watchtower: always populate Tower in ClientSession

In this commit, we make sure to always populate the Tower member of a
ClientSession. This is done for consistency.

watchtower/wtclient/client.go

@@ -354,8 +354,8 @@ func New(config *Config) (*TowerClient, error) {
 // optional filter can be provided to filter out any undesired client sessions.
 //
 // NOTE: This method should only be used when deserialization of a
-// ClientSession's Tower and SessionPrivKey fields is desired, otherwise, the
+// ClientSession's SessionPrivKey field is desired, otherwise, the existing
-// existing ListClientSessions method should be used.
+// ListClientSessions method should be used.
 func getClientSessions(db DB, keyRing ECDHKeyRing, forTower *wtdb.TowerID,
 	passesFilter func(*wtdb.ClientSession) bool) (
 	map[wtdb.SessionID]*wtdb.ClientSession, error) {
@@ -371,12 +371,6 @@ func getClientSessions(db DB, keyRing ECDHKeyRing, forTower *wtdb.TowerID,
 	// requests. This prevents us from having to store the private keys on
 	// disk.
 	for _, s := range sessions {
-		tower, err := db.LoadTowerByID(s.TowerID)
-		if err != nil {
-			return nil, err
-		}
-		s.Tower = tower
-
 		towerKeyDesc, err := keyRing.DeriveKey(keychain.KeyLocator{
 			Family: keychain.KeyFamilyTowerSession,
 			Index:  s.KeyIndex,

watchtower/wtdb/client_db.go

@@ -288,7 +288,7 @@ func (c *ClientDB) CreateTower(lnAddr *lnwire.NetAddress) (*Tower, error) {
 			}
 			towerID := TowerIDFromBytes(towerIDBytes)
 			towerSessions, err := listClientSessions(
-				sessions, &towerID,
+				sessions, towers, &towerID,
 			)
 			if err != nil {
 				return err
@@ -389,7 +389,9 @@ func (c *ClientDB) RemoveTower(pubKey *btcec.PublicKey, addr net.Addr) error {
 			return ErrUninitializedDB
 		}
 		towerID := TowerIDFromBytes(towerIDBytes)
-		towerSessions, err := listClientSessions(sessions, &towerID)
+		towerSessions, err := listClientSessions(
+			sessions, towers, &towerID,
+		)
 		if err != nil {
 			return err
 		}
@@ -685,8 +687,14 @@ func (c *ClientDB) ListClientSessions(id *TowerID) (
 		if sessions == nil {
 			return ErrUninitializedDB
 		}
+
+		towers := tx.ReadBucket(cTowerBkt)
+		if towers == nil {
+			return ErrUninitializedDB
+		}
+
 		var err error
-		clientSessions, err = listClientSessions(sessions, id)
+		clientSessions, err = listClientSessions(sessions, towers, id)
 		return err
 	}, func() {
 		clientSessions = nil
@@ -701,7 +709,7 @@ func (c *ClientDB) ListClientSessions(id *TowerID) (
 // 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 listClientSessions(sessions kvdb.RBucket,
+func listClientSessions(sessions, towers kvdb.RBucket,
 	id *TowerID) (map[SessionID]*ClientSession, error) {
 
 	clientSessions := make(map[SessionID]*ClientSession)
@@ -710,7 +718,7 @@ func listClientSessions(sessions kvdb.RBucket,
 		// the CommittedUpdates and AckedUpdates on startup to resume
 		// committed updates and compute the highest known commit height
 		// for each channel.
-		session, err := getClientSession(sessions, k)
+		session, err := getClientSession(sessions, towers, k)
 		if err != nil {
 			return err
 		}
@@ -1022,8 +1030,8 @@ func (c *ClientDB) AckUpdate(id *SessionID, seqNum uint16,
 
 // getClientSessionBody loads the body of a ClientSession from the sessions
 // bucket corresponding to the serialized session id. This does not deserialize
-// the CommittedUpdates or AckUpdates associated with the session. If the caller
+// the CommittedUpdates, AckUpdates or the Tower associated with the session.
-// requires this info, use getClientSession.
+// If the caller requires this info, use getClientSession.
 func getClientSessionBody(sessions kvdb.RBucket,
 	idBytes []byte) (*ClientSession, error) {
 
@@ -1050,9 +1058,9 @@ func getClientSessionBody(sessions kvdb.RBucket,
 }
 
 // getClientSession loads the full ClientSession associated with the serialized
-// session id. This method populates the CommittedUpdates and AckUpdates in
+// session id. This method populates the CommittedUpdates, AckUpdates and Tower
-// addition to the ClientSession's body.
+// in addition to the ClientSession's body.
-func getClientSession(sessions kvdb.RBucket,
+func getClientSession(sessions, towers kvdb.RBucket,
 	idBytes []byte) (*ClientSession, error) {
 
 	session, err := getClientSessionBody(sessions, idBytes)
@@ -1060,6 +1068,12 @@ func getClientSession(sessions kvdb.RBucket,
 		return nil, err
 	}
 
+	// Fetch the tower associated with this session.
+	tower, err := getTower(towers, session.TowerID.Bytes())
+	if err != nil {
+		return nil, err
+	}
+
 	// Fetch the committed updates for this session.
 	commitedUpdates, err := getClientSessionCommits(sessions, idBytes)
 	if err != nil {
@@ -1072,6 +1086,7 @@ func getClientSession(sessions kvdb.RBucket,
 		return nil, err
 	}
 
+	session.Tower = tower
 	session.CommittedUpdates = commitedUpdates
 	session.AckedUpdates = ackedUpdates
 

watchtower/wtmock/client_db.go

@@ -220,6 +220,7 @@ func (m *ClientDB) listClientSessions(
 		if tower != nil && *tower != session.TowerID {
 			continue
 		}
+		session.Tower = m.towers[session.TowerID]
 		sessions[session.ID] = &session
 	}