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tendermint/p2p/pex/pex_reactor.go

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package pex
import (
"fmt"
"reflect"
"sort"
"sync"
"time"
"github.com/pkg/errors"
amino "github.com/tendermint/go-amino"
cmn "github.com/tendermint/tendermint/libs/common"
"github.com/tendermint/tendermint/p2p"
"github.com/tendermint/tendermint/p2p/conn"
)
type Peer = p2p.Peer
const (
// PexChannel is a channel for PEX messages
PexChannel = byte(0x00)
// over-estimate of max NetAddress size
// hexID (40) + IP (16) + Port (2) + Name (100) ...
// NOTE: dont use massive DNS name ..
maxAddressSize = 256
// NOTE: amplificaiton factor!
// small request results in up to maxMsgSize response
maxMsgSize = maxAddressSize * maxGetSelection
// ensure we have enough peers
defaultEnsurePeersPeriod = 30 * time.Second
// Seed/Crawler constants
// We want seeds to only advertise good peers. Therefore they should wait at
// least as long as we expect it to take for a peer to become good before
// disconnecting.
// see consensus/reactor.go: blocksToContributeToBecomeGoodPeer
// 10000 blocks assuming 1s blocks ~ 2.7 hours.
defaultSeedDisconnectWaitPeriod = 3 * time.Hour
defaultCrawlPeerInterval = 2 * time.Minute // don't redial for this. TODO: back-off. what for?
defaultCrawlPeersPeriod = 30 * time.Second // check some peers every this
maxAttemptsToDial = 16 // ~ 35h in total (last attempt - 18h)
// if node connects to seed, it does not have any trusted peers.
// Especially in the beginning, node should have more trusted peers than
// untrusted.
biasToSelectNewPeers = 30 // 70 to select good peers
)
// PEXReactor handles PEX (peer exchange) and ensures that an
// adequate number of peers are connected to the switch.
//
// It uses `AddrBook` (address book) to store `NetAddress`es of the peers.
//
// ## Preventing abuse
//
// Only accept pexAddrsMsg from peers we sent a corresponding pexRequestMsg too.
// Only accept one pexRequestMsg every ~defaultEnsurePeersPeriod.
type PEXReactor struct {
p2p.BaseReactor
book AddrBook
config *PEXReactorConfig
ensurePeersPeriod time.Duration // TODO: should go in the config
// maps to prevent abuse
requestsSent *cmn.CMap // ID->struct{}: unanswered send requests
lastReceivedRequests *cmn.CMap // ID->time.Time: last time peer requested from us
seedAddrs []*p2p.NetAddress
attemptsToDial sync.Map // address (string) -> {number of attempts (int), last time dialed (time.Time)}
}
func (r *PEXReactor) minReceiveRequestInterval() time.Duration {
// NOTE: must be less than ensurePeersPeriod, otherwise we'll request
// peers too quickly from others and they'll think we're bad!
return r.ensurePeersPeriod / 3
}
// PEXReactorConfig holds reactor specific configuration data.
type PEXReactorConfig struct {
// Seed/Crawler mode
SeedMode bool
// Seeds is a list of addresses reactor may use
// if it can't connect to peers in the addrbook.
Seeds []string
}
type _attemptsToDial struct {
number int
lastDialed time.Time
}
// NewPEXReactor creates new PEX reactor.
func NewPEXReactor(b AddrBook, config *PEXReactorConfig) *PEXReactor {
r := &PEXReactor{
book: b,
config: config,
ensurePeersPeriod: defaultEnsurePeersPeriod,
requestsSent: cmn.NewCMap(),
lastReceivedRequests: cmn.NewCMap(),
}
r.BaseReactor = *p2p.NewBaseReactor("PEXReactor", r)
return r
}
// OnStart implements BaseService
func (r *PEXReactor) OnStart() error {
err := r.book.Start()
if err != nil && err != cmn.ErrAlreadyStarted {
return err
}
numOnline, seedAddrs, err := r.checkSeeds()
if err != nil {
return err
} else if numOnline == 0 && r.book.Empty() {
return errors.New("Address book is empty, and could not connect to any seed nodes")
}
r.seedAddrs = seedAddrs
// Check if this node should run
// in seed/crawler mode
if r.config.SeedMode {
go r.crawlPeersRoutine()
} else {
go r.ensurePeersRoutine()
}
return nil
}
// OnStop implements BaseService
func (r *PEXReactor) OnStop() {
r.book.Stop()
}
// GetChannels implements Reactor
func (r *PEXReactor) GetChannels() []*conn.ChannelDescriptor {
return []*conn.ChannelDescriptor{
{
ID: PexChannel,
Priority: 1,
SendQueueCapacity: 10,
},
}
}
// AddPeer implements Reactor by adding peer to the address book (if inbound)
// or by requesting more addresses (if outbound).
func (r *PEXReactor) AddPeer(p Peer) {
if p.IsOutbound() {
// For outbound peers, the address is already in the books -
// either via DialPeersAsync or r.Receive.
