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sess.go
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sess.go
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package kcp
import (
"crypto/rand"
"encoding/binary"
"io"
"net"
"sync"
"sync/atomic"
"time"
"github.com/pkg/errors"
"github.com/klauspost/crc32"
"golang.org/x/net/ipv4"
)
type errTimeout struct {
error
}
func (errTimeout) Timeout() bool { return true }
func (errTimeout) Temporary() bool { return true }
func (errTimeout) Error() string { return "i/o timeout" }
const (
defaultWndSize = 128 // default window size, in packet
nonceSize = 16 // magic number
crcSize = 4 // 4bytes packet checksum
cryptHeaderSize = nonceSize + crcSize
mtuLimit = 2048
txQueueLimit = 8192
rxFecLimit = 8192
defaultKeepAliveInterval = 10 * time.Second
)
const (
errBrokenPipe = "broken pipe"
)
var (
xmitBuf sync.Pool
)
func init() {
xmitBuf.New = func() interface{} {
return make([]byte, mtuLimit)
}
}
type (
// UDPSession defines a KCP session implemented by UDP
UDPSession struct {
kcp *KCP // the core ARQ
l *Listener // point to server listener if it's a server socket
fec *FEC // forward error correction
conn net.PacketConn // the underlying packet socket
block BlockCrypt
remote net.Addr
rd time.Time // read deadline
wd time.Time // write deadline
sockbuff []byte // kcp receiving is based on packet, I turn it into stream
die chan struct{}
chReadEvent chan struct{}
chWriteEvent chan struct{}
chTicker chan time.Time
chUDPOutput chan []byte
headerSize int
ackNoDelay bool
isClosed bool
keepAliveInterval time.Duration
mu sync.Mutex
}
setReadBuffer interface {
SetReadBuffer(bytes int) error
}
setWriteBuffer interface {
SetWriteBuffer(bytes int) error
}
)
// newUDPSession create a new udp session for client or server
func newUDPSession(conv uint32, dataShards, parityShards int, l *Listener, conn net.PacketConn, remote net.Addr, block BlockCrypt) *UDPSession {
sess := new(UDPSession)
sess.chTicker = make(chan time.Time, 1)
sess.chUDPOutput = make(chan []byte, txQueueLimit)
sess.die = make(chan struct{})
sess.chReadEvent = make(chan struct{}, 1)
sess.chWriteEvent = make(chan struct{}, 1)
sess.remote = remote
sess.conn = conn
sess.keepAliveInterval = defaultKeepAliveInterval
sess.l = l
sess.block = block
sess.fec = newFEC(rxFecLimit, dataShards, parityShards)
// calculate header size
if sess.block != nil {
sess.headerSize += cryptHeaderSize
}
if sess.fec != nil {
sess.headerSize += fecHeaderSizePlus2
}
sess.kcp = NewKCP(conv, func(buf []byte, size int) {
if size >= IKCP_OVERHEAD {
ext := xmitBuf.Get().([]byte)[:sess.headerSize+size]
copy(ext[sess.headerSize:], buf)
select {
case sess.chUDPOutput <- ext:
case <-sess.die:
}
}
})
sess.kcp.WndSize(defaultWndSize, defaultWndSize)
sess.kcp.SetMtu(IKCP_MTU_DEF - sess.headerSize)
go sess.updateTask()
go sess.outputTask()
if sess.l == nil { // it's a client connection
go sess.readLoop()
atomic.AddUint64(&DefaultSnmp.ActiveOpens, 1)
} else {
atomic.AddUint64(&DefaultSnmp.PassiveOpens, 1)
}
currestab := atomic.AddUint64(&DefaultSnmp.CurrEstab, 1)
maxconn := atomic.LoadUint64(&DefaultSnmp.MaxConn)
if currestab > maxconn {
atomic.CompareAndSwapUint64(&DefaultSnmp.MaxConn, maxconn, currestab)
}
return sess
}
// Read implements the Conn Read method.
