mirror of
https://github.com/v2fly/v2ray-core.git
synced 2024-06-29 18:45:23 +00:00
766 lines
17 KiB
Go
766 lines
17 KiB
Go
// Package kcp - A Fast and Reliable ARQ Protocol
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//
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// Acknowledgement:
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// skywind3000@github for inventing the KCP protocol
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// xtaci@github for translating to Golang
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package kcp
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import (
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"encoding/binary"
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"github.com/v2ray/v2ray-core/common/alloc"
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)
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const (
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IKCP_RTO_NDL = 30 // no delay min rto
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IKCP_RTO_MIN = 100 // normal min rto
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IKCP_RTO_DEF = 200
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IKCP_RTO_MAX = 60000
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IKCP_CMD_PUSH = 81 // cmd: push data
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IKCP_CMD_ACK = 82 // cmd: ack
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IKCP_CMD_WASK = 83 // cmd: window probe (ask)
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IKCP_CMD_WINS = 84 // cmd: window size (tell)
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IKCP_ASK_SEND = 1 // need to send IKCP_CMD_WASK
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IKCP_ASK_TELL = 2 // need to send IKCP_CMD_WINS
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IKCP_WND_SND = 32
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IKCP_WND_RCV = 32
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IKCP_MTU_DEF = 1350
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IKCP_ACK_FAST = 3
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IKCP_INTERVAL = 100
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IKCP_OVERHEAD = 24
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IKCP_DEADLINK = 20
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IKCP_THRESH_INIT = 2
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IKCP_THRESH_MIN = 2
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IKCP_PROBE_INIT = 7000 // 7 secs to probe window size
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IKCP_PROBE_LIMIT = 120000 // up to 120 secs to probe window
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)
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// Output is a closure which captures conn and calls conn.Write
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type Output func(buf []byte)
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/* encode 8 bits unsigned int */
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func ikcp_encode8u(p []byte, c byte) []byte {
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p[0] = c
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return p[1:]
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}
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/* decode 8 bits unsigned int */
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func ikcp_decode8u(p []byte, c *byte) []byte {
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*c = p[0]
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return p[1:]
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}
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/* encode 16 bits unsigned int (lsb) */
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func ikcp_encode16u(p []byte, w uint16) []byte {
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binary.LittleEndian.PutUint16(p, w)
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return p[2:]
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}
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/* decode 16 bits unsigned int (lsb) */
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func ikcp_decode16u(p []byte, w *uint16) []byte {
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*w = binary.LittleEndian.Uint16(p)
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return p[2:]
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}
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/* encode 32 bits unsigned int (lsb) */
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func ikcp_encode32u(p []byte, l uint32) []byte {
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binary.LittleEndian.PutUint32(p, l)
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return p[4:]
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}
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/* decode 32 bits unsigned int (lsb) */
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func ikcp_decode32u(p []byte, l *uint32) []byte {
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*l = binary.LittleEndian.Uint32(p)
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return p[4:]
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}
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func _imin_(a, b uint32) uint32 {
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if a <= b {
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return a
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} else {
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return b
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}
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}
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func _imax_(a, b uint32) uint32 {
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if a >= b {
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return a
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} else {
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return b
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}
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}
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func _itimediff(later, earlier uint32) int32 {
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return (int32)(later - earlier)
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}
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// Segment defines a KCP segment
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type Segment struct {
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conv uint32
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cmd uint32
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frg uint32
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wnd uint32
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ts uint32
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sn uint32
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una uint32
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resendts uint32
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fastack uint32
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xmit uint32
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data *alloc.Buffer
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}
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// encode a segment into buffer
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func (seg *Segment) encode(ptr []byte) []byte {
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ptr = ikcp_encode32u(ptr, seg.conv)
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ptr = ikcp_encode8u(ptr, uint8(seg.cmd))
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ptr = ikcp_encode8u(ptr, uint8(seg.frg))
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ptr = ikcp_encode16u(ptr, uint16(seg.wnd))
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ptr = ikcp_encode32u(ptr, seg.ts)
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ptr = ikcp_encode32u(ptr, seg.sn)
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ptr = ikcp_encode32u(ptr, seg.una)
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ptr = ikcp_encode16u(ptr, uint16(seg.data.Len()))
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return ptr
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}
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func (this *Segment) Release() {
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this.data.Release()
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this.data = nil
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}
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// NewSegment creates a KCP segment
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func NewSegment() *Segment {
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return &Segment{
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data: alloc.NewSmallBuffer().Clear(),
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}
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}
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// KCP defines a single KCP connection
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type KCP struct {
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conv, mtu, mss, state uint32
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snd_una, snd_nxt, rcv_nxt uint32
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ts_recent, ts_lastack, ssthresh uint32
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rx_rttvar, rx_srtt, rx_rto uint32
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snd_wnd, rcv_wnd, rmt_wnd, cwnd, probe uint32
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current, interval, ts_flush, xmit uint32
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updated bool
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ts_probe, probe_wait uint32
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dead_link, incr uint32
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snd_queue *SendingQueue
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rcv_queue []*Segment
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snd_buf []*Segment
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rcv_buf *ReceivingWindow
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acklist []uint32
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buffer []byte
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fastresend int32
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congestionControl bool
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output Output
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}
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// NewKCP create a new kcp control object, 'conv' must equal in two endpoint
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// from the same connection.