// Ask it for more peers if we need.
if r.book.NeedMoreAddrs() {
r.RequestAddrs(p)
}
} else {
// inbound peer is its own source
addr := p.NodeInfo().NetAddress()
src := addr
// add to book. dont RequestAddrs right away because
// we don't trust inbound as much - let ensurePeersRoutine handle it.
err := r.book.AddAddress(addr, src)
r.logErrAddrBook(err)
}
}
func (r *PEXReactor) logErrAddrBook(err error) {
if err != nil {
switch err.(type) {
case ErrAddrBookNilAddr:
r.Logger.Error("Failed to add new address", "err", err)
default:
// non-routable, self, full book, private, etc.
r.Logger.Debug("Failed to add new address", "err", err)
}
}
}
// RemovePeer implements Reactor.
func (r *PEXReactor) RemovePeer(p Peer, reason interface{}) {
id := string(p.ID())
r.requestsSent.Delete(id)
r.lastReceivedRequests.Delete(id)
}
// Receive implements Reactor by handling incoming PEX messages.
func (r *PEXReactor) Receive(chID byte, src Peer, msgBytes []byte) {
msg, err := decodeMsg(msgBytes)
if err != nil {
r.Logger.Error("Error decoding message", "src", src, "chId", chID, "msg", msg, "err", err, "bytes", msgBytes)
r.Switch.StopPeerForError(src, err)
return
}
r.Logger.Debug("Received message", "src", src, "chId", chID, "msg", msg)
switch msg := msg.(type) {
case *pexRequestMessage:
// Check we're not receiving too many requests
if err := r.receiveRequest(src); err != nil {
r.Switch.StopPeerForError(src, err)
return
}
// Seeds disconnect after sending a batch of addrs
// NOTE: this is a prime candidate for amplification attacks
// so it's important we
// 1) restrict how frequently peers can request
// 2) limit the output size
if r.config.SeedMode {
r.SendAddrs(src, r.book.GetSelectionWithBias(biasToSelectNewPeers))
r.Switch.StopPeerGracefully(src)
} else {
r.SendAddrs(src, r.book.GetSelection())
}
case *pexAddrsMessage:
// If we asked for addresses, add them to the book
if err := r.ReceiveAddrs(msg.Addrs, src); err != nil {
r.Switch.StopPeerForError(src, err)
return
}
default:
r.Logger.Error(fmt.Sprintf("Unknown message type %v", reflect.TypeOf(msg)))
}
}
// enforces a minimum amount of time between requests
func (r *PEXReactor) receiveRequest(src Peer) error {
id := string(src.ID())
v := r.lastReceivedRequests.Get(id)
if v == nil {
// initialize with empty time
lastReceived := time.Time{}
r.lastReceivedRequests.Set(id, lastReceived)
return nil
}
lastReceived := v.(time.Time)
if lastReceived.Equal(time.Time{}) {
// first time gets a free pass. then we start tracking the time
lastReceived = time.Now()
r.lastReceivedRequests.Set(id, lastReceived)
return nil
}
now := time.Now()
minInterval := r.minReceiveRequestInterval()
if now.Sub(lastReceived) < minInterval {
return fmt.Errorf("Peer (%v) sent next PEX request too soon. lastReceived: %v, now: %v, minInterval: %v. Disconnecting",
src.ID(),
lastReceived,
now,
minInterval,
)
}
r.lastReceivedRequests.Set(id, now)
return nil
}
// RequestAddrs asks peer for more addresses if we do not already
// have a request out for this peer.
func (r *PEXReactor) RequestAddrs(p Peer) {
r.Logger.Debug("Request addrs", "from", p)
id := string(p.ID())
if r.requestsSent.Has(id) {
return
}
r.requestsSent.Set(id, struct{}{})
p.Send(PexChannel, cdc.MustMarshalBinaryBare(&pexRequestMessage{}))
}
// ReceiveAddrs adds the given addrs to the addrbook if theres an open
// request for this peer and deletes the open request.