func (s *UDPSession) Read(b []byte) (n int, err error) {
for {
s.mu.Lock()
if len(s.sockbuff) > 0 { // copy from buffer
n = copy(b, s.sockbuff)
s.sockbuff = s.sockbuff[n:]
s.mu.Unlock()
return n, nil
}
if s.isClosed {
s.mu.Unlock()
return 0, errors.New(errBrokenPipe)
}
if !s.rd.IsZero() {
if time.Now().After(s.rd) { // timeout
s.mu.Unlock()
return 0, errTimeout{}
}
}
if n := s.kcp.PeekSize(); n > 0 { // data arrived
if len(b) >= n {
s.kcp.Recv(b)
} else {
buf := make([]byte, n)
s.kcp.Recv(buf)
n = copy(b, buf)
s.sockbuff = buf[n:] // store remaining bytes into sockbuff for next read
}
s.mu.Unlock()
atomic.AddUint64(&DefaultSnmp.BytesReceived, uint64(n))
return n, nil
}
var timeout *time.Timer
var c <-chan time.Time
if !s.rd.IsZero() {
delay := s.rd.Sub(time.Now())
timeout = time.NewTimer(delay)
c = timeout.C
}
s.mu.Unlock()
// wait for read event or timeout
select {
case <-s.chReadEvent:
case <-c:
case <-s.die:
}
if timeout != nil {
timeout.Stop()
}
}
}
// Write implements the Conn Write method.
func (s *UDPSession) Write(b []byte) (n int, err error) {
for {
s.mu.Lock()
if s.isClosed {
s.mu.Unlock()
return 0, errors.New(errBrokenPipe)
}
if !s.wd.IsZero() {
if time.Now().After(s.wd) { // timeout
s.mu.Unlock()
return 0, errTimeout{}
}
}
if s.kcp.WaitSnd() < int(s.kcp.snd_wnd) {
n = len(b)
max := s.kcp.mss << 8
for {
if len(b) <= int(max) { // in most cases
s.kcp.Send(b)
break
} else {
s.kcp.Send(b[:max])
b = b[max:]
}
}
s.kcp.current = currentMs()
s.kcp.flush()
s.mu.Unlock()
atomic.AddUint64(&DefaultSnmp.BytesSent, uint64(n))
return n, nil
}
var timeout *time.Timer
var c <-chan time.Time
if !s.wd.IsZero() {
delay := s.wd.Sub(time.Now())
timeout = time.NewTimer(delay)
c = timeout.C
}
s.mu.Unlock()
// wait for write event or timeout
select {
case <-s.chWriteEvent:
case <-c:
case <-s.die:
}
if timeout != nil {
timeout.Stop()
}
}
}
// Close closes the connection.
func (s *UDPSession) Close() error {
s.mu.Lock()
defer s.mu.Unlock()
if s.isClosed {
return errors.New(errBrokenPipe)
}
close(s.die)
s.isClosed = true
atomic.AddUint64(&DefaultSnmp.CurrEstab, ^uint64(0))
if s.l == nil { // client socket close
return s.conn.Close()
}
return nil
}
// LocalAddr returns the local network address. The Addr returned is shared by all invocations of LocalAddr, so do not modify it.
func (s *UDPSession) LocalAddr() net.Addr { return s.conn.LocalAddr() }
// RemoteAddr returns the remote network address. The Addr returned is shared by all invocations of RemoteAddr, so do not modify it.
func (s *UDPSession) RemoteAddr() net.Addr { return s.remote }
// SetDeadline sets the deadline associated with the listener. A zero time value disables the deadline.
func (s *UDPSession) SetDeadline(t time.Time) error {
s.mu.Lock()
defer s.mu.Unlock()
s.rd = t
s.wd = t
return nil
}
// SetReadDeadline implements the Conn SetReadDeadline method.
func (s *UDPSession) SetReadDeadline(t time.Time) error {
s.mu.Lock()
defer s.mu.Unlock()
s.rd = t
return nil
}
// SetWriteDeadline implements the Conn SetWriteDeadline method.
