ipaddress module fails on rfc4007 scoped IPv6 addresses

@terryjreedy

BPO	34788
Nosy	@terryjreedy, @ncoghlan, @asvetlov, @lisroach, @miss-islington, @tirkarthi, @mic4ael, @opavlyuk, @ohwgiles
PRs	bpo-34788: Add support for scoped IPv6 addresses #13772 gh-88178: IPv6Address.exploded with scope_id #25824

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/asvetlov'
closed_at = <Date 2020-02-26.14:43:17.234>
created_at = <Date 2018-09-24.14:30:02.985>
labels = ['type-feature', 'library', '3.9']
title = 'ipaddress module fails on rfc4007 scoped IPv6 addresses'
updated_at = <Date 2021-05-02.22:00:23.352>
user = 'https://bugs.python.org/JeremyMcMillan'

bugs.python.org fields:

activity = <Date 2021-05-02.22:00:23.352>
actor = 'ohwgiles'
assignee = 'asvetlov'
closed = True
closed_date = <Date 2020-02-26.14:43:17.234>
closer = 'asvetlov'
components = ['Library (Lib)']
creation = <Date 2018-09-24.14:30:02.985>
creator = 'Jeremy McMillan'
dependencies = []
files = []
hgrepos = []
issue_num = 34788
keywords = ['patch']
message_count = 10.0
messages = ['326240', '326312', '328960', '339928', '339978', '347186', '347976', '348893', '361358', '362693']
nosy_count = 11.0
nosy_names = ['terry.reedy', 'ncoghlan', 'pmoody', 'asvetlov', 'lisroach', 'miss-islington', 'xtreak', 'Jeremy McMillan', 'mic4ael', 'opavlyuk', 'ohwgiles']
pr_nums = ['13772', '25824']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue34788'
versions = ['Python 3.9']

ipaddress module has no support for scoped IPv6 addresses which prevents the use of ipaddress.ip_address() and ipaddress.IPv6Address() with (always available by default on IPv6 systems) RFC conforming IPv6 link local addresses that specify interface scope.

https://tools.ietf.org/html/rfc4007

This is bad because interface scope is required for connect() and bind() operations on multihomed machines, and virtualized or software defined networking will make this case very common.

eg.

>>> ipaddress.IPv6Address('fe80::dead:dead:beef:ffff')
IPv6Address('fe80::dead:dead:beef:ffff')
>>> ipaddress.IPv6Address('fe80::dead:dead:beef:ffff%eth0')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ipaddress.py", line 1900, in __init__
    self._ip = self._ip_int_from_string(addr_str)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ipaddress.py", line 1716, in _ip_int_from_string
    raise AddressValueError("%s in %r" % (exc, ip_str)) from None
ipaddress.AddressValueError: Only hex digits permitted in 'ffff%eth0' in 'fe80::dead:dead:beef:ffff%eth0'
>>> ipaddress.IPv6Interface('fe80::dead:dead:beef:ffff%eth0')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ipaddress.py", line 2060, in __init__
    IPv6Address.__init__(self, addr[0])
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ipaddress.py", line 1900, in __init__
    self._ip = self._ip_int_from_string(addr_str)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ipaddress.py", line 1716, in _ip_int_from_string
    raise AddressValueError("%s in %r" % (exc, ip_str)) from None
ipaddress.AddressValueError: Only hex digits permitted in 'ffff%eth0' in 'fe80::dead:dead:beef:ffff%eth0'

subclass workaround implementation example

https://github.com/isbm/salt/blob/976fe19d73ca6bf5df375eaa15d77ce4a5a54b7a/salt/_compat.py#L125

I think this is something that would be good to have. Jeremy would you care to make a PR for this?

I would like to fix this problem if nobody is against that. I stumbled upon the very same thing recently and I think it would be a nice opportunity to contribute.

I think the code in SaltStack to handle scoped IPv6 addresses is mature, so please look at these examples.

https://github.com/saltstack/salt/blob/2085cb1078f187adf82a0cf19b39d350ff1bbd50/salt/_compat.py#L125

Pull request needs a review.

FWIW: Marking Component: Documentation means that the issue is only about changing the doc. Hence the auto-assignment to the nebulous docs group, which no longer exists in the form it once did. Enhancement issues nearly always need a doc change but are not marked 'Documentation'. I am not sure what Jeremy's original intent was, but the actual PR is mostly code implementing and testing the newly documented addition.

Please, pay attention to this issue. Pull request needs core review.

Nick, can you comment on this and review the revised PR?

New changeset 21da76d by opavlyuk in branch 'master':
bpo-34788: Add support for scoped IPv6 addresses (GH-13772)
21da76d

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ipaddress module fails on rfc4007 scoped IPv6 addresses #78969

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ipaddress module fails on rfc4007 scoped IPv6 addresses #78969

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JeremyMcMillan commented on Sep 24, 2018

JeremyMcMillan commented on Sep 25, 2018

lisroach commented on Oct 30, 2018

mic4ael commented on Apr 11, 2019

JeremyMcMillan commented on Apr 11, 2019

opavlyuk commented on Jul 3, 2019

terryjreedy commented on Jul 15, 2019

opavlyuk commented on Aug 2, 2019

terryjreedy commented on Feb 4, 2020

miss-islington commented on Feb 26, 2020

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