plugeth/p2p/dial.go
Dmitry Shulyak 14c76371ba p2p: when peer is removed remove it also from dial history (#16060)
This change removes a peer information from dialing history
when peer is removed from static list. It allows to force a
server to re-dial concrete peer if it is needed.

In our case we are running geth node on mobile devices, and
it is common for a network connection to flap on mobile.
Almost every time it flaps or network connection is changed
from cellular to wifi peers are disconnected with read
timeout. And usually it takes 30 seconds (default expiration
timeout) to recover connection with static peers after
connectivity is restored.

This change allows us to reconnect with peers almost
immediately and it seems harmless enough.
2018-02-21 15:03:26 +01:00

435 lines
12 KiB
Go

// 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 (
"container/heap"
"crypto/rand"
"errors"
"fmt"
"net"
"time"
"github.com/ethereum/go-ethereum/log"
"github.com/ethereum/go-ethereum/p2p/discover"
"github.com/ethereum/go-ethereum/p2p/netutil"
)
const (
// This is the amount of time spent waiting in between
// redialing a certain node.
dialHistoryExpiration = 30 * time.Second
// Discovery lookups are throttled and can only run
// once every few seconds.
lookupInterval = 4 * time.Second
// If no peers are found for this amount of time, the initial bootnodes are
// attempted to be connected.
fallbackInterval = 20 * time.Second
// 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(*discover.Node) (net.Conn, error)
}
// TCPDialer implements the NodeDialer interface by using a net.Dialer to
// create TCP connections to nodes in the network
type TCPDialer struct {
*net.Dialer
}
// Dial creates a TCP connection to the node
func (t TCPDialer) Dial(dest *discover.Node) (net.Conn, error) {
addr := &net.TCPAddr{IP: dest.IP, Port: int(dest.TCP)}
return t.Dialer.Dial("tcp", addr.String())
}
// dialstate schedules dials and discovery lookups.
// it get's a chance to compute new tasks on every iteration
// of the main loop in Server.run.
type dialstate struct {
maxDynDials int
ntab discoverTable
netrestrict *netutil.Netlist
lookupRunning bool
dialing map[discover.NodeID]connFlag
lookupBuf []*discover.Node // current discovery lookup results
randomNodes []*discover.Node // filled from Table
static map[discover.NodeID]*dialTask
hist *dialHistory
start time.Time // time when the dialer was first used
bootnodes []*discover.Node // default dials when there are no peers
}
type discoverTable interface {
Self() *discover.Node
Close()
Resolve(target discover.NodeID) *discover.Node
Lookup(target discover.NodeID) []*discover.Node
ReadRandomNodes([]*discover.Node) int
}
// the dial history remembers recent dials.
type dialHistory []pastDial
// pastDial is an entry in the dial history.
type pastDial struct {
id discover.NodeID
exp time.Time
}
type task interface {
Do(*Server)
}
// A dialTask is generated for each node that is dialed. Its
// fields cannot be accessed while the task is running.
type dialTask struct {
flags connFlag
dest *discover.Node
lastResolved time.Time
resolveDelay time.Duration
}
// discoverTask runs discovery table operations.
// Only one discoverTask is active at any time.
// discoverTask.Do performs a random lookup.
type discoverTask struct {
results []*discover.Node
}
// A waitExpireTask is generated if there are no other tasks
// to keep the loop in Server.run ticking.
type waitExpireTask struct {
time.Duration
}
func newDialState(static []*discover.Node, bootnodes []*discover.Node, ntab discoverTable, maxdyn int, netrestrict *netutil.Netlist) *dialstate {
s := &dialstate{
maxDynDials: maxdyn,
ntab: ntab,
netrestrict: netrestrict,
static: make(map[discover.NodeID]*dialTask),
dialing: make(map[discover.NodeID]connFlag),
bootnodes: make([]*discover.Node, len(bootnodes)),
randomNodes: make([]*discover.Node, maxdyn/2),
hist: new(dialHistory),
}
copy(s.bootnodes, bootnodes)
for _, n := range static {
s.addStatic(n)
}
return s
}
func (s *dialstate) addStatic(n *discover.Node) {
// This overwites the task instead of updating an existing
// entry, giving users the opportunity to force a resolve operation.
s.static[n.ID] = &dialTask{flags: staticDialedConn, dest: n}
}
func (s *dialstate) removeStatic(n *discover.Node) {
// This removes a task so future attempts to connect will not be made.
