htlcswitch: introduce and embed packetHandler interface in ChannelLink

This will allow separating the now-private *htlcPacket methods from
the publicly-used ChannelLink interface methods.

htlcswitch/interfaces.go

@@ -41,6 +41,22 @@ type InvoiceDatabase interface {
 	HodlUnsubscribeAll(subscriber chan<- interface{})
 }
 
+// packetHandler is an interface used exclusively by the Switch to handle
+// htlcPacket and pass them to the link implementation.
+type packetHandler interface {
+	// handleSwitchPacket handles the switch packets. These packets might
+	// be forwarded to us from another channel link in case the htlc
+	// update came from another peer or if the update was created by user
+	// initially.
+	//
+	// NOTE: This function should block as little as possible.
+	handleSwitchPacket(*htlcPacket) error
+
+	// handleLocalAddPacket handles a locally-initiated UpdateAddHTLC
+	// packet. It will be processed synchronously.
+	handleLocalAddPacket(*htlcPacket) error
+}
+
 // ChannelLink is an interface which represents the subsystem for managing the
 // incoming htlc requests, applying the changes to the channel, and also
 // propagating/forwarding it to htlc switch.
@@ -62,18 +78,8 @@ type InvoiceDatabase interface {
 type ChannelLink interface {
 	// TODO(roasbeef): modify interface to embed mail boxes?
 
-	// HandleSwitchPacket handles the switch packets. This packets might be
+	// Embed the packetHandler interface.
-	// forwarded to us from another channel link in case the htlc update
+	packetHandler
-	// came from another peer or if the update was created by user
-	// initially.
-	//
-	// NOTE: This function MUST be non-blocking (or block as little as
-	// possible).
-	HandleSwitchPacket(*htlcPacket) error
-
-	// HandleLocalAddPacket handles a locally-initiated UpdateAddHTLC
-	// packet. It will be processed synchronously.
-	HandleLocalAddPacket(*htlcPacket) error
 
 	// HandleChannelUpdate handles the htlc requests as settle/add/fail
 	// which sent to us from remote peer we have a channel with.

htlcswitch/link.go

@@ -2387,23 +2387,23 @@ func (l *channelLink) String() string {
 	return l.channel.ChannelPoint().String()
 }
 
-// HandleSwitchPacket handles the switch packets. This packets which might be
+// handleSwitchPacket handles the switch packets. This packets which might be
 // forwarded to us from another channel link in case the htlc update came from
 // another peer or if the update was created by user
 //
-// NOTE: Part of the ChannelLink interface.
+// NOTE: Part of the packetHandler interface.
-func (l *channelLink) HandleSwitchPacket(pkt *htlcPacket) error {
+func (l *channelLink) handleSwitchPacket(pkt *htlcPacket) error {
 	l.log.Tracef("received switch packet inkey=%v, outkey=%v",
 		pkt.inKey(), pkt.outKey())
 
 	return l.mailBox.AddPacket(pkt)
 }
 
-// HandleLocalAddPacket handles a locally-initiated UpdateAddHTLC packet. It
+// handleLocalAddPacket handles a locally-initiated UpdateAddHTLC packet. It
 // will be processed synchronously.
 //
-// NOTE: Part of the ChannelLink interface.
+// NOTE: Part of the packetHandler interface.
-func (l *channelLink) HandleLocalAddPacket(pkt *htlcPacket) error {
+func (l *channelLink) handleLocalAddPacket(pkt *htlcPacket) error {
 	l.log.Tracef("received switch packet outkey=%v", pkt.outKey())
 
 	// Create a buffered result channel to prevent the link from blocking.

htlcswitch/link_isolated_test.go

@@ -56,7 +56,7 @@ func (l *linkTestContext) sendHtlcAliceToBob(htlcID int,
 		l.t.Fatalf("expected 1 adds, found %d", len(fwdActions.Adds))
 	}
 
