package torrent import ( "net" "net/netip" "sync" pp "github.com/anacrolix/torrent/peer_protocol" ) type pexEventType int const ( pexAdd pexEventType = iota pexDrop ) // internal, based on BEP11 const ( pexTargAdded = 25 // put drops on hold when the number of alive connections is lower than this pexMaxHold = 25 // length of the drop hold-back buffer pexMaxDelta = 50 // upper bound on added+added6 and dropped+dropped6 in a single PEX message ) // represents a single connection (t=pexAdd) or disconnection (t=pexDrop) event type pexEvent struct { t pexEventType addr netip.AddrPort f pp.PexPeerFlags next *pexEvent // event feed list } // facilitates efficient de-duplication while generating PEX messages type pexMsgFactory struct { msg pp.PexMsg added map[netip.AddrPort]struct{} dropped map[netip.AddrPort]struct{} } func (me *pexMsgFactory) DeltaLen() int { return int(max( int64(len(me.added)), int64(len(me.dropped)))) } type addrKey = netip.AddrPort // Returns the key to use to identify a given addr in the factory. func (me *pexMsgFactory) addrKey(addr netip.AddrPort) addrKey { return addr } // Returns whether the entry was added (we can check if we're cancelling out another entry and so // won't hit the limit consuming this event). func (me *pexMsgFactory) add(e pexEvent) { key := me.addrKey(e.addr) if _, ok := me.added[key]; ok { return } if me.added == nil { me.added = make(map[addrKey]struct{}, pexMaxDelta) } addr := krpcNodeAddrFromAddrPort(e.addr) m := &me.msg switch { case addr.IP.To4() != nil: if _, ok := me.dropped[key]; ok { if i := m.Dropped.Index(addr); i >= 0 { m.Dropped = append(m.Dropped[:i], m.Dropped[i+1:]...) } delete(me.dropped, key) return } m.Added = append(m.Added, addr) m.AddedFlags = append(m.AddedFlags, e.f) case len(addr.IP) == net.IPv6len: if _, ok := me.dropped[key]; ok { if i := m.Dropped6.Index(addr); i >= 0 { m.Dropped6 = append(m.Dropped6[:i], m.Dropped6[i+1:]...) } delete(me.dropped, key) return } m.Added6 = append(m.Added6, addr) m.Added6Flags = append(m.Added6Flags, e.f) default: panic(addr) } me.added[key] = struct{}{} } // Returns whether the entry was added (we can check if we're cancelling out another entry and so // won't hit the limit consuming this event). func (me *pexMsgFactory) drop(e pexEvent) { addr := krpcNodeAddrFromAddrPort(e.addr) key := me.addrKey(e.addr) if me.dropped == nil { me.dropped = make(map[addrKey]struct{}, pexMaxDelta) } if _, ok := me.dropped[key]; ok { return } m := &me.msg switch { case addr.IP.To4() != nil: if _, ok := me.added[key]; ok { if i := m.Added.Index(addr); i >= 0 { m.Added = append(m.Added[:i], m.Added[i+1:]...) m.AddedFlags = append(m.AddedFlags[:i], m.AddedFlags[i+1:]...) } delete(me.added, key) return } m.Dropped = append(m.Dropped, addr) case len(addr.IP) == net.IPv6len: if _, ok := me.added[key]; ok { if i := m.Added6.Index(addr); i >= 0 { m.Added6 = append(m.Added6[:i], m.Added6[i+1:]...) m.Added6Flags = append(m.Added6Flags[:i], m.Added6Flags[i+1:]...) } delete(me.added, key) return } m.Dropped6 = append(m.Dropped6, addr) } me.dropped[key] = struct{}{} } func (me *pexMsgFactory) append(event pexEvent) { switch event.t { case pexAdd: me.add(event) case pexDrop: me.drop(event) default: panic(event.t) } } func (me *pexMsgFactory) PexMsg() *pp.PexMsg { return &me.msg } // Per-torrent PEX state type pexState struct { sync.RWMutex tail *pexEvent // event feed list hold []pexEvent // delayed drops nc int // net number of alive conns msg0 pexMsgFactory // initial message } // Reset wipes the state clean, releasing resources. Called from Torrent.Close(). func (s *pexState) Reset() { s.Lock() defer s.Unlock() s.tail = nil s.hold = nil s.nc = 0 s.msg0 = pexMsgFactory{} } func (s *pexState) append(e *pexEvent) { if s.tail != nil { s.tail.next = e } s.tail = e s.msg0.append(*e) } func (s *pexState) Add(c *PeerConn) { e, err := c.pexEvent(pexAdd) if err != nil { return } s.Lock() defer s.Unlock() s.nc++ if s.nc >= pexTargAdded { for _, e := range s.hold { ne := e s.append(&ne) } s.hold = s.hold[:0] } c.pex.Listed = true s.append(&e) } func (s *pexState) Drop(c *PeerConn) { if !c.pex.Listed { // skip connections which were not previously Added return } e, err := c.pexEvent(pexDrop) if err != nil { return } s.Lock() defer s.Unlock() s.nc-- if s.nc < pexTargAdded && len(s.hold) < pexMaxHold { s.hold = append(s.hold, e) } else { s.append(&e) } } // Generate a PEX message based on the event feed. // Also returns a pointer to pass to the subsequent calls // to produce incremental deltas. func (s *pexState) Genmsg(start *pexEvent) (pp.PexMsg, *pexEvent) { s.RLock() defer s.RUnlock() if start == nil { return *s.msg0.PexMsg(), s.tail } var msg pexMsgFactory last := start for e := start.next; e != nil; e = e.next { if msg.DeltaLen() >= pexMaxDelta { break } msg.append(*e) last = e } return *msg.PexMsg(), last } // The same as Genmsg but just counts up the distinct events that haven't been sent. func (s *pexState) numPending(start *pexEvent) (num int) { s.RLock() defer s.RUnlock() if start == nil { return s.msg0.PexMsg().Len() } for e := start.next; e != nil; e = e.next { num++ } return }