(ITS#6093) correct hostname resolving problem in guess_service_principal()

[mikbec@web.de]

Full_Name: Mike Becher
Version: HEAD of 2.4
OS: Linux
URL: ftp://ftp.openldap.org/incoming/mike-becher-090504.libraries-libldap.patch
Submission from: (NULL) (84.150.168.64)


patch file name: mike-becher-090504.libraries-libldap.patch
patch subject: correct hostname resolving problem in guess_service_principal()

patch description:
In AD (Active Directory) enviroment this patch removes the problem
with potentially invalid hostname "DomainDnsZones.MY.DOMAIN" which
might be given in the "host" string. Instead (if possible) hostname of
AD-DC will be tried first to which the caller is connected to.
It uses function ldap_host_connected_to() provided in os-ip.c to do a
reverse lookup on the address to get the official hostname of connected
host.  This is necessary for kerberos to work right, since the
official hostname is used as the kerberos instance.