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bpo-45129 Remove deprecated reuse_address (GH-28207)
Due to significant security concerns, the reuse_address parameter of asyncio.loop.create_datagram_endpoint, deprecated in Python 3.9, is now removed. This is because of the behavior of the socket option SO_REUSEADDR in UDP. Co-authored-by: Łukasz Langa <[email protected]>
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Lines changed: 33 additions & 70 deletions

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‎Doc/library/asyncio-eventloop.rst‎

Lines changed: 19 additions & 19 deletions
Original file line numberDiff line numberDiff line change
@@ -493,24 +493,9 @@ Opening network connections
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.. coroutinemethod:: loop.create_datagram_endpoint(protocol_factory, \
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local_addr=None, remote_addr=None, *, \
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family=0, proto=0, flags=0, \
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reuse_address=None, reuse_port=None, \
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reuse_port=None, \
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allow_broadcast=None, sock=None)
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.. note::
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The parameter *reuse_address* is no longer supported, as using
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:py:data:`~sockets.SO_REUSEADDR` poses a significant security concern for
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UDP. Explicitly passing ``reuse_address=True`` will raise an exception.
503-
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When multiple processes with differing UIDs assign sockets to an
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identical UDP socket address with ``SO_REUSEADDR``, incoming packets can
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become randomly distributed among the sockets.
507-
508-
For supported platforms, *reuse_port* can be used as a replacement for
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similar functionality. With *reuse_port*,
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:py:data:`~sockets.SO_REUSEPORT` is used instead, which specifically
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prevents processes with differing UIDs from assigning sockets to the same
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socket address.
513-
514499
Create a datagram connection.
515500

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The socket family can be either :py:data:`~socket.AF_INET`,
@@ -557,16 +542,31 @@ Opening network connections
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:ref:`UDP echo server protocol <asyncio-udp-echo-server-protocol>` examples.
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.. versionchanged:: 3.4.4
560-
The *family*, *proto*, *flags*, *reuse_address*, *reuse_port,
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The *family*, *proto*, *flags*, *reuse_address*, *reuse_port*,
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*allow_broadcast*, and *sock* parameters were added.
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.. versionchanged:: 3.8.1
564-
The *reuse_address* parameter is no longer supported due to security
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concerns.
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The *reuse_address* parameter is no longer supported, as using
550+
:py:data:`~sockets.SO_REUSEADDR` poses a significant security concern for
551+
UDP. Explicitly passing ``reuse_address=True`` will raise an exception.
552+
553+
When multiple processes with differing UIDs assign sockets to an
554+
identical UDP socket address with ``SO_REUSEADDR``, incoming packets can
555+
become randomly distributed among the sockets.
556+
557+
For supported platforms, *reuse_port* can be used as a replacement for
558+
similar functionality. With *reuse_port*,
559+
:py:data:`~sockets.SO_REUSEPORT` is used instead, which specifically
560+
prevents processes with differing UIDs from assigning sockets to the same
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socket address.
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.. versionchanged:: 3.8
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Added support for Windows.
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566+
.. versionchanged:: 3.11
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The *reuse_address* parameter, disabled since Python 3.9.0, 3.8.1,
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3.7.6 and 3.6.10, has been entirely removed.
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570570
.. coroutinemethod:: loop.create_unix_connection(protocol_factory, \
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path=None, *, ssl=None, sock=None, \
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server_hostname=None, ssl_handshake_timeout=None)

‎Doc/whatsnew/3.11.rst‎

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Original file line numberDiff line numberDiff line change
@@ -254,6 +254,12 @@ Removed
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Use ``bdist_wheel`` (wheel packages) instead.
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(Contributed by Hugo van Kemenade in :issue:`45124`.)
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257+
* Due to significant security concerns, the *reuse_address* parameter of
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:meth:`asyncio.loop.create_datagram_endpoint`, disabled in Python 3.9, is
259+
now entirely removed. This is because of the behavior of the socket option
260+
``SO_REUSEADDR`` in UDP.
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(Contributed by Hugo van Kemenade in :issue:`45129`.)
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* Remove :meth:`__getitem__` methods of
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:class:`xml.dom.pulldom.DOMEventStream`, :class:`wsgiref.util.FileWrapper`
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and :class:`fileinput.FileInput`, deprecated since Python 3.9.