// If there's no open request for the src peer, it returns an error.
func (r *PEXReactor) ReceiveAddrs(addrs []*p2p.NetAddress, src Peer) error {
id := string(src.ID())
if !r.requestsSent.Has(id) {
return cmn.NewError("Received unsolicited pexAddrsMessage")
}
r.requestsSent.Delete(id)
srcAddr := src.NodeInfo().NetAddress()
for _, netAddr := range addrs {
// NOTE: GetSelection methods should never return nil addrs
if netAddr == nil {
return cmn.NewError("received nil addr")
}
err := r.book.AddAddress(netAddr, srcAddr)
r.logErrAddrBook(err)
// If this address came from a seed node, try to connect to it without waiting.
for _, seedAddr := range r.seedAddrs {
if seedAddr.Equals(srcAddr) {
r.ensurePeers()
}
}
}
return nil
}
// SendAddrs sends addrs to the peer.
func (r *PEXReactor) SendAddrs(p Peer, netAddrs []*p2p.NetAddress) {
p.Send(PexChannel, cdc.MustMarshalBinaryBare(&pexAddrsMessage{Addrs: netAddrs}))
}
// SetEnsurePeersPeriod sets period to ensure peers connected.
func (r *PEXReactor) SetEnsurePeersPeriod(d time.Duration) {
r.ensurePeersPeriod = d
}
// Ensures that sufficient peers are connected. (continuous)
func (r *PEXReactor) ensurePeersRoutine() {
var (
seed = cmn.NewRand()
jitter = seed.Int63n(r.ensurePeersPeriod.Nanoseconds())
)
// Randomize first round of communication to avoid thundering herd.
// If no potential peers are present directly start connecting so we guarantee
// swift setup with the help of configured seeds.
if r.hasPotentialPeers() {
time.Sleep(time.Duration(jitter))
}
// fire once immediately.
// ensures we dial the seeds right away if the book is empty
r.ensurePeers()
// fire periodically
ticker := time.NewTicker(r.ensurePeersPeriod)
for {
select {
case <-ticker.C:
r.ensurePeers()
case <-r.Quit():
ticker.Stop()
return
}
}
}
// ensurePeers ensures that sufficient peers are connected. (once)
//
// heuristic that we haven't perfected yet, or, perhaps is manually edited by
// the node operator. It should not be used to compute what addresses are
// already connected or not.
func (r *PEXReactor) ensurePeers() {
var (
out, in, dial = r.Switch.NumPeers()
numToDial = r.Switch.MaxNumOutboundPeers() - (out + dial)
)
r.Logger.Info(
"Ensure peers",
"numOutPeers", out,
"numInPeers", in,
"numDialing", dial,
"numToDial", numToDial,
)
if numToDial <= 0 {
return
}
// bias to prefer more vetted peers when we have fewer connections.
// not perfect, but somewhate ensures that we prioritize connecting to more-vetted
// NOTE: range here is [10, 90]. Too high ?
newBias := cmn.MinInt(out, 8)*10 + 10
toDial := make(map[p2p.ID]*p2p.NetAddress)
// Try maxAttempts times to pick numToDial addresses to dial
maxAttempts := numToDial * 3
for i := 0; i < maxAttempts && len(toDial) < numToDial; i++ {
try := r.book.PickAddress(newBias)
if try == nil {
continue
}
if _, selected := toDial[try.ID]; selected {
continue
}
if r.Switch.IsDialingOrExistingAddress(try) {
continue
}
// TODO: consider moving some checks from toDial into here
// so we don't even consider dialing peers that we want to wait
// before dialling again, or have dialed too many times already
r.Logger.Info("Will dial address", "addr", try)
toDial[try.ID] = try
}
// Dial picked addresses
for _, addr := range toDial {
go r.dialPeer(addr)
}
// If we need more addresses, pick a random peer and ask for more.
if r.book.NeedMoreAddrs() {
peers := r.Switch.Peers().List()
peersCount := len(peers)
if peersCount > 0 {
peer := peers[cmn.RandInt()%peersCount] // nolint: gas
r.Logger.Info("We need more addresses. Sending pexRequest to random peer", "peer", peer)
r.RequestAddrs(peer)
}
}
// If we are not connected to nor dialing anybody, fallback to dialing a seed.
