htlcswitch+peer: CreateAndAddLink in switch, add messageSwitch to peer

This commit allows the peer to be tested without relying on a raw
htlcswitch.Switch pointer. This is accomplished by using a messageSwitch
interface and adding the CreateAndAddLink method to the
htlcswitch.Switch.

htlcswitch/switch.go

@@ -1956,6 +1956,15 @@ func (s *Switch) Stop() error {
 	return nil
 }
 
+// CreateAndAddLink will create a link and then add it to the internal maps
+// when given a ChannelLinkConfig and LightningChannel.
+func (s *Switch) CreateAndAddLink(linkCfg ChannelLinkConfig,
+	lnChan *lnwallet.LightningChannel) error {
+
+	link := NewChannelLink(linkCfg, lnChan)
+	return s.AddLink(link)
+}
+
 // AddLink is used to initiate the handling of the add link command. The
 // request will be propagated and handled in the main goroutine.
 func (s *Switch) AddLink(link ChannelLink) error {

peer/brontide.go

@@ -177,7 +177,7 @@ type Config struct {
 
 	// Switch is a pointer to the htlcswitch. It is used to setup, get, and
 	// tear-down ChannelLinks.
-	Switch *htlcswitch.Switch
+	Switch messageSwitch
 
 	// InterceptSwitch is a pointer to the InterceptableSwitch, a wrapper around
 	// the regular Switch. We only export it here to pass ForwardPackets to the
@@ -841,18 +841,17 @@ func (p *Brontide) addLink(chanPoint *wire.OutPoint,
 		HtlcNotifier:            p.cfg.HtlcNotifier,
 	}
 
-	link := htlcswitch.NewChannelLink(linkCfg, lnChan)
-
 	// Before adding our new link, purge the switch of any pending or live
 	// links going by the same channel id. If one is found, we'll shut it
 	// down to ensure that the mailboxes are only ever under the control of
 	// one link.
-	p.cfg.Switch.RemoveLink(link.ChanID())
+	chanID := lnwire.NewChanIDFromOutPoint(chanPoint)
+	p.cfg.Switch.RemoveLink(chanID)
 
 	// With the channel link created, we'll now notify the htlc switch so
 	// this channel can be used to dispatch local payments and also
 	// passively forward payments.
-	return p.cfg.Switch.AddLink(link)
+	return p.cfg.Switch.CreateAndAddLink(linkCfg, lnChan)
 }
 
 // maybeSendNodeAnn sends our node announcement to the remote peer if at least

peer/interfaces.go

@@ -4,9 +4,36 @@ import (
 	"net"
 	"time"
 
+	"github.com/lightningnetwork/lnd/htlcswitch"
+	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
+// messageSwitch is an interface that abstracts managing the lifecycle of
+// abstract links. This is intended for peer package usage only.
+type messageSwitch interface {
+	// BestHeight returns the best height known to the messageSwitch.
+	BestHeight() uint32
+
+	// CircuitModifier returns a reference to the messageSwitch's internal
+	// CircuitModifier which abstracts the paths payments take and allows
+	// modifying them.
+	CircuitModifier() htlcswitch.CircuitModifier
+
+	// RemoveLink removes an abstract link given a ChannelID.
+	RemoveLink(cid lnwire.ChannelID)
+
+	// CreateAndAddLink creates an abstract link in the messageSwitch given
+	// a ChannelLinkConfig and raw LightningChannel pointer.
+	CreateAndAddLink(cfg htlcswitch.ChannelLinkConfig,
+		lnChan *lnwallet.LightningChannel) error
+
+	// GetLinksByInterface retrieves abstract links (represented by the
+	// ChannelUpdateHandler interface) based on the provided public key.
+	GetLinksByInterface(pub [33]byte) ([]htlcswitch.ChannelUpdateHandler,
+		error)
+}
+
 // LinkUpdater is an interface implemented by most messages in BOLT 2 that are
 // allowed to update the channel state.
 type LinkUpdater interface {

peer/test_utils.go

@@ -29,7 +29,6 @@ import (
 	"github.com/lightningnetwork/lnd/netann"
 	"github.com/lightningnetwork/lnd/queue"
 	"github.com/lightningnetwork/lnd/shachain"
-	"github.com/lightningnetwork/lnd/ticker"
 	"github.com/stretchr/testify/require"
 )
 
