convenience: SO_REUSEPORT is not available on WSL platform (Linux on Windows)

https://github.com/eventlet/eventlet/issues/380
https://github.com/eventlet/eventlet/issues/418

eventlet/convenience.py

@@ -3,6 +3,7 @@ import warnings
 
 from eventlet import greenpool
 from eventlet import greenthread
+from eventlet import support
 from eventlet.green import socket
 from eventlet.support import greenlets as greenlet
 
@@ -26,6 +27,10 @@ class ReuseRandomPortWarning(Warning):
     pass
 
 
+class ReusePortUnavailableWarning(Warning):
+    pass
+
+
 def listen(addr, family=socket.AF_INET, backlog=50, reuse_addr=True, reuse_port=None):
     """Convenience function for opening server sockets.  This
     socket can be used in :func:`~eventlet.serve` or a custom ``accept()`` loop.
@@ -55,7 +60,20 @@ def listen(addr, family=socket.AF_INET, backlog=50, reuse_addr=True, reuse_port=
         reuse_port = True
     if reuse_port and hasattr(socket, 'SO_REUSEPORT'):
         # NOTE(zhengwei): linux kernel >= 3.9
-        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+        try:
+            sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+        except OSError as ex:
+            if support.get_errno(ex) in (22, 92):
+                # A famous platform defines unsupported socket option.
+                # https://github.com/eventlet/eventlet/issues/380
+                # https://github.com/eventlet/eventlet/issues/418
+                warnings.warn(
+                    '''socket.SO_REUSEPORT is defined but not supported.
+                    On Windows: known bug, wontfix.
+                    On other systems: please comment in the issue linked below.
+                    More information: https://github.com/eventlet/eventlet/issues/380''',
+                    ReusePortUnavailableWarning, stacklevel=3)
+
     sock.bind(addr)
     sock.listen(backlog)
     return sock

tests/convenience_test.py

@@ -6,6 +6,7 @@ from eventlet import convenience, debug
 from eventlet.green import socket
 from eventlet.support import six
 import tests
+import tests.mock
 
 
 certificate_file = os.path.join(os.path.dirname(__file__), 'test_server.crt')
@@ -167,3 +168,29 @@ def test_reuse_random_port_warning():
         eventlet.listen(('localhost', 0), reuse_port=True).close()
         assert len(w) == 1
         assert issubclass(w[0].category, convenience.ReuseRandomPortWarning)
+
+
+@tests.skip_unless(hasattr(socket, 'SO_REUSEPORT'))
+def test_reuseport_oserror():
+    # https://github.com/eventlet/eventlet/issues/380
+    # https://github.com/eventlet/eventlet/issues/418
+    err22 = OSError(22, 'Invalid argument')
+
+    sock1 = eventlet.listen(('localhost', 0))
+    addr = sock1.getsockname()
+    sock1.close()
+
+    original_socket_init = socket.socket.__init__
+
+    def patched(self, *a, **kw):
+        original_socket_init(self, *a, **kw)
+        self.setsockopt = tests.mock.Mock(side_effect=err22)
+
+    with warnings.catch_warnings(record=True) as w:
+        try:
+            socket.socket.__init__ = patched
+            eventlet.listen(addr, reuse_addr=False, reuse_port=True).close()
+        finally:
+            socket.socket.__init__ = original_socket_init
+        assert len(w) == 1
+        assert issubclass(w[0].category, convenience.ReusePortUnavailableWarning)