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

Alexandre Petrescu <alexandre.petrescu@gmail.com> Tue, 28 March 2017 01:11 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 20:11:24 -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, but I guess you
> actually meant fe81::/16.  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).

If this code runs on an Ethernet interface, then I think it is wrong. 
BEcause the link-local prefix on an Ethernet interface is fe80::/64, and 
not fe80::/10.

IN6_IS_ADDR_LINK_LOCAL run on Ethernet should use a mask of 64bits, not 
10bits, as it currently does.

In general, a generic IN6_IS_ADDR_LINKLOCAL is good to use a /10 mask. 
But some different IN6_IS_ADDR_LINK_LOCAL_ETHERNET is good with mask /64.

fe81::1 on Ethernet is not a Link Local address.

fe81::1 in general _is_ a Link Local address.

(and, yes, ideally, it would be good to make that 64 a parameter even of 
Ethernet, but that is a separate discussion).

Alex

>
> --
> JINMEI, Tatuya
>