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package p2p
import (
"bytes"
"fmt"
"math/rand"
"reflect"
"time"
wire "github.com/tendermint/go-wire"
cmn "github.com/tendermint/tmlibs/common"
)
const (
// PexChannel is a channel for PEX messages
PexChannel = byte(0x00)
// period to ensure peers connected
defaultEnsurePeersPeriod = 30 * time.Second
minNumOutboundPeers = 10
maxPexMessageSize = 1048576 // 1MB
// maximum messages one peer can send to us during `msgCountByPeerFlushInterval`
defaultMaxMsgCountByPeer = 1000
msgCountByPeerFlushInterval = 1 * time.Hour
)
// 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
//
// For now, it just limits the number of messages from one peer to
// `defaultMaxMsgCountByPeer` messages per `msgCountByPeerFlushInterval` (1000
// msg/hour).
//
// NOTE [2017-01-17]:
// Limiting is fine for now. Maybe down the road we want to keep track of the
// quality of peer messages so if peerA keeps telling us about peers we can't
// connect to then maybe we should care less about peerA. But I don't think
// that kind of complexity is priority right now.
type PEXReactor struct {
BaseReactor
book *AddrBook
ensurePeersPeriod time.Duration
// tracks message count by peer, so we can prevent abuse
msgCountByPeer *cmn.CMap
maxMsgCountByPeer uint16
}
// NewPEXReactor creates new PEX reactor.
func NewPEXReactor(b *AddrBook) *PEXReactor {
r := &PEXReactor{
book: b,
ensurePeersPeriod: defaultEnsurePeersPeriod,
msgCountByPeer: cmn.NewCMap(),
maxMsgCountByPeer: defaultMaxMsgCountByPeer,
}
r.BaseReactor = *NewBaseReactor("PEXReactor", r)
return r
}
// OnStart implements BaseService
func (r *PEXReactor) OnStart() error {
r.BaseReactor.OnStart()
r.book.Start()
go r.ensurePeersRoutine()
go r.flushMsgCountByPeer()
return nil
}
// OnStop implements BaseService
func (r *PEXReactor) OnStop() {
r.BaseReactor.OnStop()
r.book.Stop()
}
// GetChannels implements Reactor
func (r *PEXReactor) GetChannels() []*ChannelDescriptor {
return []*ChannelDescriptor{
&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 it was added in DialSeeds or when we
// received the peer's address in r.Receive
if r.book.NeedMoreAddrs() {
r.RequestPEX(p)
}
} else { // For inbound connections, the peer is its own source
addr, err := NewNetAddressString(p.NodeInfo().ListenAddr)
if err != nil {
// this should never happen
r.Logger.Error("Error in AddPeer: invalid peer address", "addr", p.NodeInfo().ListenAddr, "err", err)
return
}
r.book.AddAddress(addr, addr)
}
}
// RemovePeer implements Reactor.
func (r *PEXReactor) RemovePeer(p Peer, reason interface{}) {
// If we aren't keeping track of local temp data for each peer here, then we
// don't have to do anything.
}
// Receive implements Reactor by handling incoming PEX messages.
func (r *PEXReactor) Receive(chID byte, src Peer, msgBytes []byte) {
srcAddrStr := src.NodeInfo().RemoteAddr
srcAddr, _ := NewNetAddressString(srcAddrStr)
r.IncrementMsgCountForPeer(srcAddrStr)
if r.ReachedMaxMsgCountForPeer(srcAddrStr) {
r.Logger.Error("Maximum number of messages reached for peer", "peer", srcAddrStr)
// TODO remove src from peers?
return
}
_, msg, err := DecodeMessage(msgBytes)
if err != nil {
r.Logger.Error("Error decoding message", "err", err)
return
}
r.Logger.Info("Received message", "msg", msg)
switch msg := msg.(type) {
case *pexRequestMessage:
// src requested some peers.
r.SendAddrs(src, r.book.GetSelection())
case *pexAddrsMessage:
// We received some peer addresses from src.
// (We don't want to get spammed with bad peers)
for _, addr := range msg.Addrs {
if addr != nil {
r.book.AddAddress(addr, srcAddr)
}
}
default:
r.Logger.Error(fmt.Sprintf("Unknown message type %v", reflect.TypeOf(msg)))
}
}
// RequestPEX asks peer for more addresses.
func (r *PEXReactor) RequestPEX(p Peer) {
p.Send(PexChannel, struct{ PexMessage }{&pexRequestMessage{}})
}
// SendAddrs sends addrs to the peer.
func (r *PEXReactor) SendAddrs(p Peer, addrs []*NetAddress) {
p.Send(PexChannel, struct{ PexMessage }{&pexAddrsMessage{Addrs: addrs}})
}
// SetEnsurePeersPeriod sets period to ensure peers connected.
func (r *PEXReactor) SetEnsurePeersPeriod(d time.Duration) {
r.ensurePeersPeriod = d
}
// SetMaxMsgCountByPeer sets maximum messages one peer can send to us during 'msgCountByPeerFlushInterval'.
func (r *PEXReactor) SetMaxMsgCountByPeer(v uint16) {
r.maxMsgCountByPeer = v
}
// ReachedMaxMsgCountForPeer returns true if we received too many
// messages from peer with address `addr`.
