15951470896

Committed 29 Jun 2025 04:23AM UTC coverage: 67.594% (-0.01%) from 67.606%

Build # 15951470896

Build Type

Pull #9751

github

Committed by

web-flow

Commit Message

Merge 599d9b051 into 6290edf14

Pull Request Pull Request #9751: multi: update Go to 1.23.10 and update some packages

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73.54

/watchtower/wtclient/client.go

package wtclient

import (
        "bytes"
        "crypto/rand"
        "errors"
        "fmt"
        "maps"
        "math/big"
        "net"
        "sync"
        "time"

        "github.com/btcsuite/btcd/btcec/v2"
        "github.com/btcsuite/btclog/v2"
        "github.com/lightningnetwork/lnd/channeldb"
        "github.com/lightningnetwork/lnd/keychain"
        "github.com/lightningnetwork/lnd/lnwallet"
        "github.com/lightningnetwork/lnd/lnwire"
        "github.com/lightningnetwork/lnd/watchtower/wtdb"
        "github.com/lightningnetwork/lnd/watchtower/wtpolicy"
        "github.com/lightningnetwork/lnd/watchtower/wtserver"
        "github.com/lightningnetwork/lnd/watchtower/wtwire"
)

const (
        // DefaultReadTimeout specifies the default duration we will wait during
        // a read before breaking out of a blocking read.
        DefaultReadTimeout = 15 * time.Second

        // DefaultWriteTimeout specifies the default duration we will wait
        // during a write before breaking out of a blocking write.
        DefaultWriteTimeout = 15 * time.Second

        // DefaultStatInterval specifies the default interval between logging
        // metrics about the client's operation.
        DefaultStatInterval = time.Minute

        // DefaultSessionCloseRange is the range over which we will generate a
        // random number of blocks to delay closing a session after its last
        // channel has been closed.
        DefaultSessionCloseRange = 288

        // DefaultMaxTasksInMemQueue is the maximum number of items to be held
        // in the in-memory queue.
        DefaultMaxTasksInMemQueue = 2000
)

// genSessionFilter constructs a filter that can be used to select sessions only
// if they match the policy of the client (namely anchor vs legacy). If
// activeOnly is set, then only active sessions will be returned.
func (c *client) genSessionFilter(
        activeOnly bool) wtdb.ClientSessionFilterFn {

        return func(session *wtdb.ClientSession) bool {
                if c.cfg.Policy.TxPolicy != session.Policy.TxPolicy {
                        return false
                }

                if !activeOnly {
                        return true
                }

                return session.Status == wtdb.CSessionActive
        }
}

// ExhaustedSessionFilter constructs a wtdb.ClientSessionFilterFn filter
// function that will filter out any sessions that have been exhausted. A
// session is considered exhausted only if it has no un-acked updates and the
// sequence number of the session is equal to the max updates of the session
// policy.
func ExhaustedSessionFilter() wtdb.ClientSessWithNumCommittedUpdatesFilterFn {
        return func(session *wtdb.ClientSession, numUnAcked uint16) bool {
                return session.SeqNum < session.Policy.MaxUpdates ||
                        numUnAcked > 0
        }
}

// RegisteredTower encompasses information about a registered watchtower with
// the client.
type RegisteredTower struct {
        *wtdb.Tower

        // Sessions is the set of sessions corresponding to the watchtower.
        Sessions map[wtdb.SessionID]*wtdb.ClientSession

        // ActiveSessionCandidate determines whether the watchtower is currently
        // being considered for new sessions.
        ActiveSessionCandidate bool
}

// BreachRetributionBuilder is a function that can be used to construct a
// BreachRetribution from a channel ID and a commitment height.
type BreachRetributionBuilder func(id lnwire.ChannelID,
        commitHeight uint64) (*lnwallet.BreachRetribution,
        channeldb.ChannelType, error)

// newTowerMsg is an internal message we'll use within the client to signal
// that a new tower can be considered.
type newTowerMsg struct {
        // tower holds the info about the new Tower or new tower address
        // required to connect to it.
        tower *Tower

        // 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
}

// staleTowerMsg is an internal message we'll use within the client to
// signal that a tower should no longer be considered.
type staleTowerMsg 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

        // addr is an optional field that when set signals that the address
        // should be removed from the watchtower's set of addresses, indicating
        // that it is stale. If it's not set, then the watchtower should be
        // no longer be considered for new sessions.
        addr net.Addr

        // 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
}

// 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
}

// terminateSessMsg is an internal message we'll use within the TowerClient to
// signal that a session should be terminated.
type terminateSessMsg struct {
        // id is the session identifier.
        id wtdb.SessionID

