Re: Objection to draft-ietf-6man-rfc4291bis-07.txt - /63 and /65 RAs on linux

Alexandre Petrescu <alexandre.petrescu@gmail.com> Thu, 02 March 2017 08:30 UTC

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Subject: Re: Objection to draft-ietf-6man-rfc4291bis-07.txt - /63 and /65 RAs on linux
To: Erik Kline <ek@google.com>
References: <20170223134026.GI5069@gir.theapt.org> <CAN-Dau0s04c=RV0Y8AGaxBPFui41TWPTB+5o0K2Lj-iah0An1w@mail.gmail.com> <CAL9jLaYirty22iGiEjEaYq3_KA1FZhxBTOBWuFOXQ9C-WPd5xQ@mail.gmail.com> <CAN-Dau0n6oFm538XdJOcuO1yg92BCDD3mBu5YfBVm_+g-gtcKA@mail.gmail.com> <CAL9jLaYO=uYgVfSZ0SoSe0SujJ1xgwEKE8WLzo_keJHywgXTtg@mail.gmail.com> <CAN-Dau1vJV5O_Ythp6THkAu4-YZXV82Upny1V+ybbjCVZQQX=A@mail.gmail.com> <27cce319-18ac-5c0e-3497-af92344f0062@gmail.com> <de4988be-6031-08d9-84ce-21c3fa4f9bc9@gmail.com> <98401ef7-cf41-b4a0-4d11-a7d840181bd0@gmail.com> <1047f5fc-ae40-be52-6bab-27f31fe5e045@gmail.com> <9a94feac-8d59-b153-d41c-04fc371e4db4@gmail.com> <CAO42Z2z7v4gDk91b6Of-1sczV88m3B9kzn0MeJU_VBJ416k6Ww@mail.gmail.com> <ae35b45a-0398-840f-fc0d-1f64dd2fcc58@gmail.com> <37851ee3-03be-8bee-6190-f4d28df86305@gmail.com> <alpine.DEB.2.02.1703012051590.30226@uplift.swm.pp.se> <b5784622-c24e-a531-4e68-249b03701941@gmail.com> <CAAedzxrSTFe0GgYuvtXPNE=R_ZCXotxL7HbKdj5A4-869rncmw@mail.gmail.com>
From: Alexandre Petrescu <alexandre.petrescu@gmail.com>
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Date: Thu, 2 Mar 2017 09:30:02 +0100
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Le 02/03/2017 à 09:14, Erik Kline a écrit :
>
>
> On 2 March 2017 at 17:11, Alexandre Petrescu
> <alexandre.petrescu@gmail.com <mailto:alexandre.petrescu@gmail.com>> wrote:
>
>
>
>     Le 01/03/2017 à 20:53, Mikael Abrahamsson a écrit :
>
>         On Wed, 1 Mar 2017, Alexandre Petrescu wrote:
>
>             For information, today on linux a /65 RA is called "illegal"
>             and a
>             /63 RA makes a Host to _not_ configure an address.  What linux
>             wants is a 64 and nothing else.  This is not normal, and
>             it's not
>             programmer's fault.
>
>
>         Could you please elaborate on the last sentence. What do you mean by
>         "not normal"?
>
>
>     It is not normal for linux kernel to complain about a plen==65 in the RA
>     - it should not complain.  Do you think it is normal?
>
>     It is not normal for a linux kernel to _not_ form an IPv6 address when
>     it receives a plen==63.  It would have been normal to append the IID to
>     it.  Do you think it is abnormal for a linux kernel to form an IPv6
>     address when it receives a plen==63?
>
>
>
> These statements have zero basis in fact.  The Linux kernel is behaving
> according to all currently available (proposed) standards.

Well... do you have a standard for IPv6 over cellular links?   Or IPv6 
over USB?  I dont.  And I consider linux to act wrongly when being sent 
an RA plen==65 on these links and refusing them as "illegal".

I think it should not refuse it on Ethernet either, but there you have a 
standard RFC2464.  And for that I agree with you.  Even though it should 
be perfectly fine to use that plen==65 to have an entry in the rt table, 
and use a manually configured address in that plen.

I dont have a standard that tells that the computer is forbidden from 
introducing a 0 between 63 and 64 such that the plen==63 plus IID==64 
make for 128.

Alex