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func NewKCP(conv uint32, mtu uint32, sendingWindowSize uint32, receivingWindowSize uint32, sendingQueueSize uint32, output Output) *KCP {
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kcp := new(KCP)
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kcp.conv = conv
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kcp.snd_wnd = sendingWindowSize
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kcp.rcv_wnd = receivingWindowSize
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kcp.rmt_wnd = IKCP_WND_RCV
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kcp.mtu = mtu
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kcp.mss = kcp.mtu - IKCP_OVERHEAD
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kcp.buffer = make([]byte, (kcp.mtu+IKCP_OVERHEAD)*3)
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kcp.rx_rto = IKCP_RTO_DEF
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kcp.interval = IKCP_INTERVAL
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kcp.ts_flush = IKCP_INTERVAL
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kcp.ssthresh = IKCP_THRESH_INIT
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kcp.dead_link = IKCP_DEADLINK
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kcp.output = output
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kcp.rcv_buf = NewReceivingWindow(receivingWindowSize)
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kcp.snd_queue = NewSendingQueue(sendingQueueSize)
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return kcp
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}
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// Recv is user/upper level recv: returns size, returns below zero for EAGAIN
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func (kcp *KCP) Recv(buffer []byte) (n int) {
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if len(kcp.rcv_queue) == 0 {
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return -1
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}
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var fast_recover bool
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if len(kcp.rcv_queue) >= int(kcp.rcv_wnd) {
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fast_recover = true
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}
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// merge fragment
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count := 0
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for _, seg := range kcp.rcv_queue {
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dataLen := seg.data.Len()
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if dataLen > len(buffer) {
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break
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}
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copy(buffer, seg.data.Value)
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seg.Release()
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buffer = buffer[dataLen:]
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n += dataLen
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count++
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}
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kcp.rcv_queue = kcp.rcv_queue[count:]
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kcp.DumpReceivingBuf()
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// fast recover
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if len(kcp.rcv_queue) < int(kcp.rcv_wnd) && fast_recover {
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// ready to send back IKCP_CMD_WINS in ikcp_flush
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// tell remote my window size
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kcp.probe |= IKCP_ASK_TELL
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}
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return
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}
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// DumpReceivingBuf moves available data from rcv_buf -> rcv_queue
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// @Private
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func (kcp *KCP) DumpReceivingBuf() {
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for {
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seg := kcp.rcv_buf.RemoveFirst()
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if seg == nil {
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break
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}
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kcp.rcv_queue = append(kcp.rcv_queue, seg)
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kcp.rcv_buf.Advance()
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kcp.rcv_nxt++
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}
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}
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// Send is user/upper level send, returns below zero for error
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func (kcp *KCP) Send(buffer []byte) int {
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nBytes := 0
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for len(buffer) > 0 && !kcp.snd_queue.IsFull() {
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var size int
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if len(buffer) > int(kcp.mss) {
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size = int(kcp.mss)
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} else {
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size = len(buffer)
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}
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seg := NewSegment()
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seg.data.Append(buffer[:size])
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kcp.snd_queue.Push(seg)
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buffer = buffer[size:]
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nBytes += size
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}
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return nBytes
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}
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// https://tools.ietf.org/html/rfc6298
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func (kcp *KCP) update_ack(rtt int32) {
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var rto uint32 = 0
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if kcp.rx_srtt == 0 {
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kcp.rx_srtt = uint32(rtt)
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kcp.rx_rttvar = uint32(rtt) / 2
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} else {
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delta := rtt - int32(kcp.rx_srtt)
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if delta < 0 {
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delta = -delta
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}
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kcp.rx_rttvar = (3*kcp.rx_rttvar + uint32(delta)) / 4
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kcp.rx_srtt = (7*kcp.rx_srtt + uint32(rtt)) / 8
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if kcp.rx_srtt < kcp.interval {
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kcp.rx_srtt = kcp.interval
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}
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}
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rto = kcp.rx_srtt + _imax_(kcp.interval, 4*kcp.rx_rttvar)
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if rto > IKCP_RTO_MAX {
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rto = IKCP_RTO_MAX
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}
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kcp.rx_rto = rto
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}
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func (kcp *KCP) shrink_buf() {
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if len(kcp.snd_buf) > 0 {
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seg := kcp.snd_buf[0]
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kcp.snd_una = seg.sn
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} else {
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kcp.snd_una = kcp.snd_nxt
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}
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}
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func (kcp *KCP) parse_ack(sn uint32) {
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if _itimediff(sn, kcp.snd_una) < 0 || _itimediff(sn, kcp.snd_nxt) >= 0 {
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return
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}
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for k, seg := range kcp.snd_buf {
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if sn == seg.sn {
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kcp.snd_buf = append(kcp.snd_buf[:k], kcp.snd_buf[k+1:]...)
