8 "github.com/anacrolix/dht/v2/krpc"
9 pp "github.com/anacrolix/torrent/peer_protocol"
15 pexAdd pexEventType = iota
19 // internal, based on BEP11
21 pexTargAdded = 25 // put drops on hold when the number of alive connections is lower than this
22 pexMaxHold = 25 // length of the drop hold-back buffer
23 pexMaxDelta = 50 // upper bound on added+added6 and dropped+dropped6 in a single PEX message
26 // represents a single connection (t=pexAdd) or disconnection (t=pexDrop) event
27 type pexEvent struct {
31 next *pexEvent // event feed list
34 // facilitates efficient de-duplication while generating PEX messages
35 type pexMsgFactory struct {
37 added map[addrKey]struct{}
38 dropped map[addrKey]struct{}
41 func (me *pexMsgFactory) DeltaLen() int {
44 int64(len(me.dropped))))
49 // Returns the key to use to identify a given addr in the factory.
50 func (me *pexMsgFactory) addrKey(addr PeerRemoteAddr) addrKey {
51 return addrKey(addr.String())
54 func addrEqual(a, b *krpc.NodeAddr) bool {
55 return a.IP.Equal(b.IP) && a.Port == b.Port
58 func addrIndex(v []krpc.NodeAddr, a *krpc.NodeAddr) int {
59 for i := 0; i < len(v); i += 1 {
60 if addrEqual(&v[i], a) {
67 // Returns whether the entry was added (we can check if we're cancelling out another entry and so
68 // won't hit the limit consuming this event).
69 func (me *pexMsgFactory) add(e pexEvent) {
70 key := me.addrKey(e.addr)
71 if _, ok := me.added[key]; ok {
75 me.added = make(map[addrKey]struct{}, pexMaxDelta)
77 addr, ok := nodeAddr(e.addr)
83 case addr.IP.To4() != nil:
84 if _, ok := me.dropped[key]; ok {
85 if i := addrIndex(m.Dropped.NodeAddrs(), &addr); i >= 0 {
86 m.Dropped = append(m.Dropped[:i], m.Dropped[i+1:]...)
88 delete(me.dropped, key)
91 m.Added = append(m.Added, addr)
92 m.AddedFlags = append(m.AddedFlags, e.f)
93 case len(addr.IP) == net.IPv6len:
94 if _, ok := me.dropped[key]; ok {
95 if i := addrIndex(m.Dropped6.NodeAddrs(), &addr); i >= 0 {
96 m.Dropped6 = append(m.Dropped6[:i], m.Dropped6[i+1:]...)
98 delete(me.dropped, key)
101 m.Added6 = append(m.Added6, addr)
102 m.Added6Flags = append(m.Added6Flags, e.f)
106 me.added[key] = struct{}{}
109 // Returns whether the entry was added (we can check if we're cancelling out another entry and so
110 // won't hit the limit consuming this event).
111 func (me *pexMsgFactory) drop(e pexEvent) {
112 addr, ok := nodeAddr(e.addr)
116 key := me.addrKey(e.addr)
117 if me.dropped == nil {
118 me.dropped = make(map[addrKey]struct{}, pexMaxDelta)
120 if _, ok := me.dropped[key]; ok {
125 case addr.IP.To4() != nil:
126 if _, ok := me.added[key]; ok {
127 if i := addrIndex(m.Added.NodeAddrs(), &addr); i >= 0 {
128 m.Added = append(m.Added[:i], m.Added[i+1:]...)
129 m.AddedFlags = append(m.AddedFlags[:i], m.AddedFlags[i+1:]...)
131 delete(me.added, key)
134 m.Dropped = append(m.Dropped, addr)
135 case len(addr.IP) == net.IPv6len:
136 if _, ok := me.added[key]; ok {
137 if i := addrIndex(m.Added6.NodeAddrs(), &addr); i >= 0 {
138 m.Added6 = append(m.Added6[:i], m.Added6[i+1:]...)
139 m.Added6Flags = append(m.Added6Flags[:i], m.Added6Flags[i+1:]...)
141 delete(me.added, key)
144 m.Dropped6 = append(m.Dropped6, addr)
146 me.dropped[key] = struct{}{}
149 func (me *pexMsgFactory) append(event pexEvent) {
160 func (me *pexMsgFactory) PexMsg() pp.PexMsg {
164 // Convert an arbitrary torrent peer Addr into one that can be represented by the compact addr
166 func nodeAddr(addr PeerRemoteAddr) (krpc.NodeAddr, bool) {
167 ipport, _ := tryIpPortFromNetAddr(addr)
168 ok := ipport.IP != nil
169 return krpc.NodeAddr{IP: shortestIP(ipport.IP), Port: ipport.Port}, ok
172 // mainly for the krpc marshallers
173 func shortestIP(ip net.IP) net.IP {
174 if ip4 := ip.To4(); ip4 != nil {
180 // Per-torrent PEX state
181 type pexState struct {
183 tail *pexEvent // event feed list
184 hold []pexEvent // delayed drops
185 rest time.Time // cooldown deadline on inbound
186 nc int // net number of alive conns
187 msg0 pexMsgFactory // initial message
190 // Reset wipes the state clean, releasing resources. Called from Torrent.Close().
191 func (s *pexState) Reset() {
198 s.msg0 = pexMsgFactory{}
201 func (s *pexState) append(e *pexEvent) {
209 func (s *pexState) Add(c *PeerConn) {
213 if s.nc >= pexTargAdded {
214 for _, e := range s.hold {
220 e := c.pexEvent(pexAdd)
225 func (s *pexState) Drop(c *PeerConn) {
227 // skip connections which were not previously Added
232 e := c.pexEvent(pexDrop)
234 if s.nc < pexTargAdded && len(s.hold) < pexMaxHold {
235 s.hold = append(s.hold, e)
241 // Generate a PEX message based on the event feed.
242 // Also returns a pointer to pass to the subsequent calls
243 // to produce incremental deltas.
244 func (s *pexState) Genmsg(start *pexEvent) (pp.PexMsg, *pexEvent) {
248 return s.msg0.PexMsg(), s.tail
250 var msg pexMsgFactory
252 for e := start.next; e != nil; e = e.next {
253 if msg.DeltaLen() >= pexMaxDelta {
259 return msg.PexMsg(), last