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watchtower/wtclient/client: hook up full client pipeline

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Conner Fromknecht 2019-03-15 02:32:27 -07:00
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commit f00b4c5e96
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watchtower/wtclient/client.go Normal file
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package wtclient
import (
"bytes"
"fmt"
"sync"
"time"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcd/chaincfg/chainhash"
"github.com/lightningnetwork/lnd/input"
"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 = 30 * time.Second
)
// Client is the primary interface used by the daemon to control a client's
// lifecycle and backup revoked states.
type Client interface {
// RegisterChannel persistently initializes any channel-dependent
// parameters within the client. This should be called during link
// startup to ensure that the client is able to support the link during
// operation.
RegisterChannel(lnwire.ChannelID) error
// 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 client is force quit, or the justice
// transaction would create dust outputs when trying to abide by the
// negotiated policy.
BackupState(*lnwire.ChannelID, *lnwallet.BreachRetribution) error
// Start initializes the watchtower client, allowing it process requests
// to backup revoked channel states.
Start() error
// Stop attempts a graceful shutdown of the watchtower client. In doing
// so, it will attempt to flush the pipeline and deliver any queued
// states to the tower before exiting.
Stop() error
// ForceQuit will forcibly shutdown the watchtower client. Calling this
// may lead to queued states being dropped.
ForceQuit()
}
// Config provides the TowerClient with access to the resources it requires to
// perform its duty. All nillable fields must be non-nil for the tower to be
// initialized properly.
type Config struct {
// Signer provides access to the wallet so that the client can sign
// justice transactions that spend from a remote party's commitment
// transaction.
Signer input.Signer
// NewAddress generates a new on-chain sweep pkscript.
NewAddress func() ([]byte, error)
// SecretKeyRing is used to derive the session keys used to communicate
// with the tower. The client only stores the KeyLocators internally so
// that we never store private keys on disk.
SecretKeyRing keychain.SecretKeyRing
// Dial connects to an addr using the specified net and returns the
// connection object.
Dial Dial
// AuthDialer establishes a brontide connection over an onion or clear
// network.
AuthDial AuthDialer
// DB provides access to the client's stable storage medium.
DB DB
// 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
// PrivateTower is the net address of a private tower. The client will
// try to create all sessions with this tower.
PrivateTower *lnwire.NetAddress
// ChainHash identifies the chain that the client is on and for which
// the tower must be watching to monitor for breaches.
ChainHash chainhash.Hash
// ForceQuitDelay is the duration after attempting to shutdown that the
// client will automatically abort any pending backups if an unclean
// shutdown is detected. If the value is less than or equal to zero, a
// call to Stop may block indefinitely. The client can always be
// ForceQuit externally irrespective of the chosen parameter.
ForceQuitDelay time.Duration
// ReadTimeout is the duration we will wait during a read before
// breaking out of a blocking read. If the value is less than or equal
// to zero, the default will be used instead.
ReadTimeout time.Duration
// WriteTimeout is the duration we will wait during a write before
// breaking out of a blocking write. If the value is less than or equal
// to zero, the default will be used instead.
WriteTimeout time.Duration
// MinBackoff defines the initial backoff applied to connections with
// watchtowers. Subsequent backoff durations will grow exponentially up
// until MaxBackoff.
MinBackoff time.Duration
// MaxBackoff defines the maximum backoff applied to conenctions with
// watchtowers. If the exponential backoff produces a timeout greater
// than this value, the backoff will be clamped to MaxBackoff.
MaxBackoff time.Duration
}
// TowerClient is a concrete implementation of the Client interface, offering a
// non-blocking, reliable subsystem for backing up revoked states to a specified
// private tower.
type TowerClient struct {
started sync.Once
stopped sync.Once
forced sync.Once
cfg *Config
pipeline *taskPipeline
negotiator SessionNegotiator
candidateSessions map[wtdb.SessionID]*wtdb.ClientSession
activeSessions sessionQueueSet
sessionQueue *sessionQueue
prevTask *backupTask
sweepPkScriptMu sync.RWMutex
sweepPkScripts map[lnwire.ChannelID][]byte
statTicker *time.Ticker
stats clientStats
wg sync.WaitGroup
forceQuit chan struct{}
}
// Compile-time constraint to ensure *TowerClient implements the Client
// interface.