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seg.Release()
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break
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}
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if _itimediff(sn, seg.sn) < 0 {
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break
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}
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}
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}
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func (kcp *KCP) parse_fastack(sn uint32) {
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if _itimediff(sn, kcp.snd_una) < 0 || _itimediff(sn, kcp.snd_nxt) >= 0 {
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return
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}
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for _, seg := range kcp.snd_buf {
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if _itimediff(sn, seg.sn) < 0 {
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break
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} else if sn != seg.sn {
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seg.fastack++
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}
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}
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}
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func (kcp *KCP) parse_una(una uint32) {
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count := 0
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for _, seg := range kcp.snd_buf {
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if _itimediff(una, seg.sn) > 0 {
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seg.Release()
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count++
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} else {
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break
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}
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}
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kcp.snd_buf = kcp.snd_buf[count:]
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}
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// ack append
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func (kcp *KCP) ack_push(sn, ts uint32) {
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kcp.acklist = append(kcp.acklist, sn, ts)
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}
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func (kcp *KCP) ack_get(p int) (sn, ts uint32) {
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return kcp.acklist[p*2+0], kcp.acklist[p*2+1]
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}
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func (kcp *KCP) parse_data(newseg *Segment) {
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sn := newseg.sn
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if _itimediff(sn, kcp.rcv_nxt+kcp.rcv_wnd) >= 0 ||
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_itimediff(sn, kcp.rcv_nxt) < 0 {
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return
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}
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idx := sn - kcp.rcv_nxt
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if !kcp.rcv_buf.Set(idx, newseg) {
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newseg.Release()
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}
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kcp.DumpReceivingBuf()
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}
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// Input when you received a low level packet (eg. UDP packet), call it
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func (kcp *KCP) Input(data []byte) int {
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//una := kcp.snd_una
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if len(data) < IKCP_OVERHEAD {
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return -1
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}
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var maxack uint32
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var flag int
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for {
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var ts, sn, una, conv uint32
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var wnd, length uint16
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var cmd, frg uint8
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if len(data) < int(IKCP_OVERHEAD) {
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break
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}
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data = ikcp_decode32u(data, &conv)
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if conv != kcp.conv {
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return -1
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}
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data = ikcp_decode8u(data, &cmd)
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data = ikcp_decode8u(data, &frg)
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data = ikcp_decode16u(data, &wnd)
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data = ikcp_decode32u(data, &ts)
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data = ikcp_decode32u(data, &sn)
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data = ikcp_decode32u(data, &una)
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data = ikcp_decode16u(data, &length)
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if len(data) < int(length) {
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return -2
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}
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if cmd != IKCP_CMD_PUSH && cmd != IKCP_CMD_ACK &&
