Weird DNS Problem

[Andrew Pritchard]

I've already checked the FAQ and the mailing list archives for similar 
questions, but none seem relevant.

I've set up Horde and Imp on my "Stable Debian 2.2r2" box, and I've been 
using it for nearly a month now without any problems - indeed it's a fine 
piece of software. I've got a DNS server set up on the box to serve my 
internal network which is also running on there, which appears to be 
working just fine. It will resolve any of the entries in it, as will any 
of the other clients on the network both forward and reverse. It will also 
resolve any "real" internet addresses just fine via my ISP's DNS servers. 
It's using PostgreSQL as the database at the backend, which is the default 
DB for Horde/IMP under this distribution.

As I say - I've been using it for about a month now, and all of a sudden 
there is a problem. The horde framework comes up almost immediately, as 
expected - so I'd be surprised if this were a resource issue. However when 
I click on the IMP link, it takes at *least* a minute for the login screen 
to come up. And everytime I try to perform an action it takes a similar 
amount of time. In the past I've experienced similar problems with things 
like POP3/IMAP/Telnet where the server hasn't been able to resolve the IP 
address of the workstation concerned, and has timed out and gone off and 
done it anyway. So I put a sniffer on the network and sure enough it's 
trying to resolve: "localhost.co.uk".

The IMAP server is on that machine, and yes I'm in the UK, so trying to 
resolve a UK server would not be unreasonable. But where has it got  
localhost.co.uk from? And which process is it that's trying to resolve 
this address - Apache, IMAP, Postgresql or something else that I'm 
missing.

The only thing I have changed recently, is the "apt-get upgrade" for the 
Samba software on there which was the latest security fix, but to be 
honest I can't see how that could be an issue - the software should be 
unrelated, and I didn't see any shared libraries being updated as part of 
that process.

Everything else seems fine on the machine, including Samba. I will try 
this evening disabling Samba (which is also running off the Inetd to 
ensure that's not giving me spurious DNS requests.) I might also try 
switching off the local DNS server so ensure that is not misconfigured in 
some odd way. What else should I check? I'm not at all convinced it's an 
apache problem, the rest of the server (such as it is) is behaving itself 
- and is as quick as I'd expect it to be. 

I will also try an 'ordinary' IMAP client to see if there is a similar 
issue, and watch for the DNS queries whilst I do that.

How can I check the Postgresql db for misconfiguration? I don't have much 
experiance with any DB, so it could be a misconfig there. If it is a 
misconfig here - I don't know how that happened - I know I don't know 
enough about DB's to not mess with that.

Yours in hope of a quick resolution,

Andrew

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