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dial.go
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dial.go
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// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package p2p
import (
"context"
crand "crypto/rand"
"encoding/binary"
"errors"
"fmt"
mrand "math/rand"
"net"
"sync"
"sync/atomic"
"time"
"github.com/ethereum/go-ethereum/common/mclock"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p/enode"
"github.com/ethereum/go-ethereum/p2p/netutil"
)
const (
// This is the amount of time spent waiting in between redialing a certain node. The
// limit is a bit higher than inboundThrottleTime to prevent failing dials in small
// private networks.
dialHistoryExpiration = inboundThrottleTime + 5*time.Second
// Config for the "Looking for peers" message.
dialStatsLogInterval = 10 * time.Second // printed at most this often
dialStatsPeerLimit = 3 // but not if more than this many dialed peers
// Endpoint resolution is throttled with bounded backoff.
initialResolveDelay = 60 * time.Second
maxResolveDelay = time.Hour
)
// NodeDialer is used to connect to nodes in the network, typically by using
// an underlying net.Dialer but also using net.Pipe in tests.
type NodeDialer interface {
Dial(context.Context, *enode.Node) (net.Conn, error)
}
type nodeResolver interface {
Resolve(*enode.Node) *enode.Node
}
// tcpDialer implements NodeDialer using real TCP connections.
type tcpDialer struct {
d *net.Dialer
}
func (t tcpDialer) Dial(ctx context.Context, dest *enode.Node) (net.Conn, error) {
addr, _ := dest.TCPEndpoint()
return t.d.DialContext(ctx, "tcp", addr.String())
}
// checkDial errors:
var (
errSelf = errors.New("is self")
errAlreadyDialing = errors.New("already dialing")
errAlreadyConnected = errors.New("already connected")
errRecentlyDialed = errors.New("recently dialed")
errNetRestrict = errors.New("not contained in netrestrict list")
errNoPort = errors.New("node does not provide TCP port")
)
// dialer creates outbound connections and submits them into Server.
// Two types of peer connections can be created:
//
// - static dials are pre-configured connections. The dialer attempts
// keep these nodes connected at all times.
//
// - dynamic dials are created from node discovery results. The dialer
// continuously reads candidate nodes from its input iterator and attempts
// to create peer connections to nodes arriving through the iterator.
type dialScheduler struct {
dialConfig
setupFunc dialSetupFunc
wg sync.WaitGroup
cancel context.CancelFunc
ctx context.Context
nodesIn chan *enode.Node
doneCh chan *dialTask
addStaticCh chan *enode.Node
remStaticCh chan *enode.Node
addPeerCh chan *conn
remPeerCh chan *conn
// Everything below here belongs to loop and
// should only be accessed by code on the loop goroutine.
dialing map[enode.ID]*dialTask // active tasks
peers map[enode.ID]struct{} // all connected peers
dialPeers int // current number of dialed peers
// The static map tracks all static dial tasks. The subset of usable static dial tasks
// (i.e. those passing checkDial) is kept in staticPool. The scheduler prefers
// launching random static tasks from the pool over launching dynamic dials from the
// iterator.
static map[enode.ID]*dialTask
staticPool []*dialTask
// The dial history keeps recently dialed nodes. Members of history are not dialed.
