mirror of
https://github.com/octoleo/syncthing.git
synced 2024-11-19 03:25:16 +00:00
999 lines
22 KiB
Go
999 lines
22 KiB
Go
// Package kcp - A Fast and Reliable ARQ Protocol
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package kcp
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import (
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"encoding/binary"
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"sync/atomic"
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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 = 1400
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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_callback is a prototype which ought capture conn and call conn.Write
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type output_callback func(buf []byte, size int)
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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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}
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return b
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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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}
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return b
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}
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func _ibound_(lower, middle, upper uint32) uint32 {
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return _imin_(_imax_(lower, middle), upper)
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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 uint8
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frg uint8
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wnd uint16
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ts uint32
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sn uint32
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una uint32
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rto uint32
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xmit uint32
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resendts uint32
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fastack uint32
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data []byte
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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, seg.cmd)
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ptr = ikcp_encode8u(ptr, seg.frg)
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ptr = ikcp_encode16u(ptr, 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_encode32u(ptr, uint32(len(seg.data)))
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atomic.AddUint64(&DefaultSnmp.OutSegs, 1)
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return ptr
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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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ssthresh uint32
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rx_rttvar, rx_srtt int32
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rx_rto, rx_minrto uint32
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snd_wnd, rcv_wnd, rmt_wnd, cwnd, probe uint32
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interval, ts_flush uint32
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nodelay, updated uint32
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ts_probe, probe_wait uint32
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dead_link, incr uint32
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fastresend int32
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nocwnd, stream int32
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snd_queue []segment
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rcv_queue []segment
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snd_buf []segment
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rcv_buf []segment
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acklist []ackItem
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buffer []byte
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output output_callback
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}
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type ackItem struct {
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sn uint32
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ts uint32
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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, output output_callback) *KCP {
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kcp := new(KCP)
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kcp.conv = conv
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kcp.snd_wnd = IKCP_WND_SND
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kcp.rcv_wnd = IKCP_WND_RCV
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kcp.rmt_wnd = IKCP_WND_RCV
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kcp.mtu = IKCP_MTU_DEF
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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.rx_minrto = IKCP_RTO_MIN
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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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return kcp
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}
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// newSegment creates a KCP segment
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func (kcp *KCP) newSegment(size int) (seg segment) {
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seg.data = xmitBuf.Get().([]byte)[:size]
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return
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}
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// delSegment recycles a KCP segment
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func (kcp *KCP) delSegment(seg segment) {
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xmitBuf.Put(seg.data)
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}
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// PeekSize checks the size of next message in the recv queue
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func (kcp *KCP) PeekSize() (length 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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seg := &kcp.rcv_queue[0]
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if seg.frg == 0 {
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return len(seg.data)
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}
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if len(kcp.rcv_queue) < int(seg.frg+1) {
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return -1
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}
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for k := range kcp.rcv_queue {
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seg := &kcp.rcv_queue[k]
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length += len(seg.data)
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if seg.frg == 0 {
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break
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}
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}
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return
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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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peeksize := kcp.PeekSize()
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if peeksize < 0 {
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return -2
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}
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if peeksize > len(buffer) {
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return -3
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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 k := range kcp.rcv_queue {
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seg := &kcp.rcv_queue[k]
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copy(buffer, seg.data)
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buffer = buffer[len(seg.data):]
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n += len(seg.data)
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count++
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kcp.delSegment(*seg)
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if seg.frg == 0 {
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break
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}
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}
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if count > 0 {
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kcp.rcv_queue = kcp.remove_front(kcp.rcv_queue, count)
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}
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// move available data from rcv_buf -> rcv_queue
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count = 0
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for k := range kcp.rcv_buf {
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seg := &kcp.rcv_buf[k]
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if seg.sn == kcp.rcv_nxt && len(kcp.rcv_queue) < int(kcp.rcv_wnd) {
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kcp.rcv_nxt++
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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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if count > 0 {
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kcp.rcv_queue = append(kcp.rcv_queue, kcp.rcv_buf[:count]...)
