FreeBSD implementation of poll(2) restricts timeout argument to be either zero, or positive, or equal to INFTIM (-1).

Unless otherwise overridden, socket timeout defaults to -1. This value is then converted to milliseconds (-1000) and used as argument to the poll syscall.

poll returns EINVAL (22), and the connection fails.

I have discovered this bug during the EINTR handling testing, and have naturally found a repro code in https://bugs.python.org/issue23618 (see connect_eintr.py, attached). On GNU/Linux, the example runs as expected.

I found an OS distinguishing behavior in https://github.com/python/cpython/blob/master/Modules/selectmodule.c#L603-L612

See Also: #31334

> See Also: #31334

Oh, I didn't know bpo-31334. This issue is basically a duplicate of bpo-31334, but triggered differently.

New changeset 28146206578ebe1b84b48e6f255738a227058c04 by Victor Stinner (Artem Khramov) in branch 'master':
bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202)
https://github.com/python/cpython/commit/28146206578ebe1b84b48e6f255738a227058c04

New changeset 123f6c4914827c4ced65d032fab74de62db31cd6 by Miss Islington (bot) in branch '3.8':
bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202)
https://github.com/python/cpython/commit/123f6c4914827c4ced65d032fab74de62db31cd6

New changeset b0b178a2b80974da910ce6a344d66cc4d9a2fcfa by Miss Islington (bot) in branch '3.7':
bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202)
https://github.com/python/cpython/commit/b0b178a2b80974da910ce6a344d66cc4d9a2fcfa

Thanks Artem Khramov for the nice analysis of the root issue! And thanks for the fix! The bug is now fixed in 3.7, 3.8 and master branches.

Python 2.7 is not affected: I added sock_call_ex() helper function in Python 3 when I implemeneted the PEP 475 (Retry system calls failing with EINTR).