Re: [Doh] meta qtypes

Patrick McManus <pmcmanus@mozilla.com> Sun, 18 March 2018 19:47 UTC

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From: Patrick McManus <pmcmanus@mozilla.com>
Date: Sun, 18 Mar 2018 19:47:54 +0000
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Subject: Re: [Doh] meta qtypes
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Section 4 has spme rules about generating http freshness lifetimes from dns
responses. Is there a text change to that you are proposing?

On Mar 18, 2018 7:08 PM, "Miek Gieben" <miek@miek.nl>; wrote:

> [ Quoting <pmcmanus@mozilla.com>; in "Re: [Doh] meta qtypes..." ]
>
>> Hi - DoH itself doesn't require axfr/etc anywhere that DNS would not (I'm
>> not aware of whether it does or not) - the text is just meant to give the
>> HTTP considerations when it does carry larger DNS responses such as that.
>>
>> WRT HTTP caching - section 4 of DoH talks about how HTTP freshness
>> lifetimes should be set for DoH responses. Is there something different
>> here?
>>
>
> This HTTP caching opens up a pretty big can of worms on what to set the
> cache
> TTL to.
>
> If we consider HTTP/2 *just* the transport than it should not be concerned
> with
> caching (i.e. TCP doesn't cache).
>
> If we do want to cache on this layer a server implementing DoH needs to
> inspect the DNS packet, it should (among other things), look for a SOA
> record to get a TTL or MINTTL, or get the minimum TTL of all the records in
> the message, or look for RRSIG expiration times and distill a minimum TTL
> from those.
>
> I think this draft should say "MUST not cache these responses".
>
> /Miek
>
> --
> Miek Gieben
>