history expHeap
historyTimer *mclock.Alarm
// for logStats
lastStatsLog mclock.AbsTime
doneSinceLastLog int
}
type dialSetupFunc func(net.Conn, connFlag, *enode.Node) error
type dialConfig struct {
self enode.ID // our own ID
maxDialPeers int // maximum number of dialed peers
maxActiveDials int // maximum number of active dials
netRestrict *netutil.Netlist // IP netrestrict list, disabled if nil
resolver nodeResolver
dialer NodeDialer
log log.Logger
clock mclock.Clock
rand *mrand.Rand
}
func (cfg dialConfig) withDefaults() dialConfig {
if cfg.maxActiveDials == 0 {
cfg.maxActiveDials = defaultMaxPendingPeers
}
if cfg.log == nil {
cfg.log = log.Root()
}
if cfg.clock == nil {
cfg.clock = mclock.System{}
}
if cfg.rand == nil {
seedb := make([]byte, 8)
crand.Read(seedb)
seed := int64(binary.BigEndian.Uint64(seedb))
cfg.rand = mrand.New(mrand.NewSource(seed))
}
return cfg
}
func newDialScheduler(config dialConfig, it enode.Iterator, setupFunc dialSetupFunc) *dialScheduler {
cfg := config.withDefaults()
d := &dialScheduler{
dialConfig: cfg,
historyTimer: mclock.NewAlarm(cfg.clock),
setupFunc: setupFunc,
dialing: make(map[enode.ID]*dialTask),
static: make(map[enode.ID]*dialTask),
peers: make(map[enode.ID]struct{}),
doneCh: make(chan *dialTask),
nodesIn: make(chan *enode.Node),
addStaticCh: make(chan *enode.Node),
remStaticCh: make(chan *enode.Node),
addPeerCh: make(chan *conn),
remPeerCh: make(chan *conn),
}
d.lastStatsLog = d.clock.Now()
d.ctx, d.cancel = context.WithCancel(context.Background())
d.wg.Add(2)
go d.readNodes(it)
go d.loop(it)
return d
}
// stop shuts down the dialer, canceling all current dial tasks.
func (d *dialScheduler) stop() {
d.cancel()
d.wg.Wait()
}
// addStatic adds a static dial candidate.
func (d *dialScheduler) addStatic(n *enode.Node) {
select {
case d.addStaticCh <- n:
case <-d.ctx.Done():
}
}
// removeStatic removes a static dial candidate.
func (d *dialScheduler) removeStatic(n *enode.Node) {
select {
case d.remStaticCh <- n:
case <-d.ctx.Done():
}
}
// peerAdded updates the peer set.
func (d *dialScheduler) peerAdded(c *conn) {
select {
case d.addPeerCh <- c:
case <-d.ctx.Done():
}
}
// peerRemoved updates the peer set.
func (d *dialScheduler) peerRemoved(c *conn) {
select {
case d.remPeerCh <- c:
case <-d.ctx.Done():
}
}
// loop is the main loop of the dialer.
func (d *dialScheduler) loop(it enode.Iterator) {
var (
nodesCh chan *enode.Node
)
loop:
for {
// Launch new dials if slots are available.
slots := d.freeDialSlots()
slots -= d.startStaticDials(slots)
if slots > 0 {
nodesCh = d.nodesIn
} else {
nodesCh = nil
}
d.rearmHistoryTimer()
d.logStats()
select {
case node := <-nodesCh:
if err := d.checkDial(node); err != nil {
d.log.Trace("Discarding dial candidate", "id", node.ID(), "ip", node.IPAddr(), "reason", err)
} else {
d.startDial(newDialTask(node, dynDialedConn))
}
case task := <-d.doneCh:
id := task.dest().ID()
delete(d.dialing, id)
d.updateStaticPool(id)
d.doneSinceLastLog++
case c := <-d.addPeerCh:
if c.is(dynDialedConn) || c.is(staticDialedConn) {
d.dialPeers++
}
id := c.node.ID()
d.peers[id] = struct{}{}
// Remove from static pool because the node is now connected.
task := d.static[id]
if task != nil && task.staticPoolIndex >= 0 {
d.removeFromStaticPool(task.staticPoolIndex)
}
// TODO: cancel dials to connected peers
case c := <-d.remPeerCh:
if c.is(dynDialedConn) || c.is(staticDialedConn) {
d.dialPeers--
}
delete(d.peers, c.node.ID())
d.updateStaticPool(c.node.ID())
case node := <-d.addStaticCh:
id := node.ID()
_, exists := d.static[id]
d.log.Trace("Adding static node", "id", id, "ip", node.IPAddr(), "added", !exists)
if exists {
continue loop
}
task := newDialTask(node, staticDialedConn)
d.static[id] = task
if d.checkDial(node) == nil {
d.addToStaticPool(task)
}
case node := <-d.remStaticCh:
id := node.ID()
task := d.static[id]
d.log.Trace("Removing static node", "id", id, "ok", task != nil)
if task != nil {
delete(d.static, id)
if task.staticPoolIndex >= 0 {
d.removeFromStaticPool(task.staticPoolIndex)
}
}
case <-d.historyTimer.C():
d.expireHistory()
case <-d.ctx.Done():
it.Close()
break loop
}
}
d.historyTimer.Stop()
for range d.dialing {
<-d.doneCh
}
d.wg.Done()
}
// readNodes runs in its own goroutine and delivers nodes from
// the input iterator to the nodesIn channel.
