ipaddress module fails on rfc4007 scoped IPv6 addresses

[JeremyMcMillan]

BPO	34788
Nosy	@terryjreedy, @ncoghlan, @asvetlov, @lisroach, @miss-islington, @tirkarthi, @mic4ael, @opavlyuk, @ohwgiles
PRs	bpo-34788: Add support for scoped IPv6 addresses #13772 bpo-44012: 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']

[JeremyMcMillan]

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'

[JeremyMcMillan]

subclass workaround implementation example

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

[lisroach]

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

[mic4ael]

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.

[JeremyMcMillan]

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

[opavlyuk]

Pull request needs a review.

[terryjreedy]

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.

[opavlyuk]

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

[terryjreedy]

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

[miss-islington]

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