func (s *UDPSession) SetWriteDeadline(t time.Time) error {
s.mu.Lock()
defer s.mu.Unlock()
s.wd = t
return nil
}
// SetWindowSize set maximum window size
func (s *UDPSession) SetWindowSize(sndwnd, rcvwnd int) {
s.mu.Lock()
defer s.mu.Unlock()
s.kcp.WndSize(sndwnd, rcvwnd)
}
// SetMtu sets the maximum transmission unit
func (s *UDPSession) SetMtu(mtu int) {
s.mu.Lock()
defer s.mu.Unlock()
s.kcp.SetMtu(mtu - s.headerSize)
}
// SetStreamMode toggles the stream mode on/off
func (s *UDPSession) SetStreamMode(enable bool) {
s.mu.Lock()
defer s.mu.Unlock()
if enable {
s.kcp.stream = 1
} else {
s.kcp.stream = 0
}
}
// SetACKNoDelay changes ack flush option, set true to flush ack immediately,
func (s *UDPSession) SetACKNoDelay(nodelay bool) {
s.mu.Lock()
defer s.mu.Unlock()
s.ackNoDelay = nodelay
}
// SetNoDelay calls nodelay() of kcp
func (s *UDPSession) SetNoDelay(nodelay, interval, resend, nc int) {
s.mu.Lock()
defer s.mu.Unlock()
s.kcp.NoDelay(nodelay, interval, resend, nc)
}
// SetDSCP sets the 6bit DSCP field of IP header, no effect if it's accepted from Listener
func (s *UDPSession) SetDSCP(dscp int) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.l == nil {
if nc, ok := s.conn.(*ConnectedUDPConn); ok {
return ipv4.NewConn(nc.Conn).SetTOS(dscp << 2)
} else if nc, ok := s.conn.(net.Conn); ok {
return ipv4.NewConn(nc).SetTOS(dscp << 2)
}
}
return nil
}
// SetReadBuffer sets the socket read buffer, no effect if it's accepted from Listener
func (s *UDPSession) SetReadBuffer(bytes int) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.l == nil {
if nc, ok := s.conn.(setReadBuffer); ok {
return nc.SetReadBuffer(bytes)
}
}
return nil
}
// SetWriteBuffer sets the socket write buffer, no effect if it's accepted from Listener
func (s *UDPSession) SetWriteBuffer(bytes int) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.l == nil {
if nc, ok := s.conn.(setWriteBuffer); ok {
return nc.SetWriteBuffer(bytes)
}
}
return nil
}
// SetKeepAlive changes per-connection NAT keepalive interval; 0 to disable, default to 10s
func (s *UDPSession) SetKeepAlive(interval int) {
s.mu.Lock()
defer s.mu.Unlock()
s.keepAliveInterval = time.Duration(interval) * time.Second
}
func (s *UDPSession) outputTask() {
// offset pre-compute
fecOffset := 0
if s.block != nil {
fecOffset = cryptHeaderSize
}
szOffset := fecOffset + fecHeaderSize
// fec data group
var cacheLine []byte
var fecGroup [][]byte
var fecCnt int
var fecMaxSize int
if s.fec != nil {
cacheLine = make([]byte, s.fec.shardSize*mtuLimit)
fecGroup = make([][]byte, s.fec.shardSize)
for k := range fecGroup {
fecGroup[k] = cacheLine[k*mtuLimit : (k+1)*mtuLimit]
}
}
// keepalive
var lastPing time.Time
ticker := time.NewTicker(5 * time.Second)
defer ticker.Stop()
for {
select {
case ext := <-s.chUDPOutput:
var ecc [][]byte
if s.fec != nil {
s.fec.markData(ext[fecOffset:])
// explicit size
binary.LittleEndian.PutUint16(ext[szOffset:], uint16(len(ext[szOffset:])))