        // 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

        // Policy is the session policy the client will propose when creating
        // new sessions with the tower. If the policy differs from any active
        // sessions recorded in the database, those sessions will be ignored and
        // new sessions will be requested immediately.
        Policy wtpolicy.Policy

        getSweepScript func(lnwire.ChannelID) ([]byte, bool)
}

// client manages backing up revoked states for all states that fall under a
// specific policy type.
type client struct {
        cfg *clientCfg

        log btclog.Logger

        pipeline *DiskOverflowQueue[*wtdb.BackupID]

        negotiator        SessionNegotiator
        candidateTowers   TowerCandidateIterator
        candidateSessions map[wtdb.SessionID]*ClientSession
        activeSessions    *sessionQueueSet

        sessionQueue *sessionQueue
        prevTask     *wtdb.BackupID

        statTicker *time.Ticker
        stats      *clientStats

        newTowers         chan *newTowerMsg
        staleTowers       chan *staleTowerMsg
        deactivateTowers  chan *deactivateTowerMsg
        terminateSessions chan *terminateSessMsg

        wg   sync.WaitGroup
        quit chan struct{}
}

// newClient initializes a new client from the provided clientCfg. An error is
// returned if the client could not be initialized.
func newClient(cfg *clientCfg) (*client, error) {
        identifier, err := cfg.Policy.BlobType.Identifier()
        if err != nil {
                return nil, err
        }
        plog := log.WithPrefix(fmt.Sprintf("(%s)", identifier))

        queueDB := cfg.DB.GetDBQueue([]byte(identifier))
        queue, err := NewDiskOverflowQueue[*wtdb.BackupID](
                queueDB, cfg.MaxTasksInMemQueue, plog,
        )
        if err != nil {
                return nil, err
        }

        c := &client{
                cfg:               cfg,
                log:               plog,
                pipeline:          queue,
                activeSessions:    newSessionQueueSet(),
                statTicker:        time.NewTicker(DefaultStatInterval),
                stats:             new(clientStats),
                newTowers:         make(chan *newTowerMsg),
                staleTowers:       make(chan *staleTowerMsg),
                deactivateTowers:  make(chan *deactivateTowerMsg),
                terminateSessions: make(chan *terminateSessMsg),
                quit:              make(chan struct{}),
        }

        candidateTowers := newTowerListIterator()
        perActiveTower := func(tower *Tower) {
                // If the tower has already been marked as active, then there is
                // no need to add it to the iterator again.
                if candidateTowers.IsActive(tower.ID) {
                        return
                }

                c.log.Infof("Using private watchtower %x, offering policy %s",
                        tower.IdentityKey.SerializeCompressed(), cfg.Policy)

                // Add the tower to the set of candidate towers.
                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, perActiveTower,
                wtdb.WithPreEvalFilterFn(c.genSessionFilter(true)),
                wtdb.WithPostEvalFilterFn(ExhaustedSessionFilter()),
        )
        if err != nil {
                return nil, err
        }

        c.candidateTowers = candidateTowers
        c.candidateSessions = candidateSessions

        c.negotiator = newSessionNegotiator(&NegotiatorConfig{
                DB:            cfg.DB,
                SecretKeyRing: cfg.SecretKeyRing,
                Policy:        cfg.Policy,
                ChainHash:     cfg.ChainHash,
                SendMessage:   c.sendMessage,
                ReadMessage:   c.readMessage,
                Dial:          c.dial,
                Candidates:    c.candidateTowers,
                MinBackoff:    cfg.MinBackoff,
                MaxBackoff:    cfg.MaxBackoff,
                Log:           plog,
        })

        return c, nil
}

// getTowerAndSessionCandidates loads all the towers from the DB and then
// fetches the sessions for each of tower. Sessions are only collected if they
// pass the sessionFilter check. If a tower has a session that does pass the
// sessionFilter check then the perActiveTower call-back will be called on that
// tower.
func getTowerAndSessionCandidates(db DB, keyRing ECDHKeyRing,
        perActiveTower func(tower *Tower),
        opts ...wtdb.ClientSessionListOption) (
        map[wtdb.SessionID]*ClientSession, error) {

        // Fetch all active towers from the DB.
        towers, err := db.ListTowers(func(tower *wtdb.Tower) bool {
                return tower.Status == wtdb.TowerStatusActive
        })
        if err != nil {
                return nil, err
        }

        candidateSessions := make(map[wtdb.SessionID]*ClientSession)
        for _, dbTower := range towers {
                tower, err := NewTowerFromDBTower(dbTower)
                if err != nil {
                        return nil, err
                }

                sessions, err := db.ListClientSessions(&tower.ID, opts...)
                if err != nil {
                        return nil, err
                }

                for _, s := range sessions {
                        cs, err := NewClientSessionFromDBSession(
                                s, tower, keyRing,
                        )
                        if err != nil {
                                return nil, err
                        }

                        // Add the session to the set of candidate sessions.
                        candidateSessions[s.ID] = cs
                }

                perActiveTower(tower)
        }

        return candidateSessions, nil
}

// getClientSessions retrieves the client sessions for a particular tower if
// specified, otherwise all client sessions for all towers are retrieved. An
// 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 SessionPrivKey field is desired, otherwise, the existing
// ListClientSessions method should be used.
func getClientSessions(db DB, keyRing ECDHKeyRing, forTower *wtdb.TowerID,
        opts ...wtdb.ClientSessionListOption) (
        map[wtdb.SessionID]*ClientSession, error) {

        dbSessions, err := db.ListClientSessions(forTower, opts...)
        if err != nil {
                return nil, err
        }

