OVS lib defer apply doesn't handle concurrency

The OVS lib deferred apply methods use a dict to save flows to add,
modify or delete when deffered apply is switched off.
If another thread adds, modifies or deletes flows on that dict during
another process called deffered_apply_off, its flows could be ignored.

This fix stash reference flows list and point the flows list to a new
cleared flows list. Then, it applies flows from the stashed flows list.

Closes-bug: #1263866
Change-Id: Ia3c6ce181e1599d1474da7eb944feff7d84f1d73
(cherry picked from commit 501213686886baccd3280e10b8856a25d3517519)

diff --git a/neutron/agent/linux/ovs_lib.py b/neutron/agent/linux/ovs_lib.py
index e1172234f8f2677280442914f949684812e84ff7..64cf1baf447e722df0a83ae7de45350720ba6838 100644 (file)
--- a/neutron/agent/linux/ovs_lib.py
+++ b/neutron/agent/linux/ovs_lib.py
@@ -206,7 +206,14 @@ class OVSBridge(BaseOVS):
 
     def defer_apply_off(self):
         LOG.debug(_('defer_apply_off'))
-        for action, flows in self.deferred_flows.items():
+        # Note(ethuleau): stash flows and disable deferred mode. Then apply
+        # flows from the stashed reference to be sure to not purge flows that
+        # were added between two ofctl commands.
+        stashed_deferred_flows, self.deferred_flows = (
+            self.deferred_flows, {'add': '', 'mod': '', 'del': ''}
+        )
+        self.defer_apply_flows = False
+        for action, flows in stashed_deferred_flows.items():
             if flows:
                 LOG.debug(_('Applying following deferred flows '
                             'to bridge %s'), self.br_name)
@@ -214,8 +221,6 @@ class OVSBridge(BaseOVS):
                     LOG.debug(_('%(action)s: %(flow)s'),
                               {'action': action, 'flow': line})
                 self.run_ofctl('%s-flows' % action, ['-'], flows)
-        self.defer_apply_flows = False
-        self.deferred_flows = {'add': '', 'mod': '', 'del': ''}
 
     def add_tunnel_port(self, port_name, remote_ip, local_ip,
                         tunnel_type=p_const.TYPE_GRE,

diff --git a/neutron/tests/unit/openvswitch/test_ovs_lib.py b/neutron/tests/unit/openvswitch/test_ovs_lib.py
index a9c1b981adfe2e74909455e51c1f08f1e9af4615..7b7d9d167bce763b3cf4c8ceebcebdf51bec31e2 100644 (file)
--- a/neutron/tests/unit/openvswitch/test_ovs_lib.py
+++ b/neutron/tests/unit/openvswitch/test_ovs_lib.py
@@ -401,6 +401,50 @@ class OVS_Lib_Test(base.BaseTestCase):
             mock.call('del-flows', ['-'], 'deleted_flow_1\n')
         ])
 
+    def test_defer_apply_flows_concurrently(self):
+        flow_expr = mock.patch.object(ovs_lib, '_build_flow_expr_str').start()
+        flow_expr.side_effect = ['added_flow_1', 'deleted_flow_1',
+                                 'modified_flow_1', 'added_flow_2',
+                                 'deleted_flow_2', 'modified_flow_2']
+
+        run_ofctl = mock.patch.object(self.br, 'run_ofctl').start()
+
+        def run_ofctl_fake(cmd, args, process_input=None):
+            self.br.defer_apply_on()
+            if cmd == 'add-flows':
+                self.br.add_flow(flow='added_flow_2')
+            elif cmd == 'del-flows':
+                self.br.delete_flows(flow='deleted_flow_2')
+            elif cmd == 'mod-flows':
+                self.br.mod_flow(flow='modified_flow_2')
+        run_ofctl.side_effect = run_ofctl_fake
+
+        self.br.defer_apply_on()
+        self.br.add_flow(flow='added_flow_1')
+        self.br.delete_flows(flow='deleted_flow_1')
+        self.br.mod_flow(flow='modified_flow_1')
+        self.br.defer_apply_off()
+
+        run_ofctl.side_effect = None
+        self.br.defer_apply_off()
+
+        flow_expr.assert_has_calls([
+            mock.call({'flow': 'added_flow_1'}, 'add'),
+            mock.call({'flow': 'deleted_flow_1'}, 'del'),
+            mock.call({'flow': 'modified_flow_1'}, 'mod'),
+            mock.call({'flow': 'added_flow_2'}, 'add'),
+            mock.call({'flow': 'deleted_flow_2'}, 'del'),
+            mock.call({'flow': 'modified_flow_2'}, 'mod')
+        ])
+        run_ofctl.assert_has_calls([
+            mock.call('add-flows', ['-'], 'added_flow_1\n'),
+            mock.call('del-flows', ['-'], 'deleted_flow_1\n'),
+            mock.call('mod-flows', ['-'], 'modified_flow_1\n'),
+            mock.call('add-flows', ['-'], 'added_flow_2\n'),
+            mock.call('del-flows', ['-'], 'deleted_flow_2\n'),
+            mock.call('mod-flows', ['-'], 'modified_flow_2\n')
+        ])
+
     def test_add_tunnel_port(self):
         pname = "tap99"
         local_ip = "1.1.1.1"