#333 Support LDAP server discovery

[Adam Tauno Williams]

Use SRV records to discover LDAP servers if no LDAP servers are defined in the configuration, but LDAP authentication is requested

[root@yannigan-white ~]# host -t srv _ldap._tcp.micore.us
_ldap._tcp.micore.us has SRV record 0 100 389 niblick.micore.us.
_ldap._tcp.micore.us has SRV record 0 100 389 whetstone.micore.us.
_ldap._tcp.micore.us has SRV record 0 100 389 arbor.micore.us.
_ldap._tcp.micore.us has SRV record 0 100 389 emery.micore.us.

[Adam Tauno Williams]

>>> import dns
>>> import dns.resolver
>>> answer = dns.resolver.query('_ldap._tcp.micore.us', 'SRV')
>>> for rdata in answer:
...     print rdata.weight, rdata.port, rdata.target.to_text()
... 
100 389 emery.micore.us.
100 389 niblick.micore.us.
100 389 whetstone.micore.us.
100 389 arbor.micore.us.

[Adam Tauno Williams]

# pip install dnspython

>>> dns.__doc__
'dnspython DNS toolkit

That DNS module works.