RE: Is it possible to query DNS for a SRV record in perl?

[K R. <kr...@ya...>]

Thank you so much, Christopher. I finally got the
script to work! It was so exciting.

kary


FROM: Christopher A BongaartsDATE: 01/14/2002
13:38:24SUBJECT: 

RE:  Is it possible to query DNS for a SRV record in
perl? 

As K Reddy once put it so eloquently:

> Instead, he suggested that I query DNS for the SRV
> record, which looks like this: 
> _.gc._tcp.us-city._sites.company.com. 
> 
> It worked when I used nslookup from a DOS prompt,
but
> I'm not sure how to look it up in UNIX. 
> I tried the Net::DNS module, but I honestly couldn't
> figure out how (or if) it works for looking up SRV
> records. 

Here is the code we use to lookup the PDC for doing
Active Directory
updates, using Net::DNS.  Call it with the domain that
you're trying
to update.  Returns a hostname and port.  Note that I
"hardcode" in
the LDAPS port (via getservbyname) since MS doesn't
define _ldaps as a 
service name.  Change ldaps to ldap in the
getservbyname, or return
$rr->port to use the port in the SRV record, if you
want non-ssl LDAP.

####snip
sub lookup_pdc {
  my ($dc) = @_;
  my $res = new Net::DNS::Resolver;
  my $query = $res->send("_ldap._tcp.pdc._msdcs.$dc",
"SRV");
  if ($query) {
    foreach $rr ($query->answer) {
      next unless $rr->type eq 'SRV';
      # return first found; find ldaps port from
services file since
      # there's no _ldaps SRV record
      return $rr->target, scalar
getservbyname('ldaps', 'tcp');
    }
  } else {
    ¬e("SRV lookup failed: " . $res->errorstring);
  }
  return;
}
####snip

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