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cmd != IKCP_CMD_WASK && cmd != IKCP_CMD_WINS {
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return -3
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}
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if kcp.rmt_wnd < uint32(wnd) {
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kcp.rmt_wnd = uint32(wnd)
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}
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//kcp.rmt_wnd = uint32(wnd)
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kcp.parse_una(una)
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kcp.shrink_buf()
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if cmd == IKCP_CMD_ACK {
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if _itimediff(kcp.current, ts) >= 0 {
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kcp.update_ack(_itimediff(kcp.current, ts))
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}
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kcp.parse_ack(sn)
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kcp.shrink_buf()
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if flag == 0 {
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flag = 1
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maxack = sn
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} else if _itimediff(sn, maxack) > 0 {
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maxack = sn
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}
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} else if cmd == IKCP_CMD_PUSH {
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if _itimediff(sn, kcp.rcv_nxt+kcp.rcv_wnd) < 0 {
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kcp.ack_push(sn, ts)
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if _itimediff(sn, kcp.rcv_nxt) >= 0 {
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seg := NewSegment()
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seg.conv = conv
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seg.cmd = uint32(cmd)
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seg.frg = uint32(frg)
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seg.wnd = uint32(wnd)
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seg.ts = ts
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seg.sn = sn
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seg.una = una
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seg.data.Append(data[:length])
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kcp.parse_data(seg)
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}
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}
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} else if cmd == IKCP_CMD_WASK {
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// ready to send back IKCP_CMD_WINS in Ikcp_flush
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// tell remote my window size
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kcp.probe |= IKCP_ASK_TELL
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} else if cmd == IKCP_CMD_WINS {
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// do nothing
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} else {
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return -3
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}
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data = data[length:]
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}
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if flag != 0 {
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kcp.parse_fastack(maxack)
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}
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/*
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if _itimediff(kcp.snd_una, una) > 0 {
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if kcp.cwnd < kcp.rmt_wnd {
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mss := kcp.mss
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if kcp.cwnd < kcp.ssthresh {
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kcp.cwnd++
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kcp.incr += mss
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} else {
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if kcp.incr < mss {
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kcp.incr = mss
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}
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kcp.incr += (mss*mss)/kcp.incr + (mss / 16)
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if (kcp.cwnd+1)*mss <= kcp.incr {
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kcp.cwnd++
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}
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}
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if kcp.cwnd > kcp.rmt_wnd {
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kcp.cwnd = kcp.rmt_wnd
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kcp.incr = kcp.rmt_wnd * mss
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}
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}
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}*/
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return 0
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}
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// flush pending data
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func (kcp *KCP) flush() {
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current := kcp.current
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buffer := kcp.buffer
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change := 0
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//lost := false
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if !kcp.updated {
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return
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}
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var seg Segment
