wtclient: add DeactivateTower method

This commit adds the DeactiateTower method to the wtclient.ClientManager
interface along with its implementation. A test is also added for the
new method.

watchtower/wtclient/client.go

@@ -132,6 +132,22 @@ type staleTowerMsg struct {
 	errChan chan error
 }
 
+// deactivateTowerMsg is an internal message we'll use within the TowerClient
+// to signal that a tower should be marked as inactive.
+type deactivateTowerMsg struct {
+	// id is the unique database identifier for the tower.
+	id wtdb.TowerID
+
+	// pubKey is the identifying public key of the watchtower.
+	pubKey *btcec.PublicKey
+
+	// errChan is the channel through which we'll send a response back to
+	// the caller when handling their request.
+	//
+	// NOTE: This channel must be buffered.
+	errChan chan error
+}
+
 // clientCfg holds the configuration values required by a client.
 type clientCfg struct {
 	*Config
@@ -167,6 +183,7 @@ type client struct {
 
 	newTowers        chan *newTowerMsg
 	staleTowers      chan *staleTowerMsg
+	deactivateTowers chan *deactivateTowerMsg
 
 	wg   sync.WaitGroup
 	quit chan struct{}
@@ -200,6 +217,7 @@ func newClient(cfg *clientCfg) (*client, error) {
 		stats:            new(clientStats),
 		newTowers:        make(chan *newTowerMsg),
 		staleTowers:      make(chan *staleTowerMsg),
+		deactivateTowers: make(chan *deactivateTowerMsg),
 		quit:             make(chan struct{}),
 	}
 
@@ -514,8 +532,8 @@ func (c *client) nextSessionQueue() (*sessionQueue, error) {
 
 // stopAndRemoveSession stops the session with the given ID and removes it from
 // the in-memory active sessions set.
-func (c *client) stopAndRemoveSession(id wtdb.SessionID) error {
-	return c.activeSessions.StopAndRemove(id)
+func (c *client) stopAndRemoveSession(id wtdb.SessionID, final bool) error {
+	return c.activeSessions.StopAndRemove(id, final)
 }
 
 // deleteSessionFromTower dials the tower that we created the session with and
@@ -694,6 +712,12 @@ func (c *client) backupDispatcher() {
 			case msg := <-c.staleTowers:
 				msg.errChan <- c.handleStaleTower(msg)
 
+			// A tower has been requested to be de-activated. We'll
+			// only allow this if the tower is not currently being
+			// used for session negotiation.
+			case msg := <-c.deactivateTowers:
+				msg.errChan <- c.handleDeactivateTower(msg)
+
 			case <-c.quit:
 				return
 			}
@@ -779,6 +803,10 @@ func (c *client) backupDispatcher() {
 			case msg := <-c.staleTowers:
 				msg.errChan <- c.handleStaleTower(msg)
 
+			// A tower has been requested to be de-activated.
+			case msg := <-c.deactivateTowers:
+				msg.errChan <- c.handleDeactivateTower(msg)
+
 			case <-c.quit:
 				return
 			}
@@ -1046,6 +1074,77 @@ func (c *client) initActiveQueue(s *ClientSession,
 	return sq
 }
 
