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- // Kcp based on https://github.com/skywind3000/kcp
- // Kept as close to original as possible.
- using System;
- using System.Collections.Generic;
- namespace kcp2k
- {
- public class Kcp
- {
- // original Kcp has a define option, which is not defined by default:
- // #define FASTACK_CONSERVE
- public const int RTO_NDL = 30; // no delay min rto
- public const int RTO_MIN = 100; // normal min rto
- public const int RTO_DEF = 200; // default RTO
- public const int RTO_MAX = 60000; // maximum RTO
- public const int CMD_PUSH = 81; // cmd: push data
- public const int CMD_ACK = 82; // cmd: ack
- public const int CMD_WASK = 83; // cmd: window probe (ask)
- public const int CMD_WINS = 84; // cmd: window size (tell)
- public const int ASK_SEND = 1; // need to send CMD_WASK
- public const int ASK_TELL = 2; // need to send CMD_WINS
- public const int WND_SND = 32; // default send window
- public const int WND_RCV = 128; // default receive window. must be >= max fragment size
- public const int MTU_DEF = 1200; // default MTU (reduced to 1200 to fit all cases: https://en.wikipedia.org/wiki/Maximum_transmission_unit ; steam uses 1200 too!)
- public const int ACK_FAST = 3;
- public const int INTERVAL = 100;
- public const int OVERHEAD = 24;
- public const int DEADLINK = 20;
- public const int THRESH_INIT = 2;
- public const int THRESH_MIN = 2;
- public const int PROBE_INIT = 7000; // 7 secs to probe window size
- public const int PROBE_LIMIT = 120000; // up to 120 secs to probe window
- public const int FASTACK_LIMIT = 5; // max times to trigger fastack
- internal struct AckItem
- {
- internal uint serialNumber;
- internal uint timestamp;
- }
- // kcp members.
- internal int state;
- readonly uint conv; // conversation
- internal uint mtu;
- internal uint mss; // maximum segment size := MTU - OVERHEAD
- internal uint snd_una; // unacknowledged. e.g. snd_una is 9 it means 8 has been confirmed, 9 and 10 have been sent
- internal uint snd_nxt;
- internal uint rcv_nxt;
- internal uint ssthresh; // slow start threshold
- internal int rx_rttval; // average deviation of rtt, used to measure the jitter of rtt
- internal int rx_srtt; // smoothed round trip time (a weighted average of rtt)
- internal int rx_rto;
- internal int rx_minrto;
- internal uint snd_wnd; // send window
- internal uint rcv_wnd; // receive window
- internal uint rmt_wnd; // remote window
- internal uint cwnd; // congestion window
- internal uint probe;
- internal uint interval;
- internal uint ts_flush;
- internal uint xmit;
- internal uint nodelay; // not a bool. original Kcp has '<2 else' check.
- internal bool updated;
- internal uint ts_probe; // timestamp probe
- internal uint probe_wait;
- internal uint dead_link;
- internal uint incr;
- internal uint current; // current time (milliseconds). set by Update.
- internal int fastresend;
- internal int fastlimit;
- internal bool nocwnd; // no congestion window
- internal readonly Queue<Segment> snd_queue = new Queue<Segment>(16); // send queue
- internal readonly Queue<Segment> rcv_queue = new Queue<Segment>(16); // receive queue
- // snd_buffer needs index removals.
- // C# LinkedList allocates for each entry, so let's keep List for now.
- internal readonly List<Segment> snd_buf = new List<Segment>(16); // send buffer
- // rcv_buffer needs index insertions and backwards iteration.
- // C# LinkedList allocates for each entry, so let's keep List for now.
- internal readonly List<Segment> rcv_buf = new List<Segment>(16); // receive buffer
- internal readonly List<AckItem> acklist = new List<AckItem>(16);
- internal byte[] buffer;
- readonly Action<byte[], int> output; // buffer, size
- // get how many packet is waiting to be sent
- public int WaitSnd => snd_buf.Count + snd_queue.Count;
- // segment pool to avoid allocations in C#.
- // this is not part of the original C code.
- readonly Pool<Segment> SegmentPool = new Pool<Segment>(
- // create new segment
- () => new Segment(),
- // reset segment before reuse
- (segment) => segment.Reset(),
- // initial capacity
- 32
- );
- // ikcp_create
- // create a new kcp control object, 'conv' must equal in two endpoint
- // from the same connection.
