watchtower: start using the new channel max heights

This commit also adds tests for the DB changes made in the previous
commit since we can now read the new field with the FetchChanInfos
method.

The commit following this one does the backfill migration.

watchtower/wtclient/client.go

@@ -17,6 +17,7 @@ import (
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channelnotifier"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
@@ -296,8 +297,7 @@ type TowerClient struct {
 	closableSessionQueue *sessionCloseMinHeap
 
 	backupMu  sync.Mutex
-	summaries         wtdb.ChannelSummaries
-	chanCommitHeights map[lnwire.ChannelID]uint64
+	chanInfos wtdb.ChannelInfos
 
 	statTicker *time.Ticker
 	stats      *ClientStats
@@ -339,9 +339,7 @@ func New(config *Config) (*TowerClient, error) {
 
 	plog := build.NewPrefixLog(prefix, log)
 
-	// Load the sweep pkscripts that have been generated for all previously
-	// registered channels.
-	chanSummaries, err := cfg.DB.FetchChanSummaries()
+	chanInfos, err := cfg.DB.FetchChanInfos()
 	if err != nil {
 		return nil, err
 	}
@@ -358,9 +356,8 @@ func New(config *Config) (*TowerClient, error) {
 		cfg:                  cfg,
 		log:                  plog,
 		pipeline:             queue,
-		chanCommitHeights:    make(map[lnwire.ChannelID]uint64),
 		activeSessions:       newSessionQueueSet(),
-		summaries:            chanSummaries,
+		chanInfos:            chanInfos,
 		closableSessionQueue: newSessionCloseMinHeap(),
 		statTicker:           time.NewTicker(DefaultStatInterval),
 		stats:                new(ClientStats),
@@ -369,44 +366,6 @@ func New(config *Config) (*TowerClient, error) {
 		quit:                 make(chan struct{}),
 	}
 
-	// perUpdate is a callback function that will be used to inspect the
-	// full set of candidate client sessions loaded from disk, and to
-	// determine the highest known commit height for each channel. This
-	// allows the client to reject backups that it has already processed for
-	// its active policy.
-	perUpdate := func(policy wtpolicy.Policy, chanID lnwire.ChannelID,
-		commitHeight uint64) {
-
-		// We only want to consider accepted updates that have been
-		// accepted under an identical policy to the client's current
-		// policy.
-		if policy != c.cfg.Policy {
-			return
-		}
-
-		c.backupMu.Lock()
-		defer c.backupMu.Unlock()
-
-		// Take the highest commit height found in the session's acked
-		// updates.
-		height, ok := c.chanCommitHeights[chanID]
-		if !ok || commitHeight > height {
-			c.chanCommitHeights[chanID] = commitHeight
-		}
-	}
-
-	perMaxHeight := func(s *wtdb.ClientSession, chanID lnwire.ChannelID,
-		height uint64) {
-
-		perUpdate(s.Policy, chanID, height)
-	}
-
-	perCommittedUpdate := func(s *wtdb.ClientSession,
-		u *wtdb.CommittedUpdate) {
-
-		perUpdate(s.Policy, u.BackupID.ChanID, u.BackupID.CommitHeight)
-	}
-
 	candidateTowers := newTowerListIterator()
 	perActiveTower := func(tower *Tower) {
 		// If the tower has already been marked as active, then there is
@@ -429,8 +388,6 @@ func New(config *Config) (*TowerClient, error) {
 	candidateSessions, err := getTowerAndSessionCandidates(
 		cfg.DB, cfg.SecretKeyRing, perActiveTower,
 		wtdb.WithPreEvalFilterFn(c.genSessionFilter(true)),
-		wtdb.WithPerMaxHeight(perMaxHeight),
-		wtdb.WithPerCommittedUpdate(perCommittedUpdate),
 		wtdb.WithPostEvalFilterFn(ExhaustedSessionFilter()),
 	)
 	if err != nil {
@@ -594,7 +551,7 @@ func (c *TowerClient) Start() error {
 
 		// Iterate over the list of registered channels and check if
 		// any of them can be marked as closed.
-		for id := range c.summaries {
+		for id := range c.chanInfos {
 			isClosed, closedHeight, err := c.isChannelClosed(id)
 			if err != nil {
 				returnErr = err
@@ -615,7 +572,7 @@ func (c *TowerClient) Start() error {
 
 			// Since the channel has been marked as closed, we can
 			// also remove it from the channel summaries map.
-			delete(c.summaries, id)
+			delete(c.chanInfos, id)
 		}
 
 		// Load all closable sessions.
@@ -732,7 +689,7 @@ func (c *TowerClient) RegisterChannel(chanID lnwire.ChannelID) error {
 
