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Kcp.java
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Kcp.java
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package io.jpower.kcp.netty;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import io.jpower.kcp.netty.internal.ReItrLinkedList;
import io.jpower.kcp.netty.internal.ReusableListIterator;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;
import io.netty.util.internal.ObjectPool;
import io.netty.util.internal.ObjectPool.Handle;
import io.netty.util.internal.logging.InternalLogger;
import io.netty.util.internal.logging.InternalLoggerFactory;
/**
* Java implementation of <a href="https://github.com/skywind3000/kcp">KCP</a>
*
* @author <a href="mailto:szhnet@gmail.com">szh</a>
*/
public class Kcp {
private static final InternalLogger log = InternalLoggerFactory.getInstance(Kcp.class);
/**
* no delay min rto
*/
public static final int IKCP_RTO_NDL = 30;
/**
* normal min rto
*/
public static final int IKCP_RTO_MIN = 100;
public static final int IKCP_RTO_DEF = 200;
public static final int IKCP_RTO_MAX = 60000;
/**
* cmd: push data
*/
public static final byte IKCP_CMD_PUSH = 81;
/**
* cmd: ack
*/
public static final byte IKCP_CMD_ACK = 82;
/**
* cmd: window probe (ask)
*/
public static final byte IKCP_CMD_WASK = 83;
/**
* cmd: window size (tell)
*/
public static final byte IKCP_CMD_WINS = 84;
/**
* need to send IKCP_CMD_WASK
*/
public static final int IKCP_ASK_SEND = 1;
/**
* need to send IKCP_CMD_WINS
*/
public static final int IKCP_ASK_TELL = 2;
public static final int IKCP_WND_SND = 32;
/**
* must >= max fragment size
*/
public static final int IKCP_WND_RCV = 128;
public static final int IKCP_MTU_DEF = 1400;
public static final int IKCP_ACK_FAST = 3;
public static final int IKCP_INTERVAL = 100;
public static final int IKCP_OVERHEAD = 24;
public static final int IKCP_DEADLINK = 20;
public static final int IKCP_THRESH_INIT = 2;
public static final int IKCP_THRESH_MIN = 2;
/**
* 7 secs to probe window size
*/
public static final int IKCP_PROBE_INIT = 7000;
/**
* up to 120 secs to probe window
*/
public static final int IKCP_PROBE_LIMIT = 120000;
/**
* max times to trigger fastack
*/
public static final int IKCP_FASTACK_LIMIT = 5;
private int conv;
private int mtu = IKCP_MTU_DEF;
private int mss = this.mtu - IKCP_OVERHEAD;
private int state;
private long sndUna;
private long sndNxt;
private long rcvNxt;
private int tsRecent;
private int tsLastack;
private int ssthresh = IKCP_THRESH_INIT;
private int rxRttvar;
private int rxSrtt;
private int rxRto = IKCP_RTO_DEF;
private int rxMinrto = IKCP_RTO_MIN;
private int sndWnd = IKCP_WND_SND;
private int rcvWnd = IKCP_WND_RCV;
private int rmtWnd = IKCP_WND_RCV;
private int cwnd;
private int probe;
private int current;
private int interval = IKCP_INTERVAL;
private int tsFlush = IKCP_INTERVAL;
private int xmit;
private int maxSegXmit;
private boolean nodelay;
private boolean updated;
private int tsProbe;
private int probeWait;
private int deadLink = IKCP_DEADLINK;
private int incr;
private LinkedList<Segment> sndQueue = new LinkedList<>();
private ReItrLinkedList<Segment> rcvQueue = new ReItrLinkedList<>();