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seg.conv = kcp.conv
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seg.cmd = IKCP_CMD_ACK
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seg.wnd = uint32(kcp.rcv_nxt + kcp.rcv_wnd)
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seg.una = kcp.rcv_nxt
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// flush acknowledges
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count := len(kcp.acklist) / 2
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ptr := buffer
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for i := 0; i < count; i++ {
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size := len(buffer) - len(ptr)
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if size+IKCP_OVERHEAD > int(kcp.mtu) {
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kcp.output(buffer[:size])
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ptr = buffer
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}
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seg.sn, seg.ts = kcp.ack_get(i)
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ptr = seg.encode(ptr)
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}
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kcp.acklist = nil
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|
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// probe window size (if remote window size equals zero)
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/*
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if kcp.rmt_wnd == 0 {
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if kcp.probe_wait == 0 {
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kcp.probe_wait = IKCP_PROBE_INIT
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kcp.ts_probe = kcp.current + kcp.probe_wait
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} else {
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if _itimediff(kcp.current, kcp.ts_probe) >= 0 {
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if kcp.probe_wait < IKCP_PROBE_INIT {
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kcp.probe_wait = IKCP_PROBE_INIT
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}
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kcp.probe_wait += kcp.probe_wait / 2
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if kcp.probe_wait > IKCP_PROBE_LIMIT {
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|
kcp.probe_wait = IKCP_PROBE_LIMIT
|
|
}
|
|
kcp.ts_probe = kcp.current + kcp.probe_wait
|
|
kcp.probe |= IKCP_ASK_SEND
|
|
}
|
|
}
|
|
} else {
|
|
kcp.ts_probe = 0
|
|
kcp.probe_wait = 0
|
|
}*/
|
|
|
|
// flush window probing commands
|
|
/*
|
|
if (kcp.probe & IKCP_ASK_SEND) != 0 {
|
|
seg.cmd = IKCP_CMD_WASK
|
|
size := len(buffer) - len(ptr)
|
|
if size+IKCP_OVERHEAD > int(kcp.mtu) {
|
|
kcp.output(buffer[:size])
|
|
ptr = buffer
|
|
}
|
|
ptr = seg.encode(ptr)
|
|
}*/
|
|
|
|
// flush window probing commands
|
|
/*
|
|
if (kcp.probe & IKCP_ASK_TELL) != 0 {
|
|
seg.cmd = IKCP_CMD_WINS
|
|
size := len(buffer) - len(ptr)
|
|
if size+IKCP_OVERHEAD > int(kcp.mtu) {
|
|
kcp.output(buffer[:size])
|
|
ptr = buffer
|
|
}
|
|
ptr = seg.encode(ptr)
|
|
}
|
|
|
|
kcp.probe = 0*/
|
|
|
|
// calculate window size
|
|
|
|
cwnd := _imin_(kcp.snd_una+kcp.snd_wnd, kcp.rmt_wnd)
|
|
if kcp.congestionControl {
|
|
cwnd = _imin_(kcp.cwnd, cwnd)
|
|
}
|
|
|
|
for !kcp.snd_queue.IsEmpty() && _itimediff(kcp.snd_nxt, cwnd) < 0 {
|
|
newseg := kcp.snd_queue.Pop()
|
|
newseg.conv = kcp.conv
|
|
newseg.cmd = IKCP_CMD_PUSH
|
|
newseg.wnd = seg.wnd
|
|
newseg.ts = current
|
|
newseg.sn = kcp.snd_nxt
|
|
newseg.una = kcp.rcv_nxt
|
|
newseg.resendts = current
|
|
newseg.fastack = 0
|
|
newseg.xmit = 0
|
|
kcp.snd_buf = append(kcp.snd_buf, newseg)
|
|
kcp.snd_nxt++
|
|
}
|
|
|
|
// calculate resent
|
|
resent := uint32(kcp.fastresend)
|
|
if kcp.fastresend <= 0 {
|
|
resent = 0xffffffff
|
|
}
|
|
|
|
// flush data segments
|
|
for _, segment := range kcp.snd_buf {
|
|
needsend := false
|
|
if segment.xmit == 0 {
|
|
needsend = true
|
|
segment.xmit++
|
|
segment.resendts = current + kcp.rx_rto + kcp.interval
|
|
} else if _itimediff(current, segment.resendts) >= 0 {
|
|
needsend = true
|
|
segment.xmit++
|
|
kcp.xmit++
|
|
segment.resendts = current + kcp.rx_rto + kcp.interval
|
|
//lost = true
|
|
} else if segment.fastack >= resent {
|
|
needsend = true
|
|
segment.xmit++
|
|
segment.fastack = 0
|
|
segment.resendts = current + kcp.rx_rto + kcp.interval
|
|
change++
|
|
}
|
|
|
|
if needsend {
|
|
segment.ts = current
|
|
segment.wnd = seg.wnd
|
|
segment.una = kcp.rcv_nxt
|
|
|
|
size := len(buffer) - len(ptr)
|
|
need := IKCP_OVERHEAD + segment.data.Len()
|
|
|
|
if size+need >= int(kcp.mtu) {
|
|
kcp.output(buffer[:size])
|
|
ptr = buffer
|
|
}
|
|
|
|
ptr = segment.encode(ptr)
|
|
copy(ptr, segment.data.Value)
|
|
ptr = ptr[segment.data.Len():]
|
|
|
|
if segment.xmit >= kcp.dead_link {
|
|
kcp.state = 0xFFFFFFFF
|
|
}
|
|
}
|
|
}
|
|
|
|
// flash remain segments
|
|
size := len(buffer) - len(ptr)
|
|
if size > 0 {
|
|
kcp.output(buffer[:size])
|
|
}
|
|
|
|
// update ssthresh
|
|
// rate halving, https://tools.ietf.org/html/rfc6937
|
|
/*
|
|
if change != 0 {
|
|
inflight := kcp.snd_nxt - kcp.snd_una
|
|
kcp.ssthresh = inflight / 2
|
|
if kcp.ssthresh < IKCP_THRESH_MIN {
|
|
kcp.ssthresh = IKCP_THRESH_MIN
|
|
}
|
|
kcp.cwnd = kcp.ssthresh + resent
|
|
kcp.incr = kcp.cwnd * kcp.mss
|
|
}*/
|
|
|
|
// congestion control, https://tools.ietf.org/html/rfc5681
|
|
/*
|
|
if lost {
|
|
kcp.ssthresh = cwnd / 2
|
|
if kcp.ssthresh < IKCP_THRESH_MIN {
|
|
kcp.ssthresh = IKCP_THRESH_MIN
|
|
}
|
|
kcp.cwnd = 1
|
|
kcp.incr = kcp.mss
|
|
}
|
|
|
|
if kcp.cwnd < 1 {
|
|
kcp.cwnd = 1
|
|
kcp.incr = kcp.mss
|
|
}*/
|
|
}
|
|
|
|
// Update updates state (call it repeatedly, every 10ms-100ms), or you can ask
|
|
// ikcp_check when to call it again (without ikcp_input/_send calling).
