watchtower: add PreEvaluateFilterFn callback

In this commit, a PreEvaluateFilterFn option is added to the
wtdb.ClientSessionListCfg and it is used instead of a separate
ClientSessionFilterFn parameter. This neatens quiet a few function
signatures.

watchtower/wtclient/client.go

@@ -410,8 +410,9 @@ func New(config *Config) (*TowerClient, error) {
 	// current policy of the client, otherwise they will be ignored and new
 	// sessions will be requested.
 	candidateSessions, err := getTowerAndSessionCandidates(
-		cfg.DB, cfg.SecretKeyRing, c.genSessionFilter(true),
-		perActiveTower, wtdb.WithPerMaxHeight(perMaxHeight),
+		cfg.DB, cfg.SecretKeyRing, perActiveTower,
+		wtdb.WithPreEvalFilterFn(c.genSessionFilter(true)),
+		wtdb.WithPerMaxHeight(perMaxHeight),
 		wtdb.WithPerCommittedUpdate(perCommittedUpdate),
 	)
 	if err != nil {
@@ -444,7 +445,6 @@ func New(config *Config) (*TowerClient, error) {
 // sessionFilter check then the perActiveTower call-back will be called on that
 // tower.
 func getTowerAndSessionCandidates(db DB, keyRing ECDHKeyRing,
-	sessionFilter wtdb.ClientSessionFilterFn,
 	perActiveTower func(tower *Tower),
 	opts ...wtdb.ClientSessionListOption) (
 	map[wtdb.SessionID]*ClientSession, error) {
@@ -461,18 +461,12 @@ func getTowerAndSessionCandidates(db DB, keyRing ECDHKeyRing,
 			return nil, err
 		}
 
-		sessions, err := db.ListClientSessions(
-			&tower.ID, sessionFilter, opts...,
-		)
+		sessions, err := db.ListClientSessions(&tower.ID, opts...)
 		if err != nil {
 			return nil, err
 		}
 
 		for _, s := range sessions {
-			if !sessionFilter(s) {
-				continue
-			}
-
 			cs, err := NewClientSessionFromDBSession(
 				s, tower, keyRing,
 			)
@@ -498,13 +492,10 @@ func getTowerAndSessionCandidates(db DB, keyRing ECDHKeyRing,
 // ClientSession's SessionPrivKey field is desired, otherwise, the existing
 // ListClientSessions method should be used.
 func getClientSessions(db DB, keyRing ECDHKeyRing, forTower *wtdb.TowerID,
-	sessionFilter wtdb.ClientSessionFilterFn,
 	opts ...wtdb.ClientSessionListOption) (
 	map[wtdb.SessionID]*ClientSession, error) {
 
-	dbSessions, err := db.ListClientSessions(
-		forTower, sessionFilter, opts...,
-	)
+	dbSessions, err := db.ListClientSessions(forTower, opts...)
 	if err != nil {
 		return nil, err
 	}
@@ -1635,7 +1626,7 @@ func (c *TowerClient) handleNewTower(msg *newTowerMsg) error {
 	// Include all of its corresponding sessions to our set of candidates.
 	sessions, err := getClientSessions(
 		c.cfg.DB, c.cfg.SecretKeyRing, &tower.ID,
-		c.genSessionFilter(true),
+		wtdb.WithPreEvalFilterFn(c.genSessionFilter(true)),
 	)
 	if err != nil {
 		return fmt.Errorf("unable to determine sessions for tower %x: "+
@@ -1721,7 +1712,7 @@ func (c *TowerClient) handleStaleTower(msg *staleTowerMsg) error {
 	// Otherwise, the tower should no longer be used for future session
 	// negotiations and backups.
 	pubKey := msg.pubKey.SerializeCompressed()
-	sessions, err := c.cfg.DB.ListClientSessions(&dbTower.ID, nil)
+	sessions, err := c.cfg.DB.ListClientSessions(&dbTower.ID)
 	if err != nil {
 		return fmt.Errorf("unable to retrieve sessions for tower %x: "+
 			"%v", pubKey, err)
@@ -1752,9 +1743,10 @@ func (c *TowerClient) RegisteredTowers(opts ...wtdb.ClientSessionListOption) (
 	if err != nil {
 		return nil, err
 	}
-	clientSessions, err := c.cfg.DB.ListClientSessions(
-		nil, c.genSessionFilter(false), opts...,
-	)
+
+	opts = append(opts, wtdb.WithPreEvalFilterFn(c.genSessionFilter(false)))
+
+	clientSessions, err := c.cfg.DB.ListClientSessions(nil, opts...)
 	if err != nil {
 		return nil, err
 	}
@@ -1795,9 +1787,9 @@ func (c *TowerClient) LookupTower(pubKey *btcec.PublicKey,
 		return nil, err
 	}
 