+// deactivateTower sends a tower deactivation request to the backupDispatcher
+// where it will be handled synchronously. The request should result in all the
+// sessions that we have with the given tower being shutdown and removed from
+// our in-memory set of active sessions.
+func (c *client) deactivateTower(id wtdb.TowerID,
+	pubKey *btcec.PublicKey) error {
+
+	errChan := make(chan error, 1)
+
+	select {
+	case c.deactivateTowers <- &deactivateTowerMsg{
+		id:      id,
+		pubKey:  pubKey,
+		errChan: errChan,
+	}:
+	case <-c.pipeline.quit:
+		return ErrClientExiting
+	}
+
+	select {
+	case err := <-errChan:
+		return err
+	case <-c.pipeline.quit:
+		return ErrClientExiting
+	}
+}
+
+// handleDeactivateTower handles a request to deactivate a tower. We will remove
+// it from the in-memory candidate set, and we will also stop any active
+// sessions we have with this tower.
+func (c *client) handleDeactivateTower(msg *deactivateTowerMsg) error {
+	// Remove the tower from our in-memory candidate set so that it is not
+	// used for any new session negotiations.
+	err := c.candidateTowers.RemoveCandidate(msg.id, nil)
+	if err != nil {
+		return err
+	}
+
+	pubKey := msg.pubKey.SerializeCompressed()
+	sessions, err := c.cfg.DB.ListClientSessions(&msg.id)
+	if err != nil {
+		return fmt.Errorf("unable to retrieve sessions for tower %x: "+
+			"%v", pubKey, err)
+	}
+
+	// Iterate over all the sessions we have for this tower and remove them
+	// from our candidate set and also from our set of started, active
+	// sessions.
+	for sessionID := range sessions {
+		delete(c.candidateSessions, sessionID)
+
+		err = c.activeSessions.StopAndRemove(sessionID, false)
+		if err != nil {
+			return fmt.Errorf("could not stop session %s: %w",
+				sessionID, err)
+		}
+	}
+
+	// If our active session queue corresponds to the stale tower, we'll
+	// proceed to negotiate a new one.
+	if c.sessionQueue != nil {
+		towerKey := c.sessionQueue.tower.IdentityKey
+
+		if bytes.Equal(pubKey, towerKey.SerializeCompressed()) {
+			c.sessionQueue = nil
+		}
+	}
+
+	return nil
+}
+
 // addTower adds a new watchtower reachable at the given address and considers
 // it for new sessions. If the watchtower already exists, then any new addresses
 // included will be considered when dialing it for session negotiations and
@@ -1152,7 +1251,7 @@ func (c *client) handleStaleTower(msg *staleTowerMsg) error {
 
 		// Shutdown the session so that any pending updates are
 		// replayed back onto the main task pipeline.
-		err = c.activeSessions.StopAndRemove(sessionID)
+		err = c.activeSessions.StopAndRemove(sessionID, true)
 		if err != nil {
 			c.log.Errorf("could not stop session %s: %w", sessionID,
 				err)

watchtower/wtclient/client_test.go

@@ -2688,6 +2688,88 @@ var clientTests = []clientTest{
 			require.NoError(h.t, err)
 		},
 	},
+	{
+		name: "de-activate a tower",
+		cfg: harnessCfg{
+			localBalance:  localBalance,
+			remoteBalance: remoteBalance,
+			policy: wtpolicy.Policy{
+				TxPolicy:   defaultTxPolicy,
+				MaxUpdates: 5,
+			},
+		},
+		fn: func(h *testHarness) {
+			const (
+				numUpdates = 10
+				chanIDInt  = 0
+			)
+
+			// Advance the channel with a few updates.
+			hints := h.advanceChannelN(chanIDInt, numUpdates)
+
+			// Backup a few these updates and wait for them to
+			// arrive at the server.
+			h.backupStates(chanIDInt, 0, numUpdates/2, nil)
+			h.server.waitForUpdates(hints[:numUpdates/2], waitTime)
+
+			// Lookup the tower and assert that it currently is
+			// seen as an active session candidate.
+			resp, err := h.clientMgr.LookupTower(
+				h.server.addr.IdentityKey,
+			)
+			require.NoError(h.t, err)
+			tower, ok := resp[blob.TypeAltruistTaprootCommit]
+			require.True(h.t, ok)
+			require.True(h.t, tower.ActiveSessionCandidate)
+
+			// Deactivate the tower.
+			err = h.clientMgr.DeactivateTower(
+				h.server.addr.IdentityKey,
+			)
+			require.NoError(h.t, err)
+
+			// Assert that it is no longer seen as an active
+			// session candidate.
+			resp, err = h.clientMgr.LookupTower(
+				h.server.addr.IdentityKey,
+			)
+			require.NoError(h.t, err)
+			tower, ok = resp[blob.TypeAltruistTaprootCommit]
+			require.True(h.t, ok)
+			require.False(h.t, tower.ActiveSessionCandidate)
+
+			// Add a new tower.
+			server2 := newServerHarness(
+				h.t, h.net, towerAddr2Str, nil,
+			)
+			server2.start()
+			h.addTower(server2.addr)
+
+			// Backup a few more states and assert that they appear
+			// on the second tower server.
+			h.backupStates(
+				chanIDInt, numUpdates/2, numUpdates-1, nil,
+			)
+			server2.waitForUpdates(
+				hints[numUpdates/2:numUpdates-1], waitTime,
+			)
+
+			// Reactivate the first tower.
+			err = h.clientMgr.AddTower(h.server.addr)
+			require.NoError(h.t, err)
+
+			// Deactivate the second tower.
+			err = h.clientMgr.DeactivateTower(
+				server2.addr.IdentityKey,
+			)
+			require.NoError(h.t, err)
+
+			// Backup the last backup and assert that it appears
+			// on the first tower.
+			h.backupStates(chanIDInt, numUpdates-1, numUpdates, nil)
+			h.server.waitForUpdates(hints[numUpdates-1:], waitTime)
+		},
+	},
 }
 