// copy data to fec group
sz := len(ext)
fecGroup[fecCnt] = fecGroup[fecCnt][:sz]
copy(fecGroup[fecCnt], ext)
fecCnt++
if sz > fecMaxSize {
fecMaxSize = sz
}
// calculate Reed-Solomon Erasure Code
if fecCnt == s.fec.dataShards {
for i := 0; i < s.fec.dataShards; i++ {
shard := fecGroup[i]
slen := len(shard)
xorBytes(shard[slen:fecMaxSize], shard[slen:fecMaxSize], shard[slen:fecMaxSize])
}
ecc = s.fec.calcECC(fecGroup, szOffset, fecMaxSize)
for k := range ecc {
s.fec.markFEC(ecc[k][fecOffset:])
ecc[k] = ecc[k][:fecMaxSize]
}
fecCnt = 0
fecMaxSize = 0
}
}
if s.block != nil {
io.ReadFull(rand.Reader, ext[:nonceSize])
checksum := crc32.ChecksumIEEE(ext[cryptHeaderSize:])
binary.LittleEndian.PutUint32(ext[nonceSize:], checksum)
s.block.Encrypt(ext, ext)
if ecc != nil {
for k := range ecc {
io.ReadFull(rand.Reader, ecc[k][:nonceSize])
checksum := crc32.ChecksumIEEE(ecc[k][cryptHeaderSize:])
binary.LittleEndian.PutUint32(ecc[k][nonceSize:], checksum)
s.block.Encrypt(ecc[k], ecc[k])
}
}
}
//if rand.Intn(100) < 80 {
if n, err := s.conn.WriteTo(ext, s.remote); err == nil {
atomic.AddUint64(&DefaultSnmp.OutSegs, 1)
atomic.AddUint64(&DefaultSnmp.OutBytes, uint64(n))
}
//}
if ecc != nil {
for k := range ecc {
if n, err := s.conn.WriteTo(ecc[k], s.remote); err == nil {
atomic.AddUint64(&DefaultSnmp.OutSegs, 1)
atomic.AddUint64(&DefaultSnmp.OutBytes, uint64(n))
}
}
}
xmitBuf.Put(ext)
case <-ticker.C: // NAT keep-alive
if len(s.chUDPOutput) == 0 {
s.mu.Lock()
interval := s.keepAliveInterval
s.mu.Unlock()
if interval > 0 && time.Now().After(lastPing.Add(interval)) {
var rnd uint16
binary.Read(rand.Reader, binary.LittleEndian, &rnd)
sz := int(rnd)%(IKCP_MTU_DEF-s.headerSize-IKCP_OVERHEAD) + s.headerSize + IKCP_OVERHEAD
ping := make([]byte, sz) // randomized ping packet
io.ReadFull(rand.Reader, ping)
s.conn.WriteTo(ping, s.remote)
lastPing = time.Now()
}
}
case <-s.die:
return
}
}
}
// kcp update, input loop
func (s *UDPSession) updateTask() {
var tc <-chan time.Time
if s.l == nil { // client
ticker := time.NewTicker(10 * time.Millisecond)
tc = ticker.C
defer ticker.Stop()
} else {
tc = s.chTicker
}
for {
select {
case <-tc:
s.mu.Lock()
current := currentMs()
s.kcp.Update(current)
if s.kcp.WaitSnd() < 2*int(s.kcp.snd_wnd) {
s.notifyWriteEvent()
}
s.mu.Unlock()
case <-s.die:
if s.l != nil { // has listener
select {
case s.l.chDeadlinks <- s.remote:
case <-s.l.die:
}
}
return
}
}
}
// GetConv gets conversation id of a session
func (s *UDPSession) GetConv() uint32 {
return s.kcp.conv
}
func (s *UDPSession) notifyReadEvent() {
select {
case s.chReadEvent <- struct{}{}:
default:
}
}
func (s *UDPSession) notifyWriteEvent() {
select {
case s.chWriteEvent <- struct{}{}:
default:
}
}
func (s *UDPSession) kcpInput(data []byte) {
current := currentMs()
if s.fec != nil {
f := s.fec.decode(data)
if f.flag == typeData || f.flag == typeFEC {
if f.flag == typeFEC {
