netdev - Re: [PATCH net] tcp: avoid setting cwnd to invalid ssthresh after cwnd reduction states

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Message-ID: <1501664843.25002.15.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Wed, 02 Aug 2017 02:07:23 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Yuchung Cheng <ycheng@...gle.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, ncardwell@...gle.com,
        edumazet@...gle.com
Subject: Re: [PATCH net] tcp: avoid setting cwnd to invalid ssthresh after
 cwnd reduction states

On Tue, 2017-08-01 at 13:22 -0700, Yuchung Cheng wrote:
> If the sender switches the congestion control during ECN-triggered
> cwnd-reduction state (CA_CWR), upon exiting recovery cwnd is set to
> the ssthresh value calculated by the previous congestion control. If
> the previous congestion control is BBR that always keep ssthresh
> to TCP_INIFINITE_SSTHRESH, cwnd ends up being infinite. The safe
> step is to avoid assigning invalid ssthresh value when recovery ends.
> 
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> Signed-off-by: Neal Cardwell <ncardwell@...gle.com>
> ---
>  net/ipv4/tcp_input.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Acked-by: Eric Dumazet <edumazet@...gle.com>