#!/usr/bin/env python

# -*- coding: utf-8 -*-

import dns.query

import dns.resolver

from dns.exception import DNSException

def query_authoritative_ns (domain, log=lambda msg: None):

default = dns.resolver.get_default_resolver()

ns = default.nameservers[0]

n = domain.split('.')

for i in xrange(len(n), 0, -1):

sub = '.'.join(n[i-1:])

log('Looking up %s on %s' % (sub, ns))

query = dns.message.make_query(sub, dns.rdatatype.NS)

response = dns.query.udp(query, ns)

rcode = response.rcode()

if rcode != dns.rcode.NOERROR:

if rcode == dns.rcode.NXDOMAIN:

raise Exception('%s does not exist.' % (sub))

else:

raise Exception('Error %s' % (dns.rcode.to_text(rcode)))

if len(response.authority) > 0:

rrsets = response.authority

elif len(response.additional) > 0:

rrsets = [response.additional]

else:

rrsets = response.answer

# Handle all RRsets, not just the first one

for rrset in rrsets:

for rr in rrset:

if rr.rdtype == dns.rdatatype.SOA:

log('Same server is authoritative for %s' % (sub))

elif rr.rdtype == dns.rdatatype.A:

ns = rr.items[0].address

log('Glue record for %s: %s' % (rr.name, ns))

elif rr.rdtype == dns.rdatatype.NS:

authority = rr.target

ns = default.query(authority).rrset[0].to_text()

log('%s [%s] is authoritative for %s; ttl %i' %

(authority, ns, sub, rrset.ttl))

result = rrset

else:

# IPv6 glue records etc

#log('Ignoring %s' % (rr))

pass

return result

import sys

def log (msg):

sys.stderr.write(msg + u'\n')

for s in sys.argv[1:]:

print query_authoritative_ns (s, log)