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From:   Eric Dumazet <edumazet@google.com>
Date:   Tue, 30 Jun 2020 14:23:44 -0700
Message-ID: <CANn89iKK2+pznYZoKZzdCu4qkA7BjJZFqc6ABof4iaS-T-9_aw@mail.gmail.com>
Subject: Re: [regression] TCP_MD5SIG on established sockets
To:     Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel <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 2:17 PM Mathieu Desnoyers
<mathieu.desnoyers@efficios.com> wrote:
>
> ----- On Jun 30, 2020, at 4:56 PM, Eric Dumazet edumazet@google.com wrote:
>
> > 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.
>
> I will ask my customer's networking team to investigate these behaviors,
> which will allow me to prepare a thorough reply to the questions raised
> by Eric and David. I expect to have an answer within 2-3 weeks at most.
>
> Thank you!


Great, I am working on adding back support for (B) & (C) by the end of
this week.