* [PATCH v2] tcp: fix infinite cwnd in tcp_complete_cwr()
@ 2012-04-30 16:00 Yuchung Cheng
2012-04-30 16:25 ` Neal Cardwell
0 siblings, 1 reply; 3+ messages in thread
From: Yuchung Cheng @ 2012-04-30 16:00 UTC (permalink / raw)
To: davem, ilpo.jarvinen, ncardwell; +Cc: nanditad, netdev, Yuchung Cheng
When the cwnd reduction is done, ssthresh may be infinite
if TCP enters CWR via ECN or F-RTO. If cwnd is not undone, i.e.,
undo_marker is set, tcp_complete_cwr() falsely set cwnd to the
infinite ssthresh value. The correct operation is to keep cwnd
intact because it has been updated in ECN or F-RTO.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
---
ChangeLog since v1:
- Add snd_cwnd_stamp timestamping in CWR mode
net/ipv4/tcp_input.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index c93b0cb..e0a9b89 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2868,11 +2868,14 @@ static inline void tcp_complete_cwr(struct sock *sk)
/* Do not moderate cwnd if it's already undone in cwr or recovery. */
if (tp->undo_marker) {
- if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR)
+ if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR) {
tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
- else /* PRR */
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+ } else if (tp->snd_ssthresh < TCP_INFINITE_SSTHRESH) {
+ /* PRR algorithm. */
tp->snd_cwnd = tp->snd_ssthresh;
- tp->snd_cwnd_stamp = tcp_time_stamp;
+ tp->snd_cwnd_stamp = tcp_time_stamp;
+ }
}
tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR);
}
--
1.7.7.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] tcp: fix infinite cwnd in tcp_complete_cwr()
2012-04-30 16:00 [PATCH v2] tcp: fix infinite cwnd in tcp_complete_cwr() Yuchung Cheng
@ 2012-04-30 16:25 ` Neal Cardwell
2012-04-30 17:45 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Neal Cardwell @ 2012-04-30 16:25 UTC (permalink / raw)
To: Yuchung Cheng; +Cc: davem, ilpo.jarvinen, nanditad, netdev
On Mon, Apr 30, 2012 at 12:00 PM, Yuchung Cheng <ycheng@google.com> wrote:
> When the cwnd reduction is done, ssthresh may be infinite
> if TCP enters CWR via ECN or F-RTO. If cwnd is not undone, i.e.,
> undo_marker is set, tcp_complete_cwr() falsely set cwnd to the
> infinite ssthresh value. The correct operation is to keep cwnd
> intact because it has been updated in ECN or F-RTO.
>
> Signed-off-by: Yuchung Cheng <ycheng@google.com>
> ---
> ChangeLog since v1:
> - Add snd_cwnd_stamp timestamping in CWR mode
>
> net/ipv4/tcp_input.c | 9 ++++++---
> 1 files changed, 6 insertions(+), 3 deletions(-)
Acked-by: Neal Cardwell <ncardwell@google.com>
neal
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] tcp: fix infinite cwnd in tcp_complete_cwr()
2012-04-30 16:25 ` Neal Cardwell
@ 2012-04-30 17:45 ` David Miller
0 siblings, 0 replies; 3+ messages in thread
From: David Miller @ 2012-04-30 17:45 UTC (permalink / raw)
To: ncardwell; +Cc: ycheng, ilpo.jarvinen, nanditad, netdev
From: Neal Cardwell <ncardwell@google.com>
Date: Mon, 30 Apr 2012 12:25:56 -0400
> On Mon, Apr 30, 2012 at 12:00 PM, Yuchung Cheng <ycheng@google.com> wrote:
>> When the cwnd reduction is done, ssthresh may be infinite
>> if TCP enters CWR via ECN or F-RTO. If cwnd is not undone, i.e.,
>> undo_marker is set, tcp_complete_cwr() falsely set cwnd to the
>> infinite ssthresh value. The correct operation is to keep cwnd
>> intact because it has been updated in ECN or F-RTO.
>>
>> Signed-off-by: Yuchung Cheng <ycheng@google.com>
>> ---
>> ChangeLog since v1:
>> - Add snd_cwnd_stamp timestamping in CWR mode
>>
>> net/ipv4/tcp_input.c | 9 ++++++---
>> 1 files changed, 6 insertions(+), 3 deletions(-)
>
> Acked-by: Neal Cardwell <ncardwell@google.com>
Applied and queued up for -stable, thanks.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2012-04-30 16:00 [PATCH v2] tcp: fix infinite cwnd in tcp_complete_cwr() Yuchung Cheng
2012-04-30 16:25 ` Neal Cardwell
2012-04-30 17:45 ` David Miller
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