if out+in+dial+len(toDial) == 0 {
r.Logger.Info("No addresses to dial nor connected peers. Falling back to seeds")
r.dialSeeds()
}
}
func (r *PEXReactor) dialAttemptsInfo(addr *p2p.NetAddress) (attempts int, lastDialed time.Time) {
_attempts, ok := r.attemptsToDial.Load(addr.DialString())
if !ok {
return
}
atd := _attempts.(_attemptsToDial)
return atd.number, atd.lastDialed
}
func (r *PEXReactor) dialPeer(addr *p2p.NetAddress) {
attempts, lastDialed := r.dialAttemptsInfo(addr)
if attempts > maxAttemptsToDial {
r.Logger.Error("Reached max attempts to dial", "addr", addr, "attempts", attempts)
r.book.MarkBad(addr)
return
}
// exponential backoff if it's not our first attempt to dial given address
if attempts > 0 {
jitterSeconds := time.Duration(cmn.RandFloat64() * float64(time.Second)) // 1s == (1e9 ns)
backoffDuration := jitterSeconds + ((1 << uint(attempts)) * time.Second)
sinceLastDialed := time.Since(lastDialed)
if sinceLastDialed < backoffDuration {
r.Logger.Debug("Too early to dial", "addr", addr, "backoff_duration", backoffDuration, "last_dialed", lastDialed, "time_since", sinceLastDialed)
return
}
}
err := r.Switch.DialPeerWithAddress(addr, false)
if err != nil {
r.Logger.Error("Dialing failed", "addr", addr, "err", err, "attempts", attempts)
// TODO: detect more "bad peer" scenarios
if _, ok := err.(p2p.ErrSwitchAuthenticationFailure); ok {
r.book.MarkBad(addr)
r.attemptsToDial.Delete(addr.DialString())
} else {
r.book.MarkAttempt(addr)
// FIXME: if the addr is going to be removed from the addrbook (hard to
// tell at this point), we need to Delete it from attemptsToDial, not
// record another attempt.
// record attempt
r.attemptsToDial.Store(addr.DialString(), _attemptsToDial{attempts + 1, time.Now()})
}
} else {
// cleanup any history
r.attemptsToDial.Delete(addr.DialString())
}
}
// checkSeeds checks that addresses are well formed.
// Returns number of seeds we can connect to, along with all seeds addrs.
// return err if user provided any badly formatted seed addresses.
// Doesn't error if the seed node can't be reached.
// numOnline returns -1 if no seed nodes were in the initial configuration.
func (r *PEXReactor) checkSeeds() (numOnline int, netAddrs []*p2p.NetAddress, err error) {
lSeeds := len(r.config.Seeds)
if lSeeds == 0 {
return -1, nil, nil
}
netAddrs, errs := p2p.NewNetAddressStrings(r.config.Seeds)
numOnline = lSeeds - len(errs)
for _, err := range errs {
switch e := err.(type) {
case p2p.ErrNetAddressLookup:
r.Logger.Error("Connecting to seed failed", "err", e)
default:
return 0, nil, errors.Wrap(e, "seed node configuration has error")
}
}
return
}
// randomly dial seeds until we connect to one or exhaust them
func (r *PEXReactor) dialSeeds() {
perm := cmn.RandPerm(len(r.seedAddrs))
// perm := r.Switch.rng.Perm(lSeeds)
for _, i := range perm {
// dial a random seed
seedAddr := r.seedAddrs[i]
err := r.Switch.DialPeerWithAddress(seedAddr, false)
if err == nil {
return
}
r.Switch.Logger.Error("Error dialing seed", "err", err, "seed", seedAddr)
}
r.Switch.Logger.Error("Couldn't connect to any seeds")
}
// AttemptsToDial returns the number of attempts to dial specific address. It
// returns 0 if never attempted or successfully connected.
func (r *PEXReactor) AttemptsToDial(addr *p2p.NetAddress) int {
lAttempts, attempted := r.attemptsToDial.Load(addr.DialString())
if attempted {
return lAttempts.(_attemptsToDial).number
}
return 0
}
//----------------------------------------------------------
// Explores the network searching for more peers. (continuous)
// Seed/Crawler Mode causes this node to quickly disconnect
// from peers, except other seed nodes.