- public Kcp(uint conv, Action<byte[], int> output)
- {
- this.conv = conv;
- this.output = output;
- snd_wnd = WND_SND;
- rcv_wnd = WND_RCV;
- rmt_wnd = WND_RCV;
- mtu = MTU_DEF;
- mss = mtu - OVERHEAD;
- rx_rto = RTO_DEF;
- rx_minrto = RTO_MIN;
- interval = INTERVAL;
- ts_flush = INTERVAL;
- ssthresh = THRESH_INIT;
- fastlimit = FASTACK_LIMIT;
- dead_link = DEADLINK;
- buffer = new byte[(mtu + OVERHEAD) * 3];
- }
- // ikcp_segment_new
- // we keep the original function and add our pooling to it.
- // this way we'll never miss it anywhere.
- Segment SegmentNew() => SegmentPool.Take();
- // ikcp_segment_delete
- // we keep the original function and add our pooling to it.
- // this way we'll never miss it anywhere.
- void SegmentDelete(Segment seg) => SegmentPool.Return(seg);
- // ikcp_recv
- // receive data from kcp state machine
- // returns number of bytes read.
- // returns negative on error.
- // note: pass negative length to peek.
- public int Receive(byte[] buffer, int len)
- {
- // kcp's ispeek feature is not supported.
- // this makes 'merge fragment' code significantly easier because
- // we can iterate while queue.Count > 0 and dequeue each time.
- // if we had to consider ispeek then count would always be > 0 and
- // we would have to remove only after the loop.
- //
- //bool ispeek = len < 0;
- if (len < 0)
- throw new NotSupportedException("Receive ispeek for negative len is not supported!");
- if (rcv_queue.Count == 0)
- return -1;
- if (len < 0) len = -len;
- int peeksize = PeekSize();
- if (peeksize < 0)
- return -2;
- if (peeksize > len)
- return -3;
- bool recover = rcv_queue.Count >= rcv_wnd;
- // merge fragment.
- int offset = 0;
- len = 0;
- // original KCP iterates rcv_queue and deletes if !ispeek.
- // removing from a c# queue while iterating is not possible, but
- // we can change to 'while Count > 0' and remove every time.
- // (we can remove every time because we removed ispeek support!)
- while (rcv_queue.Count > 0)
- {
- // unlike original kcp, we dequeue instead of just getting the
- // entry. this is fine because we remove it in ANY case.
- Segment seg = rcv_queue.Dequeue();
- Buffer.BlockCopy(seg.data.GetBuffer(), 0, buffer, offset, (int)seg.data.Position);
- offset += (int)seg.data.Position;
- len += (int)seg.data.Position;
- uint fragment = seg.frg;
- // note: ispeek is not supported in order to simplify this loop
- // unlike original kcp, we don't need to remove seg from queue
- // because we already dequeued it.
- // simply delete it
- SegmentDelete(seg);
- if (fragment == 0)
- break;
- }
- // move available data from rcv_buf -> rcv_queue
- int removed = 0;
- foreach (Segment seg in rcv_buf)
- {
- if (seg.sn == rcv_nxt && rcv_queue.Count < rcv_wnd)
- {
- // can't remove while iterating. remember how many to remove
- // and do it after the loop.
- // note: don't return segment. we only add it to rcv_queue
- ++removed;
- // add
- rcv_queue.Enqueue(seg);
- rcv_nxt++;
- }
- else
- {
- break;
- }
- }
- rcv_buf.RemoveRange(0, removed);
- // fast recover
- if (rcv_queue.Count < rcv_wnd && recover)
- {
- // ready to send back CMD_WINS in flush
- // tell remote my window size
- probe |= ASK_TELL;
- }
- return len;
- }
- // ikcp_peeksize
- // check the size of next message in the recv queue
- public int PeekSize()
- {
- int length = 0;
- if (rcv_queue.Count == 0) return -1;
- Segment seq = rcv_queue.Peek();
- if (seq.frg == 0) return (int)seq.data.Position;
- if (rcv_queue.Count < seq.frg + 1) return -1;
- foreach (Segment seg in rcv_queue)
- {
- length += (int)seg.data.Position;
- if (seg.frg == 0) break;
- }
- return length;
- }
- // ikcp_send
- // sends byte[] to the other end.
