netdev - Re: [PATCH v2] tcp: relookup sock for RST+ACK packets handled by obsolete req sock

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Date:   Mon, 15 Mar 2021 15:07:55 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Alexander Ovechkin <ovov@...dex-team.ru>
Cc:     netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>, zeil@...dex-team.ru,
        dmtrmonakhov@...dex-team.ru, olegsenin@...dex-team.ru
Subject: Re: [PATCH v2] tcp: relookup sock for RST+ACK packets handled by
 obsolete req sock

On Mon, Mar 15, 2021 at 12:06 PM Alexander Ovechkin <ovov@...dex-team.ru> wrote:
>
> Currently tcp_check_req can be called with obsolete req socket for which big
> socket have been already created (because of CPU race or early demux
> assigning req socket to multiple packets in gro batch).
>
> Commit e0f9759f530bf789e984 ("tcp: try to keep packet if SYN_RCV race
> is lost") added retry in case when tcp_check_req is called for PSH|ACK packet.
> But if client sends RST+ACK immediatly after connection being
> established (it is performing healthcheck, for example) retry does not
> occur. In that case tcp_check_req tries to close req socket,
> leaving big socket active.
>
> Fixes: e0f9759f530 ("tcp: try to keep packet if SYN_RCV race is lost")
> Signed-off-by: Alexander Ovechkin <ovov@...dex-team.ru>
> Reported-by: Oleg Senin <olegsenin@...dex-team.ru>
> ---

SGTM, thanks.

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