* [PATCH] tcp: undo spurious timeout after SACK reneging
@ 2013-03-24 20:42 Yuchung Cheng
2013-03-24 20:50 ` Neal Cardwell
0 siblings, 1 reply; 3+ messages in thread
From: Yuchung Cheng @ 2013-03-24 20:42 UTC (permalink / raw)
To: davem, ncardwell, edumazet, nanditad; +Cc: netdev, Yuchung Cheng
On SACK reneging the sender immediately retransmits and forces a
timeout but disables Eifel (undo). If the (buggy) receiver does not
drop any packet this can trigger a false slow-start retransmit storm
driven by the ACKs of the original packets. This can be detected with
undo and TCP timestamps.
Signed-off-by: Yuchung Cheng <ycheng@google.com>
---
net/ipv4/tcp_input.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index b2b3619..6d9ca35 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1858,11 +1858,8 @@ void tcp_enter_loss(struct sock *sk, int how)
if (tcp_is_reno(tp))
tcp_reset_reno_sack(tp);
- if (!how) {
- /* Push undo marker, if it was plain RTO and nothing
- * was retransmitted. */
- tp->undo_marker = tp->snd_una;
- } else {
+ tp->undo_marker = tp->snd_una;
+ if (how) {
tp->sacked_out = 0;
tp->fackets_out = 0;
}
--
1.8.1.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] tcp: undo spurious timeout after SACK reneging
2013-03-24 20:42 [PATCH] tcp: undo spurious timeout after SACK reneging Yuchung Cheng
@ 2013-03-24 20:50 ` Neal Cardwell
2013-03-24 21:28 ` David Miller
0 siblings, 1 reply; 3+ messages in thread
From: Neal Cardwell @ 2013-03-24 20:50 UTC (permalink / raw)
To: Yuchung Cheng; +Cc: David Miller, Eric Dumazet, Nandita Dukkipati, Netdev
On Sun, Mar 24, 2013 at 4:42 PM, Yuchung Cheng <ycheng@google.com> wrote:
> On SACK reneging the sender immediately retransmits and forces a
> timeout but disables Eifel (undo). If the (buggy) receiver does not
> drop any packet this can trigger a false slow-start retransmit storm
> driven by the ACKs of the original packets. This can be detected with
> undo and TCP timestamps.
>
> Signed-off-by: Yuchung Cheng <ycheng@google.com>
> ---
> net/ipv4/tcp_input.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)
Acked-by: Neal Cardwell <ncardwell@google.com>
neal
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] tcp: undo spurious timeout after SACK reneging
2013-03-24 20:50 ` Neal Cardwell
@ 2013-03-24 21:28 ` David Miller
0 siblings, 0 replies; 3+ messages in thread
From: David Miller @ 2013-03-24 21:28 UTC (permalink / raw)
To: ncardwell; +Cc: ycheng, edumazet, nanditad, netdev
From: Neal Cardwell <ncardwell@google.com>
Date: Sun, 24 Mar 2013 16:50:41 -0400
> On Sun, Mar 24, 2013 at 4:42 PM, Yuchung Cheng <ycheng@google.com> wrote:
>> On SACK reneging the sender immediately retransmits and forces a
>> timeout but disables Eifel (undo). If the (buggy) receiver does not
>> drop any packet this can trigger a false slow-start retransmit storm
>> driven by the ACKs of the original packets. This can be detected with
>> undo and TCP timestamps.
>>
>> Signed-off-by: Yuchung Cheng <ycheng@google.com>
>> ---
>> net/ipv4/tcp_input.c | 7 ++-----
>> 1 file changed, 2 insertions(+), 5 deletions(-)
>
> Acked-by: Neal Cardwell <ncardwell@google.com>
Applied.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2013-03-24 21:28 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2013-03-24 20:42 [PATCH] tcp: undo spurious timeout after SACK reneging Yuchung Cheng
2013-03-24 20:50 ` Neal Cardwell
2013-03-24 21:28 ` David Miller
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