Optimize interface_exists_on_bridge

Currently interface_exists_on_bridge[1] lists all files in a folder and
searchs for the file associated to the interface.

This change proposes to look for the file existence directly.

[1] neutron.plugins.ml2.drivers.linuxbridge.agent.linuxbridge_neutron_agent

Closes-Bug: #1509890
Change-Id: I23cd1edc92912b35bdc23ba0af2318b86f2cfd48

neutron/plugins/ml2/drivers/linuxbridge/agent/linuxbridge_neutron_agent.py

@@ -62,6 +62,7 @@ BRIDGE_NAME_PREFIX = "brq"
 # NOTE(toabctl): Don't use /sys/devices/virtual/net here because not all tap
 # devices are listed here (i.e. when using Xen)
 BRIDGE_FS = "/sys/class/net/"
+BRIDGE_INTERFACE_FS = BRIDGE_FS + "%(bridge)s/brif/%(interface)s"
 BRIDGE_INTERFACES_FS = BRIDGE_FS + "%s/brif/"
 BRIDGE_PORT_FS_FOR_DEVICE = BRIDGE_FS + "%s/brport"
 VXLAN_INTERFACE_PREFIX = "vxlan-"
@@ -119,12 +120,10 @@ class LinuxBridgeManager(object):
             sys.exit(1)
         return device
 
-    def interface_exists_on_bridge(self, bridge, interface):
-        directory = '/sys/class/net/%s/brif' % bridge
-        for filename in os.listdir(directory):
-            if filename == interface:
-                return True
-        return False
+    @staticmethod
+    def interface_exists_on_bridge(bridge, interface):
+        return os.path.exists(
+            BRIDGE_INTERFACE_FS % {'bridge': bridge, 'interface': interface})
 
     def get_existing_bridge_name(self, physical_network):
         if not physical_network:

neutron/tests/common/net_helpers.py

@@ -43,6 +43,8 @@ from neutron.tests import base as tests_base
 from neutron.tests.common import base as common_base
 from neutron.tests import tools
 
+UNDEFINED = object()
+
 NS_PREFIX = 'test-'
 BR_PREFIX = 'test-br'
 PORT_PREFIX = 'test-port'
@@ -527,12 +529,14 @@ class LinuxBridgeFixture(fixtures.Fixture):
     :type namespace: str
     """
 
-    def __init__(self, prefix=BR_PREFIX):
+    def __init__(self, prefix=BR_PREFIX, namespace=UNDEFINED):
         super(LinuxBridgeFixture, self).__init__()
         self.prefix = prefix
+        self.namespace = namespace
 
     def _setUp(self):
-        self.namespace = self.useFixture(NamespaceFixture()).name
+        if self.namespace is UNDEFINED:
+            self.namespace = self.useFixture(NamespaceFixture()).name
         self.bridge = common_base.create_resource(
             self.prefix,
             bridge_lib.BridgeDevice.addbr,

neutron/tests/functional/agent/test_l2_lb_agent.py

@@ -19,6 +19,7 @@ import testtools
 
 from neutron.plugins.ml2.drivers.linuxbridge.agent import \
     linuxbridge_neutron_agent
+from neutron.tests.common import net_helpers
 from neutron.tests.functional.agent.linux import test_ip_lib
 
 LOG = logging.getLogger(__name__)
@@ -34,6 +35,13 @@ class LinuxBridgeAgentTests(test_ip_lib.IpLibTestFramework):
         mock.patch('neutron.agent.rpc.PluginReportStateAPI').start()
         cfg.CONF.set_override('enable_vxlan', False, 'VXLAN')
 
+    def create_bridge_port_fixture(self):
+        bridge = self.useFixture(
+            net_helpers.LinuxBridgeFixture(namespace=None)).bridge
+        port_fixture = self.useFixture(
+            net_helpers.LinuxBridgePortFixture(bridge))
+        return port_fixture
+
     def test_validate_interface_mappings(self):
         mappings = {'physnet1': 'int1', 'physnet2': 'int2'}
         with testtools.ExpectedException(SystemExit):
@@ -56,3 +64,15 @@ class LinuxBridgeAgentTests(test_ip_lib.IpLibTestFramework):
             self.generate_device_details()._replace(namespace=None,
                                                     name='br-eth1'))
         lba.LinuxBridgeManager(mappings, {})
+
+    def test_interface_exists_on_bridge(self):
+        port_fixture = self.create_bridge_port_fixture()
+        self.assertTrue(
+            lba.LinuxBridgeManager.interface_exists_on_bridge(
+                port_fixture.bridge.name, port_fixture.br_port.name))
+
+    def test_interface_exists_not_on_bridge(self):
+        port_fixture = self.create_bridge_port_fixture()
+        self.assertFalse(
+            lba.LinuxBridgeManager.interface_exists_on_bridge(
+                port_fixture.bridge.name, port_fixture.port.name))

neutron/tests/unit/plugins/ml2/drivers/linuxbridge/agent/test_linuxbridge_neutron_agent.py

@@ -402,8 +402,9 @@ class TestLinuxBridgeManager(base.BaseTestCase):
             exit.assert_called_once_with(1)
 
     def test_interface_exists_on_bridge(self):
-        with mock.patch.object(os, 'listdir') as listdir_fn:
-            listdir_fn.return_value = ["abc"]
+        with mock.patch.object(os.path, 'exists') as exists_fn:
+            exists_fn.side_effect = (
+                lambda p: p == '/sys/class/net/br-int/brif/abc')
             self.assertTrue(
                 self.lbm.interface_exists_on_bridge("br-int", "abc")
             )