Bug#343140: libc6: resolver always checks search list in /etc/resolv.conf
On Wed, Dec 14, 2005 at 11:41:38AM -0800, Edward Buck wrote:
> If it's a frequently used feature, it wasn't available until sarge.
> Woody did not behave this way (I checked).
Huh?
$ cat /etc/debian_version
3.0
$ cat /etc/resolv.conf
search hpcc.sztaki.hu lpds.sztaki.hu sztaki.hu
nameserver 127.0.0.1
$ ping rs2.lvs
PING rs2.lvs.sztaki.hu (193.6.200.132): 56 data bytes
...
It is definitely available in Woody. I'm using it regularly.
> Also, this "new" feature
> completely breaks software that doesn't expect this feature, since
> postfix, telnet and others are doing WAY more DNS queries than they
> should. Depending on how many search domains are listed and how many
> caching nameservers are listed, in my case (2 search domains and 2
> nameservers) I count at least 4 unnecessary queries. That's very bad.
Well, why do you have any search domains then? It is for human
convenience only, and a mail server usually does not have regular user
accounts so no need for such convenience features.
> Sure, I can do that with telnet interactively. How do I tell postfix to
> do that without a patch? I guess I could try setting the ndots option
> to postfix's environment but that seems like a bad hack. The current
> behavior makes using the search lines impossible for busy servers,
> especially mail servers that do DNS queries for every piece of mail.
> Just imagine the excess DNS load on a server processing a million e-mail
> messages a day. That's what I'm seeing.
For such setups I suggest running some local DNS-catching solution (nscd
or a local caching-only name server).
Gabor
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