// NOTE: assumes the value in the CMap is non-nil
func (r *PEXReactor) ReachedMaxMsgCountForPeer(addr string) bool {
return r.msgCountByPeer.Get(addr).(uint16) >= r.maxMsgCountByPeer
}
// Increment or initialize the msg count for the peer in the CMap
func (r *PEXReactor) IncrementMsgCountForPeer(addr string) {
var count uint16
countI := r.msgCountByPeer.Get(addr)
if countI != nil {
count = countI.(uint16)
}
count++
r.msgCountByPeer.Set(addr, count)
}
// Ensures that sufficient peers are connected. (continuous)
func (r *PEXReactor) ensurePeersRoutine() {
// Randomize when routine starts
ensurePeersPeriodMs := r.ensurePeersPeriod.Nanoseconds() / 1e6
time.Sleep(time.Duration(rand.Int63n(ensurePeersPeriodMs)) * time.Millisecond)
// fire once immediately.
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)
//
// Old bucket / New bucket are arbitrary categories to denote whether an
// address is vetted or not, and this needs to be determined over time via a
// 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.
//
// TODO Basically, we need to work harder on our good-peer/bad-peer marking.
// What we're currently doing in terms of marking good/bad peers is just a
// placeholder. It should not be the case that an address becomes old/vetted
// upon a single successful connection.
func (r *PEXReactor) ensurePeers() {
numOutPeers, _, numDialing := r.Switch.NumPeers()
numToDial := minNumOutboundPeers - (numOutPeers + numDialing)
r.Logger.Info("Ensure peers", "numOutPeers", numOutPeers, "numDialing", numDialing, "numToDial", numToDial)
if numToDial <= 0 {
return
}
toDial := make(map[string]*NetAddress)
// Try to pick numToDial addresses to dial.
for i := 0; i < numToDial; i++ {
// The purpose of newBias is to first prioritize old (more vetted) peers
// when we have few connections, but to allow for new (less vetted) peers
// if we already have many connections. This algorithm isn't perfect, but
// it somewhat ensures that we prioritize connecting to more-vetted
// peers.
newBias := cmn.MinInt(numOutPeers, 8)*10 + 10
var picked *NetAddress
// Try to fetch a new peer 3 times.
// This caps the maximum number of tries to 3 * numToDial.
for j := 0; j < 3; j++ {
try := r.book.PickAddress(newBias)
if try == nil {
break
}
_, alreadySelected := toDial[try.IP.String()]
alreadyDialing := r.Switch.IsDialing(try)
alreadyConnected := r.Switch.Peers().Has(try.IP.String())
if alreadySelected || alreadyDialing || alreadyConnected {
// r.Logger.Info("Cannot dial address", "addr", try,
// "alreadySelected", alreadySelected,
// "alreadyDialing", alreadyDialing,
// "alreadyConnected", alreadyConnected)
continue
} else {
r.Logger.Info("Will dial address", "addr", try)
picked = try
break
}
}
if picked == nil {
continue
}
toDial[picked.IP.String()] = picked
}
// Dial picked addresses
for _, item := range toDial {
go func(picked *NetAddress) {
_, err := r.Switch.DialPeerWithAddress(picked, false)
if err != nil {
r.book.MarkAttempt(picked)
}
}(item)
}
// If we need more addresses, pick a random peer and ask for more.
if r.book.NeedMoreAddrs() {
if peers := r.Switch.Peers().List(); len(peers) > 0 {
i := rand.Int() % len(peers)
peer := peers[i]
r.Logger.Info("No addresses to dial. Sending pexRequest to random peer", "peer", peer)
r.RequestPEX(peer)
}
}
}
func (r *PEXReactor) flushMsgCountByPeer() {
ticker := time.NewTicker(msgCountByPeerFlushInterval)
for {
select {
case <-ticker.C:
r.msgCountByPeer.Clear()
case <-r.Quit:
ticker.Stop()
return
}
}
}
//-----------------------------------------------------------------------------
// Messages
const (
msgTypeRequest = byte(0x01)
msgTypeAddrs = byte(0x02)
)
// PexMessage is a primary type for PEX messages. Underneath, it could contain
// either pexRequestMessage, or pexAddrsMessage messages.
type PexMessage interface{}
var _ = wire.RegisterInterface(
struct{ PexMessage }{},
wire.ConcreteType{&pexRequestMessage{}, msgTypeRequest},
wire.ConcreteType{&pexAddrsMessage{}, msgTypeAddrs},
)
// DecodeMessage implements interface registered above.
func DecodeMessage(bz []byte) (msgType byte, msg PexMessage, err error) {
msgType = bz[0]
n := new(int)
r := bytes.NewReader(bz)
msg = wire.ReadBinary(struct{ PexMessage }{}, r, maxPexMessageSize, n, &err).(struct{ PexMessage }).PexMessage
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 []*NetAddress
}
func (m *pexAddrsMessage) String() string {
return fmt.Sprintf("[pexAddrs %v]", m.Addrs)
}