ProactorEventLoop cannot open connection to ::1

[sebastienbourdeauducq]

BPO	27500
Nosy	@gvanrossum, @gpshead, @vstinner, @1st1, @miss-islington, @alexbers
PRs	bpo-27500: Fix sttaic ver of getaddrinfo to resolve IPv6 addresses #7993 [3.7] bpo-27500: Fix static version of getaddrinfo to resolve IPv6 (GH-7993) #8000 [3.6] bpo-27500: Fix static version of getaddrinfo to resolve IPv6 (GH-7993) #8001

^{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 2019-01-15.12:13:50.175>
created_at = <Date 2016-07-12.17:55:35.017>
labels = ['expert-asyncio']
title = 'ProactorEventLoop cannot open connection to ::1'
updated_at = <Date 2019-01-15.12:24:02.730>
user = 'https://bugs.python.org/sebastienbourdeauducq'

bugs.python.org fields:

activity = <Date 2019-01-15.12:24:02.730>
actor = 'sebastien.bourdeauducq'
assignee = 'none'
closed = True
closed_date = <Date 2019-01-15.12:13:50.175>
closer = 'vstinner'
components = ['asyncio']
creation = <Date 2016-07-12.17:55:35.017>
creator = 'sebastien.bourdeauducq'
dependencies = []
files = []
hgrepos = []
issue_num = 27500
keywords = ['patch']
message_count = 11.0
messages = ['270258', '270263', '288712', '317997', '320660', '320675', '320676', '320693', '320694', '320695', '333692']
nosy_count = 7.0
nosy_names = ['gvanrossum', 'gregory.p.smith', 'vstinner', 'yselivanov', 'sebastien.bourdeauducq', 'miss-islington', 'bay']
pr_nums = ['7993', '8000', '8001']
priority = 'high'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue27500'
versions = ['Python 3.5']

[sebastienbourdeauducq]

The following code fails with "OSError: [WinError 10022] An invalid argument was supplied".

import asyncio
loop = asyncio.ProactorEventLoop()
asyncio.set_event_loop(loop)
loop.run_until_complete(asyncio.open_connection("::1", 4242))

This is a regression in 3.5.2. 3.5.1 does not have this bug. Connecting to 127.0.0.1 does not cause the problem.

[sebastienbourdeauducq]

The first offending commit is this one:
03df54d

more specifically "return af, type, proto, '', (host, port)". For IPv6, it should be "(host, port, flow info, scope id)" instead of just "(host, port)".

[sebastienbourdeauducq]

This is still a problem with Python 3.5.3 and 3.6.0.

[sebastienbourdeauducq]

Any chance someone could look into this bug?

[alexbers]

The bug is reproducible on Python 3.7. The connect call always fails when I
try to use connect to any IPv6 address with ProactorEventLoop.

The bug can be bypassed by adding "%0" to the IPv6 address. This will cause
to trigger this if construction:

cpython/Lib/asyncio/base_events.py

Line 133 in e76ac9d

if '%' in host:

As mentioned by Sebastian, it happen because the _ipaddr_info function returns
only the host and the port for IPv6: return af, type, proto, '', (host, port)

cpython/Lib/asyncio/base_events.py

Line 142 in e76ac9d

return af, type, proto, '', (host, port)

This (host, port) tuple used in ConnectEx call, but it expect 4-element tuple
to connect IPv6:

cpython/Modules/overlapped.c

Line 1090 in 55edd0c

else if (PyArg_ParseTuple(obj,

Instead it tries to connect, using IPv4 and fails.

The bug can be fixed by doing the following:
if af == socket.AF_INET6:
return af, type, proto, '', (host, port, 0, 0)
else:
return af, type, proto, '', (host, port)

instead of
return af, type, proto, '', (host, port)

in

cpython/Lib/asyncio/base_events.py

Line 142 in e76ac9d

return af, type, proto, '', (host, port)

[gvanrossum]

Somebody please submit a PR so this can be fixed in 3.7.1 and the fix can
be backported to 3.6.7.

[1st1]

Somebody please submit a PR so this can be fixed in 3.7.1 and the fix can
be backported to 3.6.7.

Somehow I overlooked this one when I was sifting the issues we needed to fix in 3.7. I've opened a PR.

[1st1]

New changeset d904c23 by Yury Selivanov in branch 'master':
bpo-27500: Fix static version of getaddrinfo to resolve IPv6 (GH-7993)
d904c23

[miss-islington]

New changeset 3ed4414 by Miss Islington (bot) in branch '3.7':
bpo-27500: Fix static version of getaddrinfo to resolve IPv6 (GH-7993)
3ed4414

[miss-islington]

New changeset c00144c by Miss Islington (bot) in branch '3.6':
bpo-27500: Fix static version of getaddrinfo to resolve IPv6 (GH-7993)
c00144c

[sebastienbourdeauducq]

Thank you!