6 "github.com/anacrolix/dht/v2/krpc"
7 pp "github.com/anacrolix/torrent/peer_protocol"
13 pexAdd pexEventType = iota
17 // internal, based on BEP11
19 pexTargAdded = 25 // put drops on hold when the number of alive connections is lower than this
20 pexMaxHold = 25 // length of the drop hold-back buffer
21 pexMaxDelta = 50 // upper bound on added+added6 and dropped+dropped6 in a single PEX message
24 // represents a single connection (t=pexAdd) or disconnection (t=pexDrop) event
25 type pexEvent struct {
31 // Combines the node addr, as required for pp.PexMsg.
32 type pexMsgAdded struct {
37 // Makes generating a PexMsg more efficient.
38 type pexMsgFactory struct {
39 added map[string]pexMsgAdded
40 dropped map[string]krpc.NodeAddr
43 func (me *pexMsgFactory) DeltaLen() int {
46 int64(len(me.dropped))))
49 // Returns the key to use to identify a given addr in the factory. Panics if we can't support the
50 // addr later in generating a PexMsg (since adding an unusable addr will cause DeltaLen to be out.)
51 func (me *pexMsgFactory) addrKey(addr krpc.NodeAddr) string {
52 if addr.IP.To4() != nil {
53 addr.IP = addr.IP.To4()
55 keyBytes, err := addr.MarshalBinary()
59 switch len(keyBytes) {
60 case compactIpv4NodeAddrElemSize:
61 case compactIpv6NodeAddrElemSize:
65 return string(keyBytes)
68 // Returns whether the entry was added (we can check if we're cancelling out another entry and so
69 // won't hit the limit consuming this event).
70 func (me *pexMsgFactory) Add(addr krpc.NodeAddr, flags pp.PexPeerFlags) bool {
71 key := me.addrKey(addr)
72 if _, ok := me.dropped[key]; ok {
73 delete(me.dropped, key)
76 if me.DeltaLen() >= pexMaxDelta {
80 me.added = make(map[string]pexMsgAdded, pexMaxDelta)
82 me.added[key] = pexMsgAdded{addr, flags}
87 // Returns whether the entry was added (we can check if we're cancelling out another entry and so
88 // won't hit the limit consuming this event).
89 func (me *pexMsgFactory) Drop(addr krpc.NodeAddr) bool {
90 key := me.addrKey(addr)
91 if _, ok := me.added[key]; ok {
95 if me.DeltaLen() >= pexMaxDelta {
98 if me.dropped == nil {
99 me.dropped = make(map[string]krpc.NodeAddr, pexMaxDelta)
101 me.dropped[key] = addr
105 // Returns whether the entry was added (we can check if we're cancelling out another entry and so
106 // won't hit the limit consuming this event).
107 func (me *pexMsgFactory) addEvent(event pexEvent) bool {
108 addr, ok := nodeAddr(event.addr)
114 return me.Add(addr, event.f)
122 var compactIpv4NodeAddrElemSize = krpc.CompactIPv4NodeAddrs{}.ElemSize()
123 var compactIpv6NodeAddrElemSize = krpc.CompactIPv6NodeAddrs{}.ElemSize()
125 func (me *pexMsgFactory) PexMsg() (ret pp.PexMsg) {
126 for key, added := range me.added {
128 case compactIpv4NodeAddrElemSize:
129 ret.Added = append(ret.Added, added.NodeAddr)
130 ret.AddedFlags = append(ret.AddedFlags, added.PexPeerFlags)
131 case compactIpv6NodeAddrElemSize:
132 ret.Added6 = append(ret.Added6, added.NodeAddr)
133 ret.Added6Flags = append(ret.Added6Flags, added.PexPeerFlags)
138 for key, addr := range me.dropped {
140 case compactIpv4NodeAddrElemSize:
141 ret.Dropped = append(ret.Dropped, addr)
142 case compactIpv6NodeAddrElemSize:
143 ret.Dropped6 = append(ret.Dropped6, addr)
151 func mustNodeAddr(addr net.Addr) krpc.NodeAddr {
152 ret, ok := nodeAddr(addr)
159 // Convert an arbitrary torrent peer Addr into one that can be represented by the compact addr
161 func nodeAddr(addr net.Addr) (_ krpc.NodeAddr, ok bool) {
162 ipport, ok := tryIpPortFromNetAddr(addr)
166 return krpc.NodeAddr{IP: shortestIP(ipport.IP), Port: ipport.Port}, true
169 // mainly for the krpc marshallers
170 func shortestIP(ip net.IP) net.IP {
171 if ip4 := ip.To4(); ip4 != nil {
177 // Per-torrent PEX state
178 type pexState struct {
179 ev []pexEvent // event feed, append-only
180 hold []pexEvent // delayed drops
181 nc int // net number of alive conns
184 func (s *pexState) Reset() {
190 func (s *pexState) Add(c *PeerConn) {
192 if s.nc >= pexTargAdded {
193 s.ev = append(s.ev, s.hold...)
196 e := c.pexEvent(pexAdd)
197 s.ev = append(s.ev, e)
201 func (s *pexState) Drop(c *PeerConn) {
203 // skip connections which were not previously Added
206 e := c.pexEvent(pexDrop)
208 if s.nc < pexTargAdded && len(s.hold) < pexMaxHold {
209 s.hold = append(s.hold, e)
211 s.ev = append(s.ev, e)
215 // Generate a PEX message based on the event feed. Also returns an index to pass to the subsequent
216 // calls, producing incremental deltas.
217 func (s *pexState) Genmsg(start int) (pp.PexMsg, int) {
218 var factory pexMsgFactory
220 for _, e := range s.ev[start:] {
221 if !factory.addEvent(e) {
226 return factory.PexMsg(), n