bpo-31922: Do not connect UDP sockets when broadcast is allowed (GH-423)

*Moved from python/asyncio#493.*

This PR fixes issue python/asyncio#480, as explained in [this comment](https://github.com/python/asyncio/issues/480#issuecomment-278703828).

The `_SelectorDatagramTransport.sendto` method has to be modified ~~so `_sock.sendto` is used in all cases (because it is tricky to reliably tell if the socket is connected or not). Could that be an issue for connected sockets?~~ *EDIT* ... so `_sock.send` is used only if `_sock` is connected.

It also protects `socket.getsockname` against `OSError` in `_SelectorTransport`. This might happen on Windows if the socket is not connected (e.g. for UDP broadcasting).


https://bugs.python.org/issue31922

2 files changed, 18 insertions, 0 deletions

diff --git a/Lib/test/test_asyncio/test_base_events.py b/Lib/test/test_asyncio/test_base_events.py
index c245c47..25420b2 100644
--- a/Lib/test/test_asyncio/test_base_events.py
+++ b/Lib/test/test_asyncio/test_base_events.py
@@ -1586,6 +1586,23 @@ class BaseEventLoopWithSelectorTests(test_utils.TestCase):
         self.assertRaises(
             OSError, self.loop.run_until_complete, coro)
 
+    def test_create_datagram_endpoint_allow_broadcast(self):
+        protocol = MyDatagramProto(create_future=True, loop=self.loop)
+        self.loop.sock_connect = sock_connect = mock.Mock()
+        sock_connect.return_value = []
+
+        coro = self.loop.create_datagram_endpoint(
+            lambda: protocol,
+            remote_addr=('127.0.0.1', 0),
+            allow_broadcast=True)
+
+        transport, _ = self.loop.run_until_complete(coro)
+        self.assertFalse(sock_connect.called)
+
+        transport.close()
+        self.loop.run_until_complete(protocol.done)
+        self.assertEqual('CLOSED', protocol.state)
+
     @patch_socket
     def test_create_datagram_endpoint_socket_err(self, m_socket):
         m_socket.getaddrinfo = socket.getaddrinfo
diff --git a/Lib/test/test_asyncio/test_selector_events.py b/Lib/test/test_asyncio/test_selector_events.py
index d0d171a..bf721b0 100644
--- a/Lib/test/test_asyncio/test_selector_events.py
+++ b/Lib/test/test_asyncio/test_selector_events.py
@@ -1065,6 +1065,7 @@ class SelectorDatagramTransportTests(test_utils.TestCase):
         self.sock.fileno.return_value = 7
 
     def datagram_transport(self, address=None):
+        self.sock.getpeername.side_effect = None if address else OSError
         transport = _SelectorDatagramTransport(self.loop, self.sock,
                                                self.protocol,
                                                address=address)