In hwprobe.py's getNetworkInfo() method, we are determining the hostname with socket.gethostname().  The hostname returned by this call does not need to return a FQDN, and it may not be resolvable from outside of the one particular machine.

Imagine a machine with two network interfaces eth0 and eth1.  eth0 has an address 192.168.0.2 and goes to a private network where it is known as myserver.private.net.  This hostname is resolvable only in the private network.  eth1 has an address 10.34.32.149 and goes to the internet.  The public DNS record, which resolves to this IP address, is myserver.redhat.com.

We do not want the hostname from the private network.  We want the hostname which is accessible and usable from the machine which manages this server (e.g. the Candlepin installation).

The snippet below is a more robust way of finding the hostname.

       for family in (AF_INET6, AF_INET):
            try:
                s = socket.socket(family)
            except socket.error:
                continue

            try:
                s.settimeout(5)
                s.connect((candlepin_server, port))
                intf_tmp = s.getsockname()[0]
                if family == AF_INET:
                    intf = intf_tmp
                else:
                    intf6 = intf_tmp
                hostname_tmp = socket.getfqdn(intf_tmp)
                if hostname_tmp != intf_tmp:
                    hostname = hostname_tmp

This snippet connects to the Candlepin installation, identifies the IP address we are connecting from and then tries to determine the FQDN from this IP address.

Since a server can have different DNS records for IPv4 and IPv6 addresses, one interface can return different hostnames.  The code above favors the IPv4 hostname as in the current state of the world that is the name that is most likely correct.