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Incorrect ipaddress.ip_address.reverse_pointer with improved textual representation of IPv4-mapped IPv6 addresses #123409

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kellyjonbrazil opened this issue Aug 27, 2024 · 4 comments
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Incorrect ipaddress.ip_address.reverse_pointer with improved textual representation of IPv4-mapped IPv6 addresses #123409

kellyjonbrazil opened this issue Aug 27, 2024 · 4 comments
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@picnixz
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stdlib Python modules in the Lib dir type-bug An unexpected behavior, bug, or error

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@kellyjonbrazil
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kellyjonbrazil commented Aug 27, 2024 •
edited by bedevere-app bot
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Bug report

Bug description:

I'm seeing strange results with python 3.13 with the ipaddress.ip_address.reverse_pointer attribute with the new improved textual representation of IPv4-mapped IPv6 addresses:

IP Address: ::FFFF:192.168.1.35

Results in a reverse_pointer of:

5.3...1...8.6.1...2.9.1.f.f.f.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa

instead of the old:

3.2.1.0.8.a.0.c.f.f.f.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa

Python 3.13:

>>> import ipaddress
>>> ip = '::FFFF:192.168.1.35'
>>> ipaddress.ip_address(ip).reverse_pointer
'5.3...1...8.6.1...2.9.1.f.f.f.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa'

Python 3.12:

>>> import ipaddress
>>> ip = '::FFFF:192.168.1.35'
>>> ipaddress.ip_address(ip).reverse_pointer
'3.2.1.0.8.a.0.c.f.f.f.f.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa'

I'm not sure which one is more valid or if a pointer record is even relevant in the context of mapped addresses. The original way seems more correct to me if nothing for the fact that there are strange extra dots in the new output.

This is related to:

Issue: #87799

PR: #29345

Originally posted by @kellyjonbrazil in #87799 (comment)

CPython versions tested on:

3.13

Operating systems tested on:

Linux

@opavlyuk

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@kellyjonbrazil kellyjonbrazil added the type-bug An unexpected behavior, bug, or error label Aug 27, 2024
This was referenced Aug 27, 2024
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@picnixz picnixz added the stdlib Python modules in the Lib dir label Aug 28, 2024
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picnixz commented Aug 28, 2024

I think there is indeed an issue with the reverse pointer of IPv6. It does not match the RFC. I'll provide a patch.

@picnixz picnixz self-assigned this Aug 28, 2024
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@kellyjonbrazil Godd catch! Thank you for logging that, and I apologize for missing it during testing.
@picnixz thank you for taking care of this!

@bedevere-app bedevere-app bot mentioned this issue Aug 28, 2024
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encukou pushed a commit that referenced this issue Sep 2, 2024
@picnixz
gh-123409: fix IPv6Address.reverse_pointer for IPv4-mapped addresses (
77a2fb4 
GH-123419)

Fix functionality that was broken with better textual representation for IPv4-mapped addresses (gh-87799)
miss-islington pushed a commit to miss-islington/cpython that referenced this issue Sep 2, 2024
@picnixz @miss-islington
pythongh-123409: fix IPv6Address.reverse_pointer for IPv4-mapped ad…
d3f2b53 
…dresses (pythonGH-123419)

Fix functionality that was broken with better textual representation for IPv4-mapped addresses (pythongh-87799)
(cherry picked from commit 77a2fb4)

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
@bedevere-app bedevere-app bot mentioned this issue Sep 2, 2024
Merged
Yhg1s pushed a commit that referenced this issue Sep 2, 2024
@miss-islington @picnixz
[3.13] gh-123409: fix IPv6Address.reverse_pointer for IPv4-mapped a…
7761ddc 
…ddresses (GH-123419) (#123606)

gh-123409: fix `IPv6Address.reverse_pointer` for IPv4-mapped addresses (GH-123419)

Fix functionality that was broken with better textual representation for IPv4-mapped addresses (gh-87799)
(cherry picked from commit 77a2fb4)

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>
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encukou commented Sep 5, 2024

Thanks @kellyjonbrazil for the report and @picnixz for the patch!

@encukou encukou closed this as completed Sep 5, 2024
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picnixz commented Sep 5, 2024 •
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You're welcome! (I hope that I didn't misread the RFC because it doesn't tell anything about mapped addresses; however I assumed that we first map IPv4 to IPv6 before taking its reverse pointer, which is what was being done in 3.12.5)

@pemensik pemensik mentioned this issue Oct 17, 2024
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