 // TestClient executes the client test suite, asserting the ability to backup

watchtower/wtclient/manager.go

@@ -38,6 +38,11 @@ type ClientManager interface {
 	// instead.
 	RemoveTower(*btcec.PublicKey, net.Addr) error
 
+	// DeactivateTower sets the given tower's status to inactive so that it
+	// is not considered for session negotiation. Its sessions will also not
+	// be used while the tower is inactive.
+	DeactivateTower(pubKey *btcec.PublicKey) error
+
 	// Stats returns the in-memory statistics of the client since startup.
 	Stats() ClientStats
 
@@ -431,6 +436,56 @@ func (m *Manager) RemoveTower(key *btcec.PublicKey, addr net.Addr) error {
 	return nil
 }
 
+// DeactivateTower sets the given tower's status to inactive so that it is not
+// considered for session negotiation. Its sessions will also not be used while
+// the tower is inactive.
+func (m *Manager) DeactivateTower(key *btcec.PublicKey) error {
+	// We'll load the tower in order to retrieve its ID within the database.
+	tower, err := m.cfg.DB.LoadTower(key)
+	if err != nil {
+		return err
+	}
+
+	m.clientsMu.Lock()
+	defer m.clientsMu.Unlock()
+
+	for _, client := range m.clients {
+		err := client.deactivateTower(tower.ID, tower.IdentityKey)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Finally, mark the tower as inactive in the DB.
+	err = m.cfg.DB.DeactivateTower(key)
+	if err != nil {
+		log.Errorf("Could not deactivate the tower. Re-activating. %v",
+			err)
+
+		// If the persisted state update fails, re-add the address to
+		// our client's in-memory state.
+		tower, newTowerErr := NewTowerFromDBTower(tower)
+		if newTowerErr != nil {
+			log.Errorf("Could not create new in-memory tower: %v",
+				newTowerErr)
+
+			return err
+		}
+
+		for _, client := range m.clients {
+			addTowerErr := client.addTower(tower)
+			if addTowerErr != nil {
+				log.Errorf("Could not re-add tower: %v",
+					addTowerErr)
+			}
+		}
+
+		return err
+	}
+
+	return nil
+}
+
 // Stats returns the in-memory statistics of the clients managed by the Manager
 // since startup.
 func (m *Manager) Stats() ClientStats {
@@ -850,7 +905,7 @@ func (m *Manager) handleClosableSessions(
 				// Stop the session and remove it from the
 				// in-memory set.
 				err = client.stopAndRemoveSession(
-					item.sessionID,
+					item.sessionID, true,
 				)
 				if err != nil {
 					log.Errorf("could not remove "+

watchtower/wtclient/session_queue.go

@@ -765,7 +765,7 @@ func (s *sessionQueueSet) AddAndStart(sessionQueue *sessionQueue) {
 
 // StopAndRemove stops the given session queue and removes it from the
 // sessionQueueSet.
-func (s *sessionQueueSet) StopAndRemove(id wtdb.SessionID) error {
+func (s *sessionQueueSet) StopAndRemove(id wtdb.SessionID, final bool) error {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
@@ -776,7 +776,7 @@ func (s *sessionQueueSet) StopAndRemove(id wtdb.SessionID) error {
 
 	delete(s.queues, id)
 
-	return queue.Stop(true)
+	return queue.Stop(final)
 }
 
 // Get fetches and returns the sessionQueue with the given ID.