From 1b1fc3fddabfb8739ef2c8f04e05a9858b42c1f7 Mon Sep 17 00:00:00 2001 From: Wei Wang Date: Fri, 5 May 2017 12:53:23 -0700 Subject: [PATCH] tcp: make congestion control optionally skip slow start after idle Congestion control modules that want full control over congestion control behavior do not want the cwnd modifications controlled by the sysctl_tcp_slow_start_after_idle code path. So skip those code paths for CC modules that use the cong_control() API. As an example, those cwnd effects are not desired for the BBR congestion control algorithm. Fixes: c0402760f565 ("tcp: new CC hook to set sending rate with rate_sample in any CA state") Signed-off-by: Wei Wang Signed-off-by: Yuchung Cheng Signed-off-by: Neal Cardwell Signed-off-by: David S. Miller --- include/net/tcp.h | 4 +++- net/ipv4/tcp_output.c | 4 +++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 8c0e5a901d64..38a7427ae902 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1234,10 +1234,12 @@ void tcp_cwnd_restart(struct sock *sk, s32 delta); static inline void tcp_slow_start_after_idle_check(struct sock *sk) { + const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; struct tcp_sock *tp = tcp_sk(sk); s32 delta; - if (!sysctl_tcp_slow_start_after_idle || tp->packets_out) + if (!sysctl_tcp_slow_start_after_idle || tp->packets_out || + ca_ops->cong_control) return; delta = tcp_time_stamp - tp->lsndtime; if (delta > inet_csk(sk)->icsk_rto) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 60111a0fc201..4858e190f6ac 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1514,6 +1514,7 @@ static void tcp_cwnd_application_limited(struct sock *sk) static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited) { + const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; struct tcp_sock *tp = tcp_sk(sk); /* Track the maximum number of outstanding packets in each @@ -1536,7 +1537,8 @@ static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited) tp->snd_cwnd_used = tp->packets_out; if (sysctl_tcp_slow_start_after_idle && - (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto) + (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto && + !ca_ops->cong_control) tcp_cwnd_application_limited(sk); /* The following conditions together indicate the starvation