Re: [DNSOP] RFC 8482 (the ANY -> HINFO hack) and DNAME

[Paul Vixie <[e-mail]>]

a correct implemention of smtp could pick up the a and aaaa from additional data without making any additional queries. it could also ignore cname records in the a/aaaa response and declare that the a/aaaa owner was wrong.

we can't break working behaviour no matter what the statistics show. a draft that said clients can expect this would also have to say servers should not expect clients to expect this.

vixie

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On 18 Nov 2019, 12:38, at 12:38, Viktor Dukhovni <[e-mail]> wrote:
>> On Nov 17, 2019, at 8:35 PM, Mark Andrews <[e-mail]> wrote:
>> 
>> Just because broken configuration don’t always cause problems doesn’t
>mean
>> that they don’t sometimes.  MTA’s need to know what names they are
>known
>> by to properly remove MX records from consideration when performing
>store and
>> forward. Email forwarding loops still occur.
>
>Postfix ignores the names, and does loop elimination by IP
>address.  It also detects loops when it sees its own name in
>the 220 banner or EHLO reply.  Relying on just canonical names
>for loop elimination is not enough.  The same IP address can
>can have multiple names even without CNAMEs.
>
>Other MTAs may look at the names and not the addresses, but
>I would hope that they also employ additional loop detection
>mechanisms, and there's ultimately the hop (Received header)
>count.
>
>-- 
>	Viktor.
>
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