Add method is_valid_port in netutils

Glance[1] and Neutron[2] need to check if a value is a valid port,
so we place the common code in oslo.utils.

[1] https://git.openstack.org/cgit/openstack/glance/tree/glance/common/utils.py#n550
[2] https://git.openstack.org/cgit/openstack/neutron/tree/neutron/extensions/securitygroup.py#n142

Change-Id: I156035396b4f686589b6f7ddfbdb0c922b8d90a0

oslo/utils/netutils.py

@@ -114,6 +114,16 @@ def is_valid_ip(address):
     return is_valid_ipv4(address) or is_valid_ipv6(address)
 
 
+def is_valid_port(port):
+    """Verify that port represents a valid port number."""
+    try:
+        val = int(port)
+    except (ValueError, TypeError):
+        return False
+
+    return (val > 0 and val <= 65535)
+
+
 def get_my_ipv4():
     """Returns the actual ipv4 of the local machine.
 

tests/test_netutils.py

@@ -178,6 +178,18 @@ class NetworkUtilsTest(test_base.BaseTestCase):
 
         self.assertFalse(netutils.is_valid_ip(''))
 
+    def test_valid_port(self):
+        valid_inputs = [1, '1', 2, '3', '5', 8, 13, 21,
+                        '80', '3246', '65535']
+        for input_str in valid_inputs:
+            self.assertTrue(netutils.is_valid_port(input_str))
+
+    def test_valid_port_fail(self):
+        invalid_inputs = ['-32768', '0', 0, '65536', 528491, '528491',
+                          '528.491', 'thirty-seven', None]
+        for input_str in invalid_inputs:
+            self.assertFalse(netutils.is_valid_port(input_str))
+
     def test_get_my_ip(self):
         sock_attrs = {
             'return_value.getsockname.return_value': ['1.2.3.4', '']}