delete(s.static, n.ID)
// This removes a previous dial timestamp so that application
// can force a server to reconnect with chosen peer immediately.
s.hist.remove(n.ID)
}
func (s *dialstate) newTasks(nRunning int, peers map[discover.NodeID]*Peer, now time.Time) []task {
if s.start.IsZero() {
s.start = now
}
var newtasks []task
addDial := func(flag connFlag, n *discover.Node) bool {
if err := s.checkDial(n, peers); err != nil {
log.Trace("Skipping dial candidate", "id", n.ID, "addr", &net.TCPAddr{IP: n.IP, Port: int(n.TCP)}, "err", err)
return false
}
s.dialing[n.ID] = flag
newtasks = append(newtasks, &dialTask{flags: flag, dest: n})
return true
}
// Compute number of dynamic dials necessary at this point.
needDynDials := s.maxDynDials
for _, p := range peers {
if p.rw.is(dynDialedConn) {
needDynDials--
}
}
for _, flag := range s.dialing {
if flag&dynDialedConn != 0 {
needDynDials--
}
}
// Expire the dial history on every invocation.
s.hist.expire(now)
// Create dials for static nodes if they are not connected.
for id, t := range s.static {
err := s.checkDial(t.dest, peers)
switch err {
case errNotWhitelisted, errSelf:
log.Warn("Removing static dial candidate", "id", t.dest.ID, "addr", &net.TCPAddr{IP: t.dest.IP, Port: int(t.dest.TCP)}, "err", err)
delete(s.static, t.dest.ID)
case nil:
s.dialing[id] = t.flags
newtasks = append(newtasks, t)
}
}
// If we don't have any peers whatsoever, try to dial a random bootnode. This
// scenario is useful for the testnet (and private networks) where the discovery
// table might be full of mostly bad peers, making it hard to find good ones.
if len(peers) == 0 && len(s.bootnodes) > 0 && needDynDials > 0 && now.Sub(s.start) > fallbackInterval {
bootnode := s.bootnodes[0]
s.bootnodes = append(s.bootnodes[:0], s.bootnodes[1:]...)
s.bootnodes = append(s.bootnodes, bootnode)
if addDial(dynDialedConn, bootnode) {
needDynDials--
}
}
// Use random nodes from the table for half of the necessary
// dynamic dials.
randomCandidates := needDynDials / 2
if randomCandidates > 0 {
n := s.ntab.ReadRandomNodes(s.randomNodes)
for i := 0; i < randomCandidates && i < n; i++ {
if addDial(dynDialedConn, s.randomNodes[i]) {
needDynDials--
}
}
}
// Create dynamic dials from random lookup results, removing tried
// items from the result buffer.
i := 0
for ; i < len(s.lookupBuf) && needDynDials > 0; i++ {
if addDial(dynDialedConn, s.lookupBuf[i]) {
needDynDials--
}
}
s.lookupBuf = s.lookupBuf[:copy(s.lookupBuf, s.lookupBuf[i:])]
// Launch a discovery lookup if more candidates are needed.
if len(s.lookupBuf) < needDynDials && !s.lookupRunning {
s.lookupRunning = true
newtasks = append(newtasks, &discoverTask{})
}
// Launch a timer to wait for the next node to expire if all
// candidates have been tried and no task is currently active.
// This should prevent cases where the dialer logic is not ticked
// because there are no pending events.
if nRunning == 0 && len(newtasks) == 0 && s.hist.Len() > 0 {
t := &waitExpireTask{s.hist.min().exp.Sub(now)}
newtasks = append(newtasks, t)
}
return newtasks
}
var (
errSelf = errors.New("is self")
errAlreadyDialing = errors.New("already dialing")
errAlreadyConnected = errors.New("already connected")
errRecentlyDialed = errors.New("recently dialed")
errNotWhitelisted = errors.New("not contained in netrestrict whitelist")
)
func (s *dialstate) checkDial(n *discover.Node, peers map[discover.NodeID]*Peer) error {
_, dialing := s.dialing[n.ID]
switch {
case dialing:
return errAlreadyDialing
case peers[n.ID] != nil:
return errAlreadyConnected
case s.ntab != nil && n.ID == s.ntab.Self().ID:
return errSelf
case s.netrestrict != nil && !s.netrestrict.Contains(n.IP):
return errNotWhitelisted
case s.hist.contains(n.ID):
return errRecentlyDialed
}
return nil
}
func (s *dialstate) taskDone(t task, now time.Time) {
switch t := t.(type) {
case *dialTask:
s.hist.add(t.dest.ID, now.Add(dialHistoryExpiration))
delete(s.dialing, t.dest.ID)
case *discoverTask:
s.lookupRunning = false
s.lookupBuf = append(s.lookupBuf, t.results...)