func (d *dialScheduler) readNodes(it enode.Iterator) {
defer d.wg.Done()
for it.Next() {
select {
case d.nodesIn <- it.Node():
case <-d.ctx.Done():
}
}
}
// logStats prints dialer statistics to the log. The message is suppressed when enough
// peers are connected because users should only see it while their client is starting up
// or comes back online.
func (d *dialScheduler) logStats() {
now := d.clock.Now()
if d.lastStatsLog.Add(dialStatsLogInterval) > now {
return
}
if d.dialPeers < dialStatsPeerLimit && d.dialPeers < d.maxDialPeers {
d.log.Info("Looking for peers", "peercount", len(d.peers), "tried", d.doneSinceLastLog, "static", len(d.static))
}
d.doneSinceLastLog = 0
d.lastStatsLog = now
}
// rearmHistoryTimer configures d.historyTimer to fire when the
// next item in d.history expires.
func (d *dialScheduler) rearmHistoryTimer() {
if len(d.history) == 0 {
return
}
d.historyTimer.Schedule(d.history.nextExpiry())
}
// expireHistory removes expired items from d.history.
func (d *dialScheduler) expireHistory() {
d.history.expire(d.clock.Now(), func(hkey string) {
var id enode.ID
copy(id[:], hkey)
d.updateStaticPool(id)
})
}
// freeDialSlots returns the number of free dial slots. The result can be negative
// when peers are connected while their task is still running.
func (d *dialScheduler) freeDialSlots() int {
slots := (d.maxDialPeers - d.dialPeers) * 2
if slots > d.maxActiveDials {
slots = d.maxActiveDials
}
free := slots - len(d.dialing)
return free
}
// checkDial returns an error if node n should not be dialed.
func (d *dialScheduler) checkDial(n *enode.Node) error {
if n.ID() == d.self {
return errSelf
}
if n.IPAddr().IsValid() && n.TCP() == 0 {
// This check can trigger if a non-TCP node is found
// by discovery. If there is no IP, the node is a static
// node and the actual endpoint will be resolved later in dialTask.
return errNoPort
}
if _, ok := d.dialing[n.ID()]; ok {
return errAlreadyDialing
}
if _, ok := d.peers[n.ID()]; ok {
return errAlreadyConnected
}
if d.netRestrict != nil && !d.netRestrict.ContainsAddr(n.IPAddr()) {
return errNetRestrict
}
if d.history.contains(string(n.ID().Bytes())) {
return errRecentlyDialed
}
return nil
}
// startStaticDials starts n static dial tasks.
func (d *dialScheduler) startStaticDials(n int) (started int) {
for started = 0; started < n && len(d.staticPool) > 0; started++ {
idx := d.rand.Intn(len(d.staticPool))
task := d.staticPool[idx]
d.startDial(task)
d.removeFromStaticPool(idx)
}
return started
}
// updateStaticPool attempts to move the given static dial back into staticPool.
func (d *dialScheduler) updateStaticPool(id enode.ID) {
task, ok := d.static[id]
if ok && task.staticPoolIndex < 0 && d.checkDial(task.dest()) == nil {
d.addToStaticPool(task)
}
}
func (d *dialScheduler) addToStaticPool(task *dialTask) {
if task.staticPoolIndex >= 0 {
panic("attempt to add task to staticPool twice")
}
d.staticPool = append(d.staticPool, task)
task.staticPoolIndex = len(d.staticPool) - 1
}
// removeFromStaticPool removes the task at idx from staticPool. It does that by moving the
// current last element of the pool to idx and then shortening the pool by one.
