test: Fix IPv6 check on BSD systems #22103

I noticed that test_ipv6_local() always returns False on macOS or FreeBSD, even though IPv6 is working perfectly fine. This causes test/functional/rpc_bind.py --ipv6 and test/functional/feature_proxy.py to skip their run. Apparently, there's a check if the port number is 0 (see here or here), while Linux has no problem with this. This is fixed by specifying any other port number than 0, e.g. 1. Still, because of SOCK_DGRAM, no actual connection is made.

Nice find, thanks for improving the test framework for *BSD users!

I can confirm that the fix also works on OpenBSD 6.9. :rocket:

master branch:

$ python3
Python 3.8.8 (default, Apr 19 2021, 10:23:47)
[Clang 10.0.1 ] on openbsd6
Type "help", "copyright", "credits" or "license" for more information.
>>> from test.functional.test_framework.netutil import test_ipv6_local
>>> test_ipv6_local()
False
>>>             

PR branch:

$ python3
Python 3.8.8 (default, Apr 19 2021, 10:23:47)
[Clang 10.0.1 ] on openbsd6
Type "help", "copyright", "credits" or "license" for more information.
>>> from test.functional.test_framework.netutil import test_ipv6_local
>>> test_ipv6_local()
True
>>>             

ACK 2be35725069fd4c589497b93e09e1c6db6946372

ACK 2be35725069fd4c589497b93e09e1c6db6946372 - nice improvement. I checked that with this change ipv6 related tests in feature_proxy.py are being run.

This causes test/functional/rpc_bind.py --ipv6 and test/functional/feature_proxy.py to skip their run.

Note that rpc_bind.py --ipv6 is still going to be skipped on anything other than Linux due to:

https://github.com/bitcoin/bitcoin/blob/619e930aa1860d92f8eebef3bc1bed8b37c606b8/test/functional/rpc_bind.py#L68-L70