- public int Send(byte[] buffer, int offset, int len)
- {
- // fragment count
- int count;
- if (len < 0) return -1;
- // streaming mode: removed. we never want to send 'hello' and
- // receive 'he' 'll' 'o'. we want to always receive 'hello'.
- // calculate amount of fragments necessary for 'len'
- if (len <= mss) count = 1;
- else count = (int)((len + mss - 1) / mss);
- // original kcp uses WND_RCV const even though rcv_wnd is the
- // runtime variable. may or may not be correct, see also:
- // see also: https://github.com/skywind3000/kcp/pull/291/files
- if (count >= WND_RCV) return -2;
- if (count == 0) count = 1;
- // fragment
- for (int i = 0; i < count; i++)
- {
- int size = len > (int)mss ? (int)mss : len;
- Segment seg = SegmentNew();
- if (len > 0)
- {
- seg.data.Write(buffer, offset, size);
- }
- // seg.len = size: WriteBytes sets segment.Position!
- seg.frg = (byte)(count - i - 1);
- snd_queue.Enqueue(seg);
- offset += size;
- len -= size;
- }
- return 0;
- }
- // ikcp_update_ack
- void UpdateAck(int rtt) // round trip time
- {
- // https://tools.ietf.org/html/rfc6298
- if (rx_srtt == 0)
- {
- rx_srtt = rtt;
- rx_rttval = rtt / 2;
- }
- else
- {
- int delta = rtt - rx_srtt;
- if (delta < 0) delta = -delta;
- rx_rttval = (3 * rx_rttval + delta) / 4;
- rx_srtt = (7 * rx_srtt + rtt) / 8;
- if (rx_srtt < 1) rx_srtt = 1;
- }
- int rto = rx_srtt + Math.Max((int)interval, 4 * rx_rttval);
- rx_rto = Utils.Clamp(rto, rx_minrto, RTO_MAX);
- }
- // ikcp_shrink_buf
- internal void ShrinkBuf()
- {
- if (snd_buf.Count > 0)
- {
- Segment seg = snd_buf[0];
- snd_una = seg.sn;
- }
- else
- {
- snd_una = snd_nxt;
- }
- }
- // ikcp_parse_ack
- // removes the segment with 'sn' from send buffer
- internal void ParseAck(uint sn)
- {
- if (Utils.TimeDiff(sn, snd_una) < 0 || Utils.TimeDiff(sn, snd_nxt) >= 0)
- return;
- // for-int so we can erase while iterating
- for (int i = 0; i < snd_buf.Count; ++i)
- {
- Segment seg = snd_buf[i];
- if (sn == seg.sn)
- {
- snd_buf.RemoveAt(i);
- SegmentDelete(seg);
- break;
- }
- if (Utils.TimeDiff(sn, seg.sn) < 0)
- {
- break;
- }
- }
- }
- // ikcp_parse_una
- void ParseUna(uint una)
- {
- int removed = 0;
- foreach (Segment seg in snd_buf)
- {
- if (Utils.TimeDiff(una, seg.sn) > 0)
- {
- // can't remove while iterating. remember how many to remove
- // and do it after the loop.
- ++removed;
- SegmentDelete(seg);
- }
- else
- {
- break;
- }
- }
- snd_buf.RemoveRange(0, removed);
- }
- // ikcp_parse_fastack
- void ParseFastack(uint sn, uint ts)
- {
- if (Utils.TimeDiff(sn, snd_una) < 0 || Utils.TimeDiff(sn, snd_nxt) >= 0)
- return;
- foreach (Segment seg in snd_buf)
- {
- if (Utils.TimeDiff(sn, seg.sn) < 0)
- {
- break;
- }
- else if (sn != seg.sn)
- {
- #if !FASTACK_CONSERVE
- seg.fastack++;
- #else
- if (Utils.TimeDiff(ts, seg.ts) >= 0)
- seg.fastack++;
- #endif
- }
- }
- }
- // ikcp_ack_push
- // appends an ack.
- void AckPush(uint sn, uint ts)
- {
- acklist.Add(new AckItem{ serialNumber = sn, timestamp = ts });
- }
- // ikcp_parse_data
- void ParseData(Segment newseg)
- {
- uint sn = newseg.sn;
- if (Utils.TimeDiff(sn, rcv_nxt + rcv_wnd) >= 0 ||
- Utils.TimeDiff(sn, rcv_nxt) < 0)
- {
- SegmentDelete(newseg);
- return;
- }
- InsertSegmentInReceiveBuffer(newseg);
- MoveReceiveBufferDataToReceiveQueue();
- }
- // inserts the segment into rcv_buf, ordered by seg.sn.