var _ Client = (*TowerClient)(nil)
// New initializes a new TowerClient from the provide Config. An error is
// returned if the client could not initialized.
func New(config *Config) (*TowerClient, error) {
// Copy the config to prevent side-effects from modifying both the
// internal and external version of the Config.
cfg := new(Config)
*cfg = *config
// Set the read timeout to the default if none was provided.
if cfg.ReadTimeout <= 0 {
cfg.ReadTimeout = DefaultReadTimeout
}
// Set the write timeout to the default if none was provided.
if cfg.WriteTimeout <= 0 {
cfg.WriteTimeout = DefaultWriteTimeout
}
// Record the tower in our database, also loading any addresses
// previously associated with its public key.
tower, err := cfg.DB.CreateTower(cfg.PrivateTower)
if err != nil {
return nil, err
}
log.Infof("Using private watchtower %s, offering policy %s",
cfg.PrivateTower, cfg.Policy)
c := &TowerClient{
cfg: cfg,
pipeline: newTaskPipeline(),
activeSessions: make(sessionQueueSet),
statTicker: time.NewTicker(DefaultStatInterval),
forceQuit: make(chan struct{}),
}
c.negotiator = newSessionNegotiator(&NegotiatorConfig{
DB: cfg.DB,
Policy: cfg.Policy,
ChainHash: cfg.ChainHash,
SendMessage: c.sendMessage,
ReadMessage: c.readMessage,
Dial: c.dial,
Candidates: newTowerListIterator(tower),
MinBackoff: cfg.MinBackoff,
MaxBackoff: cfg.MaxBackoff,
})
// Next, load all active sessions from the db into the client. We will
// use any of these session if their policies match the current policy
// of the client, otherwise they will be ignored and new sessions will
// be requested.
c.candidateSessions, err = c.cfg.DB.ListClientSessions()
if err != nil {
return nil, err
}
// Finally, load the sweep pkscripts that have been generated for all
// previously registered channels.
c.sweepPkScripts, err = c.cfg.DB.FetchChanPkScripts()
if err != nil {
return nil, err
}
return c, 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 *TowerClient) Start() error {
var err error
c.started.Do(func() {
log.Infof("Starting watchtower client")
// 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.
for _, session := range c.candidateSessions {
if len(session.CommittedUpdates) > 0 {
log.Infof("Starting session=%s to process "+
"%d committed backups", session.ID,
len(session.CommittedUpdates))
c.initActiveQueue(session)
}
}
// 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
}
// Start the task pipeline to which new backup tasks will be
// submitted from active links.
c.pipeline.Start()
c.wg.Add(1)
go c.backupDispatcher()
log.Infof("Watchtower client started successfully")
})
return err
}
// Stop idempotently initiates a graceful shutdown of the watchtower client.
func (c *TowerClient) Stop() error {
c.stopped.Do(func() {
log.Debugf("Stopping watchtower client")
// 1. Shutdown the backup queue, which will prevent any further
// updates from being accepted. In practice, the links should be
// shutdown before the client has been stopped, so all updates
// would have been added prior.
c.pipeline.Stop()
// 2. To ensure we don't hang forever on shutdown due to
// unintended failures, we'll delay a call to force quit the
// pipeline if a ForceQuitDelay is specified. This will have no
// effect if the pipeline shuts down cleanly before the delay
// fires.
//
// For full safety, this can be set to 0 and wait out
// indefinitely. However for mobile clients which may have a
// limited amount of time to exit before the background process
// is killed, this offers a way to ensure the process
// terminates.
if c.cfg.ForceQuitDelay > 0 {
time.AfterFunc(c.cfg.ForceQuitDelay, c.ForceQuit)
}
// 3. Once the backup queue has shutdown, wait for the main
// dispatcher to exit. The backup queue will signal it's
// completion to the dispatcher, which releases the wait group
// after all tasks have been assigned to session queues.
c.wg.Wait()
// 4. Since all valid tasks have been assigned to session
// queues, we no longer need to negotiate sessions.
c.negotiator.Stop()
log.Debugf("Waiting for active session queues to finish "+
"draining, stats: %s", c.stats)
// 5. Shutdown all active session queues in parallel. These will
// exit once all updates have been acked by the watchtower.
