Re: [multipathtcp] potential MPTCP proxy charter item

Joe Touch <touch@isi.edu> Tue, 08 November 2016 16:44 UTC

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To: mohamed.boucadair@orange.com, Mirja Kühlewind <mirja.kuehlewind@tik.ee.ethz.ch>, "Olivier.Bonaventure@uclouvain.be" <Olivier.Bonaventure@uclouvain.be>
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From: Joe Touch <touch@isi.edu>
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Date: Tue, 08 Nov 2016 08:43:44 -0800
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Subject: Re: [multipathtcp] potential MPTCP proxy charter item
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On 11/8/2016 7:06 AM, mohamed.boucadair@orange.com wrote:
>> Please explain. If there is option information in the SYN data, then a
>> > legacy peer is allowed to keep that data (and ACK it) in the SYN ACK.
>> > 
>> > So now it has option info that it interprets as data.
> [Med] But a legacy node is not allowed to pass it to the application till the 3WHS is completed. https://tools.ietf.org/html/rfc793#section-3.4 says the following:
Agreed.

So now you have an option that violates 1122 because the receiver is
ignoring an option it doesn't understand but it would be an error to
continue with that connection.

Even if you assume that's true, you have another problem.

You've just opened a connection using a pair of ports. You sent a RST,
but RSTs are not reliable. So you can't reuse that port pair until
TIME-WAIT expires.

If you declare it "off" for an endpoint, do you ever check again?

Also, you can never use this option with TFO (which *would* try to pass
the data to the app) . I think you mentioned that, but then it's clearly
not generic.

Joe