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) {
71 key := me.addrKey(addr)
72 if _, ok := me.dropped[key]; ok {
73 delete(me.dropped, key)
77 me.added = make(map[string]pexMsgAdded, pexMaxDelta)
79 me.added[key] = pexMsgAdded{addr, flags}
83 // Returns whether the entry was added (we can check if we're cancelling out another entry and so
84 // won't hit the limit consuming this event).
85 func (me *pexMsgFactory) Drop(addr krpc.NodeAddr) {
86 key := me.addrKey(addr)
87 if _, ok := me.added[key]; ok {
91 if me.dropped == nil {
92 me.dropped = make(map[string]krpc.NodeAddr, pexMaxDelta)
94 me.dropped[key] = addr
97 func (me *pexMsgFactory) addEvent(event pexEvent) {
98 addr, ok := nodeAddr(event.addr)
104 me.Add(addr, event.f)
112 var compactIpv4NodeAddrElemSize = krpc.CompactIPv4NodeAddrs{}.ElemSize()
113 var compactIpv6NodeAddrElemSize = krpc.CompactIPv6NodeAddrs{}.ElemSize()
115 func (me *pexMsgFactory) PexMsg() (ret pp.PexMsg) {
116 for key, added := range me.added {
118 case compactIpv4NodeAddrElemSize:
119 ret.Added = append(ret.Added, added.NodeAddr)
120 ret.AddedFlags = append(ret.AddedFlags, added.PexPeerFlags)
121 case compactIpv6NodeAddrElemSize:
122 ret.Added6 = append(ret.Added6, added.NodeAddr)
123 ret.Added6Flags = append(ret.Added6Flags, added.PexPeerFlags)
128 for key, addr := range me.dropped {
130 case compactIpv4NodeAddrElemSize:
131 ret.Dropped = append(ret.Dropped, addr)
132 case compactIpv6NodeAddrElemSize:
133 ret.Dropped6 = append(ret.Dropped6, addr)
141 func mustNodeAddr(addr net.Addr) krpc.NodeAddr {
142 ret, ok := nodeAddr(addr)
149 // Convert an arbitrary torrent peer Addr into one that can be represented by the compact addr
151 func nodeAddr(addr net.Addr) (_ krpc.NodeAddr, ok bool) {
152 ipport, ok := tryIpPortFromNetAddr(addr)
156 return krpc.NodeAddr{IP: shortestIP(ipport.IP), Port: ipport.Port}, true
159 // mainly for the krpc marshallers
160 func shortestIP(ip net.IP) net.IP {
161 if ip4 := ip.To4(); ip4 != nil {
167 // Per-torrent PEX state
168 type pexState struct {
169 ev []pexEvent // event feed, append-only
170 hold []pexEvent // delayed drops
171 nc int // net number of alive conns
174 func (s *pexState) Reset() {
180 func (s *pexState) Add(c *PeerConn) {
182 if s.nc >= pexTargAdded {
183 s.ev = append(s.ev, s.hold...)
186 e := c.pexEvent(pexAdd)
187 s.ev = append(s.ev, e)
191 func (s *pexState) Drop(c *PeerConn) {
193 // skip connections which were not previously Added
196 e := c.pexEvent(pexDrop)
198 if s.nc < pexTargAdded && len(s.hold) < pexMaxHold {
199 s.hold = append(s.hold, e)
201 s.ev = append(s.ev, e)
205 // Generate a PEX message based on the event feed. Also returns an index to pass to the subsequent
206 // calls, producing incremental deltas.
207 func (s *pexState) Genmsg(start int) (pp.PexMsg, int) {
208 var factory pexMsgFactory
210 for _, e := range s.ev[start:] {
211 if start > 0 && factory.DeltaLen() >= pexMaxDelta {
217 return factory.PexMsg(), n