bpo-27456: Ensure TCP_NODELAY is set on linux (#4231)

Lib/test/test_asyncio/test_base_events.py

@@ -107,13 +107,6 @@ class BaseEventTests(test_utils.TestCase):
         self.assertIsNone(
             base_events._ipaddr_info('::3%lo0', 1, INET6, STREAM, TCP))
 
-        if hasattr(socket, 'SOCK_NONBLOCK'):
-            self.assertEqual(
-                None,
-                base_events._ipaddr_info(
-                    '1.2.3.4', 1, INET, STREAM | socket.SOCK_NONBLOCK, TCP))
-
-
     def test_port_parameter_types(self):
         # Test obscure kinds of arguments for "port".
         INET = socket.AF_INET

Lib/test/test_asyncio/test_selector_events.py

@@ -15,6 +15,7 @@ from asyncio.selector_events import BaseSelectorEventLoop
 from asyncio.selector_events import _SelectorTransport
 from asyncio.selector_events import _SelectorSocketTransport
 from asyncio.selector_events import _SelectorDatagramTransport
+from asyncio.selector_events import _set_nodelay
 from test.test_asyncio import utils as test_utils
 
 
@@ -1493,5 +1494,31 @@ class SelectorDatagramTransportTests(test_utils.TestCase):
                 'Fatal error on transport\nprotocol:.*\ntransport:.*'),
             exc_info=(ConnectionRefusedError, MOCK_ANY, MOCK_ANY))
 
+
+class TestSelectorUtils(test_utils.TestCase):
+    def check_set_nodelay(self, sock):
+        opt = sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY)
+        self.assertFalse(opt)
+
+        _set_nodelay(sock)
+
+        opt = sock.getsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY)
+        self.assertTrue(opt)
+
+    @unittest.skipUnless(hasattr(socket, 'TCP_NODELAY'),
+                         'need socket.TCP_NODELAY')
+    def test_set_nodelay(self):
+        sock = socket.socket(family=socket.AF_INET, type=socket.SOCK_STREAM,
+                             proto=socket.IPPROTO_TCP)
+        with sock:
+            self.check_set_nodelay(sock)
+
+        sock = socket.socket(family=socket.AF_INET, type=socket.SOCK_STREAM,
+                             proto=socket.IPPROTO_TCP)
+        with sock:
+            sock.setblocking(False)
+            self.check_set_nodelay(sock)
+
+
 if __name__ == '__main__':
     unittest.main()