From d13de3b19d99ed09561baa349071e7c57cad9ec7 Mon Sep 17 00:00:00 2001
From: skywind3000 <skywind3000@163.com>
Date: Thu, 14 May 2026 11:34:05 +0800
Subject: [PATCH] congestion control: basically finish

---
 ikcp.c | 114 +++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 90 insertions(+), 24 deletions(-)

diff --git a/ikcp.c b/ikcp.c
index 6f23c70..b455317 100644
--- a/ikcp.c
+++ b/ikcp.c
@@ -973,14 +973,22 @@ void ikcp_flush(ikcpcb *kcp)
 	int count, size, i;
 	IUINT32 resent, cwnd;
 	IUINT32 rtomin;
+	IUINT32 prior_cwnd;
+	IUINT32 eff_cwnd, cur_inflight;
 	struct IQUEUEHEAD *p;
 	int change = 0;
 	int lost = 0;
 	IKCPSEG seg;
 
-	// 'ikcp_update' haven't been called. 
+	// 'ikcp_update' hasn't been called yet. 
 	if (kcp->updated == 0) return;
 
+	if (kcp->ccops && kcp->ccops->on_tick) {
+		kcp->ccops->on_tick(kcp);
+	}
+
+	prior_cwnd = kcp->cwnd;
+
 	seg.conv = kcp->conv;
 	seg.cmd = IKCP_CMD_ACK;
 	seg.frg = 0;
@@ -1052,7 +1060,7 @@ void ikcp_flush(ikcpcb *kcp)
 
 	// calculate window size
 	cwnd = _imin_(kcp->snd_wnd, kcp->rmt_wnd);
-	if (kcp->nocwnd == 0) cwnd = _imin_(kcp->cwnd, cwnd);
+	if (kcp->ccops != NULL || kcp->nocwnd == 0) cwnd = _imin_(kcp->cwnd, cwnd);
 
 	// move data from snd_queue to snd_buf
 	while (_itimediff(kcp->snd_nxt, kcp->snd_una + cwnd) < 0) {
@@ -1076,6 +1084,22 @@ void ikcp_flush(ikcpcb *kcp)
 		newseg->rto = kcp->rx_rto;
 		newseg->fastack = 0;
 		newseg->xmit = 0;
+
+		if (kcp->ccops && kcp->ccops->on_pkt_sent) {
+			kcp->ccops->on_pkt_sent(kcp, newseg->sn, current, newseg->len, kcp->nsnd_buf - 1);
+		}
+	}
+
+	// check on_app_limited
+	if (kcp->ccops && kcp->ccops->on_app_limited) {
+		if (iqueue_is_empty(&kcp->snd_queue)) {
+			eff_cwnd = _imin_(kcp->snd_wnd, kcp->rmt_wnd);
+			eff_cwnd = _imin_(kcp->cwnd, eff_cwnd);
+			cur_inflight = kcp->nsnd_buf;
+			if (cur_inflight < eff_cwnd) {
+				kcp->ccops->on_app_limited(kcp, cur_inflight);
+			}
+		}
 	}
 
 	// calculate resent
@@ -1144,7 +1168,7 @@ void ikcp_flush(ikcpcb *kcp)
 		}
 	}
 
-	// flash remain segments
+	// flash remaining segments
 	size = (int)(ptr - buffer);
 	if (size > 0) {
 		ikcp_output(kcp, buffer, size);
@@ -1152,20 +1176,30 @@ void ikcp_flush(ikcpcb *kcp)
 
 	// update ssthresh
 	if (change) {
-		IUINT32 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;
+		if (kcp->ccops && kcp->ccops->on_fast_retransmit) {
+			kcp->ccops->on_fast_retransmit(kcp, (IUINT32)change, kcp->nsnd_buf, prior_cwnd);
+		}
+		else {
+			IUINT32 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;
+		}
 	}
 
 	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->ccops && kcp->ccops->on_timeout) {
+			kcp->ccops->on_timeout(kcp, prior_cwnd);
+		}
+		else {
+			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) {
@@ -1176,9 +1210,9 @@ void ikcp_flush(ikcpcb *kcp)
 
 
 //---------------------------------------------------------------------
-// update 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. 
+// update state (call it repeatedly, every 10ms-100ms), or you can ask
+// ikcp_check when to call it again (if no ikcp_input/_send calls occur).
+// 'current' - current timestamp in milliseconds.
 //---------------------------------------------------------------------
 void ikcp_update(ikcpcb *kcp, IUINT32 current)
 {
@@ -1209,13 +1243,13 @@ void ikcp_update(ikcpcb *kcp, IUINT32 current)
 
 
 //---------------------------------------------------------------------
-// Determine 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)
+// Determines when you should invoke ikcp_update next:
+// returns the timestamp (in milliseconds) at which you should call
+// ikcp_update, assuming no ikcp_input/_send calls occur in between.
+// You can call ikcp_update at that time instead of calling it repeatedly.
+// Important for reducing unnecessary ikcp_update invocations. Use it to
+// schedule ikcp_update (e.g., implementing an epoll-like mechanism,
+// or optimizing ikcp_update when handling massive kcp connections).
 //---------------------------------------------------------------------
 IUINT32 ikcp_check(const ikcpcb *kcp, IUINT32 current)
 {
@@ -1334,3 +1368,35 @@ IUINT32 ikcp_getconv(const void *ptr)
 }
 
 
+//---------------------------------------------------------------------
+// install congestion control
+//---------------------------------------------------------------------
+int ikcp_setcc(ikcpcb *kcp, const struct IKCPOPS *ops)
+{
+	assert(kcp);
+	if (kcp->ccops && kcp->ccops->release) {
+		kcp->ccops->release(kcp);
+	}
+	kcp->congest = NULL;
+	kcp->ccops = ops;
+	if (ops) {
+		if (ops->init) {
+			if (ops->init(kcp) < 0) {
+				kcp->ccops = NULL;
+				kcp->congest = NULL;
+				if (kcp->cwnd < 1) kcp->cwnd = 1;
+				kcp->incr = kcp->cwnd * kcp->mss;
+				return -1;
+			}
+		}
+	}
+	else {
+		if (kcp->cwnd < 1) kcp->cwnd = 1;
+		kcp->incr = kcp->cwnd * kcp->mss;
+		if (kcp->incr < kcp->mss) kcp->incr = kcp->mss;
+	}
+	return 0;
+}
+
+
+