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kcp.rcv_buf = kcp.remove_front(kcp.rcv_buf, count)
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}
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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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// 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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var count int
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if len(buffer) == 0 {
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return -1
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}
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// append to previous segment in streaming mode (if possible)
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if kcp.stream != 0 {
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n := len(kcp.snd_queue)
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if n > 0 {
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seg := &kcp.snd_queue[n-1]
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if len(seg.data) < int(kcp.mss) {
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capacity := int(kcp.mss) - len(seg.data)
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extend := capacity
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if len(buffer) < capacity {
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extend = len(buffer)
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}
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// grow slice, the underlying cap is guaranteed to
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// be larger than kcp.mss
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oldlen := len(seg.data)
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seg.data = seg.data[:oldlen+extend]
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copy(seg.data[oldlen:], buffer)
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buffer = buffer[extend:]
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}
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}
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if len(buffer) == 0 {
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return 0
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}
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}
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if len(buffer) <= int(kcp.mss) {
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count = 1
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} else {
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count = (len(buffer) + int(kcp.mss) - 1) / int(kcp.mss)
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}
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if count > 255 {
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return -2
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}
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if count == 0 {
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count = 1
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}
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for i := 0; i < count; i++ {
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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 := kcp.newSegment(size)
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copy(seg.data, buffer[:size])
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if kcp.stream == 0 { // message mode
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seg.frg = uint8(count - i - 1)
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} else { // stream mode
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seg.frg = 0
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}
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kcp.snd_queue = append(kcp.snd_queue, seg)
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buffer = buffer[size:]
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}
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return 0
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}
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func (kcp *KCP) update_ack(rtt int32) {
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// https://tools.ietf.org/html/rfc6298
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var rto uint32
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if kcp.rx_srtt == 0 {
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kcp.rx_srtt = rtt
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kcp.rx_rttvar = rtt >> 1
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} else {
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delta := rtt - kcp.rx_srtt
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kcp.rx_srtt += delta >> 3
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if delta < 0 {
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delta = -delta
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}
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if rtt < kcp.rx_srtt-kcp.rx_rttvar {
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// if the new RTT sample is below the bottom of the range of
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// what an RTT measurement is expected to be.
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// give an 8x reduced weight versus its normal weighting
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kcp.rx_rttvar += (delta - kcp.rx_rttvar) >> 5
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} else {
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kcp.rx_rttvar += (delta - kcp.rx_rttvar) >> 2
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}
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}
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rto = uint32(kcp.rx_srtt) + _imax_(kcp.interval, uint32(kcp.rx_rttvar)<<2)
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kcp.rx_rto = _ibound_(kcp.rx_minrto, rto, IKCP_RTO_MAX)
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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 := range kcp.snd_buf {
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seg := &kcp.snd_buf[k]
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if sn == seg.sn {
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kcp.delSegment(*seg)
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copy(kcp.snd_buf[k:], kcp.snd_buf[k+1:])
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kcp.snd_buf[len(kcp.snd_buf)-1] = segment{}
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kcp.snd_buf = kcp.snd_buf[:len(kcp.snd_buf)-1]
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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 k := range kcp.snd_buf {
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seg := &kcp.snd_buf[k]
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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 k := range kcp.snd_buf {
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seg := &kcp.snd_buf[k]
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if _itimediff(una, seg.sn) > 0 {
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kcp.delSegment(*seg)
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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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if count > 0 {
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kcp.snd_buf = kcp.remove_front(kcp.snd_buf, count)
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}
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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, ackItem{sn, ts})
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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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kcp.delSegment(newseg)
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return
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}
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n := len(kcp.rcv_buf) - 1
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insert_idx := 0
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repeat := false
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for i := n; i >= 0; i-- {
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seg := &kcp.rcv_buf[i]
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if seg.sn == sn {
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repeat = true
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atomic.AddUint64(&DefaultSnmp.RepeatSegs, 1)
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break
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}
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if _itimediff(sn, seg.sn) > 0 {
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insert_idx = i + 1
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break
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}
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}
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if !repeat {
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if insert_idx == n+1 {
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kcp.rcv_buf = append(kcp.rcv_buf, newseg)
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} else {
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kcp.rcv_buf = append(kcp.rcv_buf, segment{})
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copy(kcp.rcv_buf[insert_idx+1:], kcp.rcv_buf[insert_idx:])
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kcp.rcv_buf[insert_idx] = newseg
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}
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} else {
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kcp.delSegment(newseg)
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}
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// move available data from rcv_buf -> rcv_queue
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count := 0
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for k := range kcp.rcv_buf {
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seg := &kcp.rcv_buf[k]
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if seg.sn == kcp.rcv_nxt && len(kcp.rcv_queue) < int(kcp.rcv_wnd) {
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kcp.rcv_nxt++
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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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if count > 0 {
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kcp.rcv_queue = append(kcp.rcv_queue, kcp.rcv_buf[:count]...)
