Add sleep before checking if ovs port is in the namespace

When network device which is ovs internal port is moved to the namespace
it may happend sometimes that it will have "shy port syndrome" [1].
Even though there is wait for device to be in namespace in the set_netns
method it may happend that device is in namespace during this check but
it dissapears for short time later and that causes failures e.g. in
functional tests like described in [2].
To avoid that, this patch proposed simple (and ugly) sleep for 1 second
before checking if port really exists in the namespace. If it will be
"shy" port it should already flap during that 1 second.

[1] https://bugs.launchpad.net/neutron/+bug/1618987
[2] https://bugs.launchpad.net/neutron/+bug/1961740

Related-Bug: #1961740
Related-Bug: #1998337
Change-Id: I442587e7ef55917f4ea873e190bf8afbc0e911e1
(cherry picked from commit 2af5fd8)

Author: slawqo

neutron/agent/linux/interface.py

@@ -356,7 +356,7 @@ def _add_device_to_namespace(self, ip_wrapper, device, namespace):
         namespace_obj = ip_wrapper.ensure_namespace(namespace)
         for i in range(9):
             try:
-                namespace_obj.add_device_to_namespace(device)
+                namespace_obj.add_device_to_namespace(device, is_ovs_port=True)
                 break
             except ip_lib.NetworkInterfaceNotFound:
                 # NOTE(slaweq): if the exception was NetworkInterfaceNotFound

neutron/agent/linux/ip_lib.py

@@ -270,9 +270,9 @@ def garbage_collect_namespace(self):
                 return True
         return False
 
-    def add_device_to_namespace(self, device):
+    def add_device_to_namespace(self, device, is_ovs_port=False):
         if self.namespace:
-            device.link.set_netns(self.namespace)
+            device.link.set_netns(self.namespace, is_ovs_port=is_ovs_port)
 
     def add_vlan(self, name, physical_interface, vlan_id):
         privileged.create_interface(name,
@@ -462,10 +462,15 @@ def set_down(self):
         privileged.set_link_attribute(
             self.name, self._parent.namespace, state='down')
 
-    def set_netns(self, namespace):
+    def set_netns(self, namespace, is_ovs_port=False):
         privileged.set_link_attribute(
             self.name, self._parent.namespace, net_ns_fd=namespace)
         self._parent.namespace = namespace
+        if is_ovs_port:
+            # NOTE(slaweq): because of the "shy port" which may dissapear for
+            # short time after it's moved to the namespace we need to wait
+            # a bit before checking if port really exists in the namespace
+            time.sleep(1)
         common_utils.wait_until_true(lambda: self.exists, timeout=5,
                                      sleep=0.5)
 

neutron/tests/unit/agent/linux/test_interface.py

@@ -468,11 +468,11 @@ def device_exists(dev, namespace=None):
                 expected.extend(
                     [mock.call().ensure_namespace(namespace),
                      mock.call().ensure_namespace().add_device_to_namespace(
-                         mock.ANY),
+                         mock.ANY, is_ovs_port=True),
                      mock.call().ensure_namespace().add_device_to_namespace(
-                         mock.ANY),
+                         mock.ANY, is_ovs_port=True),
                      mock.call().ensure_namespace().add_device_to_namespace(
-                         mock.ANY)])
+                         mock.ANY, is_ovs_port=True)])
             expected.extend([
                 mock.call(namespace=namespace),
                 mock.call().device('tap0'),

neutron/tests/unit/agent/linux/test_ip_lib.py

@@ -506,7 +506,8 @@ def fake_create_interface(ifname, namespace, kind, **kwargs):
     def test_add_device_to_namespace(self):
         dev = mock.Mock()
         ip_lib.IPWrapper(namespace='ns').add_device_to_namespace(dev)
-        dev.assert_has_calls([mock.call.link.set_netns('ns')])
+        dev.assert_has_calls(
+            [mock.call.link.set_netns('ns', is_ovs_port=False)])
 
     def test_add_device_to_namespace_is_none(self):
         dev = mock.Mock()