func (r *PEXReactor) crawlPeersRoutine() {
// Do an initial crawl
r.crawlPeers()
// Fire periodically
ticker := time.NewTicker(defaultCrawlPeersPeriod)
for {
select {
case <-ticker.C:
r.attemptDisconnects()
r.crawlPeers()
case <-r.Quit():
return
}
}
}
// hasPotentialPeers indicates if there is a potential peer to connect to, by
// consulting the Switch as well as the AddrBook.
func (r *PEXReactor) hasPotentialPeers() bool {
out, in, dial := r.Switch.NumPeers()
return out+in+dial > 0 && len(r.book.ListOfKnownAddresses()) > 0
}
// crawlPeerInfo handles temporary data needed for the
// network crawling performed during seed/crawler mode.
type crawlPeerInfo struct {
// The listening address of a potential peer we learned about
Addr *p2p.NetAddress
// The last time we attempt to reach this address
LastAttempt time.Time
// The last time we successfully reached this address
LastSuccess time.Time
}
// oldestFirst implements sort.Interface for []crawlPeerInfo
// based on the LastAttempt field.
type oldestFirst []crawlPeerInfo
func (of oldestFirst) Len() int { return len(of) }
func (of oldestFirst) Swap(i, j int) { of[i], of[j] = of[j], of[i] }
func (of oldestFirst) Less(i, j int) bool { return of[i].LastAttempt.Before(of[j].LastAttempt) }
// getPeersToCrawl returns addresses of potential peers that we wish to validate.
// NOTE: The status information is ordered as described above.
func (r *PEXReactor) getPeersToCrawl() []crawlPeerInfo {
var of oldestFirst
// TODO: be more selective
addrs := r.book.ListOfKnownAddresses()
for _, addr := range addrs {
if len(addr.ID()) == 0 {
continue // dont use peers without id
}
of = append(of, crawlPeerInfo{
Addr: addr.Addr,
LastAttempt: addr.LastAttempt,
LastSuccess: addr.LastSuccess,
})
}
sort.Sort(of)
return of
}
// crawlPeers will crawl the network looking for new peer addresses. (once)
func (r *PEXReactor) crawlPeers() {
peerInfos := r.getPeersToCrawl()
now := time.Now()
// Use addresses we know of to reach additional peers
for _, pi := range peerInfos {
// Do not attempt to connect with peers we recently dialed
if now.Sub(pi.LastAttempt) < defaultCrawlPeerInterval {
continue
}
// Otherwise, attempt to connect with the known address
err := r.Switch.DialPeerWithAddress(pi.Addr, false)
if err != nil {
r.book.MarkAttempt(pi.Addr)
continue
}
// Ask for more addresses
peer := r.Switch.Peers().Get(pi.Addr.ID)
if peer != nil {
r.RequestAddrs(peer)
}
}
}
// attemptDisconnects checks if we've been with each peer long enough to disconnect
func (r *PEXReactor) attemptDisconnects() {
for _, peer := range r.Switch.Peers().List() {
if peer.Status().Duration < defaultSeedDisconnectWaitPeriod {
continue
}
if peer.IsPersistent() {
continue
}
r.Switch.StopPeerGracefully(peer)
}
}
//-----------------------------------------------------------------------------
// Messages
// PexMessage is a primary type for PEX messages. Underneath, it could contain
// either pexRequestMessage, or pexAddrsMessage messages.
type PexMessage interface{}
func RegisterPexMessage(cdc *amino.Codec) {
cdc.RegisterInterface((*PexMessage)(nil), nil)
cdc.RegisterConcrete(&pexRequestMessage{}, "tendermint/p2p/PexRequestMessage", nil)
cdc.RegisterConcrete(&pexAddrsMessage{}, "tendermint/p2p/PexAddrsMessage", nil)
}
func decodeMsg(bz []byte) (msg PexMessage, err error) {
if len(bz) > maxMsgSize {
return msg, fmt.Errorf("Msg exceeds max size (%d > %d)", len(bz), maxMsgSize)
}
err = cdc.UnmarshalBinaryBare(bz, &msg)
return
}
/*
A pexRequestMessage requests additional peer addresses.
*/
type pexRequestMessage struct {
}
func (m *pexRequestMessage) String() string {
return "[pexRequest]"
}
/*
A message with announced peer addresses.
*/
type pexAddrsMessage struct {
Addrs []*p2p.NetAddress
}
func (m *pexAddrsMessage) String() string {
return fmt.Sprintf("[pexAddrs %v]", m.Addrs)
}