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From:   Eric Dumazet <edumazet@google.com>
Date:   Tue, 30 Jun 2020 13:56:10 -0700
Message-ID: <CANn89i+b-LeaPvaaHvj0yc0mJ2qwZ0981fQHVp0+sqXYp=kdkA@mail.gmail.com>
Subject: Re: [regression] TCP_MD5SIG on established sockets
To:     David Miller <davem@davemloft.net>
Cc:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        LKML <linux-kernel@vger.kernel.org>,
        netdev <netdev@vger.kernel.org>,
        Yuchung Cheng <ycheng@google.com>,
        Jonathan Rajotte-Julien <joraj@efficios.com>
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On Tue, Jun 30, 2020 at 1:44 PM David Miller <davem@davemloft.net> wrote:
>
> From: Eric Dumazet <edumazet@google.com>
> Date: Tue, 30 Jun 2020 13:39:27 -0700
>
> > The (C) & (B) case are certainly doable.
> >
> > A) case is more complex, I have no idea of breakages of various TCP
> > stacks if a flow got SACK
> > at some point (in 3WHS) but suddenly becomes Reno.
>
> I agree that C and B are the easiest to implement without having to
> add complicated code to handle various negotiated TCP option
> scenerios.
>
> It does seem to be that some entities do A, or did I misread your
> behavioral analysis of various implementations Mathieu?
>
> Thanks.

Yes, another question about Mathieu cases is do determine the behavior
of all these stacks vs :
SACK option
TCP TS option.