route/vendor/github.com/xtaci/kcp-go/sess.go

948 lines
24 KiB
Go

package kcp
import (
"crypto/rand"
"encoding/binary"
"hash/crc32"
"io"
"net"
"sync"
"sync/atomic"
"time"
"github.com/pkg/errors"
"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 (
// 16-bytes magic number for each packet
nonceSize = 16
// 4-bytes packet checksum
crcSize = 4
// overall crypto header size
cryptHeaderSize = nonceSize + crcSize
// maximum packet size
mtuLimit = 1500
// FEC keeps rxFECMulti* (dataShard+parityShard) ordered packets in memory
rxFECMulti = 3
// accept backlog
acceptBacklog = 128
// prerouting(to session) queue
qlen = 128
)
const (
errBrokenPipe = "broken pipe"
errInvalidOperation = "invalid operation"
)
var (
// global packet buffer
// shared among sending/receiving/FEC
xmitBuf sync.Pool
)
func init() {
xmitBuf.New = func() interface{} {
return make([]byte, mtuLimit)
}
}
type (
// UDPSession defines a KCP session implemented by UDP
UDPSession struct {
updaterIdx int // record slice index in updater
conn net.PacketConn // the underlying packet connection
kcp *KCP // KCP ARQ protocol
l *Listener // point to the Listener if it's accepted by Listener
block BlockCrypt // block encryption
// kcp receiving is based on packets
// recvbuf turns packets into stream
recvbuf []byte
bufptr []byte
// extended output buffer(with header)
ext []byte
// FEC
fecDecoder *fecDecoder
fecEncoder *fecEncoder
// settings
remote net.Addr // remote peer address
rd time.Time // read deadline
wd time.Time // write deadline
headerSize int // the overall header size added before KCP frame
ackNoDelay bool // send ack immediately for each incoming packet
writeDelay bool // delay kcp.flush() for Write() for bulk transfer
dup int // duplicate udp packets
// notifications
die chan struct{} // notify session has Closed
chReadEvent chan struct{} // notify Read() can be called without blocking
chWriteEvent chan struct{} // notify Write() can be called without blocking
chErrorEvent chan error // notify Read() have an error
isClosed bool // flag the session has Closed
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.die = make(chan struct{})
sess.chReadEvent = make(chan struct{}, 1)
sess.chWriteEvent = make(chan struct{}, 1)
sess.chErrorEvent = make(chan error, 1)
sess.remote = remote
sess.conn = conn
sess.l = l
sess.block = block
sess.recvbuf = make([]byte, mtuLimit)
// FEC initialization
sess.fecDecoder = newFECDecoder(rxFECMulti*(dataShards+parityShards), dataShards, parityShards)
if sess.block != nil {
sess.fecEncoder = newFECEncoder(dataShards, parityShards, cryptHeaderSize)
} else {
sess.fecEncoder = newFECEncoder(dataShards, parityShards, 0)
}
// calculate header size
if sess.block != nil {
sess.headerSize += cryptHeaderSize
}
if sess.fecEncoder != nil {
sess.headerSize += fecHeaderSizePlus2
}
// only allocate extended packet buffer
// when the extra header is required
if sess.headerSize > 0 {
sess.ext = make([]byte, mtuLimit)
}
sess.kcp = NewKCP(conv, func(buf []byte, size int) {
if size >= IKCP_OVERHEAD {
sess.output(buf[:size])
}
})
sess.kcp.SetMtu(IKCP_MTU_DEF - sess.headerSize)
// add current session to the global updater,
// which periodically calls sess.update()
updater.addSession(sess)
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 net.Conn
func (s *UDPSession) Read(b []byte) (n int, err error) {
for {
s.mu.Lock()
if len(s.bufptr) > 0 { // copy from buffer into b
n = copy(b, s.bufptr)
s.bufptr = s.bufptr[n:]
s.mu.Unlock()
return n, nil
}
if s.isClosed {
s.mu.Unlock()
return 0, errors.New(errBrokenPipe)
}
if size := s.kcp.PeekSize(); size > 0 { // peek data size from kcp
atomic.AddUint64(&DefaultSnmp.BytesReceived, uint64(size))
if len(b) >= size { // direct write to b
s.kcp.Recv(b)
s.mu.Unlock()
return size, nil
}
// resize kcp receive buffer
// to make sure recvbuf has enough capacity
if cap(s.recvbuf) < size {
s.recvbuf = make([]byte, size)
}
// resize recvbuf slice length
s.recvbuf = s.recvbuf[:size]
s.kcp.Recv(s.recvbuf)
n = copy(b, s.recvbuf) // copy to b
s.bufptr = s.recvbuf[n:] // update pointer
s.mu.Unlock()
return n, nil
}
// read deadline