private ReItrLinkedList<Segment> sndBuf = new ReItrLinkedList<>();
private ReItrLinkedList<Segment> rcvBuf = new ReItrLinkedList<>();
private ReusableListIterator<Segment> rcvQueueItr = rcvQueue.listIterator();
private ReusableListIterator<Segment> sndBufItr = sndBuf.listIterator();
private ReusableListIterator<Segment> rcvBufItr = rcvBuf.listIterator();
private int[] acklist = new int[8];
private int ackcount;
private Object user;
private int fastresend;
private int fastlimit = IKCP_FASTACK_LIMIT;
private boolean nocwnd;
private boolean stream;
private KcpOutput output;
private ByteBufAllocator byteBufAllocator = ByteBufAllocator.DEFAULT;
/**
* automatically set conv
*/
private boolean autoSetConv;
private KcpMetric metric = new KcpMetric(this);
private static long int2Uint(int i) {
return i & 0xFFFFFFFFL;
}
private static int ibound(int lower, int middle, int upper) {
return Math.min(Math.max(lower, middle), upper);
}
private static int itimediff(int later, int earlier) {
return later - earlier;
}
private static int itimediff(long later, long earlier) {
return (int) (later - earlier);
}
private static void output(ByteBuf data, Kcp kcp) {
if (log.isDebugEnabled()) {
log.debug("{} [RO] {} bytes", kcp, data.readableBytes());
}
if (data.readableBytes() == 0) {
return;
}
kcp.output.out(data, kcp);
}
private static int encodeSeg(ByteBuf buf, Segment seg) {
int offset = buf.writerIndex();
buf.writeIntLE(seg.conv);
buf.writeByte(seg.cmd);
buf.writeByte(seg.frg);
buf.writeShortLE(seg.wnd);
buf.writeIntLE(seg.ts);
buf.writeIntLE((int) seg.sn);
buf.writeIntLE((int) seg.una);
buf.writeIntLE(seg.data.readableBytes());
return buf.writerIndex() - offset;
}
private static class Segment {
private final Handle<Segment> recyclerHandle;
private int conv;
private byte cmd;
private short frg;
private int wnd;
private int ts;
private long sn;
private long una;
private int resendts;
private int rto;
private int fastack;
private int xmit;
private ByteBuf data;
private static final ObjectPool<Segment> RECYCLER = ObjectPool.newPool(Segment::new);
private Segment(Handle<Segment> recyclerHandle) {
this.recyclerHandle = recyclerHandle;
}
void recycle(boolean releaseBuf) {
conv = 0;
cmd = 0;
frg = 0;
wnd = 0;
ts = 0;
sn = 0;
una = 0;
resendts = 0;
rto = 0;
fastack = 0;
xmit = 0;
if (releaseBuf) {
data.release();
}
data = null;
recyclerHandle.recycle(this);
}
static Segment createSegment(ByteBufAllocator byteBufAllocator, int size) {
Segment seg = RECYCLER.get();
if (size == 0) {
seg.data = byteBufAllocator.ioBuffer(0, 0);
} else {
seg.data = byteBufAllocator.ioBuffer(size);
}
return seg;
}
static Segment createSegment(ByteBuf buf) {
Segment seg = RECYCLER.get();
seg.data = buf;
return seg;
}
}
public Kcp(int conv, KcpOutput output) {
this.conv = conv;
this.output = output;
}
public void release() {
release(sndBuf);
release(rcvBuf);
release(sndQueue);
release(rcvQueue);
}
private void release(List<Segment> segQueue) {
for (Segment seg : segQueue) {
seg.recycle(true);
}
segQueue.clear();
}
private ByteBuf tryCreateOrOutput(ByteBuf buffer, int need) {
if (buffer == null) {
buffer = createFlushByteBuf();
} else if (buffer.readableBytes() + need > mtu) {