atomic.AddUint64(&DefaultSnmp.FECSegs, 1)
}
if recovers := s.fec.input(f); recovers != nil {
s.mu.Lock()
s.kcp.current = current
for k := range recovers {
sz := binary.LittleEndian.Uint16(recovers[k])
if int(sz) <= len(recovers[k]) && sz >= 2 {
if ret := s.kcp.Input(recovers[k][2:sz], false); ret != 0 {
atomic.AddUint64(&DefaultSnmp.KCPInErrors, 1)
}
} else {
atomic.AddUint64(&DefaultSnmp.FECErrs, 1)
}
}
s.mu.Unlock()
atomic.AddUint64(&DefaultSnmp.FECRecovered, uint64(len(recovers)))
}
}
if f.flag == typeData {
s.mu.Lock()
s.kcp.current = current
if ret := s.kcp.Input(data[fecHeaderSizePlus2:], true); ret != 0 {
atomic.AddUint64(&DefaultSnmp.KCPInErrors, 1)
}
s.mu.Unlock()
}
} else {
s.mu.Lock()
s.kcp.current = current
if ret := s.kcp.Input(data, true); ret != 0 {
atomic.AddUint64(&DefaultSnmp.KCPInErrors, 1)
}
s.mu.Unlock()
}
// notify reader
s.mu.Lock()
if n := s.kcp.PeekSize(); n > 0 {
s.notifyReadEvent()
}
if s.ackNoDelay {
s.kcp.current = current
s.kcp.flush()
}
s.mu.Unlock()
atomic.AddUint64(&DefaultSnmp.InSegs, 1)
}
func (s *UDPSession) receiver(ch chan []byte) {
for {
data := xmitBuf.Get().([]byte)[:mtuLimit]
if n, _, err := s.conn.ReadFrom(data); err == nil && n >= s.headerSize+IKCP_OVERHEAD {
select {
case ch <- data[:n]:
case <-s.die:
}
} else if err != nil {
return
} else {
atomic.AddUint64(&DefaultSnmp.InErrs, 1)
}
}
}
// read loop for client session
func (s *UDPSession) readLoop() {
chPacket := make(chan []byte, txQueueLimit)
go s.receiver(chPacket)
for {
select {
case data := <-chPacket:
raw := data
dataValid := false
if s.block != nil {
s.block.Decrypt(data, data)
data = data[nonceSize:]
checksum := crc32.ChecksumIEEE(data[crcSize:])
if checksum == binary.LittleEndian.Uint32(data) {
data = data[crcSize:]
dataValid = true
} else {
atomic.AddUint64(&DefaultSnmp.InCsumErrors, 1)
}
} else if s.block == nil {
dataValid = true
}
if dataValid {
s.kcpInput(data)
}
xmitBuf.Put(raw)
case <-s.die:
return
}
}
}
type (
// Listener defines a server listening for connections
Listener struct {
block BlockCrypt
dataShards, parityShards int
fec *FEC // for fec init test
conn net.PacketConn
sessions map[string]*UDPSession
chAccepts chan *UDPSession
chDeadlinks chan net.Addr
headerSize int
die chan struct{}
rxbuf sync.Pool
rd atomic.Value
wd atomic.Value
}
packet struct {
from net.Addr
data []byte
}
)
// monitor incoming data for all connections of server
func (l *Listener) monitor() {
chPacket := make(chan packet, txQueueLimit)
go l.receiver(chPacket)
ticker := time.NewTicker(10 * time.Millisecond)
defer ticker.Stop()
for {
select {
case p := <-chPacket:
raw := p.data
data := p.data
from := p.from
dataValid := false
if l.block != nil {
l.block.Decrypt(data, data)
data = data[nonceSize:]
checksum := crc32.ChecksumIEEE(data[crcSize:])
if checksum == binary.LittleEndian.Uint32(data) {
data = data[crcSize:]
dataValid = true
} else {
atomic.AddUint64(&DefaultSnmp.InCsumErrors, 1)
