PEX: impede full-meching in tracker-less swarms by adding a cooldown minute

diff --git a/pex.go b/pex.go
index 83376d481c16b30b4d342c0322d90fc7742f84c5..a808af2bc0f9bc6c3724b5d8c4663e03182d67e6 100644 (file)
--- a/pex.go
+++ b/pex.go
@@ -3,6 +3,7 @@ package torrent
 import (
        "net"
        "sync"
+       "time"
 
        "github.com/anacrolix/dht/v2/krpc"
        pp "github.com/anacrolix/torrent/peer_protocol"
@@ -179,6 +180,7 @@ func shortestIP(ip net.IP) net.IP {
 type pexState struct {
        ev        []pexEvent    // event feed, append-only
        hold      []pexEvent    // delayed drops
+       rest      time.Time     // cooldown deadline on inbound
        nc        int           // net number of alive conns
        initCache pexMsgFactory // last generated initial message
        initSeq   int           // number of events which went into initCache
@@ -190,6 +192,7 @@ func (s *pexState) Reset() {
        s.ev = nil
        s.hold = nil
        s.nc = 0
+       s.rest = time.Time{}
        s.initLock.Lock()
        s.initCache = pexMsgFactory{}
        s.initSeq = 0

diff --git a/pexconn.go b/pexconn.go
index b3719ec869f2a24618b3ec75934c11b17ca7fd09..2940c4d28ae3c3d8d549dbaa471a50da5849aab5 100644 (file)
--- a/pexconn.go
+++ b/pexconn.go
@@ -88,6 +88,15 @@ func (s *pexConnState) Share(postfn messageWriter) bool {
 
 // Recv is called from the reader goroutine
 func (s *pexConnState) Recv(payload []byte) error {
+       if !s.torrent.wantPeers() {
+               s.dbg.Printf("peer reserve ok, incoming PEX discarded")
+               return nil
+       }
+       if time.Now().Before(s.torrent.pex.rest) {
+               s.dbg.Printf("in cooldown period, incoming PEX discarded")
+               return nil
+       }
+
        rx, err := pp.LoadPexMsg(payload)
        if err != nil {
                return fmt.Errorf("error unmarshalling PEX message: %s", err)
@@ -100,8 +109,10 @@ func (s *pexConnState) Recv(payload []byte) error {
        peers.AppendFromPex(rx.Added6, rx.Added6Flags)
        peers.AppendFromPex(rx.Added, rx.AddedFlags)
        s.dbg.Printf("adding %d peers from PEX", len(peers))
-       s.torrent.addPeers(peers)
-       // s.dbg.Print("known swarm now:", s.torrent.KnownSwarm())
+       if len(peers) > 0 {
+               s.torrent.pex.rest = time.Now().Add(pexInterval)
+               s.torrent.addPeers(peers)
+       }
 
        // one day we may also want to:
        // - check if the peer is not flooding us with PEX updates