[3.15] gh-160429: Ignore ConnectionResetError from shutdown() when closing proactor sockets (GH-160909) (#161391)

gh-160429: Ignore ConnectionResetError from shutdown() when closing proactor sockets (GH-160909)

* gh-160429: Ignore ConnectionResetError from shutdown() when closing proactor sockets

* Update Lib/asyncio/proactor_events.py

---------
(cherry picked from commit 7b06d6f)

Co-authored-by: Zap777 <124182405+devanshc777@users.noreply.github.com>
Co-authored-by: Andrew Svetlov <andrew.svetlov@gmail.com>

Author: 3 people

Lib/asyncio/proactor_events.py

@@ -164,7 +164,12 @@ def _call_connection_lost(self, exc):
             # just close our end.  First calling shutdown() seems to
             # cure it, but maybe using DisconnectEx() would be better.
             if hasattr(self._sock, 'shutdown') and self._sock.fileno() != -1:
-                self._sock.shutdown(socket.SHUT_RDWR)
+                try:
+                    self._sock.shutdown(socket.SHUT_RDWR)
+                except ConnectionError:
+                    # The connection is already gone.
+                    # The peer has already reset the connection.
+                    pass
             self._sock.close()
             self._sock = None
             server = self._server

Lib/test/test_asyncio/test_proactor_events.py

@@ -336,6 +336,20 @@ def test_call_connection_lost(self):
         self.assertTrue(self.protocol.connection_lost.called)
         self.assertTrue(self.sock.close.called)
 
+    def test_call_connection_lost_shutdown_reset(self):
+        # gh-160429: a ConnectionResetError from shutdown() must not skip
+        # closing the socket and detaching the transport from its server.
+        server = mock.Mock()
+        tr = _ProactorSocketTransport(self.loop, self.sock, self.protocol,
+                                      server=server)
+        self.sock.shutdown.side_effect = ConnectionResetError
+        tr._call_connection_lost(None)
+        self.protocol.connection_lost.assert_called_once_with(None)
+        self.sock.close.assert_called_once_with()
+        server._detach.assert_called_once_with(tr)
+        self.assertIsNone(tr._sock)
+        self.assertTrue(tr._called_connection_lost)
+
     def test_write_eof(self):
         tr = self.socket_transport()
         self.assertTrue(tr.can_write_eof())

Misc/NEWS.d/next/Library/2026-10-29-21-43-53.gh-issue-160429.eWapMs.rst

@@ -0,0 +1,3 @@
+Fix :class:`asyncio.ProactorEventLoop` socket transports leaving the socket
+open, and :meth:`asyncio.Server.wait_closed` hanging, when the peer resets
+the connection while the transport is being closed.