- // drops the segment if one with the same seg.sn already exists.
- // goes through receive buffer in reverse order for performance.
- //
- // note: see KcpTests.InsertSegmentInReceiveBuffer test!
- // note: 'insert or delete' can be done in different ways, but let's
- // keep consistency with original C kcp.
- internal void InsertSegmentInReceiveBuffer(Segment newseg)
- {
- bool repeat = false; // 'duplicate'
- // original C iterates backwards, so we need to do that as well.
- int i;
- for (i = rcv_buf.Count - 1; i >= 0; i--)
- {
- Segment seg = rcv_buf[i];
- if (seg.sn == newseg.sn)
- {
- // duplicate segment found. nothing will be added.
- repeat = true;
- break;
- }
- if (Utils.TimeDiff(newseg.sn, seg.sn) > 0)
- {
- // this entry's sn is < newseg.sn, so let's stop
- break;
- }
- }
- // no duplicate? then insert.
- if (!repeat)
- {
- rcv_buf.Insert(i + 1, newseg);
- }
- // duplicate. just delete it.
- else
- {
- SegmentDelete(newseg);
- }
- }
- // move available data from rcv_buf -> rcv_queue
- void MoveReceiveBufferDataToReceiveQueue()
- {
- int removed = 0;
- foreach (Segment seg in rcv_buf)
- {
- if (seg.sn == rcv_nxt && rcv_queue.Count < rcv_wnd)
- {
- // can't remove while iterating. remember how many to remove
- // and do it after the loop.
- ++removed;
- rcv_queue.Enqueue(seg);
- rcv_nxt++;
- }
- else
- {
- break;
- }
- }
- rcv_buf.RemoveRange(0, removed);
- }
- // ikcp_input
- // used when you receive a low level packet (e.g. UDP packet)
- // => original kcp uses offset=0, we made it a parameter so that high
- // level can skip the channel byte more easily
- public int Input(byte[] data, int offset, int size)
- {
- uint prev_una = snd_una;
- uint maxack = 0;
- uint latest_ts = 0;
- int flag = 0;
- if (data == null || size < OVERHEAD) return -1;
- while (true)
- {
- uint ts = 0;
- uint sn = 0;
- uint len = 0;
- uint una = 0;
- uint conv_ = 0;
- ushort wnd = 0;
- byte cmd = 0;
- byte frg = 0;
- // enough data left to decode segment (aka OVERHEAD bytes)?
- if (size < OVERHEAD) break;
- // decode segment
- offset += Utils.Decode32U(data, offset, ref conv_);
- if (conv_ != conv) return -1;
- offset += Utils.Decode8u(data, offset, ref cmd);
- offset += Utils.Decode8u(data, offset, ref frg);
- offset += Utils.Decode16U(data, offset, ref wnd);
- offset += Utils.Decode32U(data, offset, ref ts);
- offset += Utils.Decode32U(data, offset, ref sn);
- offset += Utils.Decode32U(data, offset, ref una);
- offset += Utils.Decode32U(data, offset, ref len);
- // subtract the segment bytes from size
- size -= OVERHEAD;
- // enough remaining to read 'len' bytes of the actual payload?
