[YLUG] Testing name lookups

[Roger Leigh]

Roger Leigh <rleigh at whinlatter.ukfsn.org> writes:

> Following some strange problems, which I believe are due to the
> glibc 2.6 name resolver, I want to test name lookups.
> Unfortunately, tools like host, nslookup and dig appear to only
> query the DNS servers in /etc/resolv.conf, whereas I want to also
> query hosts.  Ideally, I want a tool which is nothing more than a
> lightweight wrapper around getipnodebyname(3) or gethostbyname(3).
> "getent hosts" appears to do this, but is not reflecting the
> behaviour I am seeing:
>
> % getent hosts localhost
> 127.0.0.1       localhost
> % getent hosts ip6-localhost
> ::1             ip6-localhost ip6-loopback
>
> My actual problem is this:
>
> % telnet ip6-localhost
> Trying 127.0.0.1...
>        ^^^^^^^^^
> telnet: Unable to connect to remote host: Connection refused
>
> Where on earth did the IPv4 localhost address just appear from ?!
> This is making all programs configured to use ip6-localhost fail to
> connect.

Just to follow up with a resolution to this:

I ended up writing a small test program to identify the cause of this,

  http://people.debian.org/~rleigh/addrtest.c

This showed that IPv6 addresses were only available when the system
had a globally scoped IPv6 address, or else all addresses (even local
ones) were not returned.  The full detail is at

  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=441857

and

  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=435646


Sorry for the noise!

Roger

-- 
  .''`.  Roger Leigh
 : :' :  Debian GNU/Linux             http://people.debian.org/~rleigh/
 `. `'   Printing on GNU/Linux?       http://gutenprint.sourceforge.net/
   `-    GPG Public Key: 0x25BFB848   Please GPG sign your mail.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 188 bytes
Desc: not available
Url : http://mailman.lug.org.uk/pipermail/york/attachments/20070912/3e1e1157/attachment.bin