netdev - Re: [regression] TCP_MD5SIG on established sockets

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Message-ID: <474095696.17969.1593551866537.JavaMail.zimbra@efficios.com>
Date:   Tue, 30 Jun 2020 17:17:46 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Jonathan Rajotte-Julien <joraj@...icios.com>
Subject: Re: [regression] TCP_MD5SIG on established sockets

----- On Jun 30, 2020, at 4:56 PM, Eric Dumazet edumazet@...gle.com wrote:

> On Tue, Jun 30, 2020 at 1:44 PM David Miller <davem@...emloft.net> wrote:
>>
>> From: Eric Dumazet <edumazet@...gle.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!

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com