-	towerSessions, err := c.cfg.DB.ListClientSessions(
-		&tower.ID, c.genSessionFilter(false), opts...,
-	)
+	opts = append(opts, wtdb.WithPreEvalFilterFn(c.genSessionFilter(false)))
+
+	towerSessions, err := c.cfg.DB.ListClientSessions(&tower.ID, opts...)
 	if err != nil {
 		return nil, err
 	}

watchtower/wtclient/client_test.go

@@ -870,7 +870,7 @@ func (h *testHarness) relevantSessions(chanID uint64) []wtdb.SessionID {
 		},
 	)
 
-	_, err := h.clientDB.ListClientSessions(nil, nil, collectSessions)
+	_, err := h.clientDB.ListClientSessions(nil, collectSessions)
 	require.NoError(h.t, err)
 
 	return sessionIDs
@@ -1969,7 +1969,7 @@ var clientTests = []clientTest{
 
 			// Also make a note of the total number of sessions the
 			// client has.
-			sessions, err := h.clientDB.ListClientSessions(nil, nil)
+			sessions, err := h.clientDB.ListClientSessions(nil)
 			require.NoError(h.t, err)
 			require.Len(h.t, sessions, 4)
 
@@ -1981,9 +1981,7 @@ var clientTests = []clientTest{
 			// marked as closable. The server should also no longer
 			// have these sessions in its DB.
 			err = wait.Predicate(func() bool {
-				sess, err := h.clientDB.ListClientSessions(
-					nil, nil,
-				)
+				sess, err := h.clientDB.ListClientSessions(nil)
 				require.NoError(h.t, err)
 
 				cs, err := h.clientDB.ListClosableSessions()

watchtower/wtclient/interface.go

@@ -60,8 +60,7 @@ type DB interface {
 	// ListClientSessions returns the set of all client sessions known to
 	// the db. An optional tower ID can be used to filter out any client
 	// sessions in the response that do not correspond to this tower.
-	ListClientSessions(*wtdb.TowerID, wtdb.ClientSessionFilterFn,
-		...wtdb.ClientSessionListOption) (
+	ListClientSessions(*wtdb.TowerID, ...wtdb.ClientSessionListOption) (
 		map[wtdb.SessionID]*wtdb.ClientSession, error)
 
 	// GetClientSession loads the ClientSession with the given ID from the

watchtower/wtdb/client_db.go

@@ -517,7 +517,7 @@ func (c *ClientDB) RemoveTower(pubKey *btcec.PublicKey, addr net.Addr) error {
 
 		towerSessions, err := c.listTowerSessions(
 			towerID, sessions, chanIDIndexBkt,
-			towersToSessionsIndex, nil,
+			towersToSessionsIndex,
 			WithPerCommittedUpdate(perCommittedUpdate),
 		)
 		if err != nil {
@@ -1055,7 +1055,7 @@ func (c *ClientDB) GetClientSession(id SessionID,
 		}
 