        // Reload the tower from disk using the tower ID contained in each
        // candidate session. We will also rederive any session keys needed to
        // be able to communicate with the towers and authenticate session
        // requests. This prevents us from having to store the private keys on
        // disk.
        sessions := make(map[wtdb.SessionID]*ClientSession)
        for _, s := range dbSessions {
                dbTower, err := db.LoadTowerByID(s.TowerID)
                if err != nil {
                        return nil, err
                }

                towerKeyDesc, err := keyRing.DeriveKey(keychain.KeyLocator{
                        Family: keychain.KeyFamilyTowerSession,
                        Index:  s.KeyIndex,
                })
                if err != nil {
                        return nil, err
                }

                sessionKeyECDH := keychain.NewPubKeyECDH(towerKeyDesc, keyRing)

                tower, err := NewTowerFromDBTower(dbTower)
                if err != nil {
                        return nil, err
                }

                sessions[s.ID] = &ClientSession{
                        ID:                s.ID,
                        ClientSessionBody: s.ClientSessionBody,
                        Tower:             tower,
                        SessionKeyECDH:    sessionKeyECDH,
                }
        }

        return sessions, nil
}

// start initializes the watchtower client by loading or negotiating an active
// session and then begins processing backup tasks from the request pipeline.
func (c *client) start() error {
        c.log.Infof("Watchtower client starting")

        // First, restart a session queue for any sessions that have
        // committed but unacked state updates. This ensures that these
        // sessions will be able to flush the committed updates after a
        // restart.
        fetchCommittedUpdates := c.cfg.DB.FetchSessionCommittedUpdates
        for _, session := range c.candidateSessions {
                committedUpdates, err := fetchCommittedUpdates(
                        &session.ID,
                )
                if err != nil {
                        return err
                }

                if len(committedUpdates) > 0 {
                        c.log.Infof("Starting session=%s to process "+
                                "%d committed backups", session.ID,
                                len(committedUpdates))

                        c.initActiveQueue(session, committedUpdates)
                }
        }

        // Now start the session negotiator, which will allow us to request new
        // session as soon as the backupDispatcher starts up.
        err := c.negotiator.Start()
        if err != nil {
                return err
        }

        // Start the task pipeline to which new backup tasks will be
        // submitted from active links.
        err = c.pipeline.Start()
        if err != nil {
                return err
        }

        c.wg.Add(1)
        go c.backupDispatcher()

        c.log.Infof("Watchtower client started successfully")

        return nil
}

// stop idempotently initiates a graceful shutdown of the watchtower client.
func (c *client) stop() error {
        var returnErr error
        c.log.Debugf("Stopping watchtower client")

        // 1. Stop the session negotiator.
        err := c.negotiator.Stop()
        if err != nil {
                returnErr = err
        }

        // 2. Stop the backup dispatcher and any other goroutines.
        close(c.quit)
        c.wg.Wait()

        // 3. If there was a left over 'prevTask' from the backup
        // dispatcher, replay that onto the pipeline.
        if c.prevTask != nil {
                err = c.pipeline.QueueBackupID(c.prevTask)
                if err != nil {
                        returnErr = err
                }
        }

        // 4. Shutdown all active session queues in parallel. These will
        // exit once all unhandled updates have been replayed to the
        // task pipeline.
        c.activeSessions.ApplyAndWait(func(s *sessionQueue) func() {
                return func() {
                        err := s.Stop(false)
                        if err != nil {
                                c.log.Errorf("could not stop session "+
                                        "queue: %s: %v", s.ID(), err)

                                returnErr = err
                        }
                }
        })

        // 5. Shutdown the backup queue, which will prevent any further
        // updates from being accepted.
        if err = c.pipeline.Stop(); err != nil {
                returnErr = err
        }

        c.log.Debugf("Client successfully stopped, stats: %s", c.stats)

        return returnErr
}

// backupState initiates a request to back up a particular revoked state. If the
// method returns nil, the backup is guaranteed to be successful unless the:
//   - justice transaction would create dust outputs when trying to abide by the
//     negotiated policy, or
//   - breached outputs contain too little value to sweep at the target sweep
//     fee rate.
func (c *client) backupState(chanID *lnwire.ChannelID,
        stateNum uint64) error {

        id := &wtdb.BackupID{
                ChanID:       *chanID,
                CommitHeight: stateNum,
        }

        return c.pipeline.QueueBackupID(id)
}

// nextSessionQueue attempts to fetch an active session from our set of
// candidate sessions. Candidate sessions with a differing policy from the
// active client's advertised policy will be ignored, but may be resumed if the
// client is restarted with a matching policy. If no candidates were found, nil
// is returned to signal that we need to request a new policy.
func (c *client) nextSessionQueue() (*sessionQueue, error) {
        // Select any candidate session at random, and remove it from the set of
        // candidate sessions.
        var candidateSession *ClientSession
        for id, sessionInfo := range c.candidateSessions {
                delete(c.candidateSessions, id)

