Re: [Technical Errata Reported] RFC4443 (6153)

Brian E Carpenter <brian.e.carpenter@gmail.com> Mon, 22 February 2021 22:54 UTC

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Subject: Re: [Technical Errata Reported] RFC4443 (6153)
To: Ole Troan <otroan@employees.org>, =?UTF-8?Q?T=c3=b6ma_Gavrichenkov?= <ximaera@gmail.com>
Cc: Brian Haberman <brian@innovationslab.net>, Daniel Ginsburg <dginsburg@gmail.com>, IPv6 IPv6 List <ipv6@ietf.org>, RFC Errata System <rfc-editor@rfc-editor.org>
References: <CALZ3u+YPnpdjMQfikKh7dfCQt0nPOVahP9LHgQKfk5ab_yg1Zw@mail.gmail.com> <9A505AD0-93C2-4CFC-A779-7985585FE2E6@employees.org>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Message-ID: <dca3b538-6bb6-f834-7161-31929f666b41@gmail.com>
Date: Tue, 23 Feb 2021 11:53:06 +1300
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On 23-Feb-21 11:27, Ole Troan wrote:
> 
> 
>> On 22 Feb 2021, at 23:12, Töma Gavrichenkov <ximaera@gmail.com> wrote:
>>
>> 
>> Peace,
>>
>> On Tue, Feb 23, 2021, 12:41 AM Ole Troan <otroan@employees.org <mailto:otroan@employees.org>> wrote:
>>
>>     It’s perfectly valid to send a packet with a link-local source and a global destination address, as long as the interface with the global address is on the same link.
>>
>>
>> I, too, think so, but RFC 4443, Section 3.1, says that a Destination Unreachable Message should be sent in that case.
>>
>> Which some of the (famous) vendors who have read the 4443 but haven't taken a look on the 4007 are already doing.
>>
> 
> And this is in the case where both SA and DA are assigned to interfaces connected to the same link?

If they are on the same link there is no layer 3 router (a.k.a. forwarding node) involved. RFC 4443 says:
"A Destination Unreachable message SHOULD be generated by a router, or
by the IPv6 layer in the originating node, in response to a packet
that cannot be delivered... If the reason for the failure to deliver is lack of a matching entry in the forwarding node's routing table, the Code field is set to 0."

I agree that there is no sane interpretation of RFC4443 that would lead to an ICMP response.

Now on a "link" with an *insane* switch that confuses layer 2 and layer 3 functions, something bad might happen. Is that what's going on here? If so, no fix to RFC4443 can solve the problem.

    Brian

> 
> I struggle to see how the paragraph in 3.1 can be misinterpreted that way. Open a bug report with the vendor in question perhaps? Or name them here. 
> It’s not obvious to me that the proposed text in the errata makes it clearer by introducing “scope zone”. 
> 
> Cheers 
> Ole
> 
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