package torrent
-import "github.com/anacrolix/dht/krpc"
+import (
+ "net"
+ "net/netip"
+ "sync"
+ "time"
-type peerExchangeMessage struct {
- Added krpc.CompactIPv4NodeAddrs `bencode:"added"`
- AddedFlags []pexPeerFlags `bencode:"added.f"`
- Added6 krpc.CompactIPv6NodeAddrs `bencode:"added6"`
- AddedFlags6 []pexPeerFlags `bencode:"added6.f"`
- Dropped krpc.CompactIPv4NodeAddrs `bencode:"dropped"`
- Dropped6 krpc.CompactIPv6NodeAddrs `bencode:"dropped6"`
-}
+ pp "github.com/anacrolix/torrent/peer_protocol"
+)
+
+type pexEventType int
-type pexPeerFlags byte
+const (
+ pexAdd pexEventType = iota
+ pexDrop
+)
+// internal, based on BEP11
const (
- pexPrefersEncryption = 0x01
- pexSeedUploadOnly = 0x02
- pexSupportsUtp = 0x04
- pexHolepunchSupport = 0x08
- pexOutgoingConn = 0x10
+ 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
+ // Torrent-wide cooldown deadline on inbound. This exists to prevent PEX from drowning out other
+ // peer address sources, until that is fixed.
+ rest time.Time
+ 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.rest = time.Time{}
+ 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
+}