                // Skip any sessions with policies that don't match the current
                // TxPolicy, as they would result in different justice
                // transactions from what is requested. These can be used again
                // if the client changes their configuration and restarting.
                if sessionInfo.Policy.TxPolicy != c.cfg.Policy.TxPolicy {
                        continue
                }

                candidateSession = sessionInfo
                break
        }

        // If none of the sessions could be used or none were found, we'll
        // return nil to signal that we need another session to be negotiated.
        if candidateSession == nil {
                return nil, nil
        }

        updates, err := c.cfg.DB.FetchSessionCommittedUpdates(
                &candidateSession.ID,
        )
        if err != nil {
                return nil, err
        }

        // Initialize the session queue and spin it up, so it can begin handling
        // updates. If the queue was already made active on startup, this will
        // simply return the existing session queue from the set.
        return c.getOrInitActiveQueue(candidateSession, updates), nil
}

// 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, final bool) error {
        return c.activeSessions.StopAndRemove(id, final)
}

// deleteSessionFromTower dials the tower that we created the session with and
// attempts to send the tower the DeleteSession message.
func (c *client) deleteSessionFromTower(sess *wtdb.ClientSession) error {
        // First, we check if we have already loaded this tower in our
        // candidate towers iterator.
        tower, err := c.candidateTowers.GetTower(sess.TowerID)
        if errors.Is(err, ErrTowerNotInIterator) {
                // If not, then we attempt to load it from the DB.
                dbTower, err := c.cfg.DB.LoadTowerByID(sess.TowerID)
                if err != nil {
                        return err
                }

                tower, err = NewTowerFromDBTower(dbTower)
                if err != nil {
                        return err
                }
        } else if err != nil {
                return err
        }

        session, err := NewClientSessionFromDBSession(
                sess, tower, c.cfg.SecretKeyRing,
        )
        if err != nil {
                return err
        }

        localInit := wtwire.NewInitMessage(
                lnwire.NewRawFeatureVector(wtwire.AltruistSessionsRequired),
                c.cfg.ChainHash,
        )

        var (
                conn wtserver.Peer

                // addrIterator is a copy of the tower's address iterator.
                // We use this copy so that iterating through the addresses does
                // not affect any other threads using this iterator.
                addrIterator = tower.Addresses.Copy()
                towerAddr    = addrIterator.Peek()
        )
        // Attempt to dial the tower with its available addresses.
        for {
                conn, err = c.dial(
                        session.SessionKeyECDH, &lnwire.NetAddress{
                                IdentityKey: tower.IdentityKey,
                                Address:     towerAddr,
                        },
                )
                if err != nil {
                        // If there are more addrs available, immediately try
                        // those.
                        nextAddr, iteratorErr := addrIterator.Next()
                        if iteratorErr == nil {
                                towerAddr = nextAddr
                                continue
                        }

                        // Otherwise, if we have exhausted the address list,
                        // exit.
                        addrIterator.Reset()

                        return fmt.Errorf("failed to dial tower(%x) at any "+
                                "available addresses",
                                tower.IdentityKey.SerializeCompressed())
                }

                break
        }
        defer conn.Close()

        // Send Init to tower.
        err = c.sendMessage(conn, localInit)
        if err != nil {
                return err
        }

        // Receive Init from tower.
        remoteMsg, err := c.readMessage(conn)
        if err != nil {
                return err
        }

        remoteInit, ok := remoteMsg.(*wtwire.Init)
        if !ok {
                return fmt.Errorf("watchtower %s responded with %T to Init",
                        towerAddr, remoteMsg)
        }

        // Validate Init.
        err = localInit.CheckRemoteInit(remoteInit, wtwire.FeatureNames)
        if err != nil {
                return err
        }

        // Send DeleteSession to tower.
        err = c.sendMessage(conn, &wtwire.DeleteSession{})
        if err != nil {
                return err
        }

        // Receive DeleteSessionReply from tower.
        remoteMsg, err = c.readMessage(conn)
        if err != nil {
                return err
        }

        deleteSessionReply, ok := remoteMsg.(*wtwire.DeleteSessionReply)
        if !ok {
                return fmt.Errorf("watchtower %s responded with %T to "+
                        "DeleteSession", towerAddr, remoteMsg)
        }

        switch deleteSessionReply.Code {
        case wtwire.CodeOK, wtwire.DeleteSessionCodeNotFound:
                return nil
        default:
                return fmt.Errorf("received error code %v in "+
                        "DeleteSessionReply when attempting to delete "+
                        "session from tower", deleteSessionReply.Code)
        }
}

// backupDispatcher processes events coming from the taskPipeline and is
// responsible for detecting when the client needs to renegotiate a session to
// fulfill continuing demand. The event loop exits if the client is quit.
//
// NOTE: This method MUST be run as a goroutine.
func (c *client) backupDispatcher() {
        defer c.wg.Done()

        c.log.Tracef("Starting backup dispatcher")
        defer c.log.Tracef("Stopping backup dispatcher")

        for {
                switch {

                // No active session queue and no additional sessions.
                case c.sessionQueue == nil && len(c.candidateSessions) == 0:
                        c.log.Infof("Requesting new session.")