output(buffer, this);
buffer = createFlushByteBuf();
}
return buffer;
}
private ByteBuf createFlushByteBuf() {
return byteBufAllocator.ioBuffer(this.mtu);
}
/**
* user/upper level recv: returns size, returns below zero for EAGAIN
*
* @param buf
* @return
*/
public int recv(ByteBuf buf) {
if (rcvQueue.isEmpty()) {
return -1;
}
int peekSize = peekSize();
if (peekSize < 0) {
return -2;
}
if (peekSize > buf.maxCapacity()) {
return -3;
}
boolean recover = false;
if (rcvQueue.size() >= rcvWnd) {
recover = true;
}
// merge fragment
int len = 0;
for (Iterator<Segment> itr = rcvQueueItr.rewind(); itr.hasNext(); ) {
Segment seg = itr.next();
len += seg.data.readableBytes();
buf.writeBytes(seg.data);
int fragment = seg.frg;
// log
if (log.isDebugEnabled()) {
log.debug("{} recv sn={}", this, seg.sn);
}
itr.remove();
seg.recycle(true);
if (fragment == 0) {
break;
}
}
assert len == peekSize;
// move available data from rcv_buf -> rcv_queue
moveRcvData();
// fast recover
if (rcvQueue.size() < rcvWnd && recover) {
// ready to send back IKCP_CMD_WINS in ikcp_flush
// tell remote my window size
probe |= IKCP_ASK_TELL;
}
return len;
}
public int recv(List<ByteBuf> bufList) {
if (rcvQueue.isEmpty()) {
return -1;
}
int peekSize = peekSize();
if (peekSize < 0) {
return -2;
}
boolean recover = false;
if (rcvQueue.size() >= rcvWnd) {
recover = true;
}
// merge fragment
int len = 0;
for (Iterator<Segment> itr = rcvQueueItr.rewind(); itr.hasNext(); ) {
Segment seg = itr.next();
len += seg.data.readableBytes();
bufList.add(seg.data);
int fragment = seg.frg;
// log
if (log.isDebugEnabled()) {
log.debug("{} recv sn={}", this, seg.sn);
}
itr.remove();
seg.recycle(false);
if (fragment == 0) {
break;
}
}
assert len == peekSize;
// move available data from rcv_buf -> rcv_queue
moveRcvData();
// fast recover
if (rcvQueue.size() < rcvWnd && recover) {
// ready to send back IKCP_CMD_WINS in ikcp_flush
// tell remote my window size
probe |= IKCP_ASK_TELL;
}
return len;
}
public int peekSize() {
if (rcvQueue.isEmpty()) {
return -1;
}
Segment seg = rcvQueue.peek();
if (seg.frg == 0) {
return seg.data.readableBytes();
}
if (rcvQueue.size() < seg.frg + 1) { // Some segments have not arrived yet
return -1;
}
int len = 0;
for (Iterator<Segment> itr = rcvQueueItr.rewind(); itr.hasNext(); ) {
Segment s = itr.next();
len += s.data.readableBytes();
if (s.frg == 0) {
break;
}
}
return len;
}
public boolean canRecv() {
if (rcvQueue.isEmpty()) {
return false;
}
Segment seg = rcvQueue.peek();
if (seg.frg == 0) {
return true;
}
if (rcvQueue.size() < seg.frg + 1) { // Some segments have not arrived yet
return false;
}
return true;
}
public int send(ByteBuf buf) {
assert mss > 0;
int len = buf.readableBytes();
if (len == 0) {
return -1;
}
int send = 0;
// append to previous segment in streaming mode (if possible)
if (stream) {
if (!sndQueue.isEmpty()) {
Segment last = sndQueue.peekLast();
ByteBuf lastData = last.data;
int lastLen = lastData.readableBytes();
if (lastLen < mss) {
int capacity = mss - lastLen;
int extend = len < capacity ? len : capacity;
if (lastData.maxWritableBytes() < extend) { // extend
ByteBuf newBuf = byteBufAllocator.ioBuffer(lastLen + extend);