 		session, err := c.getClientSession(
-			sessionsBkt, chanIDIndexBkt, id[:], nil, opts...,
+			sessionsBkt, chanIDIndexBkt, id[:], opts...,
 		)
 		if err != nil {
 			return err
@@ -1073,8 +1073,7 @@ func (c *ClientDB) GetClientSession(id SessionID,
 // optional tower ID can be used to filter out any client sessions in the
 // response that do not correspond to this tower.
 func (c *ClientDB) ListClientSessions(id *TowerID,
-	filterFn ClientSessionFilterFn, opts ...ClientSessionListOption) (
-	map[SessionID]*ClientSession, error) {
+	opts ...ClientSessionListOption) (map[SessionID]*ClientSession, error) {
 
 	var clientSessions map[SessionID]*ClientSession
 	err := kvdb.View(c.db, func(tx kvdb.RTx) error {
@@ -1093,7 +1092,7 @@ func (c *ClientDB) ListClientSessions(id *TowerID,
 		var err error
 		if id == nil {
 			clientSessions, err = c.listClientAllSessions(
-				sessions, chanIDIndexBkt, filterFn, opts...,
+				sessions, chanIDIndexBkt, opts...,
 			)
 			return err
 		}
@@ -1106,7 +1105,7 @@ func (c *ClientDB) ListClientSessions(id *TowerID,
 
 		clientSessions, err = c.listTowerSessions(
 			*id, sessions, chanIDIndexBkt, towerToSessionIndex,
-			filterFn, opts...,
+			opts...,
 		)
 		return err
 	}, func() {
@@ -1121,8 +1120,7 @@ func (c *ClientDB) ListClientSessions(id *TowerID,
 
 // listClientAllSessions returns the set of all client sessions known to the db.
 func (c *ClientDB) listClientAllSessions(sessions, chanIDIndexBkt kvdb.RBucket,
-	filterFn ClientSessionFilterFn, opts ...ClientSessionListOption) (
-	map[SessionID]*ClientSession, error) {
+	opts ...ClientSessionListOption) (map[SessionID]*ClientSession, error) {
 
 	clientSessions := make(map[SessionID]*ClientSession)
 	err := sessions.ForEach(func(k, _ []byte) error {
@@ -1131,7 +1129,7 @@ func (c *ClientDB) listClientAllSessions(sessions, chanIDIndexBkt kvdb.RBucket,
 		// committed updates and compute the highest known commit height
 		// for each channel.
 		session, err := c.getClientSession(
-			sessions, chanIDIndexBkt, k, filterFn, opts...,
+			sessions, chanIDIndexBkt, k, opts...,
 		)
 		if errors.Is(err, ErrSessionFailedFilterFn) {
 			return nil
@@ -1153,8 +1151,8 @@ func (c *ClientDB) listClientAllSessions(sessions, chanIDIndexBkt kvdb.RBucket,
 // listTowerSessions returns the set of all client sessions known to the db
 // that are associated with the given tower id.
 func (c *ClientDB) listTowerSessions(id TowerID, sessionsBkt, chanIDIndexBkt,
-	towerToSessionIndex kvdb.RBucket, filterFn ClientSessionFilterFn,
-	opts ...ClientSessionListOption) (map[SessionID]*ClientSession, error) {
+	towerToSessionIndex kvdb.RBucket, opts ...ClientSessionListOption) (
+	map[SessionID]*ClientSession, error) {
 
