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 { if err := r.BaseReactor.OnStart(); err != nil { return err } _, err := r.book.Start() if err != nil { return err } 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{ { 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 { // peer gave us a bad ListenAddr. TODO: punish 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, err := NewNetAddressString(srcAddrStr) if err != nil { // this should never happen. TODO: cancel conn r.Logger.Error("Error in Receive: invalid peer address", "addr", srcAddrStr, "err", err) return } 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. // NOTE: we might send an empty selection r.SendAddrs(src, r.book.GetSelection()) case *pexAddrsMessage: // We received some peer addresses from src. // TODO: (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 } // bias to prefer more vetted peers when we have fewer connections. // not perfect, but somewhate ensures that we prioritize connecting to more-vetted newBias := cmn.MinInt(numOutPeers, 8)*10 + 10 toDial := make(map[string]*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.IP.String()]; selected { continue } if dialling := r.Switch.IsDialing(try); dialling { continue } if connected := r.Switch.Peers().Has(try.IP.String()); connected { continue } r.Logger.Info("Will dial address", "addr", try) toDial[try.IP.String()] = try } // 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) }