8 g "github.com/anacrolix/generics"
10 "github.com/anacrolix/log"
12 pp "github.com/anacrolix/torrent/peer_protocol"
16 pexRetryDelay = 10 * time.Second
17 pexInterval = 1 * time.Minute
20 // per-connection PEX state
21 type pexConnState struct {
23 xid pp.ExtensionNumber
32 // Running record of live connections the remote end of the connection purports to have.
33 remoteLiveConns map[netip.AddrPort]g.Option[pp.PexPeerFlags]
37 func (s *pexConnState) IsEnabled() bool {
41 // Init is called from the reader goroutine upon the extended handshake completion
42 func (s *pexConnState) Init(c *PeerConn) {
43 xid, ok := c.PeerExtensionIDs[pp.ExtensionNamePex]
44 if !ok || xid == 0 || c.t.cl.config.DisablePEX {
50 s.info = c.t.cl.logger.WithDefaultLevel(log.Info)
51 s.dbg = c.logger.WithDefaultLevel(log.Debug)
52 s.readyfn = c.tickleWriter
53 s.gate = make(chan struct{}, 1)
54 s.timer = time.AfterFunc(0, func() {
56 s.readyfn() // wake up the writer
61 // schedule next PEX message
62 func (s *pexConnState) sched(delay time.Duration) {
66 // generate next PEX message for the peer; returns nil if nothing yet to send
67 func (s *pexConnState) genmsg() *pp.PexMsg {
68 tx, last := s.torrent.pex.Genmsg(s.last)
76 func (s *pexConnState) numPending() int {
80 return s.torrent.pex.numPending(s.last)
83 // Share is called from the writer goroutine if when it is woken up with the write buffers empty
84 // Returns whether there's more room on the send buffer to write to.
85 func (s *pexConnState) Share(postfn messageWriter) bool {
88 if tx := s.genmsg(); tx != nil {
89 s.dbg.Print("sending PEX message: ", tx)
90 flow := postfn(tx.Message(s.xid))
94 // no PEX to send this time - try again shortly
95 s.sched(pexRetryDelay)
102 func (s *pexConnState) updateRemoteLiveConns(rx pp.PexMsg) (errs []error) {
103 for _, dropped := range rx.Dropped {
104 addrPort, _ := ipv4AddrPortFromKrpcNodeAddr(dropped)
105 delete(s.remoteLiveConns, addrPort)
107 for _, dropped := range rx.Dropped6 {
108 addrPort, _ := ipv6AddrPortFromKrpcNodeAddr(dropped)
109 delete(s.remoteLiveConns, addrPort)
111 for i, added := range rx.Added {
112 addr := netip.AddrFrom4([4]byte(added.IP.To4()))
113 addrPort := netip.AddrPortFrom(addr, uint16(added.Port))
114 flags := g.SliceGet(rx.AddedFlags, i)
115 g.MakeMapIfNilAndSet(&s.remoteLiveConns, addrPort, flags)
117 for i, added := range rx.Added6 {
118 addr := netip.AddrFrom16([16]byte(added.IP.To16()))
119 addrPort := netip.AddrPortFrom(addr, uint16(added.Port))
120 flags := g.SliceGet(rx.Added6Flags, i)
121 g.MakeMapIfNilAndSet(&s.remoteLiveConns, addrPort, flags)
126 // Recv is called from the reader goroutine
127 func (s *pexConnState) Recv(payload []byte) error {
128 rx, err := pp.LoadPexMsg(payload)
130 return fmt.Errorf("unmarshalling pex message: %w", err)
132 s.dbg.Printf("received pex message: %v", rx)
133 torrent.Add("pex added peers received", int64(len(rx.Added)))
134 torrent.Add("pex added6 peers received", int64(len(rx.Added6)))
136 // "Clients must batch updates to send no more than 1 PEX message per minute."
137 timeSinceLastRecv := time.Since(s.lastRecv)
138 if timeSinceLastRecv < 45*time.Second {
139 return fmt.Errorf("last received only %v ago", timeSinceLastRecv)
141 s.lastRecv = time.Now()
142 s.updateRemoteLiveConns(rx)
145 peers.AppendFromPex(rx.Added6, rx.Added6Flags)
146 peers.AppendFromPex(rx.Added, rx.AddedFlags)
147 added := s.torrent.addPeers(peers)
148 s.dbg.Printf("got %v peers over pex, added %v", len(peers), added)
150 // one day we may also want to:
151 // - check if the peer is not flooding us with PEX updates
152 // - handle drops somehow
153 // - detect malicious peers
158 func (s *pexConnState) Close() {