 	// If a pkscript for this channel already exists, the channel has been
 	// previously registered.
-	if _, ok := c.summaries[chanID]; ok {
+	if _, ok := c.chanInfos[chanID]; ok {
 		return nil
 	}
 
@@ -752,8 +709,10 @@ func (c *TowerClient) RegisterChannel(chanID lnwire.ChannelID) error {
 
 	// Finally, cache the pkscript in our in-memory cache to avoid db
 	// lookups for the remainder of the daemon's execution.
-	c.summaries[chanID] = wtdb.ClientChanSummary{
+	c.chanInfos[chanID] = &wtdb.ChannelInfo{
+		ClientChanSummary: wtdb.ClientChanSummary{
 			SweepPkScript: pkScript,
+		},
 	}
 
 	return nil
@@ -770,16 +729,23 @@ func (c *TowerClient) BackupState(chanID *lnwire.ChannelID,
 
 	// Make sure that this channel is registered with the tower client.
 	c.backupMu.Lock()
-	if _, ok := c.summaries[*chanID]; !ok {
+	info, ok := c.chanInfos[*chanID]
+	if !ok {
 		c.backupMu.Unlock()
 
 		return ErrUnregisteredChannel
 	}
 
 	// Ignore backups that have already been presented to the client.
-	height, ok := c.chanCommitHeights[*chanID]
-	if ok && stateNum <= height {
+	var duplicate bool
+	info.MaxHeight.WhenSome(func(maxHeight uint64) {
+		if stateNum <= maxHeight {
+			duplicate = true
+		}
+	})
+	if duplicate {
 		c.backupMu.Unlock()
+
 		c.log.Debugf("Ignoring duplicate backup for chanid=%v at "+
 			"height=%d", chanID, stateNum)
 
@@ -789,7 +755,7 @@ func (c *TowerClient) BackupState(chanID *lnwire.ChannelID,
 	// This backup has a higher commit height than any known backup for this
 	// channel. We'll update our tip so that we won't accept it again if the
 	// link flaps.
-	c.chanCommitHeights[*chanID] = stateNum
+	c.chanInfos[*chanID].MaxHeight = fn.Some(stateNum)
 	c.backupMu.Unlock()
 
 	id := &wtdb.BackupID{
@@ -899,7 +865,7 @@ func (c *TowerClient) handleClosedChannel(chanID lnwire.ChannelID,
 	defer c.backupMu.Unlock()
 
 	// We only care about channels registered with the tower client.
-	if _, ok := c.summaries[chanID]; !ok {
+	if _, ok := c.chanInfos[chanID]; !ok {
 		return nil
 	}
 
@@ -924,8 +890,7 @@ func (c *TowerClient) handleClosedChannel(chanID lnwire.ChannelID,
 		return fmt.Errorf("could not track closable sessions: %w", err)
 	}
 
-	delete(c.summaries, chanID)
-	delete(c.chanCommitHeights, chanID)
+	delete(c.chanInfos, chanID)
 
 	return nil
 }
@@ -1332,7 +1297,7 @@ func (c *TowerClient) backupDispatcher() {
 // the prevTask, and should be reprocessed after obtaining a new sessionQueue.
 func (c *TowerClient) processTask(task *wtdb.BackupID) {
 	c.backupMu.Lock()
-	summary, ok := c.summaries[task.ChanID]
+	summary, ok := c.chanInfos[task.ChanID]
 	if !ok {
 		c.backupMu.Unlock()
 

watchtower/wtclient/interface.go

@@ -81,10 +81,10 @@ type DB interface {
 	// successfully backed up using the given session.
 	NumAckedUpdates(id *wtdb.SessionID) (uint64, error)
 
-	// FetchChanSummaries loads a mapping from all registered channels to
-	// their channel summaries. Only the channels that have not yet been
+	// FetchChanInfos loads a mapping from all registered channels to
+	// their wtdb.ChannelInfo. Only the channels that have not yet been
 	// marked as closed will be loaded.
-	FetchChanSummaries() (wtdb.ChannelSummaries, error)
+	FetchChanInfos() (wtdb.ChannelInfos, error)
 
 	// MarkChannelClosed will mark a registered channel as closed by setting
 	// its closed-height as the given block height. It returns a list of

watchtower/wtdb/client_chan_summary.go

@@ -3,11 +3,29 @@ package wtdb
 import (
 	"io"
 
