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Bug#575209: marked as done (Please resolv domain names with hyphens as border chars)

Your message dated Thu, 25 Mar 2010 06:48:58 -0700
with message-id <20100325134858.GC30616@dario.dodds.net>
and subject line [bjorn@mork.no: Re: Bug#575209: closed by Holger Levsen <holger@layer-acht.org> (Re:  Bug#575209: general: Error resolving hostname [resent])]
has caused the Debian Bug report #575209,
regarding Please resolv domain names with hyphens as border chars
to be marked as done.

This means that you claim that the problem has been dealt with.
If this is not the case it is now your responsibility to reopen the
Bug report if necessary, and/or fix the problem forthwith.

(NB: If you are a system administrator and have no idea what this
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-- 
575209: http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=575209
Debian Bug Tracking System
Contact owner@bugs.debian.org with problems
--- Begin Message --- 
Package: general
Severity: important

Dear all,  I've found something that is most propbably a bug in Linux's resolv
system, when trying to open a specific page with Epiphany (but any other
browser will fail as well, please try out yourself). To reproduce, please visit
<http://www.deviantart.com/> and search for "SNES". On the first results page a
picture called "SNES World HD" should appear. Try to click this picture.  Your
browser will fail to resolv the hostname and even ping won't be able to:    $
ping KeR-.deviantart.com   ping: unknown host KeR-.deviantart.com   However,
nslookup returns the right IP address and this page even loads under both
Windows XP and Mac OS X:    $ nslookup KeR-.deviantart.com    Server:
134.147.57.130   Address:      134.147.57.130#53    Non-authoritative answer:
KeR-.deviantart.com   canonical name = www.deviantart.com.   Name:
www.deviantart.com   Address: 8.10.77.140  I believe this bug is caused by the
dash character in the domain name, but I don't have any further knowledge of
Linux's resolv system. As you are the experts, please point me to where I can
help to trace this bug.  Cheers, Fabian


-- System Information:
Debian Release: squeeze/sid
  APT prefers unstable
  APT policy: (550, 'unstable'), (400, 'experimental')
Architecture: i386 (i686)

Kernel: Linux 2.6.32-2-686 (SMP w/1 CPU core)
Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

--- End Message ---
--- Begin Message --- 
This cogently addresses the reasons for the bug reopening.  Closing again
with this explanation.

----- Forwarded message from Bjørn Mork <bjorn@mork.no> -----

Date: Thu, 25 Mar 2010 14:17:26 +0100
From: Bjørn Mork <bjorn@mork.no>
To: debian-devel@lists.debian.org
Cc: debian-glibc@lists.debian.org
Cc: debian-devel@lists.debian.org
Subject: Re: Bug#575209: closed by Holger Levsen <holger@layer-acht.org> (Re:
	Bug#575209: general: Error resolving hostname [resent])
User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux)

Fabian Greffrath <fabian@greffrath.com> writes:

> - Sites with domain names like <ker-.deviantart.com> do already exist!
> Do you think they should be accessible by any other proprietary
> operating system, but not Debian? Not really!

Anyone can enter bogus data in the DNS.  Neither the existence of such
data nor the failure to detect it by other operating systems are
arguments for allowing it in Debian.  Literally anyone can add an
invalid A record and make an OS which accepts it.

> - There is already an inconsistency among the different
> implementations in Debian (or Linux as a whole), as e.g. ping and any
> other program using gethostbyname() fail to resolv, whereas nslookup
> and host succeed.

This is not an inconsistency.  

gethostbyname(), getaddrinfo() etc look up hostnames, whereas dig,
nslookup and host query the DNS.  The distinction is that almost
anything is allowed in DNS, while a hostname must obey the updated
version of RFC 952 (as amended by RFC 1123).  See e.g.
http://www.mail-archive.com/dnsop@ietf.org/msg01731.html for an
excellent explanation of the difference.

> - The advice in the cited RFC is already ignored. Domain names that
> start with a digit, e.g. 12345.foo.bar, can be resolved, whereas the
> RFC tells us "They [labels] must start with a letter, end with a
> letter or digit [...]". So let's just relax the rules in the RFC (they
> are only recommendations after all) a bit more to also allow hyphens
> as border characters in labels. It doesn't harm anyone, it just
> enables us to resolv a few more actual domain names!

This rule has been formally changed by the standards track RFC 1123.
That is something quite different than "the cited RFC is already
ignored"!

> the advice of RFC 1035

which is the standards track RFC describing the *domain name system*
which is so much more than host names.  It is irrelevant wrt the
discussion of valid hostnames.

Unfortunately this RFC is one of the most confusing ever written, mixing
a lot of irrelevant informational data with the actual standard.  It
should have merely referred to RFC 822 (updated several times) and RFC
952 (amended several times) for the restrictions on valid mail and host
names.  The verbose examples copying restrictions imposed by other
standards have always been confusing, and of course even more so after
the other standards were changed...

> RFC 1178:

which is an informational RFC.

> RFC 952:

which is the standards RFC describing valid hostnames.  This should be
obeyed, as amended by other RFCs.

> RFC 1123:

which is a standards track RFC updating and clarifying lots of other
standards.  Among the changes is the modification of RFC 952 wrt labels
starting with a digit.

You forgot to mention RFC 2181 which is a standards track RFC trying to
fix a few of the errors in RFC 1035, among those the mixture of standard
requirements and informational text.  Although as irrelevant to this
discussion as RFC 1035 itself, I believe it helps understand the
distinction between valid DNS labels and valid host or mail names.




Bjørn

----- End forwarded message -----

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Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
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--- End Message ---
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