newBuf.writeBytes(lastData);
lastData.release();
lastData = last.data = newBuf;
}
lastData.writeBytes(buf, extend);
len = buf.readableBytes();
send = extend;
if (len == 0) {
return send;
}
}
}
}
int count = 0;
if (len <= mss) {
count = 1;
} else {
count = (len + mss - 1) / mss;
}
if (!stream && count >= IKCP_WND_RCV) { // Maybe don't need the condition in stream mode
return -2;
}
if (count == 0) { // impossible
count = 1;
}
// segment
for (int i = 0; i < count; i++) {
int size = len > mss ? mss : len;
Segment seg = Segment.createSegment(buf.readRetainedSlice(size));
seg.frg = (short) (stream ? 0 : count - i - 1);
sndQueue.add(seg);
len = buf.readableBytes();
send += size;
}
return send;
}
private void updateAck(int rtt) {
if (rxSrtt == 0) {
rxSrtt = rtt;
rxRttvar = rtt / 2;
} else {
int delta = rtt - rxSrtt;
if (delta < 0) {
delta = -delta;
}
rxRttvar = (3 * rxRttvar + delta) / 4;
rxSrtt = (7 * rxSrtt + rtt) / 8;
if (rxSrtt < 1) {
rxSrtt = 1;
}
}
int rto = rxSrtt + Math.max(interval, 4 * rxRttvar);
rxRto = ibound(rxMinrto, rto, IKCP_RTO_MAX);
}
private void shrinkBuf() {
if (sndBuf.size() > 0) {
Segment seg = sndBuf.peek();
sndUna = seg.sn;
} else {
sndUna = sndNxt;
}
}
private void parseAck(long sn) {
if (itimediff(sn, sndUna) < 0 || itimediff(sn, sndNxt) >= 0) {
return;
}
for (Iterator<Segment> itr = sndBufItr.rewind(); itr.hasNext(); ) {
Segment seg = itr.next();
if (sn == seg.sn) {
itr.remove();
seg.recycle(true);
break;
}
if (itimediff(sn, seg.sn) < 0) {
break;
}
}
}
private void parseUna(long una) {
for (Iterator<Segment> itr = sndBufItr.rewind(); itr.hasNext(); ) {
Segment seg = itr.next();
if (itimediff(una, seg.sn) > 0) {
itr.remove();
seg.recycle(true);
} else {
break;
}
}
}
private void parseFastack(long sn) {
if (itimediff(sn, sndUna) < 0 || itimediff(sn, sndNxt) >= 0) {
return;
}
for (Iterator<Segment> itr = sndBufItr.rewind(); itr.hasNext(); ) {
Segment seg = itr.next();
if (itimediff(sn, seg.sn) < 0) {
break;
} else if (sn != seg.sn) {
seg.fastack++;
}
}
}
private void ackPush(long sn, int ts) {
int newSize = 2 * (ackcount + 1);
if (newSize > acklist.length) {
int newCapacity = acklist.length << 1; // double capacity
if (newCapacity < 0) {
throw new OutOfMemoryError();
}
int[] newArray = new int[newCapacity];
System.arraycopy(acklist, 0, newArray, 0, acklist.length);
this.acklist = newArray;
}
acklist[2 * ackcount] = (int) sn;
acklist[2 * ackcount + 1] = ts;
ackcount++;
}
private void parseData(Segment newSeg) {
long sn = newSeg.sn;
if (itimediff(sn, rcvNxt + rcvWnd) >= 0 || itimediff(sn, rcvNxt) < 0) {
newSeg.recycle(true);
return;
}
boolean repeat = false;
boolean findPos = false;
ListIterator<Segment> listItr = null;
if (rcvBuf.size() > 0) {
listItr = rcvBufItr.rewind(rcvBuf.size());
while (listItr.hasPrevious()) {
Segment seg = listItr.previous();
if (seg.sn == sn) {
repeat = true;
break;
}
if (itimediff(sn, seg.sn) > 0) {
findPos = true;
break;
}
}
}
if (repeat) {
newSeg.recycle(true);
} else if (listItr == null) {
rcvBuf.add(newSeg);
} else {
if (findPos) {
listItr.next();
}
listItr.add(newSeg);
}
// move available data from rcv_buf -> rcv_queue
moveRcvData(); // Invoke the method only if the segment is not repeat?
