ipaddress.reverse_pointer returns nonsense if prefixed input is given

Bug report

ipaddress.reverse_pointer does not seem to validate its input at all. For example:

$ python3
Python 3.10.4 (main, Apr  2 2022, 09:04:19) [GCC 11.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import ipaddress
>>> ipaddress.ip_network('2001:db8:1:2:3:4:5::/64',False).reverse_pointer
'4.6./.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.0.1.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa'
>>> 

This is very obviously wrong.

In this case of prefixed input, the output should be cut to the appropriate prefix length, yielding
2.0.0.0.1.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa as output. It is ok to assume /128 as the default, converting 2001:db8:1:2:3:4:5:: to 0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.0.1.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa, but input longer than that is an error.

Prefixed address strings are for example important when generating zone names for the server side of IPv6 reverse DNS. Run-of-the-mill network client software is unlikely to use this for addresses shorter than /128, but for the server side it is an important use case.

Greetings
Marc

首先執行報告中的 Python 重現程式，並追蹤 ipaddress.reverse_pointer 進入點，以了解帶前綴的輸入如何處理。完成標準是：帶前綴的 IPv6 輸入產生依其前綴長度截短的反向指標名稱，預設的不帶前綴輸入視為 /128，並拒絕長於 /128 的輸入。