Re: Objection to draft-ietf-6man-rfc4291bis-07.txt

Alexandre Petrescu <alexandre.petrescu@gmail.com> Mon, 27 March 2017 22:25 UTC

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Subject: Re: Objection to draft-ietf-6man-rfc4291bis-07.txt
To: =?UTF-8?B?56We5piO6YGU5ZOJ?= <jinmei@wide.ad.jp>
References: <20170223134026.GI5069@gir.theapt.org> <6DA95097-8730-4353-A0C9-3EB4719EA891@google.com> <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> <CAJE_bqdZezDRti5LqCKnmU9QkwwhdejP22gXwk3wLKiS0mhx+Q@mail.gmail.com> <dfc8570d-fff0-39fe-a53f-db2c81c0ec8f@gmail.com> <CAJE_bqdHv0vw_kFFBZ2NE98t0nhkCR5rz8f=UOpwmvqtVjNqhg@mail.gmail.com>
Cc: 6man WG <ipv6@ietf.org>
From: Alexandre Petrescu <alexandre.petrescu@gmail.com>
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Date: Mon, 27 Mar 2017 17:25:02 -0500
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Le 27/03/2017 à 16:24, 神明達哉 a écrit :
> At Mon, 27 Mar 2017 16:00:58 -0500, Alexandre Petrescu
> <alexandre.petrescu@gmail.com>; wrote:
>
>>> On the other hand, BSDs' implementation of the
>>> IN6_IS_ADDR_LINKLOCAL() macro only checks the first 10 bits:
>>>
>>> #define IN6_IS_ADDR_LINKLOCAL(a)        \ (((a)->s6_addr[0] ==
>>> 0xfe) && (((a)->s6_addr[1] & 0xc0) == 0x80))
>>
>> Tatuya, masking it that way it means that fe81::/10 is also
>> recognized as an LL address prefix, right?  I think it is good,
>> but just checking.
>
> fe81::/10 is just an "abnormal" form of fe80::/10,

Err, I dont think fe81::/10 is an abnormal LL.  I think fe81::/10, 
fe82::/10, ... febf::/10 are all normal forms of LL.

> but I guess you actually meant fe81::/16.

I did not mean fe81::/16, I meant fe81::/10.

fe80      is: 1111 1110 1000 0000
fe80::/10 is: 1111 1110 10
fe81::/10 is: 1111 1110 10

Alex

> Assuming so, your understanding is correct: an address that matches
> fe81::/16 is recognized as unicast link-local wherever the
> IN6_IS_ADDR_LINKLOCAL macro is used for the test.  For example, BSD
> kernels consider this kind of address to be unicast link-local in the
> validation of received RA:
>
> if (!IN6_IS_ADDR_LINKLOCAL(&saddr6)) { nd6log((LOG_ERR,
> "nd6_ra_input: src %s is not link-local\n", ip6_sprintf(ip6bufs,
> &saddr6))); goto bad; } (this code only checks the first 10 bits).
>
> -- JINMEI, Tatuya
>