c.activeSessions.ApplyAndWait(func(s *sessionQueue) func() {
return s.Stop
})
// Skip log if force quitting.
select {
case <-c.forceQuit:
return
default:
}
log.Debugf("Client successfully stopped, stats: %s", c.stats)
})
return nil
}
// ForceQuit idempotently initiates an unclean shutdown of the watchtower
// client. This should only be executed if Stop is unable to exit cleanly.
func (c *TowerClient) ForceQuit() {
c.forced.Do(func() {
log.Infof("Force quitting watchtower client")
// Cancel log message from stop.
close(c.forceQuit)
// 1. Shutdown the backup queue, which will prevent any further
// updates from being accepted. In practice, the links should be
// shutdown before the client has been stopped, so all updates
// would have been added prior.
c.pipeline.ForceQuit()
// 2. Once the backup queue has shutdown, wait for the main
// dispatcher to exit. The backup queue will signal it's
// completion to the dispatcher, which releases the wait group
// after all tasks have been assigned to session queues.
c.wg.Wait()
// 3. Since all valid tasks have been assigned to session
// queues, we no longer need to negotiate sessions.
c.negotiator.Stop()
// 4. Force quit all active session queues in parallel. These
// will exit once all updates have been acked by the watchtower.
c.activeSessions.ApplyAndWait(func(s *sessionQueue) func() {
return s.ForceQuit
})
log.Infof("Watchtower client unclean shutdown complete, "+
"stats: %s", c.stats)
})
}
// RegisterChannel persistently initializes any channel-dependent parameters
// within the client. This should be called during link startup to ensure that
// the client is able to support the link during operation.
func (c *TowerClient) RegisterChannel(chanID lnwire.ChannelID) error {
c.sweepPkScriptMu.Lock()
defer c.sweepPkScriptMu.Unlock()
// If a pkscript for this channel already exists, the channel has been
// previously registered.
if _, ok := c.sweepPkScripts[chanID]; ok {
return nil
}
// Otherwise, generate a new sweep pkscript used to sweep funds for this
// channel.
pkScript, err := c.cfg.NewAddress()
if err != nil {
return err
}
// Persist the sweep pkscript so that restarts will not introduce
// address inflation when the channel is reregistered after a restart.
err = c.cfg.DB.AddChanPkScript(chanID, pkScript)
if err != nil {
return err
}
// Finally, cache the pkscript in our in-memory cache to avoid db
// lookups for the remainder of the daemon's execution.
c.sweepPkScripts[chanID] = pkScript
return nil
}
// 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:
// - client is force quit,
// - 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 *TowerClient) BackupState(chanID *lnwire.ChannelID,
breachInfo *lnwallet.BreachRetribution) error {
// Retrieve the cached sweep pkscript used for this channel.
c.sweepPkScriptMu.RLock()
sweepPkScript, ok := c.sweepPkScripts[*chanID]
c.sweepPkScriptMu.RUnlock()
if !ok {
return ErrUnregisteredChannel
}
task := newBackupTask(chanID, breachInfo, sweepPkScript)
return c.pipeline.QueueBackupTask(task)
}
// 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 *TowerClient) nextSessionQueue() *sessionQueue {
// Select any candidate session at random, and remove it from the set of
// candidate sessions.
var candidateSession *wtdb.ClientSession
for id, sessionInfo := range c.candidateSessions {
delete(c.candidateSessions, id)
// Skip any sessions with policies that don't match the current
// configuration. These can be used again if the client changes
// their configuration back.
if sessionInfo.Policy != c.cfg.Policy {
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
}
// 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)
}
// 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 after all tasks have been
// received from the upstream taskPipeline, or the taskPipeline is force quit.