                        // Immediately request a new session.
                        c.negotiator.RequestSession()

                        // Wait until we receive the newly negotiated session.
                        // All backups sent in the meantime are queued in the
                        // revoke queue, as we cannot process them.
                awaitSession:
                        select {
                        case session := <-c.negotiator.NewSessions():
                                c.log.Infof("Acquired new session with id=%s",
                                        session.ID)
                                c.candidateSessions[session.ID] = session
                                c.stats.sessionAcquired()

                                // We'll continue to choose the newly negotiated
                                // session as our active session queue.
                                continue

                        case <-c.statTicker.C:
                                c.log.Infof("Client stats: %s", c.stats)

                        // A new tower has been requested to be added. We'll
                        // update our persisted and in-memory state and consider
                        // its corresponding sessions, if any, as new
                        // candidates.
                        case msg := <-c.newTowers:
                                msg.errChan <- c.handleNewTower(msg.tower)

                        // A tower has been requested to be removed. We'll
                        // only allow removal of it if the address in question
                        // is not currently being used for session negotiation.
                        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)

                        // A request has come through to terminate a session.
                        case msg := <-c.terminateSessions:
                                msg.errChan <- c.handleTerminateSession(msg)

                        case <-c.quit:
                                return
                        }

                        // Instead of looping, we'll jump back into the select
                        // case and await the delivery of the session to prevent
                        // us from re-requesting additional sessions.
                        goto awaitSession

                // No active session queue but have additional sessions.
                case c.sessionQueue == nil && len(c.candidateSessions) > 0:
                        // We've exhausted the prior session, we'll pop another
                        // from the remaining sessions and continue processing
                        // backup tasks.
                        var err error
                        c.sessionQueue, err = c.nextSessionQueue()
                        if err != nil {
                                c.log.Errorf("error fetching next session "+
                                        "queue: %v", err)
                        }

                        if c.sessionQueue != nil {
                                c.log.Debugf("Loaded next candidate session "+
                                        "queue id=%s", c.sessionQueue.ID())
                        }

                // Have active session queue, process backups.
                case c.sessionQueue != nil:
                        if c.prevTask != nil {
                                c.processTask(c.prevTask)

                                // Continue to ensure the sessionQueue is
                                // properly initialized before attempting to
                                // process more tasks from the pipeline.
                                continue
                        }

                        // Normal operation where new tasks are read from the
                        // pipeline.
                        select {

                        // If any sessions are negotiated while we have an
                        // active session queue, queue them for future use.
                        // This shouldn't happen with the current design, so
                        // it doesn't hurt to select here just in case. In the
                        // future, we will likely allow more asynchrony so that
                        // we can request new sessions before the session is
                        // fully empty, which this case would handle.
                        case session := <-c.negotiator.NewSessions():
                                c.log.Warnf("Acquired new session with id=%s "+
                                        "while processing tasks", session.ID)
                                c.candidateSessions[session.ID] = session
                                c.stats.sessionAcquired()

                        case <-c.statTicker.C:
                                c.log.Infof("Client stats: %s", c.stats)

                        // Process each backup task serially from the queue of
                        // revoked states.
                        case task, ok := <-c.pipeline.NextBackupID():
                                // All backups in the pipeline have been
                                // processed, it is now safe to exit.
                                if !ok {
                                        return
                                }

                                c.log.Debugf("Processing %v", task)

                                c.stats.taskReceived()
                                c.processTask(task)

                        // A new tower has been requested to be added. We'll
                        // update our persisted and in-memory state and consider
                        // its corresponding sessions, if any, as new
                        // candidates.
                        case msg := <-c.newTowers:
                                msg.errChan <- c.handleNewTower(msg.tower)

                        // A tower has been removed, so we'll remove certain
                        // information that's persisted and also in our
                        // in-memory state depending on the request, and set any
                        // of its corresponding candidate sessions as inactive.
                        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)

                        // A request has come through to terminate a session.
                        case msg := <-c.terminateSessions:
                                msg.errChan <- c.handleTerminateSession(msg)

                        case <-c.quit:
                                return
                        }
                }
        }
}

// processTask attempts to schedule the given backupTask on the active
// sessionQueue. The task will either be accepted or rejected, after which the
// appropriate modifications to the client's state machine will be made. After
// every invocation of processTask, the caller should ensure that the
// sessionQueue hasn't been exhausted before proceeding to the next task. Tasks
// that are rejected because the active sessionQueue is full will be cached as
// the prevTask, and should be reprocessed after obtaining a new sessionQueue.
func (c *client) processTask(task *wtdb.BackupID) {
        script, ok := c.cfg.getSweepScript(task.ChanID)
        if !ok {
                log.Infof("not processing task for unregistered channel: %s",
                        task.ChanID)

                return
        }

        backupTask := newBackupTask(*task, script)

        status, accepted := c.sessionQueue.AcceptTask(backupTask)
        if accepted {
                c.taskAccepted(task, status)
        } else {
                c.taskRejected(task, status)
        }
}

// taskAccepted processes the acceptance of a task by a sessionQueue depending
// on the state the sessionQueue is in *after* the task is added. The client's
// prevTask is always removed as a result of this call. The client's
// sessionQueue will be removed if accepting the task left the sessionQueue in
// an exhausted state.
func (c *client) taskAccepted(task *wtdb.BackupID,
        newStatus sessionQueueStatus) {

        c.log.Infof("Queued %v successfully for session %v", task,
                c.sessionQueue.ID())

        c.stats.taskAccepted()