 	towerIndexBkt := towerToSessionIndex.NestedReadBucket(id.Bytes())
 	if towerIndexBkt == nil {
@@ -1168,7 +1166,7 @@ func (c *ClientDB) listTowerSessions(id TowerID, sessionsBkt, chanIDIndexBkt,
 		// committed updates and compute the highest known commit height
 		// for each channel.
 		session, err := c.getClientSession(
-			sessionsBkt, chanIDIndexBkt, k, filterFn, opts...,
+			sessionsBkt, chanIDIndexBkt, k, opts...,
 		)
 		if errors.Is(err, ErrSessionFailedFilterFn) {
 			return nil
@@ -2140,6 +2138,13 @@ type ClientSessionListCfg struct {
 	// PerCommittedUpdate will, if set, be called for each of the session's
 	// committed (un-acked) updates.
 	PerCommittedUpdate PerCommittedUpdateCB
+
+	// PreEvaluateFilterFn will be run after loading a session from the DB
+	// and _before_ any of the other call-back functions in
+	// ClientSessionListCfg. Therefore, if a session fails this filter
+	// function, then it will not be passed to any of the other call backs
+	// and won't be included in the return list.
+	PreEvaluateFilterFn ClientSessionFilterFn
 }
 
 // NewClientSessionCfg constructs a new ClientSessionListCfg.
@@ -2174,12 +2179,22 @@ func WithPerCommittedUpdate(cb PerCommittedUpdateCB) ClientSessionListOption {
 	}
 }
 
+// WithPreEvalFilterFn constructs a functional option that will set a call-back
+// function that will be called immediately after loading a session. If the
+// session fails this filter function, then it will not be passed to any of the
+// other evaluation call-back functions.
+func WithPreEvalFilterFn(fn ClientSessionFilterFn) ClientSessionListOption {
+	return func(cfg *ClientSessionListCfg) {
+		cfg.PreEvaluateFilterFn = fn
+	}
+}
+
 // getClientSession loads the full ClientSession associated with the serialized
 // session id. This method populates the CommittedUpdates, AckUpdates and Tower
 // in addition to the ClientSession's body.
 func (c *ClientDB) getClientSession(sessionsBkt, chanIDIndexBkt kvdb.RBucket,
-	idBytes []byte, filterFn ClientSessionFilterFn,
-	opts ...ClientSessionListOption) (*ClientSession, error) {
+	idBytes []byte, opts ...ClientSessionListOption) (*ClientSession,
+	error) {
 
 	cfg := NewClientSessionCfg()
 	for _, o := range opts {
@@ -2191,7 +2206,7 @@ func (c *ClientDB) getClientSession(sessionsBkt, chanIDIndexBkt kvdb.RBucket,
 		return nil, err
 	}
 
-	if filterFn != nil && !filterFn(session) {
+	if cfg.PreEvaluateFilterFn != nil && !cfg.PreEvaluateFilterFn(session) {
 		return nil, ErrSessionFailedFilterFn
 	}
 

watchtower/wtdb/client_db_test.go

@@ -52,12 +52,11 @@ func (h *clientDBHarness) insertSession(session *wtdb.ClientSession,
 }
 
 func (h *clientDBHarness) listSessions(id *wtdb.TowerID,
-	filterFn wtdb.ClientSessionFilterFn,
 	opts ...wtdb.ClientSessionListOption) map[wtdb.SessionID]*wtdb.ClientSession {
 
 	h.t.Helper()
 
-	sessions, err := h.db.ListClientSessions(id, filterFn, opts...)
+	sessions, err := h.db.ListClientSessions(id, opts...)
 	require.NoError(h.t, err, "unable to list client sessions")
 
 	return sessions
@@ -84,7 +83,7 @@ func (h *clientDBHarness) createTower(lnAddr *lnwire.NetAddress,
 	require.ErrorIs(h.t, err, expErr)
 	require.NotZero(h.t, tower.ID, "tower id should never be 0")
 
-	for _, session := range h.listSessions(&tower.ID, nil) {
+	for _, session := range h.listSessions(&tower.ID) {
 		require.Equal(h.t, wtdb.CSessionActive, session.Status)
 	}
 
@@ -127,7 +126,7 @@ func (h *clientDBHarness) removeTower(pubKey *btcec.PublicKey, addr net.Addr,
 			return
 		}
 
