Writing Network Tools with Python (Part 1: DNS Resolution)

In this article, we'll be taking a look at a few ways in which Python can make your life easier.  All of the examples in this part will pertain to DNS.

Resolve A Records (FQDN to IPv4)

from dns import resolver

results = resolver.query('0.pool.ntp.org', 'A')
for result in results:
    print(result)

103.105.51.156
138.197.114.122
45.33.103.94
71.255.99.178

Resolve AAAA Records (FQDN to IPv6)

from dns import resolver

results = resolver.query('cnn.com', 'AAAA')
for result in results:
    print(result)

2a04:4e42::323
2a04:4e42:200::323
2a04:4e42:400::323
2a04:4e42:600::323

Resolve PTR Records (Reverse Lookup; IPv4 to FQDN)

from dns import reversename, resolver

results = resolver.query(reversename.from_address('10.1.1.100'), 'PTR')
for result in results:
    print(result)

gitlab.example.com.

Resolve MX Records (Mail Servers for Domain)

from dns import resolver

results = resolver.query('gmail.com', 'MX')
for result in results:
    print(result)

30 alt3.gmail-smtp-in.l.google.com.
40 alt4.gmail-smtp-in.l.google.com.
5 gmail-smtp-in.l.google.com.
10 alt1.gmail-smtp-in.l.google.com.
20 alt2.gmail-smtp-in.l.google.com.

Check if Domain is a Super or Sub Domain

from dns import name

print(name.from_text('www.tyler-wright.com').is_subdomain(name.from_text('tyler-wright.com')))

True

from dns import name

print(name.from_text('www.tyler-wright.com').is_superdomain(name.from_text('tyler-wright.com')))

False