var timeout *time.Timer
var c <-chan time.Time
if !s.rd.IsZero() {
if time.Now().After(s.rd) {
s.mu.Unlock()
return 0, errTimeout{}
}
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:
case err = <-s.chErrorEvent:
if timeout != nil {
timeout.Stop()
}
return n, err
}
if timeout != nil {
timeout.Stop()
}
}
}
// Write implements net.Conn
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)
}
// api flow control
if s.kcp.WaitSnd() < int(s.kcp.snd_wnd) {
n = len(b)
for {
if len(b) <= int(s.kcp.mss) {
s.kcp.Send(b)
break
} else {
s.kcp.Send(b[:s.kcp.mss])
b = b[s.kcp.mss:]
}
}
if !s.writeDelay {
s.kcp.flush(false)
}
s.mu.Unlock()
atomic.AddUint64(&DefaultSnmp.BytesSent, uint64(n))
return n, nil
}
// write deadline
var timeout *time.Timer
var c <-chan time.Time
if !s.wd.IsZero() {
if time.Now().After(s.wd) {
s.mu.Unlock()
return 0, errTimeout{}
}
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 {
// remove this session from updater & listener(if necessary)
updater.removeSession(s)
if s.l != nil { // notify listener
s.l.closeSession(s.remote)
}
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
}
// SetWriteDelay delays write for bulk transfer until the next update interval
func (s *UDPSession) SetWriteDelay(delay bool) {
s.mu.Lock()
defer s.mu.Unlock()
s.writeDelay = delay
}
// 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(not including UDP header)
func (s *UDPSession) SetMtu(mtu int) bool {
if mtu > mtuLimit {
return false
}
s.mu.Lock()
defer s.mu.Unlock()
s.kcp.SetMtu(mtu - s.headerSize)
return true
}
// 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
}
// SetDUP duplicates udp packets for kcp output, for testing purpose only
func (s *UDPSession) SetDUP(dup int) {
s.mu.Lock()
defer s.mu.Unlock()
s.dup = dup
}
// SetNoDelay calls nodelay() of kcp
// https://github.com/skywind3000/kcp/blob/master/README.en.md#protocol-configuration
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.UDPConn).SetTOS(dscp << 2)
} else if nc, ok := s.conn.(net.Conn); ok {
return ipv4.NewConn(nc).SetTOS(dscp << 2)
}
}
return errors.New(errInvalidOperation)
}
// 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 errors.New(errInvalidOperation)
}
// 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 errors.New(errInvalidOperation)
}
// output pipeline entry
// steps for output data processing:
// 0. Header extends
// 1. FEC
// 2. CRC32
// 3. Encryption
// 4. WriteTo kernel
func (s *UDPSession) output(buf []byte) {
var ecc [][]byte
// 0. extend buf's header space(if necessary)
ext := buf
if s.headerSize > 0 {
ext = s.ext[:s.headerSize+len(buf)]
copy(ext[s.headerSize:], buf)
}
// 1. FEC encoding
if s.fecEncoder != nil {
ecc = s.fecEncoder.encode(ext)
}
// 2&3. crc32 & encryption
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)
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])
}
}
// 4. WriteTo kernel
nbytes := 0
npkts := 0
for i := 0; i < s.dup+1; i++ {
if n, err := s.conn.WriteTo(ext, s.remote); err == nil {
nbytes += n
npkts++
}
}
for k := range ecc {
if n, err := s.conn.WriteTo(ecc[k], s.remote); err == nil {
nbytes += n
npkts++
}
}
atomic.AddUint64(&DefaultSnmp.OutPkts, uint64(npkts))
atomic.AddUint64(&DefaultSnmp.OutBytes, uint64(nbytes))
}
// kcp update, returns interval for next calling
func (s *UDPSession) update() (interval time.Duration) {
s.mu.Lock()
s.kcp.flush(false)
if s.kcp.WaitSnd() < int(s.kcp.snd_wnd) {
s.notifyWriteEvent()
}
interval = time.Duration(s.kcp.interval) * time.Millisecond
s.mu.Unlock()
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) {
var kcpInErrors, fecErrs, fecRecovered, fecParityShards uint64
if s.fecDecoder != nil {
f := s.fecDecoder.decodeBytes(data)
s.mu.Lock()
if f.flag == typeData {
if ret := s.kcp.Input(data[fecHeaderSizePlus2:], true, s.ackNoDelay); ret != 0 {
kcpInErrors++
}
}
if f.flag == typeData || f.flag == typeFEC {
if f.flag == typeFEC {
fecParityShards++
}
recovers := s.fecDecoder.decode(f)
for _, r := range recovers {
if len(r) >= 2 { // must be larger than 2bytes
sz := binary.LittleEndian.Uint16(r)
if int(sz) <= len(r) && sz >= 2 {
if ret := s.kcp.Input(r[2:sz], false, s.ackNoDelay); ret == 0 {