-		for _, session := range h.listSessions(&tower.ID, nil) {
+		for _, session := range h.listSessions(&tower.ID) {
 			require.Equal(h.t, wtdb.CSessionInactive,
 				session.Status, "expected status for session "+
 					"%v to be %v, got %v", session.ID,
@@ -301,7 +300,7 @@ func testCreateClientSession(h *clientDBHarness) {
 
 	// First, assert that this session is not already present in the
 	// database.
-	_, ok := h.listSessions(nil, nil)[session.ID]
+	_, ok := h.listSessions(nil)[session.ID]
 	require.Falsef(h.t, ok, "session for id %x should not exist yet",
 		session.ID)
 
@@ -329,7 +328,7 @@ func testCreateClientSession(h *clientDBHarness) {
 	h.insertSession(session, nil)
 
 	// Verify that the session now exists in the database.
-	_, ok = h.listSessions(nil, nil)[session.ID]
+	_, ok = h.listSessions(nil)[session.ID]
 	require.Truef(h.t, ok, "session for id %x should exist now", session.ID)
 
 	// Attempt to insert the session again, which should fail due to the
@@ -377,7 +376,7 @@ func testFilterClientSessions(h *clientDBHarness) {
 	// We should see the expected sessions for each tower when filtering
 	// them.
 	for towerID, expectedSessions := range towerSessions {
-		sessions := h.listSessions(&towerID, nil)
+		sessions := h.listSessions(&towerID)
 		require.Len(h.t, sessions, len(expectedSessions))
 
 		for _, expectedSession := range expectedSessions {

watchtower/wtmock/client_db.go

@@ -89,7 +89,7 @@ func (m *ClientDB) CreateTower(lnAddr *lnwire.NetAddress) (*wtdb.Tower, error) {
 		tower = m.towers[towerID]
 		tower.AddAddress(lnAddr.Address)
 
-		towerSessions, err := m.listClientSessions(&towerID, nil)
+		towerSessions, err := m.listClientSessions(&towerID)
 		if err != nil {
 			return nil, err
 		}
@@ -141,7 +141,7 @@ func (m *ClientDB) RemoveTower(pubKey *btcec.PublicKey, addr net.Addr) error {
 		return nil
 	}
 
-	towerSessions, err := m.listClientSessions(&tower.ID, nil)
+	towerSessions, err := m.listClientSessions(&tower.ID)
 	if err != nil {
 		return err
 	}
@@ -226,20 +226,19 @@ func (m *ClientDB) MarkBackupIneligible(_ lnwire.ChannelID, _ uint64) error {
 // optional tower ID can be used to filter out any client sessions in the
 // response that do not correspond to this tower.
 func (m *ClientDB) ListClientSessions(tower *wtdb.TowerID,
-	filterFn wtdb.ClientSessionFilterFn,
 	opts ...wtdb.ClientSessionListOption) (
 	map[wtdb.SessionID]*wtdb.ClientSession, error) {
 
 	m.mu.Lock()
 	defer m.mu.Unlock()
-	return m.listClientSessions(tower, filterFn, opts...)
+
+	return m.listClientSessions(tower, opts...)
 }
 
 // listClientSessions returns the set of all client sessions known to the db. An
 // optional tower ID can be used to filter out any client sessions in the
 // response that do not correspond to this tower.
 func (m *ClientDB) listClientSessions(tower *wtdb.TowerID,
-	filterFn wtdb.ClientSessionFilterFn,
 	opts ...wtdb.ClientSessionListOption) (
 	map[wtdb.SessionID]*wtdb.ClientSession, error) {
 
@@ -255,7 +254,9 @@ func (m *ClientDB) listClientSessions(tower *wtdb.TowerID,
 			continue
 		}
 
-		if filterFn != nil && !filterFn(&session) {
+		if cfg.PreEvaluateFilterFn != nil &&
+			!cfg.PreEvaluateFilterFn(&session) {
+
 			continue
 		}