netdev - Re: [PATCH] tcp: fix sequence numbers for repaired sockets re-using TIME-WAIT sockets

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Date:   Thu, 12 Jul 2018 14:34:36 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     sbaranoff@...il.com
Cc:     netdev@...r.kernel.org, avagin@...tuozzo.com, xemul@...tuozzo.com,
        edumazet@...gle.com, kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH] tcp: fix sequence numbers for repaired sockets
 re-using TIME-WAIT sockets

From: Stefan Baranoff <sbaranoff@...il.com>
Date: Tue, 10 Jul 2018 17:25:20 -0400

> This patch fixes a bug where the sequence numbers of a socket created using
> TCP repair functionality are lower than set after connect is called.
> This occurs when the repair socket overlaps with a TIME-WAIT socket and
> triggers the re-use code. The amount lower is equal to the number of times
> that a particular IP/port set is re-used and then put back into TIME-WAIT.
> Re-using the first time the sequence number is 1 lower, closing that socket
> and then re-opening (with repair) a new socket with the same addresses/ports
> puts the sequence number 2 lower than set via setsockopt. The third time is
> 3 lower, etc. I have not tested what the limit of this acrewal is, if any.
> 
> The fix is, if a socket is in repair mode, to respect the already set
> sequence number and timestamp when it would have already re-used the
> TIME-WAIT socket.
> 
> Signed-off-by: Stefan Baranoff <sbaranoff@...il.com>

Applied.