From 4780566784b3968ab9fd6cc94bab72421813f004 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Mon, 14 Nov 2016 16:42:01 +0100 Subject: [PATCH] dctcp: update cwnd on congestion event draft-ietf-tcpm-dctcp-02 says: ... when the sender receives an indication of congestion (ECE), the sender SHOULD update cwnd as follows: cwnd = cwnd * (1 - DCTCP.Alpha / 2) So, lets do this and reduce cwnd more smoothly (and faster), as per current congestion estimate. Cc: Lawrence Brakmo Cc: Andrew Shewmaker Cc: Glenn Judd Cc: Daniel Borkmann Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- net/ipv4/tcp_dctcp.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/ipv4/tcp_dctcp.c b/net/ipv4/tcp_dctcp.c index ab37c6775630..51139175bf61 100644 --- a/net/ipv4/tcp_dctcp.c +++ b/net/ipv4/tcp_dctcp.c @@ -188,8 +188,8 @@ static void dctcp_ce_state_1_to_0(struct sock *sk) static void dctcp_update_alpha(struct sock *sk, u32 flags) { - const struct tcp_sock *tp = tcp_sk(sk); struct dctcp *ca = inet_csk_ca(sk); + struct tcp_sock *tp = tcp_sk(sk); u32 acked_bytes = tp->snd_una - ca->prior_snd_una; /* If ack did not advance snd_una, count dupack as MSS size. @@ -229,6 +229,13 @@ static void dctcp_update_alpha(struct sock *sk, u32 flags) WRITE_ONCE(ca->dctcp_alpha, alpha); dctcp_reset(tp, ca); } + + if (flags & CA_ACK_ECE) { + unsigned int cwnd = dctcp_ssthresh(sk); + + if (cwnd != tp->snd_cwnd) + tp->snd_cwnd = cwnd; + } } static void dctcp_state(struct sock *sk, u8 new_state) -- 2.20.1