func (d *dialScheduler) removeFromStaticPool(idx int) {
task := d.staticPool[idx]
end := len(d.staticPool) - 1
d.staticPool[idx] = d.staticPool[end]
d.staticPool[idx].staticPoolIndex = idx
d.staticPool[end] = nil
d.staticPool = d.staticPool[:end]
task.staticPoolIndex = -1
}
// startDial runs the given dial task in a separate goroutine.
func (d *dialScheduler) startDial(task *dialTask) {
node := task.dest()
d.log.Trace("Starting p2p dial", "id", node.ID(), "ip", node.IPAddr(), "flag", task.flags)
hkey := string(node.ID().Bytes())
d.history.add(hkey, d.clock.Now().Add(dialHistoryExpiration))
d.dialing[node.ID()] = task
go func() {
task.run(d)
d.doneCh <- task
}()
}
// A dialTask generated for each node that is dialed.
type dialTask struct {
staticPoolIndex int
flags connFlag
// These fields are private to the task and should not be
// accessed by dialScheduler while the task is running.
destPtr atomic.Pointer[enode.Node]
lastResolved mclock.AbsTime
resolveDelay time.Duration
}
func newDialTask(dest *enode.Node, flags connFlag) *dialTask {
t := &dialTask{flags: flags, staticPoolIndex: -1}
t.destPtr.Store(dest)
return t
}
type dialError struct {
error
}
func (t *dialTask) dest() *enode.Node {
return t.destPtr.Load()
}
func (t *dialTask) run(d *dialScheduler) {
if t.needResolve() && !t.resolve(d) {
return
}
err := t.dial(d, t.dest())
if err != nil {
// For static nodes, resolve one more time if dialing fails.
if _, ok := err.(*dialError); ok && t.flags&staticDialedConn != 0 {
if t.resolve(d) {
t.dial(d, t.dest())
}
}
}
}
func (t *dialTask) needResolve() bool {
return t.flags&staticDialedConn != 0 && !t.dest().IPAddr().IsValid()
}
// resolve attempts to find the current endpoint for the destination
// using discovery.
//
// Resolve operations are throttled with backoff to avoid flooding the
// discovery network with useless queries for nodes that don't exist.
// The backoff delay resets when the node is found.
func (t *dialTask) resolve(d *dialScheduler) bool {
if d.resolver == nil {
return false
}
if t.resolveDelay == 0 {
t.resolveDelay = initialResolveDelay
}
if t.lastResolved > 0 && time.Duration(d.clock.Now()-t.lastResolved) < t.resolveDelay {
return false
}
node := t.dest()
resolved := d.resolver.Resolve(node)
t.lastResolved = d.clock.Now()
if resolved == nil {
t.resolveDelay *= 2
if t.resolveDelay > maxResolveDelay {
t.resolveDelay = maxResolveDelay
}
d.log.Debug("Resolving node failed", "id", node.ID(), "newdelay", t.resolveDelay)
return false
}
// The node was found.
t.resolveDelay = initialResolveDelay
t.destPtr.Store(resolved)
resAddr, _ := resolved.TCPEndpoint()
d.log.Debug("Resolved node", "id", resolved.ID(), "addr", resAddr)
return true
}
// dial performs the actual connection attempt.
func (t *dialTask) dial(d *dialScheduler, dest *enode.Node) error {
dialMeter.Mark(1)
fd, err := d.dialer.Dial(d.ctx, dest)
if err != nil {
addr, _ := dest.TCPEndpoint()
d.log.Trace("Dial error", "id", dest.ID(), "addr", addr, "conn", t.flags, "err", cleanupDialErr(err))
dialConnectionError.Mark(1)
return &dialError{err}
}
return d.setupFunc(newMeteredConn(fd), t.flags, dest)
}
func (t *dialTask) String() string {
node := t.dest()
id := node.ID()
return fmt.Sprintf("%v %x %v:%d", t.flags, id[:8], node.IPAddr(), node.TCP())
}
func cleanupDialErr(err error) error {
if netErr, ok := err.(*net.OpError); ok && netErr.Op == "dial" {
return netErr.Err
}
return err
}