@@ -307,28 +306,7 @@ func createTestPeer(notifier chainntnfs.ChainNotifier,
 		},
 	}
 
-	_, currentHeight, err := chainIO.GetBestBlock()
-	if err != nil {
-		return nil, nil, nil, err
-	}
-
-	htlcSwitch, err := htlcswitch.New(htlcswitch.Config{
-		DB:             dbAlice,
-		SwitchPackager: channeldb.NewSwitchPackager(),
-		Notifier:       notifier,
-		FwdEventTicker: ticker.New(
-			htlcswitch.DefaultFwdEventInterval),
-		LogEventTicker: ticker.New(
-			htlcswitch.DefaultLogInterval),
-		AckEventTicker: ticker.New(
-			htlcswitch.DefaultAckInterval),
-	}, uint32(currentHeight))
-	if err != nil {
-		return nil, nil, nil, err
-	}
-	if err = htlcSwitch.Start(); err != nil {
-		return nil, nil, nil, err
-	}
+	htlcSwitch := &mockMessageSwitch{}
 
 	nodeSignerAlice := netann.NewNodeSigner(aliceKeySigner)
 
@@ -342,7 +320,7 @@ func createTestPeer(notifier chainntnfs.ChainNotifier,
 		Graph:                    dbAlice.ChannelGraph(),
 		MessageSigner:            nodeSignerAlice,
 		OurPubKey:                aliceKeyPub,
-		IsChannelActive:          htlcSwitch.HasActiveLink,
+		IsChannelActive:          func(lnwire.ChannelID) bool { return true },
 		ApplyChannelUpdate:       func(*lnwire.ChannelUpdate) error { return nil },
 	})
 	if err != nil {
@@ -374,7 +352,7 @@ func createTestPeer(notifier chainntnfs.ChainNotifier,
 		Switch:      htlcSwitch,
 
 		ChanActiveTimeout: chanActiveTimeout,
-		InterceptSwitch:   htlcswitch.NewInterceptableSwitch(htlcSwitch),
+		InterceptSwitch:   htlcswitch.NewInterceptableSwitch(nil),
 
 		ChannelDB:      dbAlice,
 		FeeEstimator:   estimator,
@@ -395,6 +373,37 @@ func createTestPeer(notifier chainntnfs.ChainNotifier,
 	return alicePeer, channelBob, cleanUpFunc, nil
 }
 
+// mockMessageSwitch is a mock implementation of the messageSwitch interface
+// used for testing without relying on a *htlcswitch.Switch in unit tests.
+type mockMessageSwitch struct{}
+
+// BestHeight currently returns a dummy value.
+func (m *mockMessageSwitch) BestHeight() uint32 {
+	return 0
+}
+
+// CircuitModifier currently returns a dummy value.
+func (m *mockMessageSwitch) CircuitModifier() htlcswitch.CircuitModifier {
+	return nil
+}
+
+// RemoveLink currently does nothing.
+func (m *mockMessageSwitch) RemoveLink(cid lnwire.ChannelID) {}
+
+// CreateAndAddLink currently returns a dummy value.
+func (m *mockMessageSwitch) CreateAndAddLink(cfg htlcswitch.ChannelLinkConfig,
+	lnChan *lnwallet.LightningChannel) error {
+
+	return nil
+}
+
+// GetLinksByInterface currently returns dummy values.
+func (m *mockMessageSwitch) GetLinksByInterface(pub [33]byte) (
+	[]htlcswitch.ChannelUpdateHandler, error) {
+
+	return nil, nil
+}
+
 type mockMessageConn struct {
 	t *testing.T