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kcp.rcv_buf = kcp.remove_front(kcp.rcv_buf, count)
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}
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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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// regular indicates a regular packet has received(not from FEC)
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func (kcp *KCP) Input(data []byte, regular, ackNoDelay bool) 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 lastackts uint32
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var flag int
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var inSegs uint64
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for {
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var ts, sn, length, una, conv uint32
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var wnd 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_decode32u(data, &length)
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if len(data) < int(length) {
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return -2
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|
}
|
|
|
|
if cmd != IKCP_CMD_PUSH && cmd != IKCP_CMD_ACK &&
|
|
cmd != IKCP_CMD_WASK && cmd != IKCP_CMD_WINS {
|
|
return -3
|
|
}
|
|
|
|
// only trust window updates from regular packets. i.e: latest update
|
|
if regular {
|
|
kcp.rmt_wnd = uint32(wnd)
|
|
}
|
|
kcp.parse_una(una)
|
|
kcp.shrink_buf()
|
|
|
|
if cmd == IKCP_CMD_ACK {
|
|
kcp.parse_ack(sn)
|
|
kcp.shrink_buf()
|
|
if flag == 0 {
|
|
flag = 1
|
|
maxack = sn
|
|
} else if _itimediff(sn, maxack) > 0 {
|
|
maxack = sn
|
|
}
|
|
lastackts = ts
|
|
} else if cmd == IKCP_CMD_PUSH {
|
|
if _itimediff(sn, kcp.rcv_nxt+kcp.rcv_wnd) < 0 {
|
|
kcp.ack_push(sn, ts)
|
|
if _itimediff(sn, kcp.rcv_nxt) >= 0 {
|
|
seg := kcp.newSegment(int(length))
|
|
seg.conv = conv
|
|
seg.cmd = cmd
|
|
seg.frg = frg
|
|
seg.wnd = wnd
|
|
seg.ts = ts
|
|
seg.sn = sn
|
|
seg.una = una
|
|
copy(seg.data, data[:length])
|
|
kcp.parse_data(seg)
|
|
} else {
|
|
atomic.AddUint64(&DefaultSnmp.RepeatSegs, 1)
|
|
}
|
|
} else {
|
|
atomic.AddUint64(&DefaultSnmp.RepeatSegs, 1)
|
|
}
|
|
} else if cmd == IKCP_CMD_WASK {
|
|
// ready to send back IKCP_CMD_WINS in Ikcp_flush
|
|
// tell remote my window size
|
|
kcp.probe |= IKCP_ASK_TELL
|
|
} else if cmd == IKCP_CMD_WINS {
|
|
// do nothing
|
|
} else {
|
|
return -3
|
|
}
|
|
|
|
inSegs++
|
|
data = data[length:]
|
|
}
|
|
atomic.AddUint64(&DefaultSnmp.InSegs, inSegs)
|
|
|
|
if flag != 0 && regular {
|
|
kcp.parse_fastack(maxack)
|
|
