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Re: [Doh] [Ext] A question on the mix of DNS and HTTP semantics

Petr Špaček <petr.spacek@nic.cz> Mon, 19 March 2018 22:38 UTC

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From: Petr Špaček <petr.spacek@nic.cz>
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Subject: Re: [Doh] [Ext] A question on the mix of DNS and HTTP semantics
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On 19.3.2018 17:03, Patrick McManus wrote:
> I agree with Stephane. DNS information in non-successful HTTP responses
> (i.e. not a 2xx) is not the answer to the question you asked in the HTTP
> request. I can't tell you what it is - its normally just defined as
> human readable explanation. It may certainly be generated by HTTP
> servers that do not understand DoH.

I agree, if there is a valid DNS message in the reply it should be HTTP
200 and anything else should be a HTTP-specific, e.g. Gateway Timeout
when DNS server/proxy timed out.

Attempting to mix HTTP and DNS semantics opens can of worms. If there is
a taste/need for something new and fancy, let's design new protocol for
stub-recursive communication with a proper REST interface from scratch.

I believe that attempts to HTTP-ify current DNS (beyond plain
encapsulation) are going to end up with epic fail... let's see.

Petr Špaček  @  CZ.NIC

> 
> 
> 
> 
> On Mon, Mar 19, 2018 at 3:39 PM, Stephane Bortzmeyer <bortzmeyer@nic.fr
> <mailto:bortzmeyer@nic.fr>> wrote:
> 
>     On Mon, Mar 19, 2018 at 11:21:27AM -0400,
>      Andrew Sullivan <ajs@anvilwalrusden.com
>     <mailto:ajs@anvilwalrusden.com>> wrote
>      a message of 29 lines which said:
> 
>     > If it were actually truncated, wouldn't the message have a TC bit
>     > set?
> 
>     Truncated for HTTP reasons (error 500 : the server crashed), not for
>     DNS reasons.
> 
>     If the DNS answer is truncated for DNS reasons (EDNS buffer size too
>     small), I would expect the HTTP status code to be 200.

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