ungleich-tools/detect-dns64-prefix.py

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2020-01-07 17:07:34 +00:00
#!/usr/bin/env python3
# Nico Schottelius, 2020-01-07
# Detect the DNS64 prefix
# Based on https://tools.ietf.org/html/draft-ietf-behave-nat64-discovery-heuristic-05
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#
# How it works:
# - ipv4only.arpa only has A records.
# - a DNS64 server will add AAAA records
# - we take this response (if any) and derive the IPv6 prefix from it
#
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import dns.resolver
import ipaddress
if __name__ == '__main__':
dns64_prefix = None
answers = dns.resolver.query('ipv4only.arpa', 'AAAA')
for rdata in answers:
address = str(rdata)
network = ipaddress.IPv6Network("{}/96".format(address),
strict=False)
# print("{}: {}".format(rdata, network))
print("{}".format(network))