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authorFlorian Westphal <fw@strlen.de>2016-11-21 14:18:38 +0100
committerDavid S. Miller <davem@davemloft.net>2016-11-21 13:20:17 -0500
commite97991832a4ea4a5f47d65f068a4c966a2eb5730 (patch)
tree870e5c09c37890d286872c9ae22382d6bf336b37 /net/ipv4/tcp_cong.c
parent85f7e7508a1d288b513493196ef406c6c06134e1 (diff)
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 <edumazet@google.com> Cc: Yuchung Cheng <ycheng@google.com> Cc: Neal Cardwell <ncardwell@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_cong.c')
-rw-r--r--net/ipv4/tcp_cong.c14
1 files changed, 12 insertions, 2 deletions
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,
};