- if (size < len || len < 0) return -2;
- if (cmd != CMD_PUSH && cmd != CMD_ACK &&
- cmd != CMD_WASK && cmd != CMD_WINS)
- return -3;
- rmt_wnd = wnd;
- ParseUna(una);
- ShrinkBuf();
- if (cmd == CMD_ACK)
- {
- if (Utils.TimeDiff(current, ts) >= 0)
- {
- UpdateAck(Utils.TimeDiff(current, ts));
- }
- ParseAck(sn);
- ShrinkBuf();
- if (flag == 0)
- {
- flag = 1;
- maxack = sn;
- latest_ts = ts;
- }
- else
- {
- if (Utils.TimeDiff(sn, maxack) > 0)
- {
- #if !FASTACK_CONSERVE
- maxack = sn;
- latest_ts = ts;
- #else
- if (Utils.TimeDiff(ts, latest_ts) > 0)
- {
- maxack = sn;
- latest_ts = ts;
- }
- #endif
- }
- }
- }
- else if (cmd == CMD_PUSH)
- {
- if (Utils.TimeDiff(sn, rcv_nxt + rcv_wnd) < 0)
- {
- AckPush(sn, ts);
- if (Utils.TimeDiff(sn, rcv_nxt) >= 0)
- {
- Segment seg = SegmentNew();
- seg.conv = conv_;
- seg.cmd = cmd;
- seg.frg = frg;
- seg.wnd = wnd;
- seg.ts = ts;
- seg.sn = sn;
- seg.una = una;
- if (len > 0)
- {
- seg.data.Write(data, offset, (int)len);
- }
- ParseData(seg);
- }
- }
- }
- else if (cmd == CMD_WASK)
- {
- // ready to send back CMD_WINS in flush
- // tell remote my window size
- probe |= ASK_TELL;
- }
- else if (cmd == CMD_WINS)
- {
- // do nothing
- }
- else
- {
- return -3;
- }
- offset += (int)len;
- size -= (int)len;
- }
- if (flag != 0)
- {
- ParseFastack(maxack, latest_ts);
- }
- // cwnd update when packet arrived
- if (Utils.TimeDiff(snd_una, prev_una) > 0)
- {
- if (cwnd < rmt_wnd)
- {
- if (cwnd < ssthresh)
- {
- cwnd++;
- incr += mss;
- }
- else
- {
- if (incr < mss) incr = mss;
- incr += (mss * mss) / incr + (mss / 16);
- if ((cwnd + 1) * mss <= incr)
- {
- cwnd = (incr + mss - 1) / ((mss > 0) ? mss : 1);
- }
- }
- if (cwnd > rmt_wnd)
- {
- cwnd = rmt_wnd;
- incr = rmt_wnd * mss;
- }
- }
- }
- return 0;
- }
- // ikcp_wnd_unused
- uint WndUnused()
- {
- if (rcv_queue.Count < rcv_wnd)
- return rcv_wnd - (uint)rcv_queue.Count;
- return 0;
- }
- // ikcp_flush
- // flush remain ack segments
- public void Flush()
- {
- int offset = 0; // buffer ptr in original C
- bool lost = false; // lost segments
- // helper functions
- void MakeSpace(int space)
- {
- if (offset + space > mtu)
- {
- output(buffer, offset);
- offset = 0;
- }
- }
- void FlushBuffer()
- {
- if (offset > 0)
- {
- output(buffer, offset);
- }
- }
- // 'ikcp_update' haven't been called.
- if (!updated) return;
- // kcp only stack allocates a segment here for performance, leaving
- // its data buffer null because this segment's data buffer is never
- // used. that's fine in C, but in C# our segment is class so we need
- // to allocate and most importantly, not forget to deallocate it
- // before returning.
- Segment seg = SegmentNew();
- seg.conv = conv;
- seg.cmd = CMD_ACK;
- seg.wnd = WndUnused();
- seg.una = rcv_nxt;
- // flush acknowledges
- foreach (AckItem ack in acklist)
- {
- MakeSpace(OVERHEAD);
- // ikcp_ack_get assigns ack[i] to seg.sn, seg.ts
- seg.sn = ack.serialNumber;
- seg.ts = ack.timestamp;
- offset += seg.Encode(buffer, offset);
- }
- acklist.Clear();
- // probe window size (if remote window size equals zero)
- if (rmt_wnd == 0)
- {
- if (probe_wait == 0)
- {
- probe_wait = PROBE_INIT;
- ts_probe = current + probe_wait;
- }
- else
- {
- if (Utils.TimeDiff(current, ts_probe) >= 0)
- {
- if (probe_wait < PROBE_INIT)
- probe_wait = PROBE_INIT;
- probe_wait += probe_wait / 2;
- if (probe_wait > PROBE_LIMIT)
- probe_wait = PROBE_LIMIT;
- ts_probe = current + probe_wait;
- probe |= ASK_SEND;
- }
- }
- }
- else
- {
- ts_probe = 0;
- probe_wait = 0;
- }
- // flush window probing commands
- if ((probe & ASK_SEND) != 0)
- {
- seg.cmd = CMD_WASK;
- MakeSpace(OVERHEAD);
- offset += seg.Encode(buffer, offset);
- }
- // flush window probing commands
- if ((probe & ASK_TELL) != 0)
- {
- seg.cmd = CMD_WINS;
- MakeSpace(OVERHEAD);
- offset += seg.Encode(buffer, offset);
- }
- probe = 0;
- // calculate window size
- uint cwnd_ = Math.Min(snd_wnd, rmt_wnd);
- // if congestion window:
- if (!nocwnd) cwnd_ = Math.Min(cwnd, cwnd_);
- // move data from snd_queue to snd_buf
- // sliding window, controlled by snd_nxt && sna_una+cwnd
- //
- // ELI5: 'snd_nxt' is what we want to send.
