[FreeBSD, OSX] Socket module: incorrect usage of poll(2)

[akhramov]

BPO	37811
Nosy	@ronaldoussoren, @vstinner, @ned-deily, @koobs, @miss-islington, @shihai1991, @akhramov
PRs	bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module #15202 [3.7] bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202) #15289 [3.8] bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202) #15290
Files	connect_eintr.py: Repro

^{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 = None
closed_at = <Date 2019-08-14.22:38:37.325>
created_at = <Date 2019-08-10.20:29:31.173>
labels = ['OS-mac', '3.8', '3.9', 'expert-IO', '3.7', 'library']
title = '[FreeBSD, OSX] Socket module: incorrect usage of poll(2)'
updated_at = <Date 2019-08-14.22:38:37.322>
user = 'https://github.com/akhramov'

bugs.python.org fields:

activity = <Date 2019-08-14.22:38:37.322>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2019-08-14.22:38:37.325>
closer = 'vstinner'
components = ['Library (Lib)', 'macOS', 'IO', 'FreeBSD']
creation = <Date 2019-08-10.20:29:31.173>
creator = 'akhramov'
dependencies = []
files = ['48537']
hgrepos = []
issue_num = 37811
keywords = ['patch']
message_count = 8.0
messages = ['349356', '349382', '349383', '349753', '349754', '349760', '349761', '349772']
nosy_count = 7.0
nosy_names = ['ronaldoussoren', 'vstinner', 'ned.deily', 'koobs', 'miss-islington', 'shihai1991', 'akhramov']
pr_nums = ['15202', '15289', '15290']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue37811'
versions = ['Python 3.7', 'Python 3.8', 'Python 3.9']

[akhramov]

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.

[shihai1991]

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

[koobs]

See Also: bpo-31334

[vstinner]

See Also: bpo-31334

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

[vstinner]

New changeset 2814620 by Victor Stinner (Artem Khramov) in branch 'master':
bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202)
2814620

[miss-islington]

New changeset 123f6c4 by Miss Islington (bot) in branch '3.8':
bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202)
123f6c4

[miss-islington]

New changeset b0b178a by Miss Islington (bot) in branch '3.7':
bpo-37811: FreeBSD, OSX: fix poll(2) usage in sockets module (GH-15202)
b0b178a

[vstinner]

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).