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
-// ChannelSummaries is a map for a given channel id to it's ClientChanSummary.
-type ChannelSummaries map[lnwire.ChannelID]ClientChanSummary
+// ChannelInfos is a map for a given channel id to it's ChannelInfo.
+type ChannelInfos map[lnwire.ChannelID]*ChannelInfo
+
+// ChannelInfo contains various useful things about a registered channel.
+//
+// NOTE: the reason for adding this struct which wraps ClientChanSummary
+// instead of extending ClientChanSummary is for faster look-up of added fields.
+// If we were to extend ClientChanSummary instead then we would need to decode
+// the entire struct each time we want to read the new fields and then re-encode
+// the struct each time we want to write to a new field.
+type ChannelInfo struct {
+	ClientChanSummary
+
+	// MaxHeight is the highest commitment height that the tower has been
+	// handed for this channel. An Option type is used to store this since
+	// a commitment height of zero is valid, and we need a way of knowing if
+	// we have seen a new height yet or not.
+	MaxHeight fn.Option[uint64]
+}
 
 // ClientChanSummary tracks channel-specific information. A new
 // ClientChanSummary is inserted in the database the first time the client

watchtower/wtdb/client_db.go

@@ -9,6 +9,7 @@ import (
 	"sync"
 
 	"github.com/btcsuite/btcd/btcec/v2"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/kvdb"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/tlv"
@@ -1308,11 +1309,11 @@ func (c *ClientDB) NumAckedUpdates(id *SessionID) (uint64, error) {
 	return numAcked, nil
 }
 
-// FetchChanSummaries loads a mapping from all registered channels to their
-// channel summaries. Only the channels that have not yet been marked as closed
-// will be loaded.
-func (c *ClientDB) FetchChanSummaries() (ChannelSummaries, error) {
-	var summaries map[lnwire.ChannelID]ClientChanSummary
+// FetchChanInfos loads a mapping from all registered channels to their
+// ChannelInfo. Only the channels that have not yet been marked as closed will
+// be loaded.
+func (c *ClientDB) FetchChanInfos() (ChannelInfos, error) {
+	var infos ChannelInfos
 
 	err := kvdb.View(c.db, func(tx kvdb.RTx) error {
 		chanDetailsBkt := tx.ReadBucket(cChanDetailsBkt)
@@ -1325,34 +1326,47 @@ func (c *ClientDB) FetchChanSummaries() (ChannelSummaries, error) {
 			if chanDetails == nil {
 				return ErrCorruptChanDetails
 			}
-
 			// If this channel has already been marked as closed,
 			// then its summary does not need to be loaded.
 			closedHeight := chanDetails.Get(cChanClosedHeight)
 			if len(closedHeight) > 0 {
 				return nil
 			}
-
 			var chanID lnwire.ChannelID
 			copy(chanID[:], k)
-
 			summary, err := getChanSummary(chanDetails)
 			if err != nil {
 				return err
 			}
 
-			summaries[chanID] = *summary
+			info := &ChannelInfo{
+				ClientChanSummary: *summary,
+			}
+
+			maxHeightBytes := chanDetails.Get(
+				cChanMaxCommitmentHeight,
+			)
+			if len(maxHeightBytes) != 0 {
+				height, err := readBigSize(maxHeightBytes)
+				if err != nil {
+					return err
+				}
+
+				info.MaxHeight = fn.Some(height)
+			}
+
+			infos[chanID] = info
 
 			return nil
 		})
 	}, func() {
-		summaries = make(map[lnwire.ChannelID]ClientChanSummary)
+		infos = make(ChannelInfos)
 	})
 	if err != nil {
 		return nil, err
 	}
 
-	return summaries, nil
+	return infos, nil
 }
 
 // RegisterChannel registers a channel for use within the client database. For

watchtower/wtdb/client_db_test.go

@@ -156,13 +156,13 @@ func (h *clientDBHarness) loadTowerByID(id wtdb.TowerID,
 	return tower
 }
 
-func (h *clientDBHarness) fetchChanSummaries() map[lnwire.ChannelID]wtdb.ClientChanSummary {
+func (h *clientDBHarness) fetchChanInfos() wtdb.ChannelInfos {
 	h.t.Helper()
 
-	summaries, err := h.db.FetchChanSummaries()
+	infos, err := h.db.FetchChanInfos()
 	require.NoError(h.t, err)
 
-	return summaries
+	return infos
 }
 
 func (h *clientDBHarness) registerChan(chanID lnwire.ChannelID,
@@ -552,7 +552,7 @@ func testRemoveTower(h *clientDBHarness) {
 func testChanSummaries(h *clientDBHarness) {
 	// First, assert that this channel is not already registered.
 	var chanID lnwire.ChannelID
-	_, ok := h.fetchChanSummaries()[chanID]
+	_, ok := h.fetchChanInfos()[chanID]
 	require.Falsef(h.t, ok, "pkscript for channel %x should not exist yet",
 		chanID)
 