}
private void moveRcvData() {
for (Iterator<Segment> itr = rcvBufItr.rewind(); itr.hasNext(); ) {
Segment seg = itr.next();
if (seg.sn == rcvNxt && rcvQueue.size() < rcvWnd) {
itr.remove();
rcvQueue.add(seg);
rcvNxt++;
} else {
break;
}
}
}
public int input(ByteBuf data) {
long oldSndUna = sndUna;
long maxack = 0;
boolean flag = false;
if (log.isDebugEnabled()) {
log.debug("{} [RI] {} bytes", this, data.readableBytes());
}
if (data == null || data.readableBytes() < IKCP_OVERHEAD) {
return -1;
}
while (true) {
int conv, len, wnd, ts;
long sn, una;
byte cmd;
short frg;
Segment seg;
if (data.readableBytes() < IKCP_OVERHEAD) {
break;
}
conv = data.readIntLE();
if (conv != this.conv && !(this.conv == 0 && autoSetConv)) {
return -4;
}
cmd = data.readByte();
frg = data.readUnsignedByte();
wnd = data.readUnsignedShortLE();
ts = data.readIntLE();
sn = data.readUnsignedIntLE();
una = data.readUnsignedIntLE();
len = data.readIntLE();
if (data.readableBytes() < len || len < 0) {
return -2;
}
if (cmd != IKCP_CMD_PUSH && cmd != IKCP_CMD_ACK && cmd != IKCP_CMD_WASK && cmd != IKCP_CMD_WINS) {
return -3;
}
if (this.conv == 0 && autoSetConv) { // automatically set conv
this.conv = conv;
}
this.rmtWnd = wnd;
parseUna(una);
shrinkBuf();
boolean readed = false;
int current = this.current;
switch (cmd) {
case IKCP_CMD_ACK: {
int rtt = itimediff(current, ts);
if (rtt >= 0) {
updateAck(rtt);
}
parseAck(sn);
shrinkBuf();
if (!flag) {
flag = true;
maxack = sn;
} else {
if (itimediff(sn, maxack) > 0) {
maxack = sn;
}
}
if (log.isDebugEnabled()) {
log.debug("{} input ack: sn={}, rtt={}, rto={}", this, sn, rtt, rxRto);
}
break;
}
case IKCP_CMD_PUSH: {
if (itimediff(sn, rcvNxt + rcvWnd) < 0) {
ackPush(sn, ts);
if (itimediff(sn, rcvNxt) >= 0) {
if (len > 0) {
seg = Segment.createSegment(data.readRetainedSlice(len));
readed = true;
} else {
seg = Segment.createSegment(byteBufAllocator, 0);
}
seg.conv = conv;
seg.cmd = cmd;
seg.frg = frg;
seg.wnd = wnd;
seg.ts = ts;
seg.sn = sn;
seg.una = una;
parseData(seg);
}
}
if (log.isDebugEnabled()) {
log.debug("{} input push: sn={}, una={}, ts={}", this, sn, una, ts);
}
break;
}
case IKCP_CMD_WASK: {
// ready to send back IKCP_CMD_WINS in ikcp_flush
// tell remote my window size
probe |= IKCP_ASK_TELL;
if (log.isDebugEnabled()) {
log.debug("{} input ask", this);
}
break;
}
case IKCP_CMD_WINS: {
// do nothing
if (log.isDebugEnabled()) {
log.debug("{} input tell: {}", this, wnd);
}
break;
}
default:
return -3;
}
if (!readed) {
data.skipBytes(len);
}
}
if (flag) {
parseFastack(maxack);
}
if (itimediff(sndUna, oldSndUna) > 0) {
if (cwnd < rmtWnd) {
int mss = this.mss;
if (cwnd < ssthresh) {
cwnd++;
incr += mss;
} else {
if (incr < mss) {
incr = mss;
}
incr += (mss * mss) / incr + (mss / 16);
if ((cwnd + 1) * mss <= incr) {
cwnd++;
}
}
if (cwnd > rmtWnd) {
cwnd = rmtWnd;
incr = rmtWnd * mss;
}
}
}
return 0;
}
private int wndUnused() {
if (rcvQueue.size() < rcvWnd) {
return rcvWnd - rcvQueue.size();
}
return 0;
}
/**
* ikcp_flush
*/
private void flush() {
int current = this.current;
// 'ikcp_update' haven't been called.