‎Lib/asyncio/base_events.py‎

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Original file line numberDiff line numberDiff line change
@@ -66,10 +66,6 @@
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# Maximum timeout passed to select to avoid OS limitations
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MAXIMUM_SELECT_TIMEOUT = 24 * 3600
6868

69-
# Used for deprecation and removal of `loop.create_datagram_endpoint()`'s
70-
# *reuse_address* parameter
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_unset = object()
72-
7369

7470
def _format_handle(handle):
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cb = handle._callback
@@ -1235,7 +1231,7 @@ async def start_tls(self, transport, protocol, sslcontext, *,
12351231
async def create_datagram_endpoint(self, protocol_factory,
12361232
local_addr=None, remote_addr=None, *,
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family=0, proto=0, flags=0,
1238-
reuse_address=_unset, reuse_port=None,
1234+
reuse_port=None,
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allow_broadcast=None, sock=None):
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"""Create datagram connection."""
12411237
if sock is not None:
@@ -1248,7 +1244,7 @@ async def create_datagram_endpoint(self, protocol_factory,
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# show the problematic kwargs in exception msg
12491245
opts = dict(local_addr=local_addr, remote_addr=remote_addr,
12501246
family=family, proto=proto, flags=flags,
1251-
reuse_address=reuse_address, reuse_port=reuse_port,
1247+
reuse_port=reuse_port,
12521248
allow_broadcast=allow_broadcast)
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problems = ', '.join(f'{k}={v}' for k, v in opts.items() if v)
12541250
raise ValueError(
@@ -1311,19 +1307,6 @@ async def create_datagram_endpoint(self, protocol_factory,
13111307

13121308
exceptions = []
13131309

1314-
# bpo-37228
1315-
if reuse_address is not _unset:
1316-
if reuse_address:
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raise ValueError("Passing `reuse_address=True` is no "
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"longer supported, as the usage of "
1319-
"SO_REUSEPORT in UDP poses a significant "
1320-
"security concern.")
1321-
else:
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warnings.warn("The *reuse_address* parameter has been "
1323-
"deprecated as of 3.5.10 and is scheduled "
1324-
"for removal in 3.11.", DeprecationWarning,
1325-
stacklevel=2)
1326-
13271310
for ((family, proto),
13281311
(local_address, remote_address)) in addr_pairs_info:
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sock = None
@@ -1407,7 +1390,6 @@ async def create_server(
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sock=None,
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backlog=100,
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ssl=None,
1410-
reuse_address=None,
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reuse_port=None,
14121394
ssl_handshake_timeout=None,
14131395
start_serving=True):
@@ -1438,8 +1420,6 @@ async def create_server(
14381420
raise ValueError(
14391421
'host/port and sock can not be specified at the same time')
14401422

1441-
if reuse_address is None:
1442-
reuse_address = os.name == 'posix' and sys.platform != 'cygwin'
14431423
sockets = []
14441424
if host == '':
14451425
hosts = [None]
@@ -1469,9 +1449,6 @@ async def create_server(
14691449
af, socktype, proto, exc_info=True)
14701450
continue
14711451
sockets.append(sock)
1472-
if reuse_address:
1473-
sock.setsockopt(
1474-
socket.SOL_SOCKET, socket.SO_REUSEADDR, True)
14751452
if reuse_port:
14761453
_set_reuseport(sock)
14771454
# Disable IPv4/IPv6 dual stack support (enabled by

‎Lib/test/test_asyncio/test_base_events.py‎

Lines changed: 0 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -1794,32 +1794,6 @@ def test_create_datagram_endpoint_sockopts(self):
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self.loop.run_until_complete(protocol.done)
17951795
self.assertEqual('CLOSED', protocol.state)
17961796

1797-
def test_create_datagram_endpoint_reuse_address_error(self):
1798-
# bpo-37228: Ensure that explicit passing of `reuse_address=True`
1799-
# raises an error, as it is not safe to use SO_REUSEADDR when using UDP
1800-
1801-
coro = self.loop.create_datagram_endpoint(
1802-
lambda: MyDatagramProto(create_future=True, loop=self.loop),
1803-
local_addr=('127.0.0.1', 0),
1804-
reuse_address=True)
1805-
1806-
with self.assertRaises(ValueError):
1807-
self.loop.run_until_complete(coro)
1808-
1809-
def test_create_datagram_endpoint_reuse_address_warning(self):
1810-
# bpo-37228: Deprecate *reuse_address* parameter
1811-
1812-
coro = self.loop.create_datagram_endpoint(
1813-
lambda: MyDatagramProto(create_future=True, loop=self.loop),
1814-
local_addr=('127.0.0.1', 0),
1815-
reuse_address=False)
1816-
1817-
with self.assertWarns(DeprecationWarning):
1818-
transport, protocol = self.loop.run_until_complete(coro)
1819-
transport.close()
1820-
self.loop.run_until_complete(protocol.done)
1821-
self.assertEqual('CLOSED', protocol.state)
1822-
18231797
@patch_socket
18241798
def test_create_datagram_endpoint_nosoreuseport(self, m_socket):
18251799
del m_socket.SO_REUSEPORT

‎Misc/NEWS.d/next/Library/2021-09-07-14-27-39.bpo-45129.vXH0gw.rst‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,6 @@
1+
Due to significant security concerns, the *reuse_address* parameter of
2+
:meth:`asyncio.loop.create_datagram_endpoint`, disabled in Python 3.9, is
3+
now entirely removed. This is because of the behavior of the socket option
4+
``SO_REUSEADDR`` in UDP.
5+
6+
Patch by Hugo van Kemenade.

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