-	err = l.aliceLink.HandleSwitchPacket(&htlcPacket{
+	err = l.aliceLink.handleSwitchPacket(&htlcPacket{
 		incomingHTLCID: uint64(htlcID),
 		htlc:           htlc,
 	})

htlcswitch/link_test.go

@@ -2247,7 +2247,7 @@ func TestChannelLinkBandwidthConsistency(t *testing.T) {
 	}
 
 	addPkt.circuit = &circuit
-	if err := aliceLink.HandleSwitchPacket(&addPkt); err != nil {
+	if err := aliceLink.handleSwitchPacket(&addPkt); err != nil {
 		t.Fatalf("unable to handle switch packet: %v", err)
 	}
 	time.Sleep(time.Millisecond * 500)
@@ -2327,7 +2327,7 @@ func TestChannelLinkBandwidthConsistency(t *testing.T) {
 	}
 
 	addPkt.circuit = &circuit
-	if err := aliceLink.HandleSwitchPacket(&addPkt); err != nil {
+	if err := aliceLink.handleSwitchPacket(&addPkt); err != nil {
 		t.Fatalf("unable to handle switch packet: %v", err)
 	}
 	time.Sleep(time.Millisecond * 500)
@@ -2467,7 +2467,7 @@ func TestChannelLinkBandwidthConsistency(t *testing.T) {
 		obfuscator: NewMockObfuscator(),
 	}
 
-	if err := aliceLink.HandleSwitchPacket(&settlePkt); err != nil {
+	if err := aliceLink.handleSwitchPacket(&settlePkt); err != nil {
 		t.Fatalf("unable to handle switch packet: %v", err)
 	}
 	time.Sleep(time.Millisecond * 500)
@@ -2571,7 +2571,7 @@ func TestChannelLinkBandwidthConsistency(t *testing.T) {
 		obfuscator: NewMockObfuscator(),
 	}
 
-	if err := aliceLink.HandleSwitchPacket(&failPkt); err != nil {
+	if err := aliceLink.handleSwitchPacket(&failPkt); err != nil {
 		t.Fatalf("unable to handle switch packet: %v", err)
 	}
 	time.Sleep(time.Millisecond * 500)
@@ -2709,7 +2709,7 @@ func TestChannelLinkTrimCircuitsPending(t *testing.T) {
 	// Since both were committed successfully, we will now deliver them to
 	// Alice's link.
 	for _, addPkt := range addPkts[:halfHtlcs] {
-		if err := alice.link.HandleSwitchPacket(addPkt); err != nil {
+		if err := alice.link.handleSwitchPacket(addPkt); err != nil {
 			t.Fatalf("unable to handle switch packet: %v", err)
 		}
 	}
@@ -2794,7 +2794,7 @@ func TestChannelLinkTrimCircuitsPending(t *testing.T) {
 	// Deliver the latter two HTLCs to Alice's links so that they can be
 	// processed and added to the in-memory commitment state.
 	for _, addPkt := range addPkts[halfHtlcs:] {
-		if err := alice.link.HandleSwitchPacket(addPkt); err != nil {
+		if err := alice.link.handleSwitchPacket(addPkt); err != nil {
 			t.Fatalf("unable to handle switch packet: %v", err)
 		}
 	}
@@ -2989,7 +2989,7 @@ func TestChannelLinkTrimCircuitsNoCommit(t *testing.T) {
 	// Since both were committed successfully, we will now deliver them to
 	// Alice's link.
 	for _, addPkt := range addPkts[:halfHtlcs] {
-		if err := alice.link.HandleSwitchPacket(addPkt); err != nil {
+		if err := alice.link.handleSwitchPacket(addPkt); err != nil {
 			t.Fatalf("unable to handle switch packet: %v", err)
 		}
 	}
@@ -3082,7 +3082,7 @@ func TestChannelLinkTrimCircuitsNoCommit(t *testing.T) {
 
 	// Deliver the last two HTLCs to the link via Alice's mailbox.
 	for _, addPkt := range addPkts[halfHtlcs:] {
-		if err := alice.link.HandleSwitchPacket(addPkt); err != nil {
+		if err := alice.link.handleSwitchPacket(addPkt); err != nil {
 			t.Fatalf("unable to handle switch packet: %v", err)
 		}
 	}
@@ -3249,7 +3249,7 @@ func TestChannelLinkTrimCircuitsRemoteCommit(t *testing.T) {
 	// Since both were committed successfully, we will now deliver them to
 	// Alice's link.
 	for _, addPkt := range addPkts {
-		if err := alice.link.HandleSwitchPacket(addPkt); err != nil {
+		if err := alice.link.handleSwitchPacket(addPkt); err != nil {
 			t.Fatalf("unable to handle switch packet: %v", err)
 		}
 	}
@@ -3390,7 +3390,7 @@ func TestChannelLinkBandwidthChanReserve(t *testing.T) {
 		t.Fatalf("unable to commit circuit: %v", err)
 	}
 
