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Re: Setting DNS Servers Manually?

On Oct 17, 2007, at 10:57 PM, Michael B Allen wrote:

> On Wed, 17 Oct 2007 21:44:17 -0700
> "Henry B. Hotz" <hotz@jpl.nasa.gov> wrote:
>> I'm not sure I understand.
>> If you put everything in the krb5.conf then it doesn't need to do SRV
>> record lookup.  You could setenv KRB5_CONFIG to an application-
>> specific config file.  Maybe you can even put the Krb servers in as
>> IP numbers instead of DNS names.  Was that the sort of thing you were
>> looking for?
> Hi Henry,
> Actually I already do that mostly. I bypass the SRV lookups by doing
> those myself. And I added a krb5_config_set function to set the kdc
> (and kpasswd_server for password setting). But still libkrb5 needs to
> do at least A record lookups and I wouldn't be surprised to find some
> logic that still provokes SRV lookups or need to do them for some  
> reason.
> Converting to IP before krb5_config_set-ing seems seems like it could
> lead to trouble since Kerberos needs FQDNs to pick out realms,  
> generate
> names, etc.
> Also, what I really want to do is channel all DNS queries through my
> DNS lib so I provide consistent DNS server fallback behavior, caching,
> server "stickiness", etc.
> But for now I would be happy if I could just overload  
> gethostbyname. So
> basically I want to create a 'libmyresolv' that has a my_gethostbyname
> function and then modify Heimdal to use it. Unfortunately the  
> libmyresolv
> would need to link with my libs that link with Heimdal which creates a
> nasty circular dependency. Still haven't wrapped my head around  
> that one.
> Mike

Stick all the hosts you care about in /etc/hosts, and configure  
nsswitch.conf for "files,dns"?

I still don't understand why you want to do this.  I can understand  
wanting to guarantee reliability for a specific application, and its  
knowledge of its peers.  I don't understand why you wouldn't want  
other applications on the same box to get the same thing though.

>> On Oct 17, 2007, at 2:38 PM, Michael B Allen wrote:
>>> Hello,
>>> I want to my apps to be configureable independantly of host
>>> settings. Is
>>> there a way to tell Heidmal to use a specific set of DNS servers?
>>> I have my own DNS routines so one option is to create and link  
>>> with my
>>> own libresolv but I'm hoping there's an easier solution.
>>> Any ideas?
>>> Off to look at the code,
>>> Mike
The opinions expressed in this message are mine,
not those of Caltech, JPL, NASA, or the US Government.
Henry.B.Hotz@jpl.nasa.gov, or hbhotz@oxy.edu