current := currentMs()
|
|
if _itimediff(current, lastackts) >= 0 {
|
|
kcp.update_ack(_itimediff(current, lastackts))
|
|
}
|
|
}
|
|
|
|
if _itimediff(kcp.snd_una, una) > 0 {
|
|
if kcp.cwnd < kcp.rmt_wnd {
|
|
mss := kcp.mss
|
|
if kcp.cwnd < kcp.ssthresh {
|
|
kcp.cwnd++
|
|
kcp.incr += mss
|
|
} else {
|
|
if kcp.incr < mss {
|
|
kcp.incr = mss
|
|
}
|
|
kcp.incr += (mss*mss)/kcp.incr + (mss / 16)
|
|
if (kcp.cwnd+1)*mss <= kcp.incr {
|
|
kcp.cwnd++
|
|
}
|
|
}
|
|
if kcp.cwnd > kcp.rmt_wnd {
|
|
kcp.cwnd = kcp.rmt_wnd
|
|
kcp.incr = kcp.rmt_wnd * mss
|
|
}
|
|
}
|
|
}
|
|
|
|
if ackNoDelay && len(kcp.acklist) > 0 { // ack immediately
|
|
kcp.flush(true)
|
|
} else if kcp.rmt_wnd == 0 && len(kcp.acklist) > 0 { // window zero
|
|
kcp.flush(true)
|
|
}
|
|
return 0
|
|
}
|
|
|
|
func (kcp *KCP) wnd_unused() uint16 {
|
|
if len(kcp.rcv_queue) < int(kcp.rcv_wnd) {
|
|
return uint16(int(kcp.rcv_wnd) - len(kcp.rcv_queue))
|
|
}
|
|
return 0
|
|
}
|
|
|
|
// flush pending data
|
|
func (kcp *KCP) flush(ackOnly bool) {
|
|
var seg segment
|
|
seg.conv = kcp.conv
|
|
seg.cmd = IKCP_CMD_ACK
|
|
seg.wnd = kcp.wnd_unused()
|
|
seg.una = kcp.rcv_nxt
|
|
|
|
buffer := kcp.buffer
|
|
// flush acknowledges
|
|
ptr := buffer
|
|
for i, ack := range kcp.acklist {
|
|
size := len(buffer) - len(ptr)
|
|
if size+IKCP_OVERHEAD > int(kcp.mtu) {
|
|
kcp.output(buffer, size)
|
|
ptr = buffer
|
|
}
|
|
// filter jitters caused by bufferbloat
|
|
if ack.sn >= kcp.rcv_nxt || len(kcp.acklist)-1 == i {
|
|
seg.sn, seg.ts = ack.sn, ack.ts
|
|
ptr = seg.encode(ptr)
|
|
}
|
|
}
|
|
kcp.acklist = kcp.acklist[0:0]
|
|
|
|
if ackOnly { // flash remain ack segments
|
|
size := len(buffer) - len(ptr)
|
|
if size > 0 {
|
|
kcp.output(buffer, size)
|
|
}
|
|
return
|
|
}
|
|
|
|
// probe window size (if remote window size equals zero)
|
|
if kcp.rmt_wnd == 0 {
|
|
current := currentMs()
|
|
if kcp.probe_wait == 0 {
|
|
kcp.probe_wait = IKCP_PROBE_INIT
|
|
kcp.ts_probe = current + kcp.probe_wait
|
|
} else {
|
|
if _itimediff(current, kcp.ts_probe) >= 0 {
|
|
if kcp.probe_wait < IKCP_PROBE_INIT {
|
|
kcp.probe_wait = IKCP_PROBE_INIT
|
|
}
|
|
kcp.probe_wait += kcp.probe_wait / 2
|
|
if kcp.probe_wait > IKCP_PROBE_LIMIT {
|
|
kcp.probe_wait = IKCP_PROBE_LIMIT
|
|
}
|
|
kcp.ts_probe = 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_wnd, kcp.rmt_wnd)
|
|
if kcp.nocwnd == 0 {
|
|
cwnd = _imin_(kcp.cwnd, cwnd)
|
|
}
|
|
|
|
// sliding window, controlled by snd_nxt && sna_una+cwnd
|
|
newSegsCount := 0
|
|
for k := range kcp.snd_queue {
|
|
if _itimediff(kcp.snd_nxt, kcp.snd_una+cwnd) >= 0 {
|
|
break
|
|
}
|
|