if (!updated) {
return;
}
Segment seg = Segment.createSegment(byteBufAllocator, 0);
seg.conv = conv;
seg.cmd = IKCP_CMD_ACK;
seg.frg = 0;
seg.wnd = wndUnused();
seg.una = rcvNxt;
seg.sn = 0;
seg.ts = 0;
ByteBuf buffer = null;
// flush acknowledges
int count = ackcount;
for (int i = 0; i < count; i++) {
buffer = tryCreateOrOutput(buffer, IKCP_OVERHEAD);
seg.sn = int2Uint(acklist[i * 2]);
seg.ts = acklist[i * 2 + 1];
encodeSeg(buffer, seg);
if (log.isDebugEnabled()) {
log.debug("{} flush ack: sn={}, ts={}", this, seg.sn, seg.ts);
}
}
ackcount = 0;
// probe window size (if remote window size equals zero)
if (rmtWnd == 0) {
if (probeWait == 0) {
probeWait = IKCP_PROBE_INIT;
tsProbe = current + probeWait;
} else {
if (itimediff(current, tsProbe) >= 0) {
if (probeWait < IKCP_PROBE_INIT) {
probeWait = IKCP_PROBE_INIT;
}
probeWait += probeWait / 2;
if (probeWait > IKCP_PROBE_LIMIT) {
probeWait = IKCP_PROBE_LIMIT;
}
tsProbe = current + probeWait;
probe |= IKCP_ASK_SEND;
}
}
} else {
tsProbe = 0;
probeWait = 0;
}
// flush window probing commands
if ((probe & IKCP_ASK_SEND) != 0) {
seg.cmd = IKCP_CMD_WASK;
buffer = tryCreateOrOutput(buffer, IKCP_OVERHEAD);
encodeSeg(buffer, seg);
if (log.isDebugEnabled()) {
log.debug("{} flush ask", this);
}
}
// flush window probing commands
if ((probe & IKCP_ASK_TELL) != 0) {
seg.cmd = IKCP_CMD_WINS;
buffer = tryCreateOrOutput(buffer, IKCP_OVERHEAD);
encodeSeg(buffer, seg);
if (log.isDebugEnabled()) {
log.debug("{} flush tell: wnd={}", this, seg.wnd);
}
}
probe = 0;
// calculate window size
int cwnd0 = Math.min(sndWnd, rmtWnd);
if (!nocwnd) {
cwnd0 = Math.min(this.cwnd, cwnd0);
}
// move data from snd_queue to snd_buf
while (itimediff(sndNxt, sndUna + cwnd0) < 0) {
Segment newSeg = sndQueue.poll();
if (newSeg == null) {
break;
}
sndBuf.add(newSeg);
newSeg.conv = conv;
newSeg.cmd = IKCP_CMD_PUSH;
newSeg.wnd = seg.wnd;
newSeg.ts = current;
newSeg.sn = sndNxt++;
newSeg.una = rcvNxt;
newSeg.resendts = current;
newSeg.rto = rxRto;
newSeg.fastack = 0;
newSeg.xmit = 0;
}
// calculate resent
int resent = fastresend > 0 ? fastresend : Integer.MAX_VALUE;
int rtomin = nodelay ? 0 : (rxRto >> 3);
// flush data segments
int change = 0;
boolean lost = false;
for (Iterator<Segment> itr = sndBufItr.rewind(); itr.hasNext(); ) {
Segment segment = itr.next();
boolean needsend = false;
if (segment.xmit == 0) {
needsend = true;