(t *testing.T) (*lnwire.UpdateAddHT
 		t.Fatalf("could not send htlc")
 	}
 
-	return htlc, hops
+	return htlc, hops, invoice.Terms.PaymentPreimage
 }
 
 // getThreeHopEvents gets the set of htlc events that we expect for a payment
@@ -3017,7 +3022,8 @@ func (n *threeHopNetwork) sendThreeHopPayment(t *testing.T) (*lnwire.UpdateAddHT
 // of events will fail on Bob's outgoing link.
 func getThreeHopEvents(channels *clusterChannels, htlcID uint64,
 	ts time.Time, htlc *lnwire.UpdateAddHTLC, hops []*hop.Payload,
-	linkError *LinkError) ([]interface{}, []interface{}, []interface{}) {
+	linkError *LinkError,
+	preimage *lntypes.Preimage) ([]interface{}, []interface{}, []interface{}) {
 
 	aliceKey := HtlcKey{
 		IncomingCircuit: zeroCircuit,
@@ -3091,6 +3097,7 @@ func getThreeHopEvents(channels *clusterChannels, htlcID uint64,
 		aliceEvents,
 		&SettleEvent{
 			HtlcKey:       aliceKey,
+			Preimage:      *preimage,
 			HtlcEventType: HtlcEventTypeSend,
 			Timestamp:     ts,
 		},
@@ -3105,6 +3112,7 @@ func getThreeHopEvents(channels *clusterChannels, htlcID uint64,
 		},
 		&SettleEvent{
 			HtlcKey:       bobKey,
+			Preimage:      *preimage,
 			HtlcEventType: HtlcEventTypeForward,
 			Timestamp:     ts,
 		},
@@ -3119,6 +3127,7 @@ func getThreeHopEvents(channels *clusterChannels, htlcID uint64,
 				},
 				OutgoingCircuit: zeroCircuit,
 			},
+			Preimage:      *preimage,
 			HtlcEventType: HtlcEventTypeReceive,
 			Timestamp:     ts,
 		},