- // 'snd_una' is what hasn't been acked yet.
- // copy up to 'cwnd_' difference between them (sliding window)
- while (Utils.TimeDiff(snd_nxt, snd_una + cwnd_) < 0)
- {
- if (snd_queue.Count == 0) break;
- Segment newseg = snd_queue.Dequeue();
- newseg.conv = conv;
- newseg.cmd = CMD_PUSH;
- newseg.wnd = seg.wnd;
- newseg.ts = current;
- newseg.sn = snd_nxt++;
- newseg.una = rcv_nxt;
- newseg.resendts = current;
- newseg.rto = rx_rto;
- newseg.fastack = 0;
- newseg.xmit = 0;
- snd_buf.Add(newseg);
- }
- // calculate resent
- uint resent = fastresend > 0 ? (uint)fastresend : 0xffffffff;
- uint rtomin = nodelay == 0 ? (uint)rx_rto >> 3 : 0;
- // flush data segments
- int change = 0;
- foreach (Segment segment in snd_buf)
- {
- bool needsend = false;
- // initial transmit
- if (segment.xmit == 0)
- {
- needsend = true;
- segment.xmit++;
- segment.rto = rx_rto;
- segment.resendts = current + (uint)segment.rto + rtomin;
- }
- // RTO
- else if (Utils.TimeDiff(current, segment.resendts) >= 0)
- {
- needsend = true;
- segment.xmit++;
- xmit++;
- if (nodelay == 0)
- {
- segment.rto += Math.Max(segment.rto, rx_rto);
- }
- else
- {
- int step = (nodelay < 2) ? segment.rto : rx_rto;
- segment.rto += step / 2;
- }
- segment.resendts = current + (uint)segment.rto;
- lost = true;
- }
- // fast retransmit
- else if (segment.fastack >= resent)
- {
- if (segment.xmit <= fastlimit || fastlimit <= 0)
- {
- needsend = true;
- segment.xmit++;
- segment.fastack = 0;
- segment.resendts = current + (uint)segment.rto;
- change++;
- }
- }
- if (needsend)
- {
- segment.ts = current;
- segment.wnd = seg.wnd;
- segment.una = rcv_nxt;
- int need = OVERHEAD + (int)segment.data.Position;
- MakeSpace(need);
- offset += segment.Encode(buffer, offset);
- if (segment.data.Position > 0)
- {
- Buffer.BlockCopy(segment.data.GetBuffer(), 0, buffer, offset, (int)segment.data.Position);
- offset += (int)segment.data.Position;
- }
- if (segment.xmit >= dead_link)
- {
- state = -1;
- }
- }
- }
- // kcp stackallocs 'seg'. our C# segment is a class though, so we
- // need to properly delete and return it to the pool now that we are
- // done with it.
- SegmentDelete(seg);
- // flash remain segments
- FlushBuffer();
- // update ssthresh
- // rate halving, https://tools.ietf.org/html/rfc6937
- if (change > 0)
- {
- uint inflight = snd_nxt - snd_una;
- ssthresh = inflight / 2;
- if (ssthresh < THRESH_MIN)
- ssthresh = THRESH_MIN;
- cwnd = ssthresh + resent;
- incr = cwnd * mss;
- }
- // congestion control, https://tools.ietf.org/html/rfc5681
- if (lost)
- {
- // original C uses 'cwnd', not kcp->cwnd!
- ssthresh = cwnd_ / 2;
- if (ssthresh < THRESH_MIN)
- ssthresh = THRESH_MIN;
- cwnd = 1;
- incr = mss;
- }
- if (cwnd < 1)
- {
- cwnd = 1;
- incr = mss;
- }
- }
- // ikcp_update
- // update state (call it repeatedly, every 10ms-100ms), or you can ask
- // Check() when to call it again (without Input/Send calling).