        // If this task was accepted, we discard anything held in the prevTask.
        // Either it was nil before, or is the task which was just accepted.
        c.prevTask = nil

        switch newStatus {

        // The sessionQueue still has capacity after accepting this task.
        case sessionQueueAvailable:

        // The sessionQueue is full after accepting this task, so we will need
        // to request a new one before proceeding.
        case sessionQueueExhausted:
                c.stats.sessionExhausted()

                c.log.Debugf("Session %s exhausted", c.sessionQueue.ID())

                // This task left the session exhausted, set it to nil and
                // proceed to the next loop, so we can consume another
                // pre-negotiated session or request another.
                c.sessionQueue = nil
        }
}

// taskRejected process the rejection of a task by a sessionQueue depending on
// the state the was in *before* the task was rejected. The client's prevTask
// will cache the task if the sessionQueue was exhausted beforehand, and nil
// the sessionQueue to find a new session. If the sessionQueue was not
// exhausted and not shutting down, the client marks the task as ineligible, as
// this implies we couldn't construct a valid justice transaction given the
// session's policy.
func (c *client) taskRejected(task *wtdb.BackupID,
        curStatus sessionQueueStatus) {

        switch curStatus {

        // The sessionQueue has available capacity but the task was rejected,
        // this indicates that the task was ineligible for backup.
        case sessionQueueAvailable:
                c.stats.taskIneligible()

                c.log.Infof("Ignoring ineligible %v", task)

                err := c.cfg.DB.MarkBackupIneligible(
                        task.ChanID, task.CommitHeight,
                )
                if err != nil {
                        c.log.Errorf("Unable to mark %v ineligible: %v",
                                task, err)

                        // It is safe to not handle this error, even if we could
                        // not persist the result. At worst, this task may be
                        // reprocessed on a subsequent start up, and will either
                        // succeed do a change in session parameters or fail in
                        // the same manner.
                }

                // If this task was rejected *and* the session had available
                // capacity, we discard anything held in the prevTask. Either it
                // was nil before, or is the task which was just rejected.
                c.prevTask = nil

        // The sessionQueue rejected the task because it is full, we will stash
        // this task and try to add it to the next available sessionQueue.
        case sessionQueueExhausted:
                c.stats.sessionExhausted()

                c.log.Debugf("Session %v exhausted, %v queued for next session",
                        c.sessionQueue.ID(), task)

                // Cache the task that we pulled off, so that we can process it
                // once a new session queue is available.
                c.sessionQueue = nil
                c.prevTask = task

        // The sessionQueue rejected the task because it is shutting down. We
        // will stash this task and try to add it to the next available
        // sessionQueue.
        case sessionQueueShuttingDown:
                c.log.Debugf("Session %v is shutting down, %v queued for "+
                        "next session", c.sessionQueue.ID(), task)

                // Cache the task that we pulled off, so that we can process it
                // once a new session queue is available.
                c.sessionQueue = nil
                c.prevTask = task
        }
}

// dial connects the peer at addr using privKey as our secret key for the
// connection. The connection will use the configured Net's resolver to resolve
// the address for either Tor or clear net connections.
func (c *client) dial(localKey keychain.SingleKeyECDH,
        addr *lnwire.NetAddress) (wtserver.Peer, error) {

        return c.cfg.AuthDial(localKey, addr, c.cfg.Dial)
}

// readMessage receives and parses the next message from the given Peer. An
// error is returned if a message is not received before the server's read
// timeout, the read off the wire failed, or the message could not be
// deserialized.
func (c *client) readMessage(peer wtserver.Peer) (wtwire.Message, error) {
        // Set a read timeout to ensure we drop the connection if nothing is
        // received in a timely manner.
        err := peer.SetReadDeadline(time.Now().Add(c.cfg.ReadTimeout))
        if err != nil {
                err = fmt.Errorf("unable to set read deadline: %w", err)
                c.log.Errorf("Unable to read msg: %v", err)
                return nil, err
        }

        // Pull the next message off the wire,
        rawMsg, err := peer.ReadNextMessage()
        if err != nil {
                err = fmt.Errorf("unable to read message: %w", err)
                c.log.Errorf("Unable to read msg: %v", err)
                return nil, err
        }

        // Parse the received message according to the watchtower wire
        // specification.
        msgReader := bytes.NewReader(rawMsg)
        msg, err := wtwire.ReadMessage(msgReader, 0)
        if err != nil {
                err = fmt.Errorf("unable to parse message: %w", err)
                c.log.Errorf("Unable to read msg: %v", err)
                return nil, err
        }

        c.logMessage(peer, msg, true)

        return msg, nil
}

// sendMessage sends a watchtower wire message to the target peer.
func (c *client) sendMessage(peer wtserver.Peer,
        msg wtwire.Message) error {

        // Encode the next wire message into the buffer.
        // TODO(conner): use buffer pool
        var b bytes.Buffer
        _, err := wtwire.WriteMessage(&b, msg, 0)
        if err != nil {
                err = fmt.Errorf("unable to encode msg: %w", err)
                c.log.Errorf("Unable to send msg: %v", err)
                return err
        }

