python / python/cpython

ipaddress IPv4Network and IPv6Network need specialized reverse_pointer property

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#125,641 12 comments 1 reaction 1 assignee View on GitHub

@Zheaoli is already working on this.

Since Oct 17, 2024.

3.12 3.13 3.14 stdlib type-bug
Dominant language
Python
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Description

Bug report

Bug description:
# Add a code block here, if required
from ipaddress import ip_network

# Generates now:
# '8.4./.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa'
assert(ip_network("2001:db8::/48").reverse_pointer == ['0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa'])

# Generates now:
# '0/29.2.0.192.in-addr.arpa'
assert(ip_network("192.0.2.0/29").reverse_pointer == [
'0.2.0.192.in-addr.arpa', '1.2.0.192.in-addr.arpa', '2.2.0.192.in-addr.arpa', '3.2.0.192.in-addr.arpa', '4.2.0.192.in-addr.arpa',
'5.2.0.192.in-addr.arpa', '6.2.0.192.in-addr.arpa', '7.2.0.192.in-addr.arpa'])

IPv4Network and IPv6Network get their implementation from _BaseAddress. But for network, it does not work as it should. It returns broken nonsense instead of helping data. Problem is unlike normal IP address, for a network range, it may return just single string for prefix lengths divisible by 8 for IPv4 and 4 for IPv6. But for other prefixes, it should return a list of domain names used.

I have implemented working generator for a list result at https://github.com/InfrastructureServices/dnsconfd/pull/70
I think something similar should be used in base ipaddress directly. If reverse_pointer should not be fixed, it should be removed from networks instead.

Related to #123409, but that is not exactly about networks. Can be verified a bit using ipcalc --reverse-dns, but even that crashes on undivisible ipv6 prefixes.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

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