Re: [OPSEC] ECMP [Tsvart last call review of draft-ietf-opsec-ipv6-eh-filtering-06]

Fernando Gont <fgont@si6networks.com> Thu, 13 December 2018 12:24 UTC

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To: Wes Hardaker <wjhns1@hardakers.net>, Brian E Carpenter <brian.e.carpenter@gmail.com>
Cc: Nick Hilliard <nick@foobar.org>, tsv-art <tsv-art@ietf.org>, OPSEC <opsec@ietf.org>, draft-ietf-opsec-ipv6-eh-filtering.all@ietf.org
References: <CAL9jLaYHVdHr+rVoWeNtXTXgLxbTaX8V9gn3424tvsLW60Kvow@mail.gmail.com> <CAN-Dau0go6_Puf0A9e7KBpk0ApJBUvcxYtezxnwNc-8pKJ3PwQ@mail.gmail.com> <4D69FA8E-FB8A-4A16-9CA6-690D8AE33C9E@strayalpha.com> <20181205122142.GJ1543@Space.Net> <F17C4944-09EC-4AAC-84A0-B660E36AAE89@strayalpha.com> <20181205133821.GL1543@Space.Net> <B6280E0C-6B20-43C1-BB34-170FB06F1EF7@strayalpha.com> <20181205135723.GN1543@Space.Net> <54C715AE-8931-4FA9-AA01-2311EB0055F0@employees.org> <20181205164558.GQ1543@Space.Net> <CCFEFC5B-53AE-4079-B64A-A72A71274FAD@employees.org> <cda0e10e-a56d-4598-dcd4-eabeeac52fb0@gmail.com> <a1b478a7-4396-3d9e-0282-c8c66250526c@gmail.com> <f86a07c8-c421-56db-005c-4db3ce4f3fe0@gmail.com> <3744b28c-3a5a-1ce4-9ff7-5374804d332e@gmail.com> <35277330-4743-4690-8ae0-9a9ab7e34f05@foobar.org> <3a182a82-b933-2d9b-52a8-24805717879b@gmail.com> <ybl4lbjsu9a.fsf@w7.hardakers.net> <d970fa54-f36b-13fd-7442-b301813567fb@gmail.com> <ybllg4vr7to.fsf@w7.hardakers.net>
From: Fernando Gont <fgont@si6networks.com>
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Date: Thu, 13 Dec 2018 08:27:55 -0300
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Subject: Re: [OPSEC] ECMP [Tsvart last call review of draft-ietf-opsec-ipv6-eh-filtering-06]
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On 11/12/18 19:56, Wes Hardaker wrote:
> Brian E Carpenter <brian.e.carpenter@gmail.com> writes:
> 
>> It's a shame. Can you characterise those sessions in any way?
>>
>> (This shouldn't invalidate ECMP/LAG usage as described in RFC6438,
>> since there it is the operator that sets the flow label.)
> 
> I had to go dig out the bug that we dealt with "way back then" (to be
> fair, btw, credit to Duane Wessles at Verisign who tracked down and
> could reproduce the issue).
[...]
> 
> 2) Some clients were sending a flowlabel for the initial TCP handshake
> and then zeroing it out in subsequent packets:
> 
> SYN:
>     .... .... .... 1101 0111 0101 0110 0100 = Flow Label: 0xd7564
> 
> SYNACK from server: (no label)
> 
> ACK from client:
>     .... .... .... 1101 0111 0101 0110 0100 = Flow Label: 0xd7564
> 
> First data packet:
>     .... .... .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
> 
> Which what was causing the problem.
> 

At least some version of FreeBSD used to do the opposite: FL set to zero
during the TCP 3WHS, and non-zero afterwards.



-- 
Fernando Gont
SI6 Networks
e-mail: fgont@si6networks.com
PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492