Re: [DNSOP] WGLC for draft-ietf-dnsop-let-localhost-be-localhost-02

Petr Špaček <> Fri, 26 January 2018 16:32 UTC

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Subject: Re: [DNSOP] WGLC for draft-ietf-dnsop-let-localhost-be-localhost-02
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On 26.1.2018 17:22, 神明達哉 wrote:
> At Fri, 26 Jan 2018 12:47:29 +0100,
> Petr Špaček <> wrote:
>>> I myself don't have a particular opinion on whether to send it to the
>>> IESG, but I don't think it's ready for it based on my understanding of
>>> the WG discussion so far.  In particular, I don't think I saw a wg
>>> consensus about one major objection to the idea: "I'd like to keep my
>>> right of configuring my DNS servers (authoritative or recursive) to
>>> return whatever I want to 'localhost' queries".  Again, I personally
>>> don't claim this right, but I see the concern.  If my observation is
>> Software is still free to provide knobs to deviate its behavior from
>> RFC, which is nothing unusual when it comes to DNS(SEC).
>> Is there a real problem to solve? My understanding is that this document
>> is stating what software should do by default.
> Hmm, that's different from my interpretation of the draft.  According
> to my usual interpretation of IETF docs, I would interpret these from
> Section 3:
>    3.  Name resolution APIs and libraries MUST recognize localhost names
>        as special, and MUST always return an appropriate IP loopback
>        address for IPv4 and IPv6 address queries and negative responses
>        for all other query types.  Name resolution APIs MUST NOT send
>        queries for localhost names to their configured recursive DNS
>        server(s).
>        As for application software, name resolution APIs and libraries
>        MUST NOT use a searchlist to resolve a localhost name.
>    4.  (Caching) recursive DNS servers MUST respond to queries for
>        localhost names with NXDOMAIN.
>    5.  Authoritative DNS servers MUST respond to queries for localhost
>        names with NXDOMAIN.
> as these are requirements without a user-configurable knob.  If the
> actual intent was just to specify the default behavior with a
> configurable knob, I'd expect SHOULD-variants are used in cases like
> these.

Oh, I can see your point. Let me rephrase what I'm trying to say:
I personally agree with the doc, it makes sense to me, and I do not
believe that its wording prevent anyone from adding knobs they want.
Software in the end will do whatever its developers wanted, which might
include knob to override any part of spec.

An example: RFC 4033 clearly states what should be done if result of
validation is "Bogus". Nonetheless, Unbound has "val-permissive-mode:
yes" which enables admin to pass bogus answers.

This is not to point finger to Unbound or anyone else! I'm just
demostrating that standard can be technically right, and still there can
be knobs allowing non-standard behavior. (Do not get me started about
stub zones, forwarding, ... and the other half of DNS :-))

I hope it clarifies the point.

Petr Špaček  @  CZ.NIC