From: Eric Dumazet <eric.duma...@gmail.com>
Date: Thu, 17 Sep 2015 08:38:00 -0700
> From: Eric Dumazet <eduma...@google.com>
>
> Tracking idle time in bictcp_cwnd_event() is imprecise, as epoch_start
> is normally set at ACK processing time, not at send time.
>
> Doing a proper fix would need to add an additional state variable,
> and does not seem worth the trouble, given CUBIC bug has been there
> forever before Jana noticed it.
>
> Let's simply not set epoch_start in the future, otherwise
> bictcp_update() could overflow and CUBIC would again
> grow cwnd too fast.
>
> This was detected thanks to a packetdrill test Neal wrote that was flaky
> before applying this fix.
>
> Fixes: 30927520dbae ("tcp_cubic: better follow cubic curve after idle period")
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Signed-off-by: Neal Cardwell <ncardw...@google.com>
> Signed-off-by: Yuchung Cheng <ych...@google.com>
> Cc: Jana Iyengar <j...@google.com>
Applied, thanks.
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