-	aliceLink.HandleSwitchPacket(addPkt)
+	_ = aliceLink.handleSwitchPacket(addPkt)
 	time.Sleep(time.Millisecond * 100)
 	assertLinkBandwidth(t, aliceLink, aliceStartingBandwidth-htlcAmt-htlcFee)
 
@@ -5139,7 +5139,7 @@ func TestChannelLinkCleanupSpuriousResponses(t *testing.T) {
 		obfuscator:     NewMockObfuscator(),
 		htlc:           &lnwire.UpdateFailHTLC{},
 	}
-	aliceLink.HandleSwitchPacket(fail0)
+	_ = aliceLink.handleSwitchPacket(fail0)
 
 	//  Bob               Alice
 	//   |<----- fal-1 ------|
@@ -5199,7 +5199,7 @@ func TestChannelLinkCleanupSpuriousResponses(t *testing.T) {
 		obfuscator:     NewMockObfuscator(),
 		htlc:           &lnwire.UpdateFailHTLC{},
 	}
-	aliceLink.HandleSwitchPacket(fail1)
+	_ = aliceLink.handleSwitchPacket(fail1)
 
 	//  Bob               Alice
 	//   |<----- fal-1 ------|
@@ -5256,7 +5256,7 @@ func TestChannelLinkCleanupSpuriousResponses(t *testing.T) {
 	// this should trigger an attempt to cleanup the spurious response.
 	// However, we expect it to result in a NOP since it is still missing
 	// its sourceRef.
-	aliceLink.HandleSwitchPacket(fail0)
+	_ = aliceLink.handleSwitchPacket(fail0)
 
 	// Allow the link enough time to process and reject the duplicate
 	// packet, we'll also check that this doesn't trigger Alice to send the
@@ -5311,7 +5311,7 @@ func TestChannelLinkCleanupSpuriousResponses(t *testing.T) {
 		obfuscator:     NewMockObfuscator(),
 		htlc:           &lnwire.UpdateFailHTLC{},
 	}
-	aliceLink.HandleSwitchPacket(fail0)
+	_ = aliceLink.handleSwitchPacket(fail0)
 
 	// Allow the link enough time to process and reject the duplicate
 	// packet, we'll also check that this doesn't trigger Alice to send the

htlcswitch/mock.go

@@ -706,12 +706,12 @@ func newMockChannelLink(htlcSwitch *Switch, chanID lnwire.ChannelID,
 	}
 }
 
-func (f *mockChannelLink) HandleSwitchPacket(pkt *htlcPacket) error {
+func (f *mockChannelLink) handleSwitchPacket(pkt *htlcPacket) error {
 	f.mailBox.AddPacket(pkt)
 	return nil
 }
 
-func (f *mockChannelLink) HandleLocalAddPacket(pkt *htlcPacket) error {
+func (f *mockChannelLink) handleLocalAddPacket(pkt *htlcPacket) error {
 	_ = f.mailBox.AddPacket(pkt)
 	return nil
 }

htlcswitch/switch.go

@@ -509,7 +509,7 @@ func (s *Switch) SendHTLC(firstHop lnwire.ShortChannelID, attemptID uint64,
 		return linkErr
 	}
 
-	return link.HandleLocalAddPacket(packet)
+	return link.handleLocalAddPacket(packet)
 }
 
 // UpdateForwardingPolicies sends a message to the switch to update the
@@ -1101,7 +1101,7 @@ func (s *Switch) handlePacketForward(packet *htlcPacket) error {
 		// Send the packet to the destination channel link which
 		// manages the channel.
 		packet.outgoingChanID = destination.ShortChanID()
-		return destination.HandleSwitchPacket(packet)
+		return destination.handleSwitchPacket(packet)
 
 	case *lnwire.UpdateFailHTLC, *lnwire.UpdateFulfillHTLC:
 		// If the source of this packet has not been set, use the