@@ -565,7 +565,7 @@ func testChanSummaries(h *clientDBHarness) {
 
 	// Assert that the channel exists and that its sweep pkscript matches
 	// the one we registered.
-	summary, ok := h.fetchChanSummaries()[chanID]
+	summary, ok := h.fetchChanInfos()[chanID]
 	require.Truef(h.t, ok, "pkscript for channel %x should not exist yet",
 		chanID)
 	require.Equal(h.t, expPkScript, summary.SweepPkScript)
@@ -767,6 +767,58 @@ func testRogueUpdates(h *clientDBHarness) {
 	require.Len(h.t, closableSessionsMap, 1)
 }
 
+// testMaxCommitmentHeights tests that the max known commitment height of a
+// channel is properly persisted.
+func testMaxCommitmentHeights(h *clientDBHarness) {
+	const maxUpdates = 5
+	t := h.t
+
+	// Initially, we expect no channels.
+	infos := h.fetchChanInfos()
+	require.Empty(t, infos)
+
+	// Create a new tower.
+	tower := h.newTower()
+
+	// Create and insert a new session.
+	session1 := h.randSession(t, tower.ID, maxUpdates)
+	h.insertSession(session1, nil)
+
+	// Create a new channel and register it.
+	chanID1 := randChannelID(t)
+	h.registerChan(chanID1, nil, nil)
+
+	// At this point, we expect one channel to be returned from
+	// fetchChanInfos but with an unset max height.
+	infos = h.fetchChanInfos()
+	require.Len(t, infos, 1)
+
+	info, ok := infos[chanID1]
+	require.True(t, ok)
+	require.True(t, info.MaxHeight.IsNone())
+
+	// Commit and ACK some updates for this channel.
+	for i := 1; i <= maxUpdates; i++ {
+		update := randCommittedUpdateForChanWithHeight(
+			t, chanID1, uint16(i), uint64(i-1),
+		)
+		lastApplied := h.commitUpdate(&session1.ID, update, nil)
+		h.ackUpdate(&session1.ID, uint16(i), lastApplied, nil)
+	}
+
+	// Assert that the max height has now been set accordingly for this
+	// channel.
+	infos = h.fetchChanInfos()
+	require.Len(t, infos, 1)
+
+	info, ok = infos[chanID1]
+	require.True(t, ok)
+	require.True(t, info.MaxHeight.IsSome())
+	info.MaxHeight.WhenSome(func(u uint64) {
+		require.EqualValues(t, maxUpdates-1, u)
+	})
+}
+
 // testMarkChannelClosed asserts the behaviour of MarkChannelClosed.
 func testMarkChannelClosed(h *clientDBHarness) {
 	tower := h.newTower()
@@ -1097,6 +1149,10 @@ func TestClientDB(t *testing.T) {
 			name: "rogue updates",
 			run:  testRogueUpdates,
 		},
+		{
+			name: "max commitment heights",
+			run:  testMaxCommitmentHeights,
+		},
 	}
 
 	for _, database := range dbs {

watchtower/wtdb/queue_test.go

@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/lightningnetwork/lnd/kvdb"
+	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/watchtower/wtdb"
 	"github.com/stretchr/testify/require"
 )
@@ -31,6 +32,14 @@ func TestDiskQueue(t *testing.T) {
 		require.NoError(t, err)
 	})
 
+	// In order to test that the queue's `onItemWrite` call back (which in
+	// this case will be set to maybeUpdateMaxCommitHeight) is executed as
+	// expected, we need to register a channel so that we can later assert
+	// that it's max height field was updated properly.
+	var chanID lnwire.ChannelID
+	err = db.RegisterChannel(chanID, []byte{})
+	require.NoError(t, err)
+
 	namespace := []byte("test-namespace")
 	queue := db.GetDBQueue(namespace)
 
@@ -110,4 +119,19 @@ func TestDiskQueue(t *testing.T) {
 	// This should not have changed the order of the tasks, they should
 	// still appear in the correct order.
 	popAndAssert(task1, task2, task3, task4, task5, task6)
+
+	// Finally, we check that the `onItemWrite` call back was executed by
+	// the queue. We do this by checking that the channel's recorded max
+	// commitment height was set correctly. It should be equal to the height
+	// recorded in task6.
+	infos, err := db.FetchChanInfos()
+	require.NoError(t, err)
+	require.Len(t, infos, 1)
+
+	info, ok := infos[chanID]
+	require.True(t, ok)
+	require.True(t, info.MaxHeight.IsSome())
+	info.MaxHeight.WhenSome(func(height uint64) {
+		require.EqualValues(t, task6.CommitHeight, height)
+	})
 }