- //
- // 'current' - current timestamp in millisec. pass it to Kcp so that
- // Kcp doesn't have to do any stopwatch/deltaTime/etc. code
- public void Update(uint currentTimeMilliSeconds)
- {
- current = currentTimeMilliSeconds;
- if (!updated)
- {
- updated = true;
- ts_flush = current;
- }
- int slap = Utils.TimeDiff(current, ts_flush);
- if (slap >= 10000 || slap < -10000)
- {
- ts_flush = current;
- slap = 0;
- }
- if (slap >= 0)
- {
- ts_flush += interval;
- if (Utils.TimeDiff(current, ts_flush) >= 0)
- {
- ts_flush = current + interval;
- }
- Flush();
- }
- }
- // ikcp_check
- // Determine when should you invoke update
- // Returns when you should invoke update in millisec, if there is no
- // input/send calling. you can call update in that time, instead of
- // call update repeatly.
- //
- // Important to reduce unnecessary update invoking. use it to schedule
- // update (e.g. implementing an epoll-like mechanism, or optimize update
- // when handling massive kcp connections).
- public uint Check(uint current_)
- {
- uint ts_flush_ = ts_flush;
- int tm_flush = 0x7fffffff;
- int tm_packet = 0x7fffffff;
- if (!updated)
- {
- return current_;
- }
- if (Utils.TimeDiff(current_, ts_flush_) >= 10000 ||
- Utils.TimeDiff(current_, ts_flush_) < -10000)
- {
- ts_flush_ = current_;
- }
- if (Utils.TimeDiff(current_, ts_flush_) >= 0)
- {
- return current_;
- }
- tm_flush = Utils.TimeDiff(ts_flush_, current_);
- foreach (Segment seg in snd_buf)
- {
- int diff = Utils.TimeDiff(seg.resendts, current_);
- if (diff <= 0)
- {
- return current_;
- }
- if (diff < tm_packet) tm_packet = diff;
- }
- uint minimal = (uint)(tm_packet < tm_flush ? tm_packet : tm_flush);
- if (minimal >= interval) minimal = interval;
- return current_ + minimal;
- }
- // ikcp_setmtu
- // Change MTU (Maximum Transmission Unit) size.
- public void SetMtu(uint mtu)
- {
- if (mtu < 50 || mtu < OVERHEAD)
- throw new ArgumentException("MTU must be higher than 50 and higher than OVERHEAD");
- buffer = new byte[(mtu + OVERHEAD) * 3];
- this.mtu = mtu;
- mss = mtu - OVERHEAD;
- }
- // ikcp_interval
- public void SetInterval(uint interval)
- {
- if (interval > 5000) interval = 5000;
- else if (interval < 10) interval = 10;
- this.interval = interval;
- }
- // ikcp_nodelay
- // configuration: https://github.com/skywind3000/kcp/blob/master/README.en.md#protocol-configuration
- // nodelay : Whether nodelay mode is enabled, 0 is not enabled; 1 enabled.
- // interval :Protocol internal work interval, in milliseconds, such as 10 ms or 20 ms.
- // resend :Fast retransmission mode, 0 represents off by default, 2 can be set (2 ACK spans will result in direct retransmission)
- // nc :Whether to turn off flow control, 0 represents “Do not turn off” by default, 1 represents “Turn off”.
- // Normal Mode: ikcp_nodelay(kcp, 0, 40, 0, 0);
- // Turbo Mode: ikcp_nodelay(kcp, 1, 10, 2, 1);
- public void SetNoDelay(uint nodelay, uint interval = INTERVAL, int resend = 0, bool nocwnd = false)
- {
- this.nodelay = nodelay;
- if (nodelay != 0)
- {
- rx_minrto = RTO_NDL;
- }
- else
- {
- rx_minrto = RTO_MIN;
- }
- if (interval >= 0)
- {
- if (interval > 5000) interval = 5000;
- else if (interval < 10) interval = 10;
- this.interval = interval;
- }
- if (resend >= 0)
- {
- fastresend = resend;
- }
- this.nocwnd = nocwnd;
- }
- // ikcp_wndsize
- public void SetWindowSize(uint sendWindow, uint receiveWindow)
- {
- if (sendWindow > 0)
- {
- snd_wnd = sendWindow;
- }
- if (receiveWindow > 0)
- {
- // must >= max fragment size
- rcv_wnd = Math.Max(receiveWindow, WND_RCV);
- }
- }
- }
- }
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