        // Set the write deadline for the connection, ensuring we drop the
        // connection if nothing is sent in a timely manner.
        err = peer.SetWriteDeadline(time.Now().Add(c.cfg.WriteTimeout))
        if err != nil {
                err = fmt.Errorf("unable to set write deadline: %w", err)
                c.log.Errorf("Unable to send msg: %v", err)
                return err
        }

        c.logMessage(peer, msg, false)

        // Write out the full message to the remote peer.
        _, err = peer.Write(b.Bytes())
        if err != nil {
                c.log.Errorf("Unable to send msg: %v", err)
        }
        return err
}

// newSessionQueue creates a sessionQueue from a ClientSession loaded from the
// database and supplying it with the resources needed by the client.
func (c *client) newSessionQueue(s *ClientSession,
        updates []wtdb.CommittedUpdate) *sessionQueue {

        return newSessionQueue(&sessionQueueConfig{
                ClientSession:          s,
                ChainHash:              c.cfg.ChainHash,
                Dial:                   c.dial,
                ReadMessage:            c.readMessage,
                SendMessage:            c.sendMessage,
                Signer:                 c.cfg.Signer,
                DB:                     c.cfg.DB,
                MinBackoff:             c.cfg.MinBackoff,
                MaxBackoff:             c.cfg.MaxBackoff,
                Log:                    c.log,
                BuildBreachRetribution: c.cfg.BuildBreachRetribution,
                TaskPipeline:           c.pipeline,
        }, updates)
}

// getOrInitActiveQueue checks the activeSessions set for a sessionQueue for the
// passed ClientSession. If it exists, the active sessionQueue is returned.
// Otherwise, a new sessionQueue is initialized and added to the set.
func (c *client) getOrInitActiveQueue(s *ClientSession,
        updates []wtdb.CommittedUpdate) *sessionQueue {

        if sq, ok := c.activeSessions.Get(s.ID); ok {
                return sq
        }

        return c.initActiveQueue(s, updates)
}

// initActiveQueue creates a new sessionQueue from the passed ClientSession,
// adds the sessionQueue to the activeSessions set, and starts the sessionQueue
// so that it can deliver any committed updates or begin accepting newly
// assigned tasks.
func (c *client) initActiveQueue(s *ClientSession,
        updates []wtdb.CommittedUpdate) *sessionQueue {

        // Initialize the session queue, providing it with all the resources it
        // requires from the client instance.
        sq := c.newSessionQueue(s, updates)

        // Add the session queue as an active session so that we remember to
        // stop it on shutdown. This method will also start the queue so that it
        // can be active in processing newly assigned tasks or to upload
        // previously committed updates.
        c.activeSessions.AddAndStart(sq)

        return sq
}

// terminateSession sets the given session's status to CSessionTerminal meaning
// that it will not be used again.
func (c *client) terminateSession(id wtdb.SessionID) error {
        errChan := make(chan error, 1)

        select {
        case c.terminateSessions <- &terminateSessMsg{
                id:      id,
                errChan: errChan,
        }:
        case <-c.pipeline.quit:
                return ErrClientExiting
        }

        select {
        case err := <-errChan:
                return err
        case <-c.pipeline.quit:
                return ErrClientExiting
        }
}

// handleTerminateSession handles a request to terminate a session. It will
// first shut down the session if it is part of the active session set, then
// it will ensure that the active session queue is set reset if it is using the
// session in question. Finally, the session's status in the DB will be updated.
func (c *client) handleTerminateSession(msg *terminateSessMsg) error {
        id := msg.id

        delete(c.candidateSessions, id)

        err := c.activeSessions.StopAndRemove(id, true)
        if err != nil {
                return fmt.Errorf("could not stop session %s: %w", id, err)
        }

        // If our active session queue corresponds to the session being
        // terminated, then we'll proceed to negotiate a new one.
        if c.sessionQueue != nil {
                if bytes.Equal(c.sessionQueue.ID()[:], id[:]) {
                        c.sessionQueue = nil
                }
        }

        return nil
}

// 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
// backups.
func (c *client) addTower(tower *Tower) error {
        errChan := make(chan error, 1)

        select {
        case c.newTowers <- &newTowerMsg{
                tower:   tower,
                errChan: errChan,
        }:
        case <-c.pipeline.quit:
                return ErrClientExiting
        }

        select {
        case err := <-errChan:
                return err
        case <-c.pipeline.quit:
                return ErrClientExiting
        }
}

// handleNewTower handles a request for a new tower to be added. If the tower
// already exists, then its corresponding sessions, if any, will be set
// considered as candidates.
func (c *client) handleNewTower(tower *Tower) error {
        c.candidateTowers.AddCandidate(tower)