newseg := kcp.snd_queue[k]
|
|
newseg.conv = kcp.conv
|
|
newseg.cmd = IKCP_CMD_PUSH
|
|
newseg.sn = kcp.snd_nxt
|
|
kcp.snd_buf = append(kcp.snd_buf, newseg)
|
|
kcp.snd_nxt++
|
|
newSegsCount++
|
|
kcp.snd_queue[k].data = nil
|
|
}
|
|
if newSegsCount > 0 {
|
|
kcp.snd_queue = kcp.remove_front(kcp.snd_queue, newSegsCount)
|
|
}
|
|
|
|
// calculate resent
|
|
resent := uint32(kcp.fastresend)
|
|
if kcp.fastresend <= 0 {
|
|
resent = 0xffffffff
|
|
}
|
|
|
|
// check for retransmissions
|
|
current := currentMs()
|
|
var change, lost, lostSegs, fastRetransSegs, earlyRetransSegs uint64
|
|
for k := range kcp.snd_buf {
|
|
segment := &kcp.snd_buf[k]
|
|
needsend := false
|
|
if segment.xmit == 0 { // initial transmit
|
|
needsend = true
|
|
segment.rto = kcp.rx_rto
|
|
segment.resendts = current + segment.rto
|
|
} else if _itimediff(current, segment.resendts) >= 0 { // RTO
|
|
needsend = true
|
|
if kcp.nodelay == 0 {
|
|
segment.rto += kcp.rx_rto
|
|
} else {
|
|
segment.rto += kcp.rx_rto / 2
|
|
}
|
|
segment.resendts = current + segment.rto
|
|
lost++
|
|
lostSegs++
|
|
} else if segment.fastack >= resent { // fast retransmit
|
|
needsend = true
|
|
segment.fastack = 0
|
|
segment.rto = kcp.rx_rto
|
|
segment.resendts = current + segment.rto
|
|
change++
|
|
fastRetransSegs++
|
|
} else if segment.fastack > 0 && newSegsCount == 0 { // early retransmit
|
|
needsend = true
|
|
segment.fastack = 0
|
|
segment.rto = kcp.rx_rto
|
|
segment.resendts = current + segment.rto
|
|
change++
|
|
earlyRetransSegs++
|
|
}
|
|
|
|
if needsend {
|
|
segment.xmit++
|
|
segment.ts = current
|
|
segment.wnd = seg.wnd
|
|
segment.una = seg.una
|
|
|
|
size := len(buffer) - len(ptr)
|
|
need := IKCP_OVERHEAD + len(segment.data)
|
|
|
|
if size+need > int(kcp.mtu) {
|
|
kcp.output(buffer, size)
|
|
current = currentMs() // time update for a blocking call
|
|
ptr = buffer
|
|
}
|
|
|
|
ptr = segment.encode(ptr)
|
|
copy(ptr, segment.data)
|
|
ptr = ptr[len(segment.data):]
|
|
|
|
if segment.xmit >= kcp.dead_link {
|
|
kcp.state = 0xFFFFFFFF
|
|
}
|
|
}
|
|
}
|
|
|
|
// flash remain segments
|
|
size := len(buffer) - len(ptr)
|
|
if size > 0 {
|
|
kcp.output(buffer, size)
|
|
}
|
|
|
|
// counter updates
|
|
sum := lostSegs
|
|
if lostSegs > 0 {
|
|
atomic.AddUint64(&DefaultSnmp.LostSegs, lostSegs)
|
|
}
|
|
if fastRetransSegs > 0 {
|
|
atomic.AddUint64(&DefaultSnmp.FastRetransSegs, fastRetransSegs)
|
|
sum += fastRetransSegs
|
|
}
|
|
if earlyRetransSegs > 0 {
|
|
atomic.AddUint64(&DefaultSnmp.EarlyRetransSegs, earlyRetransSegs)
|
|
sum += earlyRetransSegs
|
|
}
|
|
if sum > 0 {
|
|
atomic.AddUint64(&DefaultSnmp.RetransSegs, sum)
