From: Frédéric Lécaille <flecaille@haproxy.com>
Date: Thu, 3 Mar 2022 06:50:45 +0000 (+0100)
Subject: MINOR: quic: More precise window update calculation
X-Git-Tag: v2.6-dev3~47
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0e7c9a71431ce55816fee76f3e6109cbda6dd3a9;p=thirdparty%2Fhaproxy.git

MINOR: quic: More precise window update calculation

When in congestion avoidance state and when acknowledging an <acked> number bytes
we must increase the congestion window by at most one datagram (<path->mtu>)
by congestion window. So thanks to this patch we apply a ratio to the current
number of acked bytes : <acked> * <path->mtu> / <cwnd>.
So, when <cwnd> bytes are acked we precisely increment <cwnd> by <path->mtu>.
Furthermore we take into an account the number of remaining acknowledged bytes
each time we increment the window by <acked> storing their values in the algorithm
struct state (->remain_acked) so that it might be take into an account at the
next ACK event.
---

diff --git a/include/haproxy/quic_cc-t.h b/include/haproxy/quic_cc-t.h
index 78af6a587c..95d9922f09 100644
--- a/include/haproxy/quic_cc-t.h
+++ b/include/haproxy/quic_cc-t.h
@@ -76,6 +76,7 @@ union quic_cc_algo_state {
 		uint64_t cwnd;
 		uint64_t ssthresh;
 		uint64_t recovery_start_time;
+		uint64_t remain_acked;
 	} nr;
 };
 
diff --git a/src/quic_cc_newreno.c b/src/quic_cc_newreno.c
index e15b302b2b..3952910153 100644
--- a/src/quic_cc_newreno.c
+++ b/src/quic_cc_newreno.c
@@ -35,6 +35,7 @@ static int quic_cc_nr_init(struct quic_cc *cc)
 	cc->algo_state.nr.cwnd = path->cwnd;
 	cc->algo_state.nr.ssthresh = QUIC_CC_INFINITE_SSTHESH;
 	cc->algo_state.nr.recovery_start_time = 0;
+	cc->algo_state.nr.remain_acked = 0;
 
 	return 1;
 }
@@ -95,17 +96,20 @@ static void quic_cc_nr_ca_cb(struct quic_cc *cc, struct quic_cc_event *ev)
 	path = container_of(cc, struct quic_path, cc);
 	switch (ev->type) {
 	case QUIC_CC_EVT_ACK:
+	{
+		uint64_t acked;
 		/* Do not increase the congestion window in recovery period. */
 		if (ev->ack.time_sent <= cc->algo_state.nr.recovery_start_time)
 			goto out;
 
-		/* Increasing the congestion window by 1 maximum packet size by
-		 * congestion window.
+		/* Increasing the congestion window by (acked / cwnd)
 		 */
-		cc->algo_state.nr.cwnd +=
-			path->mtu * QUIC_MAX(1ULL, (unsigned long long)ev->ack.acked / cc->algo_state.nr.cwnd);
+		acked = ev->ack.acked * path->mtu + cc->algo_state.nr.remain_acked;
+		cc->algo_state.nr.remain_acked = acked % cc->algo_state.nr.cwnd;
+		cc->algo_state.nr.cwnd += acked / cc->algo_state.nr.cwnd;
 		path->cwnd = cc->algo_state.nr.cwnd;
 		break;
+	}
 
 	case QUIC_CC_EVT_LOSS:
 		/* Do not decrease the congestion window when already in recovery period. */