|
|
// 'current' - current timestamp in millisec.
|
|
func (kcp *KCP) Update(current uint32) {
|
|
var slap int32
|
|
|
|
kcp.current = current
|
|
|
|
if !kcp.updated {
|
|
kcp.updated = true
|
|
kcp.ts_flush = kcp.current
|
|
}
|
|
|
|
slap = _itimediff(kcp.current, kcp.ts_flush)
|
|
|
|
if slap >= 10000 || slap < -10000 {
|
|
kcp.ts_flush = kcp.current
|
|
slap = 0
|
|
}
|
|
|
|
if slap >= 0 {
|
|
kcp.ts_flush += kcp.interval
|
|
if _itimediff(kcp.current, kcp.ts_flush) >= 0 {
|
|
kcp.ts_flush = kcp.current + kcp.interval
|
|
}
|
|
kcp.flush()
|
|
}
|
|
}
|
|
|
|
// Check determines when should you invoke ikcp_update:
|
|
// returns when you should invoke ikcp_update in millisec, if there
|
|
// is no ikcp_input/_send calling. you can call ikcp_update in that
|
|
// time, instead of call update repeatly.
|
|
// Important to reduce unnacessary ikcp_update invoking. use it to
|
|
// schedule ikcp_update (eg. implementing an epoll-like mechanism,
|
|
// or optimize ikcp_update when handling massive kcp connections)
|
|
func (kcp *KCP) Check(current uint32) uint32 {
|
|
ts_flush := kcp.ts_flush
|
|
tm_flush := int32(0x7fffffff)
|
|
tm_packet := int32(0x7fffffff)
|
|
minimal := uint32(0)
|
|
if !kcp.updated {
|
|
return current
|
|
}
|
|
|
|
if _itimediff(current, ts_flush) >= 10000 ||
|
|
_itimediff(current, ts_flush) < -10000 {
|
|
ts_flush = current
|
|
}
|
|
|
|
if _itimediff(current, ts_flush) >= 0 {
|
|
return current
|
|
}
|
|
|
|
tm_flush = _itimediff(ts_flush, current)
|
|
|
|
for _, seg := range kcp.snd_buf {
|
|
diff := _itimediff(seg.resendts, current)
|
|
if diff <= 0 {
|
|
return current
|
|
}
|
|
if diff < tm_packet {
|
|
tm_packet = diff
|
|
}
|
|
}
|
|
|
|
minimal = uint32(tm_packet)
|
|
if tm_packet >= tm_flush {
|
|
minimal = uint32(tm_flush)
|
|
}
|
|
if minimal >= kcp.interval {
|
|
minimal = kcp.interval
|
|
}
|
|
|
|
return current + minimal
|
|
}
|
|
|
|
// NoDelay options
|
|
// fastest: ikcp_nodelay(kcp, 1, 20, 2, 1)
|
|
// nodelay: 0:disable(default), 1:enable
|
|
// interval: internal update timer interval in millisec, default is 100ms
|
|
// resend: 0:disable fast resend(default), 1:enable fast resend
|
|
// nc: 0:normal congestion control(default), 1:disable congestion control
|
|
func (kcp *KCP) NoDelay(interval uint32, resend int, congestionControl bool) int {
|
|
kcp.interval = interval
|
|
|
|
if resend >= 0 {
|
|
kcp.fastresend = int32(resend)
|
|
}
|
|
kcp.congestionControl = congestionControl
|
|
return 0
|
|
}
|
|
|
|
// WaitSnd gets how many packet is waiting to be sent
|
|
func (kcp *KCP) WaitSnd() uint32 {
|
|
return uint32(len(kcp.snd_buf)) + kcp.snd_queue.Len()
|
|
}
|
|
|
|
func (this *KCP) ClearSendQueue() {
|
|
this.snd_queue.Clear()
|
|
|
|
for _, seg := range this.snd_buf {
|
|
seg.Release()
|
|
}
|
|
|
|
this.snd_buf = nil
|
|
}
|