From e97991832a4ea4a5f47d65f068a4c966a2eb5730 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Mon, 21 Nov 2016 14:18:38 +0100 Subject: [PATCH] tcp: make undo_cwnd mandatory for congestion modules The undo_cwnd fallback in the stack doubles cwnd based on ssthresh, which un-does reno halving behaviour. It seems more appropriate to let congctl algorithms pair .ssthresh and .undo_cwnd properly. Add a 'tcp_reno_undo_cwnd' function and wire it up for all congestion algorithms that used to rely on the fallback. Cc: Eric Dumazet Cc: Yuchung Cheng Cc: Neal Cardwell Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- include/net/tcp.h | 1 + net/ipv4/tcp_cong.c | 14 ++++++++++++-- net/ipv4/tcp_dctcp.c | 1 + net/ipv4/tcp_hybla.c | 1 + net/ipv4/tcp_input.c | 5 +---- net/ipv4/tcp_lp.c | 1 + net/ipv4/tcp_vegas.c | 1 + net/ipv4/tcp_westwood.c | 1 + 8 files changed, 19 insertions(+), 6 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 123979fe12bf..7de80739adab 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -958,6 +958,7 @@ u32 tcp_slow_start(struct tcp_sock *tp, u32 acked); void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked); u32 tcp_reno_ssthresh(struct sock *sk); +u32 tcp_reno_undo_cwnd(struct sock *sk); void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked); extern struct tcp_congestion_ops tcp_reno; diff --git a/net/ipv4/tcp_cong.c b/net/ipv4/tcp_cong.c index 1294af4e0127..38905ec5f508 100644 --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -68,8 +68,9 @@ int tcp_register_congestion_control(struct tcp_congestion_ops *ca) { int ret = 0; - /* all algorithms must implement ssthresh and cong_avoid ops */ - if (!ca->ssthresh || !(ca->cong_avoid || ca->cong_control)) { + /* all algorithms must implement these */ + if (!ca->ssthresh || !ca->undo_cwnd || + !(ca->cong_avoid || ca->cong_control)) { pr_err("%s does not implement required ops\n", ca->name); return -EINVAL; } @@ -441,10 +442,19 @@ u32 tcp_reno_ssthresh(struct sock *sk) } EXPORT_SYMBOL_GPL(tcp_reno_ssthresh); +u32 tcp_reno_undo_cwnd(struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + return max(tp->snd_cwnd, tp->snd_ssthresh << 1); +} +EXPORT_SYMBOL_GPL(tcp_reno_undo_cwnd); + struct tcp_congestion_ops tcp_reno = { .flags = TCP_CONG_NON_RESTRICTED, .name = "reno", .owner = THIS_MODULE, .ssthresh = tcp_reno_ssthresh, .cong_avoid = tcp_reno_cong_avoid, + .undo_cwnd = tcp_reno_undo_cwnd, }; diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c index 51139175bf61..bde22ebb92a8 100644 --- a/net/ipv4/tcp_dctcp.c +++ b/net/ipv4/tcp_dctcp.c @@ -342,6 +342,7 @@ static struct tcp_congestion_ops dctcp __read_mostly = { static struct tcp_congestion_ops dctcp_reno __read_mostly = { .ssthresh = tcp_reno_ssthresh, .cong_avoid = tcp_reno_cong_avoid, + .undo_cwnd = tcp_reno_undo_cwnd, .get_info = dctcp_get_info, .owner = THIS_MODULE, .name = "dctcp-reno", diff --git a/net/ipv4/tcp_hybla.c b/net/ipv4/tcp_hybla.c index 083831e359df..0f7175c3338e 100644 --- a/net/ipv4/tcp_hybla.c +++ b/net/ipv4/tcp_hybla.c @@ -166,6 +166,7 @@ static void hybla_cong_avoid(struct sock *sk, u32 ack, u32 acked) static struct tcp_congestion_ops tcp_hybla __read_mostly = { .init = hybla_init, .ssthresh = tcp_reno_ssthresh, + .undo_cwnd = tcp_reno_undo_cwnd, .cong_avoid = hybla_cong_avoid, .set_state = hybla_state, diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index a70046fea0e8..22e6a2097ff6 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -2394,10 +2394,7 @@ static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss) if (tp->prior_ssthresh) { const struct inet_connection_sock *icsk = inet_csk(sk); - if (icsk->icsk_ca_ops->undo_cwnd) - tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); - else - tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1); + tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); if (tp->prior_ssthresh > tp->snd_ssthresh) { tp->snd_ssthresh = tp->prior_ssthresh; diff --git a/net/ipv4/tcp_lp.c b/net/ipv4/tcp_lp.c index c67ece1390c2..046fd3910873 100644 --- a/net/ipv4/tcp_lp.c +++ b/net/ipv4/tcp_lp.c @@ -316,6 +316,7 @@ static void tcp_lp_pkts_acked(struct sock *sk, const struct ack_sample *sample) static struct tcp_congestion_ops tcp_lp __read_mostly = { .init = tcp_lp_init, .ssthresh = tcp_reno_ssthresh, + .undo_cwnd = tcp_reno_undo_cwnd, .cong_avoid = tcp_lp_cong_avoid, .pkts_acked = tcp_lp_pkts_acked, diff --git a/net/ipv4/tcp_vegas.c b/net/ipv4/tcp_vegas.c index 4c4bac1b5eab..218cfcc77650 100644 --- a/net/ipv4/tcp_vegas.c +++ b/net/ipv4/tcp_vegas.c @@ -307,6 +307,7 @@ EXPORT_SYMBOL_GPL(tcp_vegas_get_info); static struct tcp_congestion_ops tcp_vegas __read_mostly = { .init = tcp_vegas_init, .ssthresh = tcp_reno_ssthresh, + .undo_cwnd = tcp_reno_undo_cwnd, .cong_avoid = tcp_vegas_cong_avoid, .pkts_acked = tcp_vegas_pkts_acked, .set_state = tcp_vegas_state, diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c index 4b03a2e2a050..fed66dc0e0f5 100644 --- a/net/ipv4/tcp_westwood.c +++ b/net/ipv4/tcp_westwood.c @@ -278,6 +278,7 @@ static struct tcp_congestion_ops tcp_westwood __read_mostly = { .init = tcp_westwood_init, .ssthresh = tcp_reno_ssthresh, .cong_avoid = tcp_reno_cong_avoid, + .undo_cwnd = tcp_reno_undo_cwnd, .cwnd_event = tcp_westwood_event, .in_ack_event = tcp_westwood_ack, .get_info = tcp_westwood_info, -- 2.20.1