fecRecovered++
} else {
kcpInErrors++
}
} else {
fecErrs++
}
} else {
fecErrs++
}
}
}
// notify reader
if n := s.kcp.PeekSize(); n > 0 {
s.notifyReadEvent()
}
s.mu.Unlock()
} else {
s.mu.Lock()
if ret := s.kcp.Input(data, true, s.ackNoDelay); ret != 0 {
kcpInErrors++
}
// notify reader
if n := s.kcp.PeekSize(); n > 0 {
s.notifyReadEvent()
}
s.mu.Unlock()
}
atomic.AddUint64(&DefaultSnmp.InPkts, 1)
atomic.AddUint64(&DefaultSnmp.InBytes, uint64(len(data)))
if fecParityShards > 0 {
atomic.AddUint64(&DefaultSnmp.FECParityShards, fecParityShards)
}
if kcpInErrors > 0 {
atomic.AddUint64(&DefaultSnmp.KCPInErrors, kcpInErrors)
}
if fecErrs > 0 {
atomic.AddUint64(&DefaultSnmp.FECErrs, fecErrs)
}
if fecRecovered > 0 {
atomic.AddUint64(&DefaultSnmp.FECRecovered, fecRecovered)
}
}
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:
return
}
} else if err != nil {
s.chErrorEvent <- err
return
} else {
atomic.AddUint64(&DefaultSnmp.InErrs, 1)
}
}
}
// read loop for client session
func (s *UDPSession) readLoop() {
chPacket := make(chan []byte, qlen)
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 // block encryption
dataShards int // FEC data shard
parityShards int // FEC parity shard
fecDecoder *fecDecoder // FEC mock initialization
conn net.PacketConn // the underlying packet connection
sessions map[string]*UDPSession // all sessions accepted by this Listener
chAccepts chan *UDPSession // Listen() backlog
chSessionClosed chan net.Addr // session close queue
headerSize int // the overall header size added before KCP frame
die chan struct{} // notify the listener has closed
rd atomic.Value // read deadline for Accept()
wd atomic.Value
}
// incoming packet
inPacket struct {
from net.Addr
data []byte
}
)
// monitor incoming data for all connections of server
func (l *Listener) monitor() {
// cache last session
var lastAddr string
var lastSession *UDPSession
chPacket := make(chan inPacket, qlen)
go l.receiver(chPacket)
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()
var s *UDPSession
var ok bool
// packets received from an address always come in batch.
// cache the session for next packet, without querying map.
if addr == lastAddr {
s, ok = lastSession, true
} else if s, ok = l.sessions[addr]; ok {
lastSession = s
lastAddr = addr
}
if !ok { // new session
if len(l.chAccepts) < cap(l.chAccepts) { // do not let new session overwhelm accept queue
var conv uint32
convValid := false
if l.fecDecoder != 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)
}
}
xmitBuf.Put(raw)
case deadlink := <-l.chSessionClosed:
delete(l.sessions, deadlink.String())
case <-l.die:
return
}
}
}
func (l *Listener) receiver(ch chan<- inPacket) {
for {
data := xmitBuf.Get().([]byte)[:mtuLimit]
if n, from, err := l.conn.ReadFrom(data); err == nil && n >= l.headerSize+IKCP_OVERHEAD {
select {
case ch <- inPacket{from, data[:n]}:
case <-l.die:
return
}
} 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 errors.New(errInvalidOperation)
}
// 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 errors.New(errInvalidOperation)
}
// 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 errors.New(errInvalidOperation)
}
// 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()
}
// closeSession notify the listener that a session has closed
func (l *Listener) closeSession(remote net.Addr) bool {
select {
case l.chSessionClosed <- remote:
return true
case <-l.die:
return false
}
}
// 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, acceptBacklog)
l.chSessionClosed = make(chan net.Addr)
l.die = make(chan struct{})
l.dataShards = dataShards
l.parityShards = parityShards
l.block = block
l.fecDecoder = newFECDecoder(rxFECMulti*(dataShards+parityShards), dataShards, parityShards)
// calculate header size
if l.block != nil {
l.headerSize += cryptHeaderSize
}
if l.fecDecoder != 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})
}
// 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
}
// returns current time in milliseconds
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 }
// 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) }