hub: implement listen as native

The function is largely inspired by the one in eventlet.
That is said, there are nothing exceptional.

Related-bug: #2087939
Change-Id: Ife65518531393fd6ad06730ef8fead02cdb1eb0f
Signed-off-by: Sahid Orentino Ferdjaoui <sahid.ferdjaoui@industrialdiscipline.com>

os_ken/lib/hub.py

@@ -18,6 +18,7 @@ import logging
 import os
 import ssl
 import socket
+import sys
 import traceback
 
 from os_ken.lib import ip
@@ -365,6 +366,26 @@ elif HUB_TYPE == 'native':
             except queue.Empty:
                 pass
 
+    def listen(addr, family=socket.AF_INET, backlog=50, reuse_addr=True,
+               reuse_port=None):
+        """
+        Largely inspired by:
+          https://github.com/eventlet/eventlet/../eventlet/convenience.py
+        """
+        sock = socket.socket(family, socket.SOCK_STREAM)
+        if reuse_addr and sys.platform[:3] != 'win':
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        elif reuse_port is None:
+            reuse_port = True
+            if reuse_port and hasattr(socket, 'SO_REUSEPORT'):
+                try:
+                    sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+                except Exception:
+                    # Not supported by the platform
+                    pass
+        sock.bind(addr)
+        sock.listen(backlog)
+        return sock
 else:
     raise NotImplementedError(
         "Invalid OSKEN_HUB_TYPE. Expected one of ('eventlet', 'native').")

os_ken/tests/unit/lib/test_hub.py

@@ -264,3 +264,88 @@ class TestThreadManagementNative(unittest.TestCase):
     @mock.patch.dict(os.environ, {"OSKEN_HUB_TYPE": "native"})
     def setUp(self):
         self.hub = importlib.reload(os_ken.lib.hub)
+
+
+class TestListenEventlet(unittest.TestCase):
+
+    @mock.patch.dict(os.environ, {"OSKEN_HUB_TYPE": "eventlet"})
+    def setUp(self):
+        self.hub = importlib.reload(os_ken.lib.hub)
+
+        self.patcher = mock.patch('eventlet.green.socket.socket')
+        self.mock_socket = self.patcher.start()
+
+        self.sock = mock.MagicMock()
+        self.mock_socket.return_value = self.sock
+
+
+class TestListenEventlet(unittest.TestCase):
+
+    @mock.patch.dict(os.environ, {"OSKEN_HUB_TYPE": "eventlet"})
+    def setUp(self):
+        self.hub = importlib.reload(os_ken.lib.hub)
+
+        self.patcher = mock.patch('eventlet.green.socket.socket')
+        self.mock_socket = self.patcher.start()
+
+        self.sock = mock.MagicMock()
+        self.mock_socket.return_value = self.sock
+
+    def tearDown(self):
+        self.patcher.stop()
+
+    def test_default_socket_creation(self):
+        addr = ('127.0.0.1', 8080)
+        sock = self.hub.listen(addr)
+
+        self.mock_socket.assert_called_once_with(
+            socket.AF_INET, socket.SOCK_STREAM)
+
+        self.sock.setsockopt.assert_has_calls([
+            mock.call(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1),
+            mock.call(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1),
+        ])
+
+        self.sock.bind.assert_called_once_with(addr)
+        self.sock.listen.assert_called_once_with(50)
+
+        self.assertEqual(self.sock, sock)
+
+    def test_socket_with_ipv6(self):
+        addr = ('::1', 8080)
+        sock = self.hub.listen(addr, family=socket.AF_INET6)
+
+        self.mock_socket.assert_called_once_with(
+            socket.AF_INET6, socket.SOCK_STREAM)
+
+        self.sock.setsockopt.assert_has_calls([
+            mock.call(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1),
+            mock.call(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1),
+        ])
+
+        self.sock.bind.assert_called_once_with(addr)
+        self.sock.listen.assert_called_once_with(50)
+
+        self.assertEqual(self.sock, sock)
+
+    def test_reuse_port_enabled(self):
+        addr = ('127.0.0.1', 8081)
+
+        sock = self.hub.listen(addr, reuse_port=True)
+
+        self.sock.setsockopt.assert_any_call(
+            socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+        self.sock.bind.assert_called_once_with(addr)
+
+
+class TestListenNative(unittest.TestCase):
+
+    @mock.patch.dict(os.environ, {"OSKEN_HUB_TYPE": "native"})
+    def setUp(self):
+        self.hub = importlib.reload(os_ken.lib.hub)
+
+        self.patcher = mock.patch('socket.socket')
+        self.mock_socket = self.patcher.start()
+
+        self.sock = mock.MagicMock()
+        self.mock_socket.return_value = self.sock