asyncio.AbstractEventLoop.sock_connect broken for AF_BLUETOOTH

[rjordens]

BPO	27929
Nosy	@asvetlov, @1st1, @Vgr255, @miss-islington, @vincentbernat
PRs	bpo-27929: resolve names only for AF_INET/AF_INET6 with asyncio #32131 [3.10] bpo-27929: resolve names only for AF_INET/AF_INET6 with asyncio (GH-32131) #32164 [3.9] bpo-27929: resolve names only for AF_INET/AF_INET6 with asyncio (GH-32131) #32165

^{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 2022-03-28.22:35:22.237>
created_at = <Date 2016-09-01.13:59:55.702>
labels = ['3.11', 'type-bug', '3.9', '3.10', 'expert-asyncio']
title = 'asyncio.AbstractEventLoop.sock_connect broken for AF_BLUETOOTH'
updated_at = <Date 2022-03-28.22:35:22.234>
user = 'https://bugs.python.org/rjordens'

bugs.python.org fields:

activity = <Date 2022-03-28.22:35:22.234>
actor = 'asvetlov'
assignee = 'none'
closed = True
closed_date = <Date 2022-03-28.22:35:22.237>
closer = 'asvetlov'
components = ['asyncio']
creation = <Date 2016-09-01.13:59:55.702>
creator = 'rjordens'
dependencies = []
files = []
hgrepos = []
issue_num = 27929
keywords = ['patch', '3.5regression']
message_count = 10.0
messages = ['274131', '274132', '274134', '274142', '274201', '276623', '276916', '416218', '416220', '416222']
nosy_count = 6.0
nosy_names = ['asvetlov', 'yselivanov', 'rjordens', 'abarry', 'miss-islington', 'bernat']
pr_nums = ['32131', '32164', '32165']
priority = 'high'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue27929'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

[rjordens]

Since 3.5.2 sock_connect() tries to be smart and resolves addresses for you if they fail a socket.inet_pton() check. But inet_pton() only supports AF_INET(6) and does not work for other address families that socket otherwise supports just fine (e.g. AF_BLUETOOTH).

Before 3.5.2, in order to happily use bluetooth sockets with asyncio, you could just do:

    sock = socket.socket(family=socket.AF_BLUETOOTH, type=socket.SOCK_STREAM,
                proto=socket.BTPROTO_RFCOMM)
    sock.setblocking(False)
    addr = "00:12:34:56:78:99"
    yield from loop.sock_connect(sock, (addr, 1))

This is a regression.

[rjordens]

The error for inet_pton() is:

>>> import socket
>>> socket.inet_pton(socket.AF_BLUETOOTH, "00:12:34:56:78:99")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
socket.error: [Errno 97] Address family not supported by protocol

And the traceback in asyncio is:

DEBUG:asyncio:Using selector: EpollSelector
Traceback (most recent call last):
  File "log.py", line 91, in <module>
    main()
  File "log.py", line 84, in main
    loop.run_until_complete(log(loop, sys.argv[1]))
  File "/usr/lib/python3.5/asyncio/base_events.py", line 387, in run_until_complete
    return future.result()
  File "/usr/lib/python3.5/asyncio/futures.py", line 274, in result
    raise self._exception
  File "/usr/lib/python3.5/asyncio/tasks.py", line 241, in _step
    result = coro.throw(exc)
  File "log.py", line 22, in log
    yield from loop.sock_connect(sock, (addr, 1))
  File "/usr/lib/python3.5/asyncio/selector_events.py", line 397, in sock_connect
    yield from resolved
  File "/usr/lib/python3.5/asyncio/futures.py", line 361, in __iter__
    yield self  # This tells Task to wait for completion.
  File "/usr/lib/python3.5/asyncio/tasks.py", line 296, in _wakeup
    future.result()
  File "/usr/lib/python3.5/asyncio/futures.py", line 274, in result
    raise self._exception
  File "/usr/lib/python3.5/concurrent/futures/thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/lib/python3.5/socket.py", line 732, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -5] No address associated with hostname

[Vgr255]

Thanks for the report! I'm unable to reproduce, as socket.AF_BLUETOOTH doesn't exist on my system, but surely someone else can.

[gvanrossum]

Looks related (possibly a duplicate) of issue bpo-27136. Also related is a fix for the latter in python/asyncio#357. That fix is already in the CPython repo, but I guess it didn't make it into 3.5.2.

[rjordens]

https://github.com/python/cpython/blob/master/Lib/asyncio/selector_events.py#L394
https://github.com/python/asyncio/blob/master/asyncio/selector_events.py#L394

AF_UNIX is special-cased.
Maybe AF_BLUETOOTH and others should use that same special treatment.
Or maybe only AF_INET, AF_INET6 should attempt resolving.

[1st1]

I'm not sure this is still relevant for the latest asyncio in 3.6. Robert, could you please test if this is still the case?

[rjordens]

It is still in cpython master e6e9ddd.

import asyncio
import socket
sock = socket.socket(family=socket.AF_BLUETOOTH,
                     type=socket.SOCK_STREAM,
                     proto=socket.BTPROTO_RFCOMM)
sock.setblocking(False)
addr = "00:12:34:56:78:99"
loop = asyncio.get_event_loop()
loop.run_until_complete(loop.sock_connect(sock, (addr, 1)))

Traceback (most recent call last):
  File "/home/rj/work/hxm/t.py", line 9, in <module>
    loop.run_until_complete(loop.sock_connect(sock, (addr, 1)))
  File "/home/rj/src/cpython/Lib/asyncio/base_events.py", line 457, in run_until_complete
    return future.result()
  File "/home/rj/src/cpython/Lib/asyncio/futures.py", line 292, in result
    raise self._exception
  File "/home/rj/src/cpython/Lib/asyncio/tasks.py", line 241, in _step
    result = coro.throw(exc)
  File "/home/rj/src/cpython/Lib/asyncio/selector_events.py", line 416, in sock_connect
    yield from resolved
  File "/home/rj/src/cpython/Lib/asyncio/futures.py", line 379, in __iter__
    yield self  # This tells Task to wait for completion.
  File "/home/rj/src/cpython/Lib/asyncio/tasks.py", line 297, in _wakeup
    future.result()
  File "/home/rj/src/cpython/Lib/asyncio/futures.py", line 292, in result
    raise self._exception
  File "/home/rj/src/cpython/Lib/concurrent/futures/thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/home/rj/src/cpython/Lib/socket.py", line 743, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -6] ai_family not supported