//
// NOTE: This method MUST be run as a goroutine.
func (c *TowerClient) backupDispatcher() {
defer c.wg.Done()
log.Tracef("Starting backup dispatcher")
defer log.Tracef("Stopping backup dispatcher")
for {
switch {
// No active session queue and no additional sessions.
case c.sessionQueue == nil && len(c.candidateSessions) == 0:
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.
select {
case session := <-c.negotiator.NewSessions():
log.Infof("Acquired new session with id=%s",
session.ID)
c.candidateSessions[session.ID] = session
c.stats.sessionAcquired()
case <-c.statTicker.C:
log.Infof("Client stats: %s", c.stats)
}
// 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.
c.sessionQueue = c.nextSessionQueue()
if c.sessionQueue != nil {
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():
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:
log.Infof("Client stats: %s", c.stats)
// Process each backup task serially from the queue of
// revoked states.
case task, ok := <-c.pipeline.NewBackupTasks():
// All backups in the pipeline have been
// processed, it is now safe to exit.
if !ok {
return
}
log.Debugf("Processing backup task chanid=%s "+
"commit-height=%d", task.id.ChanID,
task.id.CommitHeight)
c.stats.taskReceived()
c.processTask(task)
}
}
}
}
// processTask attempts to schedule the given backupTask on the active
// sessionQueue. The task will either be accepted or rejected, afterwhich 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 *TowerClient) processTask(task *backupTask) {
status, accepted := c.sessionQueue.AcceptTask(task)
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 *TowerClient) taskAccepted(task *backupTask, newStatus reserveStatus) {
log.Infof("Backup chanid=%s commit-height=%d accepted successfully",
task.id.ChanID, task.id.CommitHeight)
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 reserveAvailable:
// The sessionQueue is full after accepting this task, so we will need
// to request a new one before proceeding.
case reserveExhausted:
c.stats.sessionExhausted()
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 before hand, and nil
// the sessionQueue to find a new session. If the sessionQueue was not
// exhausted, 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 *TowerClient) taskRejected(task *backupTask, curStatus reserveStatus) {
switch curStatus {
// The sessionQueue has available capacity but the task was rejected,
// this indicates that the task was ineligible for backup.
case reserveAvailable:
c.stats.taskIneligible()
log.Infof("Backup chanid=%s commit-height=%d is ineligible",
task.id.ChanID, task.id.CommitHeight)
err := c.cfg.DB.MarkBackupIneligible(
task.id.ChanID, task.id.CommitHeight,
)
if err != nil {
log.Errorf("Unable to mark task chanid=%s "+
"commit-height=%d ineligible: %v",
task.id.ChanID, task.id.CommitHeight, 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 reserveExhausted:
c.stats.sessionExhausted()
log.Debugf("Session %s exhausted, backup chanid=%s "+
"commit-height=%d queued for next session",
c.sessionQueue.ID(), task.id.ChanID,
task.id.CommitHeight)
// 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 *TowerClient) dial(privKey *btcec.PrivateKey,
addr *lnwire.NetAddress) (wtserver.Peer, error) {
return c.cfg.AuthDial(privKey, 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 *TowerClient) 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: %v", err)
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: %v", err)
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: %v", err)
log.Errorf("Unable to read msg: %v", err)
return nil, err
}
logMessage(peer, msg, true)
return msg, nil
}
// sendMessage sends a watchtower wire message to the target peer.
func (c *TowerClient) 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: %v", err)
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: %v", err)
log.Errorf("Unable to send msg: %v", err)
return err
}
logMessage(peer, msg, false)
// Write out the full message to the remote peer.
_, err = peer.Write(b.Bytes())
if err != nil {
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 *TowerClient) newSessionQueue(s *wtdb.ClientSession) *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,
})
}
// 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 *TowerClient) getOrInitActiveQueue(s *wtdb.ClientSession) *sessionQueue {
if sq, ok := c.activeSessions[s.ID]; ok {
return sq
}
return c.initActiveQueue(s)
}
// 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 *TowerClient) initActiveQueue(s *wtdb.ClientSession) *sessionQueue {
// Initialize the session queue, providing it with all of the resources
// it requires from the client instance.
sq := c.newSessionQueue(s)
// Add the session queue as an active session so that we remember to
// stop it on shutdown.
c.activeSessions.Add(sq)
// Start the queue so that it can be active in processing newly assigned
// tasks or to upload previously committed updates.
sq.Start()
return sq
}
// logMessage writes information about a message received from a remote peer,
// using directional prepositions to signal whether the message was sent or
// received.
func 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 + ")"
}
log.Debugf("%s %s%v %s %x@%s", action, msg.MsgType(), summary,
preposition, peer.RemotePub().SerializeCompressed(),
peer.RemoteAddr())
}