How to get correct Hostname from reverse DNS lookup using Python?

I need to:

1. Get the host IP from a client request (DONE)
2. Perform a reverse DNS lookup (DONE)
3. Then compare the resulting hostname with the hostname on the Subject Alternative Name (SAN) of the clients SSL cert. (PROBLEM)

• I need to compare the results of a rdns lookup as "https://knowledge.com" with the SAN shown on the client cert "https://knowledge.com"

If I do a manual reverse lookup on a company using this tool and the domain name, I'm given the IP address:

Here's what I have in Python so far:

import socket request_ip = xxx.xxx.101.75 # Full IP address actually used def reverse_dns(request_ip): if socket.inet_aton(request_ip): try: r_dns = socket.gethostbyaddr(request_ip) except: logging.error('######## Host IP reverse DNS lookup failed. ########') else: logging.error('######## Host IP is not a valid IP address. ########') return r_dns reverse_dns = reverse_dns(request_ip) 

Problem:

• The list returned from the rdns lookup does not contain the actual hostname but rather a hosting company(?) and IP itself.

('xxx-xxx-101-75.somedata.com', [], ['xxx.xxx.101.75'])

• How do I get the actual hostname ("https://knowledge.com") as a response from the reverse DNS lookup?