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