}
} else if l.block == nil {
dataValid = true
}
if dataValid {
addr := from.String()
s, ok := l.sessions[addr]
if !ok { // new session
var conv uint32
convValid := false
if l.fec != nil {
isfec := binary.LittleEndian.Uint16(data[4:])
if isfec == typeData {
conv = binary.LittleEndian.Uint32(data[fecHeaderSizePlus2:])
convValid = true
}
} else {
conv = binary.LittleEndian.Uint32(data)
convValid = true
}
if convValid {
s := newUDPSession(conv, l.dataShards, l.parityShards, l, l.conn, from, l.block)
s.kcpInput(data)
l.sessions[addr] = s
l.chAccepts <- s
}
} else {
s.kcpInput(data)
}
}
l.rxbuf.Put(raw)
case deadlink := <-l.chDeadlinks:
delete(l.sessions, deadlink.String())
case <-l.die:
return
case <-ticker.C:
now := time.Now()
for _, s := range l.sessions {
select {
case s.chTicker <- now:
default:
}
}
}
}
}
func (l *Listener) receiver(ch chan packet) {
for {
data := l.rxbuf.Get().([]byte)[:mtuLimit]
if n, from, err := l.conn.ReadFrom(data); err == nil && n >= l.headerSize+IKCP_OVERHEAD {
ch <- packet{from, data[:n]}
} else if err != nil {
return
} else {
atomic.AddUint64(&DefaultSnmp.InErrs, 1)
}
}
}
// SetReadBuffer sets the socket read buffer for the Listener
func (l *Listener) SetReadBuffer(bytes int) error {
if nc, ok := l.conn.(setReadBuffer); ok {
return nc.SetReadBuffer(bytes)
}
return nil
}
// SetWriteBuffer sets the socket write buffer for the Listener
func (l *Listener) SetWriteBuffer(bytes int) error {
if nc, ok := l.conn.(setWriteBuffer); ok {
return nc.SetWriteBuffer(bytes)
}
return nil
}
// SetDSCP sets the 6bit DSCP field of IP header
func (l *Listener) SetDSCP(dscp int) error {
if nc, ok := l.conn.(net.Conn); ok {
return ipv4.NewConn(nc).SetTOS(dscp << 2)
}
return nil
}
// Accept implements the Accept method in the Listener interface; it waits for the next call and returns a generic Conn.
func (l *Listener) Accept() (net.Conn, error) {
return l.AcceptKCP()
}
// AcceptKCP accepts a KCP connection
func (l *Listener) AcceptKCP() (*UDPSession, error) {
var timeout <-chan time.Time
if tdeadline, ok := l.rd.Load().(time.Time); ok && !tdeadline.IsZero() {
timeout = time.After(tdeadline.Sub(time.Now()))
}
select {
case <-timeout:
return nil, &errTimeout{}
case c := <-l.chAccepts:
return c, nil
case <-l.die:
return nil, errors.New(errBrokenPipe)
}
}
// SetDeadline sets the deadline associated with the listener. A zero time value disables the deadline.
func (l *Listener) SetDeadline(t time.Time) error {
l.SetReadDeadline(t)
l.SetWriteDeadline(t)
return nil
}
// SetReadDeadline implements the Conn SetReadDeadline method.
func (l *Listener) SetReadDeadline(t time.Time) error {
l.rd.Store(t)
return nil
}
// SetWriteDeadline implements the Conn SetWriteDeadline method.
func (l *Listener) SetWriteDeadline(t time.Time) error {
l.wd.Store(t)
return nil
}
// Close stops listening on the UDP address. Already Accepted connections are not closed.
