gh-91227: Ignore ERROR_PORT_UNREACHABLE

Lib/asyncio/windows_events.py

@@ -461,7 +461,9 @@ def finish_socket_func(trans, key, ov):
         try:
             return ov.getresult()
         except OSError as exc:
-            if exc.winerror in (_overlapped.ERROR_NETNAME_DELETED,
+            if exc.winerror == _overlapped.ERROR_PORT_UNREACHABLE:
+                return b'', None
+            elif exc.winerror in (_overlapped.ERROR_NETNAME_DELETED,
                                 _overlapped.ERROR_OPERATION_ABORTED):
                 raise ConnectionResetError(*exc.args)
             else:
@@ -515,7 +517,9 @@ def finish_recv(trans, key, ov):
             try:
                 return ov.getresult()
             except OSError as exc:
-                if exc.winerror in (_overlapped.ERROR_NETNAME_DELETED,
+                if exc.winerror == _overlapped.ERROR_PORT_UNREACHABLE:
+                    return b'', None
+                elif exc.winerror in (_overlapped.ERROR_NETNAME_DELETED,
                                     _overlapped.ERROR_OPERATION_ABORTED):
                     raise ConnectionResetError(*exc.args)
                 else:

Lib/test/test_asyncio/test_events.py

@@ -1374,6 +1374,77 @@ def test_create_datagram_endpoint_sock(self):
         tr.close()
         self.loop.run_until_complete(pr.done)
 
+    def test_datagram_send_to_non_listening_address(self):
+        # see:
+        #   https://github.com/python/cpython/issues/91227
+        #   https://github.com/python/cpython/issues/88906
+        #   https://bugs.python.org/issue47071
+        #   https://bugs.python.org/issue44743
+        # The Proactor event loop would fail to receive datagram messages after
+        # sending a message to an address that wasn't listening.
+        loop = self.loop
+
+        class Protocol(asyncio.DatagramProtocol):
+
+            _received_datagram = None
+
+            def datagram_received(self, data, addr):
+                self._received_datagram.set_result(data)
+
+            async def wait_for_datagram_received(self):
+                self._received_datagram = loop.create_future()
+                result = await asyncio.wait_for(self._received_datagram, 10)
+                self._received_datagram = None
+                return result
+
+        def create_socket():
+            sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+            sock.setblocking(False)
+            sock.bind(('127.0.0.1', 0))
+            return sock
+
+        socket_1 = create_socket()
+        transport_1, protocol_1 = loop.run_until_complete(
+            loop.create_datagram_endpoint(Protocol, sock=socket_1)
+        )
+        addr_1 = socket_1.getsockname()
+
+        socket_2 = create_socket()
+        transport_2, protocol_2 = loop.run_until_complete(
+            loop.create_datagram_endpoint(Protocol, sock=socket_2)
+        )
+        addr_2 = socket_2.getsockname()
+
+        # creating and immediately closing this to try to get an address that
+        # is not listening
+        socket_3 = create_socket()
+        transport_3, protocol_3 = loop.run_until_complete(
+            loop.create_datagram_endpoint(Protocol, sock=socket_3)
+        )
+        addr_3 = socket_3.getsockname()
+        transport_3.abort()
+
+        transport_1.sendto(b'a', addr=addr_2)
+        assert loop.run_until_complete(
+            protocol_2.wait_for_datagram_received()
+        ) == b'a'
+
+        transport_2.sendto(b'b', addr=addr_1)
+        assert loop.run_until_complete(
+            protocol_1.wait_for_datagram_received()
+        ) == b'b'
+
+        # this should send to an address that isn't listening
+        transport_1.sendto(b'c', addr=addr_3)
+        loop.run_until_complete(asyncio.sleep(0))
+
+        # transport 1 should still be able to receive messages after sending to
+        # an address that wasn't listening
+        transport_2.sendto(b'd', addr=addr_1)
+        assert loop.run_until_complete(
+            protocol_1.wait_for_datagram_received()
+        ) == b'd'
+
     def test_internal_fds(self):
         loop = self.create_event_loop()
         if not isinstance(loop, selector_events.BaseSelectorEventLoop):

Misc/NEWS.d/next/Windows/2024-02-24-23-03-43.gh-issue-91227.sL4zWC.rst

@@ -0,0 +1 @@
+Fix the asyncio ProactorEventLoop implementation so that sending a datagram to an address that is not listening does not prevent receiving any more datagrams.

Modules/overlapped.c

@@ -2038,6 +2038,7 @@ overlapped_exec(PyObject *module)
     WINAPI_CONSTANT(F_DWORD,  ERROR_OPERATION_ABORTED);
     WINAPI_CONSTANT(F_DWORD,  ERROR_SEM_TIMEOUT);
     WINAPI_CONSTANT(F_DWORD,  ERROR_PIPE_BUSY);
+    WINAPI_CONSTANT(F_DWORD,  ERROR_PORT_UNREACHABLE);
     WINAPI_CONSTANT(F_DWORD,  INFINITE);
     WINAPI_CONSTANT(F_HANDLE, INVALID_HANDLE_VALUE);
     WINAPI_CONSTANT(F_HANDLE, NULL);