How to get CNAME with sockets ?

[Sheila King]

On 17 Feb 2002 02:52:05 GMT, bokr at oz.net (Bengt Richter) wrote in
comp.lang.python in article <a4n5sl$9uj$0 at 216.39.172.122>:

> I don't know what you are really doing, but that sounds like
> systematically dialing all phone numbers in various area codes
> until you get Arnold Schwarzenegger ;-)
> 
> Can't you get a copy of the 'phone directory and find him yourself?
> Or do you need to visit with all those others?
> 
> Or is the metaphor totally inapplicable? ;-)

I don't think the metaphor is *totally* inapplicable, but I can see why
you would draw that conclusion without looking at the code.

Here is a snippet from the original Perl module:

==============(begin snippet)==============
    BUILDLIST: 
    for ( "a".."z", "1..9999" ) { 
        my $query = $resolver->query ($_.'.'.$zone);
        my $rr; next BUILDLIST unless $query;
        foreach $rr ($query->answer) { 
            my $pushed = 0;
            if ($rr->type eq "A") { 
                push @list, $rr->address; 
                $pushed = 1;
            } elsif ($rr->type eq "CNAME") { 
                if ($rr->cname eq 'list.terminator') { 
                    pop @list if $pushed;
                    last BUILDLIST;
                } elsif ($rr->cname eq "skip") { 
                    pop @list if $pushed;
                    next BUILDLIST;
                }
            }
        }
============(end snippet)==================

It's more like, the hosts will be
a.zone
b.zone
c.zone
etc...
until there are no more hosts. The last host will have a CNAME that
resolves to list.terminator. I don't know WHY the original code adds
subdomains 1..9999 onto the list, since there are currently only TWO
razor servers that I can discover in the default zone, which is
razor.vipul.net

In my own Python adaptation, I did this:

===========(begin snippet)=================
subdomainlist = list(string.ascii_lowercase)

zone = 'razor.vipul.net'
host_IP_list =[]
response_times = {}

for subd in subdomainlist:
    host = '%s.%s' % (subd, zone)
    try:
        IPaddy = socket.gethostbyname(host)
        host_IP_list.append(IPaddy)
    except socket.error, e:
        pipe = os.popen('dnsquery -t CNAME %s' % host)
        data = pipe.read()
        if data.find('list.terminator') > -1:
            break
===========(end snippet)=================

Notice that I left the 1..9999 off.

By the way, that isn't the complete translation of the razor-discover
client. Only a snip. And it isn't portable, either. Designed to work on
my web host with tools they have installed.

-- 
Sheila King
http://www.thinkspot.net/sheila/

"When introducing your puppy to an adult cat,
restrain the puppy, not the cat." -- Gwen Bailey,
_The Perfect Puppy: How to Raise a Well-behaved Dog_