|
|
}
|
|
|
|
// 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 > 0 {
|
|
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() {
|
|
var slap int32
|
|
|
|
current := currentMs()
|
|
if kcp.updated == 0 {
|
|
kcp.updated = 1
|
|
kcp.ts_flush = current
|
|
}
|
|
|
|
slap = _itimediff(current, kcp.ts_flush)
|
|
|
|
if slap >= 10000 || slap < -10000 {
|
|
kcp.ts_flush = current
|
|
slap = 0
|
|
}
|
|
|
|
if slap >= 0 {
|
|
kcp.ts_flush += kcp.interval
|
|
if _itimediff(current, kcp.ts_flush) >= 0 {
|
|
kcp.ts_flush = current + kcp.interval
|
|
}
|
|
kcp.flush(false)
|
|
}
|
|
}
|
|
|
|
// 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() uint32 {
|
|
current := currentMs()
|
|
ts_flush := kcp.ts_flush
|
|
tm_flush := int32(0x7fffffff)
|
|
tm_packet := int32(0x7fffffff)
|
|
minimal := uint32(0)
|
|
if kcp.updated == 0 {
|
|
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 k := range kcp.snd_buf {
|
|
seg := &kcp.snd_buf[k]
|
|
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
|
|
}
|
|
|
|
// SetMtu changes MTU size, default is 1400
|
|
func (kcp *KCP) SetMtu(mtu int) int {
|
|
if mtu < 50 || mtu < IKCP_OVERHEAD {
|
|
return -1
|
|
}
|
|
buffer := make([]byte, (mtu+IKCP_OVERHEAD)*3)
|
|
if buffer == nil {
|
|
return -2
|
|
}
|
|
kcp.mtu = uint32(mtu)
|
|
kcp.mss = kcp.mtu - IKCP_OVERHEAD
|
|
kcp.buffer = buffer
|
|
return 0
|
|
}
|
|
|
|
// 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(nodelay, interval, resend, nc int) int {
|
|
if nodelay >= 0 {
|
|
kcp.nodelay = uint32(nodelay)
|
|
if nodelay != 0 {
|
|
kcp.rx_minrto = IKCP_RTO_NDL
|
|
} else {
|
|
kcp.rx_minrto = IKCP_RTO_MIN
|
|
}
|
|
}
|
|
if interval >= 0 {
|
|
if interval > 5000 {
|
|
interval = 5000
|
|
} else if interval < 10 {
|
|
interval = 10
|
|
}
|
|
kcp.interval = uint32(interval)
|
|
}
|
|
if resend >= 0 {
|
|
kcp.fastresend = int32(resend)
|
|
}
|
|
if nc >= 0 {
|
|
kcp.nocwnd = int32(nc)
|
|
}
|
|
return 0
|
|
}
|
|
|
|
// WndSize sets maximum window size: sndwnd=32, rcvwnd=32 by default
|
|
func (kcp *KCP) WndSize(sndwnd, rcvwnd int) int {
|
|
if sndwnd > 0 {
|
|
kcp.snd_wnd = uint32(sndwnd)
|
|
}
|
|
if rcvwnd > 0 {
|
|
kcp.rcv_wnd = uint32(rcvwnd)
|
|
}
|
|
return 0
|
|
}
|
|
|
|
// WaitSnd gets how many packet is waiting to be sent
|
|
func (kcp *KCP) WaitSnd() int {
|
|
return len(kcp.snd_buf) + len(kcp.snd_queue)
|
|
}
|
|
|
|
// remove front n elements from queue
|
|
func (kcp *KCP) remove_front(q []segment, n int) []segment {
|
|
newn := copy(q, q[n:])
|
|
for i := newn; i < len(q); i++ {
|
|
q[i] = segment{} // manual set nil for GC
|
|
}
|
|
return q[:newn]
|
|
}
|