Commit 47805667 authored by Florian Westphal's avatar Florian Westphal Committed by David S. Miller
Browse files

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: default avatarFlorian Westphal <>
Signed-off-by: default avatarDavid S. Miller <>
parent 0fa1dfd6
......@@ -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)
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment