Merge branch 'tcp_cubic-fix-spurious-HYSTART_DELAY-on-RTT-decrease' (3b0e7dc0) · Commits · 戴 / test

Neal Cardwell says: ==================== tcp_cubic: fix spurious HYSTART_DELAY on RTT decrease This series fixes a long-standing bug in the TCP CUBIC HYSTART_DELAY mechanim recently reported by Mirja Kuehlewind. The code can cause a spurious exit of slow start in some particular cases: upon an RTT decrease that happens on the 9th or later ACK in a round trip. This series fixes the original Hystart code and also the recent BPF implementation. ==================== Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_cubic.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -432,10 +432,9 @@ static void hystart_update(struct sock *sk, u32 delay)

		if (hystart_detect & HYSTART_DELAY) {
		/* obtain the minimum delay of more than sampling packets */
		if (ca->sample_cnt < HYSTART_MIN_SAMPLES) {
		if (ca->curr_rtt > delay)
		ca->curr_rtt = delay;

		if (ca->sample_cnt < HYSTART_MIN_SAMPLES) {
		ca->sample_cnt++;
		} else {
		if (ca->curr_rtt > ca->delay_min +

tools/testing/selftests/bpf/progs/bpf_cubic.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -480,10 +480,9 @@ static __always_inline void hystart_update(struct sock *sk, __u32 delay)

		if (hystart_detect & HYSTART_DELAY) {
		/* obtain the minimum delay of more than sampling packets */
		if (ca->sample_cnt < HYSTART_MIN_SAMPLES) {
		if (ca->curr_rtt > delay)
		ca->curr_rtt = delay;

		if (ca->sample_cnt < HYSTART_MIN_SAMPLES) {
		ca->sample_cnt++;
		} else {
		if (ca->curr_rtt > ca->delay_min +

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