func (l *Listener) Close() error {
close(l.die)
return l.conn.Close()
}
// Addr returns the listener's network address, The Addr returned is shared by all invocations of Addr, so do not modify it.
func (l *Listener) Addr() net.Addr {
return l.conn.LocalAddr()
}
// Listen listens for incoming KCP packets addressed to the local address laddr on the network "udp",
func Listen(laddr string) (net.Listener, error) {
return ListenWithOptions(laddr, nil, 0, 0)
}
// ListenWithOptions listens for incoming KCP packets addressed to the local address laddr on the network "udp" with packet encryption,
// dataShards, parityShards defines Reed-Solomon Erasure Coding parameters
func ListenWithOptions(laddr string, block BlockCrypt, dataShards, parityShards int) (*Listener, error) {
udpaddr, err := net.ResolveUDPAddr("udp", laddr)
if err != nil {
return nil, errors.Wrap(err, "net.ResolveUDPAddr")
}
conn, err := net.ListenUDP("udp", udpaddr)
if err != nil {
return nil, errors.Wrap(err, "net.ListenUDP")
}
return ServeConn(block, dataShards, parityShards, conn)
}
// ServeConn serves KCP protocol for a single packet connection.
func ServeConn(block BlockCrypt, dataShards, parityShards int, conn net.PacketConn) (*Listener, error) {
l := new(Listener)
l.conn = conn
l.sessions = make(map[string]*UDPSession)
l.chAccepts = make(chan *UDPSession, 1024)
l.chDeadlinks = make(chan net.Addr, 1024)
l.die = make(chan struct{})
l.dataShards = dataShards
l.parityShards = parityShards
l.block = block
l.fec = newFEC(rxFecLimit, dataShards, parityShards)
l.rxbuf.New = func() interface{} {
return make([]byte, mtuLimit)
}
// calculate header size
if l.block != nil {
l.headerSize += cryptHeaderSize
}
if l.fec != nil {
l.headerSize += fecHeaderSizePlus2
}
go l.monitor()
return l, nil
}
// Dial connects to the remote address "raddr" on the network "udp"
func Dial(raddr string) (net.Conn, error) {
return DialWithOptions(raddr, nil, 0, 0)
}
// DialWithOptions connects to the remote address "raddr" on the network "udp" with packet encryption
func DialWithOptions(raddr string, block BlockCrypt, dataShards, parityShards int) (*UDPSession, error) {
udpaddr, err := net.ResolveUDPAddr("udp", raddr)
if err != nil {
return nil, errors.Wrap(err, "net.ResolveUDPAddr")
}
udpconn, err := net.DialUDP("udp", nil, udpaddr)
if err != nil {
return nil, errors.Wrap(err, "net.DialUDP")
}
return NewConn(raddr, block, dataShards, parityShards, &ConnectedUDPConn{udpconn, udpconn})
}
// NewConn establishes a session and talks KCP protocol over a packet connection.
func NewConn(raddr string, block BlockCrypt, dataShards, parityShards int, conn net.PacketConn) (*UDPSession, error) {
udpaddr, err := net.ResolveUDPAddr("udp", raddr)
if err != nil {
return nil, errors.Wrap(err, "net.ResolveUDPAddr")
}
var convid uint32
binary.Read(rand.Reader, binary.LittleEndian, &convid)
return newUDPSession(convid, dataShards, parityShards, nil, conn, udpaddr, block), nil
}
func currentMs() uint32 {
return uint32(time.Now().UnixNano() / int64(time.Millisecond))
}
// ConnectedUDPConn is a wrapper for net.UDPConn which converts WriteTo syscalls
// to Write syscalls that are 4 times faster on some OS'es. This should only be
// used for connections that were produced by a net.Dial* call.
type ConnectedUDPConn struct {
*net.UDPConn
Conn net.Conn // underlying connection if any
}
// WriteTo redirects all writes to the Write syscall, which is 4 times faster.
func (c *ConnectedUDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
return c.Write(b)
}