}
}
func (t *dialTask) Do(srv *Server) {
if t.dest.Incomplete() {
if !t.resolve(srv) {
return
}
}
err := t.dial(srv, t.dest)
if err != nil {
log.Trace("Dial error", "task", t, "err", err)
// Try resolving the ID of static nodes if dialing failed.
if _, ok := err.(*dialError); ok && t.flags&staticDialedConn != 0 {
if t.resolve(srv) {
t.dial(srv, t.dest)
}
}
}
}
// 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(srv *Server) bool {
if srv.ntab == nil {
log.Debug("Can't resolve node", "id", t.dest.ID, "err", "discovery is disabled")
return false
}
if t.resolveDelay == 0 {
t.resolveDelay = initialResolveDelay
}
if time.Since(t.lastResolved) < t.resolveDelay {
return false
}
resolved := srv.ntab.Resolve(t.dest.ID)
t.lastResolved = time.Now()
if resolved == nil {
t.resolveDelay *= 2
if t.resolveDelay > maxResolveDelay {
t.resolveDelay = maxResolveDelay
}
log.Debug("Resolving node failed", "id", t.dest.ID, "newdelay", t.resolveDelay)
return false
}
// The node was found.
t.resolveDelay = initialResolveDelay
t.dest = resolved
log.Debug("Resolved node", "id", t.dest.ID, "addr", &net.TCPAddr{IP: t.dest.IP, Port: int(t.dest.TCP)})
return true
}
type dialError struct {
error
}
// dial performs the actual connection attempt.
func (t *dialTask) dial(srv *Server, dest *discover.Node) error {
fd, err := srv.Dialer.Dial(dest)
if err != nil {
return &dialError{err}
}
mfd := newMeteredConn(fd, false)
return srv.SetupConn(mfd, t.flags, dest)
}
func (t *dialTask) String() string {
return fmt.Sprintf("%v %x %v:%d", t.flags, t.dest.ID[:8], t.dest.IP, t.dest.TCP)
}
func (t *discoverTask) Do(srv *Server) {
// newTasks generates a lookup task whenever dynamic dials are
// necessary. Lookups need to take some time, otherwise the
// event loop spins too fast.
next := srv.lastLookup.Add(lookupInterval)
if now := time.Now(); now.Before(next) {
time.Sleep(next.Sub(now))
}
srv.lastLookup = time.Now()
var target discover.NodeID
rand.Read(target[:])
t.results = srv.ntab.Lookup(target)
}
func (t *discoverTask) String() string {
s := "discovery lookup"
if len(t.results) > 0 {
s += fmt.Sprintf(" (%d results)", len(t.results))
}
return s
}
func (t waitExpireTask) Do(*Server) {
time.Sleep(t.Duration)
}
func (t waitExpireTask) String() string {
return fmt.Sprintf("wait for dial hist expire (%v)", t.Duration)
}
// Use only these methods to access or modify dialHistory.
func (h dialHistory) min() pastDial {
return h[0]
}
func (h *dialHistory) add(id discover.NodeID, exp time.Time) {
heap.Push(h, pastDial{id, exp})
}
func (h *dialHistory) remove(id discover.NodeID) bool {
for i, v := range *h {
if v.id == id {
heap.Remove(h, i)
return true
}
}
return false
}
func (h dialHistory) contains(id discover.NodeID) bool {
for _, v := range h {
if v.id == id {
return true
}
}
return false
}
func (h *dialHistory) expire(now time.Time) {
for h.Len() > 0 && h.min().exp.Before(now) {
heap.Pop(h)
}
}
// heap.Interface boilerplate
func (h dialHistory) Len() int { return len(h) }
func (h dialHistory) Less(i, j int) bool { return h[i].exp.Before(h[j].exp) }
func (h dialHistory) Swap(i, j int) { h[i], h[j] = h[j], h[i] }
func (h *dialHistory) Push(x interface{}) {
*h = append(*h, x.(pastDial))
}
func (h *dialHistory) Pop() interface{} {
old := *h
n := len(old)
x := old[n-1]
*h = old[0 : n-1]
return x
}