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 21da76d1f1b527d62b2e9ef79dd9aa514d996341 by opavlyuk in branch 'master':
bpo-34788: Add support for scoped IPv6 addresses (GH-13772)
https://github.com/python/cpython/commit/21da76d1f1b527d62b2e9ef79dd9aa514d996341