Re: Refresh of DNS servers

["William M. Perry" <wmperry@kadath.us>]

Ralf Angeli wrote:

>* Derrell Lipman (2004-02-02) writes:
>
>  
>
>>The name servers are typically listed in /etc/resolv.conf which is one of the
>>configuration files for the resolver.  The resolver library [see resolver(3)]
>>which most applications that needs DNS services links with, only reads its
>>configuration files when res_init() is called, which typically occurs only
>>when the very first resolver services are required.  It's likely not gnus
>>that's caching the old nameserver, but rather the resolver library in emacs.
>>Since emacs is still running, the resolver library is not reinitializing.  I
>>don't know of any way to force a reinitialization, although one may exist
>>(some signal, possibly).
>>    
>>
>
>This sounds reasonable.  Does anybody have a hint where I could start
>to look for this stuff?  I grepped the Gnus and Emacs source
>directories for "dns", "res_init" and variations of "nameserv" and
>"resolv" but this didn't yield a usable result (I only found some
>utility functions in `net-utils.el'.  Maybe I missed something?).  I
>also tried to dig into `gnus-group-get-new-news' but got lost
>somewhere in the middle.
>  
>
You would need to make C level changes.  And is (probably?) going to 
vary from OS to OS.  I am pretty sure you can do it on linux by just doing:

if (res_state && (res_state->options & RES_INIT))
{
   res_state->options |= ~RES_INIT;
   res_init();
}

Solaris is similar.  There are also some tricks you could play to notice 
this by enumerating the interfaces and seeing if any of them are 
dynamically assigned.  Hrmm... linux doesn't appear to support that.  
Solaris does though. ;)

-bp