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reliable_udp.go
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reliable_udp.go
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package main
import (
"bytes"
"crypto/rand"
"io"
"log"
"net"
"time"
)
const (
kReliableRecvCacheSize = 8
kReliableSendAcksCount = 4
)
type reliableUdp struct {
stopChan chan struct{}
failChan <-chan time.Time
doneHandshake chan struct{}
ctrlSendChan chan *packet
conn *net.UDPConn
sendingPid uint32
waitingAck map[uint32]chan<- struct{}
ctrlRecvChan <-chan *packet
recvedPackets [kReliableRecvCacheSize]*packet
recvingPid uint32
acks ackArray
sslRecvChan chan *packet
sslRecvBuf bytes.Buffer
connected bool
keyId byte
localSid sessionId
remoteSid sessionId
}
func dialReliableUdp(conn *net.UDPConn, ctrlRecvChan <-chan *packet) *reliableUdp {
ru := &reliableUdp{
stopChan: make(chan struct{}),
failChan: time.After(time.Minute),
doneHandshake: make(chan struct{}),
conn: conn,
ctrlSendChan: make(chan *packet),
waitingAck: make(map[uint32]chan<- struct{}),
ctrlRecvChan: ctrlRecvChan,
sslRecvChan: make(chan *packet),
}
io.ReadFull(rand.Reader, ru.localSid[:])
ru.start()
ru.ctrlSendChan <- &packet{
opCode: kProtoControlHardResetClientV2,
}
return ru
}
func (ru *reliableUdp) start() {
go func() {
for {
if !ru.iterate() {
break
}
}
}()
}
func (ru *reliableUdp) stop() {
ru.stopChan <- struct{}{}
}
func (ru *reliableUdp) iterate() bool {
var ackTimeout <-chan time.Time
if len(ru.acks) > 0 {
ackTimeout = time.After(time.Microsecond)
}
select {
case <-ru.stopChan:
return false
case <-ru.failChan:
log.Fatalf("can't negotiate with peer within 60 seconds")
case <-ru.doneHandshake:
ru.failChan = nil
case packet := <-ru.ctrlRecvChan:
ru.recvCtrlPacket(packet)
case packet := <-ru.ctrlSendChan:
packet.id = ru.sendingPid
ru.sendingPid++
ru.waitingAck[packet.id] = ru.sendCtrlPacket(packet)
case <-ackTimeout:
ru.sendCtrlPacket(&packet{opCode: kProtoAckV1})
}
return true
}
func (ru *reliableUdp) recvCtrlPacket(packet *packet) {
packet = decodeCtrlPacket(packet)
if packet.opCode != kProtoAckV1 {
ru.acks = append(ru.acks, packet.id)
}
for _, ack := range packet.acks {
if _, ok := ru.waitingAck[ack]; ok {
ru.waitingAck[ack] <- struct{}{}
delete(ru.waitingAck, ack)
}
}
if packet.id-ru.recvingPid >= kReliableRecvCacheSize {
return
}
if ru.recvedPackets[packet.id-ru.recvingPid] != nil {
return
}
ru.recvedPackets[packet.id-ru.recvingPid] = packet
switch packet.opCode {
case kProtoControlHardResetServerV2:
copy(ru.remoteSid[:], packet.localSid[:])
ru.connected = true
case kProtoControlV1:
i := 0
for ru.recvedPackets[i] != nil {
ru.sslRecvChan <- ru.recvedPackets[i]
i++
ru.recvingPid++
}
copy(ru.recvedPackets[:kReliableRecvCacheSize-i], ru.recvedPackets[i:])
}
}
func (ru *reliableUdp) sendCtrlPacket(packet *packet) chan<- struct{} {
copy(packet.localSid[:], ru.localSid[:])
copy(packet.remoteSid[:], ru.remoteSid[:])
nAck := len(ru.acks)
if nAck > kReliableSendAcksCount {
nAck = kReliableSendAcksCount
}
packet.acks = make(ackArray, nAck)
copy(packet.acks, ru.acks)
_, err := ru.conn.Write(encodeCtrlPacket(packet))
if err != nil {
log.Fatalf("can't send packet to peer: %v", err)
}
ru.acks = ru.acks[nAck:]
if packet.opCode != kProtoAckV1 {
packet.acks = nil
return startRetrySendCtrlPacket(ru.conn, packet)
}
return nil
}
func startRetrySendCtrlPacket(conn *net.UDPConn, packet *packet) chan<- struct{} {
stopChan := make(chan struct{})
buf := encodeCtrlPacket(packet)
go func() {
totalSeconds := 0
for i := 1; totalSeconds < 60; i *= 2 {
totalSeconds += i
select {
case <-stopChan:
return
case <-time.After(time.Duration(i) * time.Second):
_, err := conn.Write(buf)
if err != nil {
log.Fatalf("can't send packet to peer: %v", err)
}
}
}
log.Fatalf("can't negotiate with peer within 60 seconds: %v", packet.id)
}()
return stopChan
}
func (ru *reliableUdp) Close() error { return nil }
func (ru *reliableUdp) LocalAddr() net.Addr { return nil }
func (ru *reliableUdp) RemoteAddr() net.Addr { return nil }
func (ru *reliableUdp) SetDeadline(t time.Time) error { return nil }
func (ru *reliableUdp) SetReadDeadline(t time.Time) error { return nil }
func (ru *reliableUdp) SetWriteDeadline(t time.Time) error { return nil }
func (ru *reliableUdp) Read(b []byte) (n int, err error) {
for ru.sslRecvBuf.Len() == 0 {
packet := <-ru.sslRecvChan
ru.sslRecvBuf.Write(packet.content)
}
return ru.sslRecvBuf.Read(b)
}
func (ru *reliableUdp) Write(b []byte) (n int, err error) {
buf := make([]byte, len(b))
copy(buf, b)
packet := &packet{
opCode: kProtoControlV1,
content: buf,
}
ru.ctrlSendChan <- packet
return len(b), nil
}