Subject: should a pure recursor know about localhost/1.0.0.127.in-addr.arpa?

From: bert hubert <[email-masked]>
Date: Tue, 11 Apr 2006 13:38:10 +0200

Hi people,

The PowerDNS recursor is currently in very big production for the first
time, I've been asked why it doesn't answer for localhost.

The recursor of PowerDNS is a pure recursor and has zero authoritative
facilities, so I've added some hardcoded support for localhost and
1.0.0.127.in-addr.arpa.

But I wonder if this is right and proper? And, if it is, should I hardcode
the IPv6 equivalents as well?

And, additionally, does it all matter? Have people heard of problems with
not being able to resolve localhost? I know DJBDNS hardcodes it too.

I've searched the namedroppers archive but localhost is kind of an awkward
search term, it pops up a lot.

Thanks.

-- 
http://www.PowerDNS.com      Open source, database driven DNS Software 
http://netherlabs.nl              Open and Closed source services

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---

From: Peter Koch <[email-masked]>
Date: Tue, 11 Apr 2006 14:17:50 +0200

Stephane Bortzmeyer <[email-masked]> wrote:

> RFC 1912 says so and our Zonecheck tool tests it:
> 
>    Certain zones should always be present in nameserver configurations:
> 
>            primary         localhost               localhost
>            primary         0.0.127.in-addr.arpa    127.0
>            primary         255.in-addr.arpa        255
>            primary         0.in-addr.arpa          0

RFC 1912 is informational only and has some outdated parts. In the dnsop WG
there's a draft under consideration (although not an official wg document:
draft-andrews-full-service-resolvers-02.txt), that aims at BCP and seeds
a list of zones each recurive server should authoritatively treat as empty.

>    There has been some extensive discussion about whether or not to
>    append the local domain to it.  The conclusion is that "localhost."
>    would be the best solution.  The reasons given include:
> 
>       "localhost" by itself is used and expected to work in some
>       systems.
> 
>       Translating 127.0.0.1 into "localhost.dom.ain" can cause some
>       software to connect back to the loopback interface when it didn't
>       want to because "localhost" is not equal to "localhost.dom.ain".

There are two different schools of thought for this. One lets the rev map
for 127.0.0.1 point to "localhost." (the localhost. TLD was reserved in RFC
2606, yet not delegated), the other lets it point to a localhost in some
appropriate domain, also setting up the correspinding A RR there.
The "localhost." approach either relies upon some search path and/or on the
presence of a "localhost." zone on the respective resursive server.

-Peter