        // Include all of its corresponding sessions to our set of candidates.
        sessions, err := getClientSessions(
                c.cfg.DB, c.cfg.SecretKeyRing, &tower.ID,
                wtdb.WithPreEvalFilterFn(c.genSessionFilter(true)),
                wtdb.WithPostEvalFilterFn(ExhaustedSessionFilter()),
        )
        if err != nil {
                return fmt.Errorf("unable to determine sessions for tower %x: "+
                        "%v", tower.IdentityKey.SerializeCompressed(), err)
        }
        maps.Copy(c.candidateSessions, sessions)

        return nil
}

// removeTower removes a watchtower from being considered for future session
// negotiations and from being used for any subsequent backups until it's added
// again. If an address is provided, then this call only serves as a way of
// removing the address from the watchtower instead.
func (c *client) removeTower(id wtdb.TowerID, pubKey *btcec.PublicKey,
        addr net.Addr) error {

        errChan := make(chan error, 1)

        select {
        case c.staleTowers <- &staleTowerMsg{
                id:      id,
                pubKey:  pubKey,
                addr:    addr,
                errChan: errChan,
        }:
        case <-c.pipeline.quit:
                return ErrClientExiting
        }

        select {
        case err := <-errChan:
                return err
        case <-c.pipeline.quit:
                return ErrClientExiting
        }
}

// handleStaleTower handles a request for an existing tower to be removed. If
// none of the tower's sessions have pending updates, then they will become
// inactive and removed as candidates. If the active session queue corresponds
// to any of these sessions, a new one will be negotiated.
func (c *client) handleStaleTower(msg *staleTowerMsg) error {
        // We'll first update our in-memory state.
        err := c.candidateTowers.RemoveCandidate(msg.id, msg.addr)
        if err != nil {
                return err
        }

        // If an address was provided, then we're only meant to remove the
        // address from the tower.
        if msg.addr != nil {
                return nil
        }

        // Otherwise, the tower should no longer be used for future session
        // negotiations and backups.

        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)
        }
        for sessionID := range sessions {
                delete(c.candidateSessions, sessionID)

                // Shutdown the session so that any pending updates are
                // replayed back onto the main task pipeline.
                err = c.activeSessions.StopAndRemove(sessionID, true)
                if err != nil {
                        c.log.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
}

// registeredTowers retrieves the list of watchtowers registered with the
// client.
func (c *client) registeredTowers(towers []*wtdb.Tower,
        opts ...wtdb.ClientSessionListOption) ([]*RegisteredTower, error) {

        // Generate a filter that will fetch all the client's sessions
        // regardless of if they are active or not.
        opts = append(opts, wtdb.WithPreEvalFilterFn(c.genSessionFilter(false)))

        clientSessions, err := c.cfg.DB.ListClientSessions(nil, opts...)
        if err != nil {
                return nil, err
        }

        // Construct a lookup map that coalesces all the sessions for a specific
        // watchtower.
        towerSessions := make(
                map[wtdb.TowerID]map[wtdb.SessionID]*wtdb.ClientSession,
        )
        for id, s := range clientSessions {
                sessions, ok := towerSessions[s.TowerID]
                if !ok {
                        sessions = make(map[wtdb.SessionID]*wtdb.ClientSession)
                        towerSessions[s.TowerID] = sessions
                }
                sessions[id] = s
        }

        registeredTowers := make([]*RegisteredTower, 0, len(towerSessions))
        for _, tower := range towers {
                isActive := c.candidateTowers.IsActive(tower.ID)
                registeredTowers = append(registeredTowers, &RegisteredTower{
                        Tower:                  tower,
                        Sessions:               towerSessions[tower.ID],
                        ActiveSessionCandidate: isActive,
                })
        }

        return registeredTowers, nil
}

// lookupTower retrieves the info of sessions held with the given tower handled
// by this client.
func (c *client) lookupTower(tower *wtdb.Tower,
        opts ...wtdb.ClientSessionListOption) (*RegisteredTower, error) {

        opts = append(opts, wtdb.WithPreEvalFilterFn(c.genSessionFilter(false)))

        towerSessions, err := c.cfg.DB.ListClientSessions(&tower.ID, opts...)
        if err != nil {
                return nil, err
        }

        return &RegisteredTower{
                Tower:                  tower,
                Sessions:               towerSessions,
                ActiveSessionCandidate: c.candidateTowers.IsActive(tower.ID),
        }, nil
}

// getStats returns the in-memory statistics of the client since startup.
func (c *client) getStats() ClientStats {
        return c.stats.getStatsCopy()
}

// policy returns the active client policy configuration.
func (c *client) policy() wtpolicy.Policy {
        return c.cfg.Policy
}

// logMessage writes information about a message received from a remote peer,
// using directional prepositions to signal whether the message was sent or
// received.
func (c *client) logMessage(
        peer wtserver.Peer, msg wtwire.Message, read bool) {

        var action = "Received"
        var preposition = "from"
        if !read {
                action = "Sending"
                preposition = "to"
        }

        summary := wtwire.MessageSummary(msg)
        if len(summary) > 0 {
                summary = "(" + summary + ")"
        }

        c.log.Debugf("%s %s%v %s %x@%s", action, msg.MsgType(), summary,
                preposition, peer.RemotePub().SerializeCompressed(),
                peer.RemoteAddr())
}

func newRandomDelay(max uint32) (uint32, error) {
        var maxDelay big.Int
        maxDelay.SetUint64(uint64(max))

        randDelay, err := rand.Int(rand.Reader, &maxDelay)
        if err != nil {
                return 0, err
        }

        return uint32(randDelay.Uint64()), nil
}

lightningnetwork / lnd / 15951470896

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