watchtower: make use of the new ClientSessionFilterFn option

In this commit, the wtclient starts making use of the new
ClientSessionFilterFn to do any session filtering instead of doing it in
memory.

watchtower/wtclient/client.go

@@ -42,12 +42,24 @@ const (
 	DefaultForceQuitDelay = 10 * time.Second
 )
 
-// genActiveSessionFilter generates a filter that selects active sessions that
+// genSessionFilter constructs a filter that can be used to select sessions only
-// also match the desired channel type, either legacy or anchor.
+// if they match the policy of the client (namely anchor vs legacy). If
-func genActiveSessionFilter(anchor bool) func(*ClientSession) bool {
+// activeOnly is set, then only active sessions will be returned.
-	return func(s *ClientSession) bool {
+func (c *TowerClient) genSessionFilter(
-		return s.Status == wtdb.CSessionActive &&
+	activeOnly bool) wtdb.ClientSessionFilterFn {
-			anchor == s.Policy.IsAnchorChannel()
+
+	return func(session *wtdb.ClientSession) bool {
+		if c.cfg.Policy.IsAnchorChannel() !=
+			session.Policy.IsAnchorChannel() {
+
+			return false
+		}
+
+		if !activeOnly {
+			return true
+		}
+
+		return session.Status == wtdb.CSessionActive
 	}
 }
 
@@ -344,13 +356,6 @@ func New(config *Config) (*TowerClient, error) {
 		perUpdate(s.Policy, u.BackupID.ChanID, u.BackupID.CommitHeight)
 	}
 
-	// Load all candidate sessions and towers from the database into the
-	// client. We will use any of these sessions if their policies match the
-	// current policy of the client, otherwise they will be ignored and new
-	// sessions will be requested.
-	isAnchorClient := cfg.Policy.IsAnchorChannel()
-	activeSessionFilter := genActiveSessionFilter(isAnchorClient)
-
 	candidateTowers := newTowerListIterator()
 	perActiveTower := func(tower *Tower) {
 		// If the tower has already been marked as active, then there is
@@ -366,9 +371,13 @@ func New(config *Config) (*TowerClient, error) {
 		candidateTowers.AddCandidate(tower)
 	}
 
+	// Load all candidate sessions and towers from the database into the
+	// client. We will use any of these sessions if their policies match the
+	// current policy of the client, otherwise they will be ignored and new
+	// sessions will be requested.
 	candidateSessions, err := getTowerAndSessionCandidates(
-		cfg.DB, cfg.SecretKeyRing, activeSessionFilter, perActiveTower,
+		cfg.DB, cfg.SecretKeyRing, c.genSessionFilter(true),
-		wtdb.WithPerMaxHeight(perMaxHeight),
+		perActiveTower, wtdb.WithPerMaxHeight(perMaxHeight),
 		wtdb.WithPerCommittedUpdate(perCommittedUpdate),
 	)
 	if err != nil {
@@ -401,7 +410,7 @@ 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 func(*ClientSession) bool,
+	sessionFilter wtdb.ClientSessionFilterFn,
 	perActiveTower func(tower *Tower),
 	opts ...wtdb.ClientSessionListOption) (
 	map[wtdb.SessionID]*ClientSession, error) {
@@ -418,7 +427,9 @@ func getTowerAndSessionCandidates(db DB, keyRing ECDHKeyRing,
 			return nil, err
 		}
 
-		sessions, err := db.ListClientSessions(&tower.ID, nil, opts...)
+		sessions, err := db.ListClientSessions(
+			&tower.ID, sessionFilter, opts...,
+		)
 		if err != nil {
 			return nil, err
 		}
@@ -438,19 +449,14 @@ func getTowerAndSessionCandidates(db DB, keyRing ECDHKeyRing,
 				towerKeyDesc, keyRing,
 			)
 
-			cs := &ClientSession{
+			// Add the session to the set of candidate sessions.
+			candidateSessions[s.ID] = &ClientSession{
 				ID:                s.ID,
 				ClientSessionBody: s.ClientSessionBody,
 				Tower:             tower,
 				SessionKeyECDH:    sessionKeyECDH,
 			}
 
-			if !sessionFilter(cs) {
-				continue
-			}
-
-			// Add the session to the set of candidate sessions.
-			candidateSessions[s.ID] = cs
 			perActiveTower(tower)
 		}
 	}
@@ -466,11 +472,13 @@ 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,
-	passesFilter func(*ClientSession) bool,
+	sessionFilter wtdb.ClientSessionFilterFn,
 	opts ...wtdb.ClientSessionListOption) (
 	map[wtdb.SessionID]*ClientSession, error) {
 
-	dbSessions, err := db.ListClientSessions(forTower, nil, opts...)
+	dbSessions, err := db.ListClientSessions(
+		forTower, sessionFilter, opts...,
+	)
 	if err != nil {
 		return nil, err
 	}
@@ -494,6 +502,7 @@ func getClientSessions(db DB, keyRing ECDHKeyRing, forTower *wtdb.TowerID,
 		if err != nil {
 			return nil, err
 		}
+
 		sessionKeyECDH := keychain.NewPubKeyECDH(towerKeyDesc, keyRing)
 
 		tower, err := NewTowerFromDBTower(dbTower)
@@ -501,20 +510,12 @@ func getClientSessions(db DB, keyRing ECDHKeyRing, forTower *wtdb.TowerID,
 			return nil, err
 		}
 
-		cs := &ClientSession{
+		sessions[s.ID] = &ClientSession{
 			ID:                s.ID,
 			ClientSessionBody: s.ClientSessionBody,
 			Tower:             tower,
 			SessionKeyECDH:    sessionKeyECDH,
 		}
-
-		// If an optional filter was provided, use it to filter out any
-		// undesired sessions.
-		if passesFilter != nil && !passesFilter(cs) {
-			continue
-		}
-
-		sessions[s.ID] = cs
 	}
 
 	return sessions, nil
@@ -1200,10 +1201,9 @@ func (c *TowerClient) handleNewTower(msg *newTowerMsg) error {
 	c.candidateTowers.AddCandidate(tower)
 
 	// Include all of its corresponding sessions to our set of candidates.
-	isAnchorClient := c.cfg.Policy.IsAnchorChannel()
-	activeSessionFilter := genActiveSessionFilter(isAnchorClient)
 	sessions, err := getClientSessions(
-		c.cfg.DB, c.cfg.SecretKeyRing, &tower.ID, activeSessionFilter,
+		c.cfg.DB, c.cfg.SecretKeyRing, &tower.ID,
+		c.genSessionFilter(true),
 	)
 	if err != nil {
 		return fmt.Errorf("unable to determine sessions for tower %x: "+
@@ -1320,7 +1320,9 @@ func (c *TowerClient) RegisteredTowers(opts ...wtdb.ClientSessionListOption) (
 	if err != nil {
 		return nil, err
 	}
-	clientSessions, err := c.cfg.DB.ListClientSessions(nil, nil, opts...)
+	clientSessions, err := c.cfg.DB.ListClientSessions(
+		nil, c.genSessionFilter(false), opts...,
+	)
 	if err != nil {
 		return nil, err
 	}
@@ -1362,7 +1364,7 @@ func (c *TowerClient) LookupTower(pubKey *btcec.PublicKey,
 	}
 
 	towerSessions, err := c.cfg.DB.ListClientSessions(
-		&tower.ID, nil, opts...,
+		&tower.ID, c.genSessionFilter(false), opts...,
 	)
 	if err != nil {
 		return nil, err