defer firewall updates to iptables data structures

One of two patches that fixes bug #1194438.

In the iptables firewall driver, each port method (update_port_filter,
prepare_port_filter, remove_port_filter) makes O(N) calls, where
N=len(firewall.ports), to IptablesManager methods that update dozens
of data structures. When the firewall methods are called in sequence,
e.g., by SecurityGroupAgentRpcMixin, the calls to IptablesManager's
methods start to add up.

This patch changes IptablesFirewallDriver to defer and coalesce calls
to IptablesManager. Now a sequence of M port method calls results in
O(N) calls to IptablesManager methods instead of O(N*M) as before.

Change-Id: If17eeaec197beae8b8aecffca1f19d4535a7226e

neutron/agent/linux/iptables_firewall.py

@@ -47,6 +47,8 @@ class IptablesFirewallDriver(firewall.FirewallDriver):
         # list of port which has security group
         self.filtered_ports = {}
         self._add_fallback_chain_v4v6()
+        self._defer_apply = False
+        self._pre_defer_filtered_ports = None
 
     @property
     def ports(self):
@@ -84,8 +86,12 @@ class IptablesFirewallDriver(firewall.FirewallDriver):
 
     def _setup_chains(self):
         """Setup ingress and egress chain for a port."""
+        if not self._defer_apply:
+            self._setup_chains_apply(self.filtered_ports)
+
+    def _setup_chains_apply(self, ports):
         self._add_chain_by_name_v4v6(SG_CHAIN)
-        for port in self.filtered_ports.values():
+        for port in ports.values():
             self._setup_chain(port, INGRESS_DIRECTION)
             self._setup_chain(port, EGRESS_DIRECTION)
             self.iptables.ipv4['filter'].add_rule(SG_CHAIN, '-j ACCEPT')
@@ -93,7 +99,11 @@ class IptablesFirewallDriver(firewall.FirewallDriver):
 
     def _remove_chains(self):
         """Remove ingress and egress chain for a port."""
-        for port in self.filtered_ports.values():
+        if not self._defer_apply:
+            self._remove_chains_apply(self.filtered_ports)
+
+    def _remove_chains_apply(self, ports):
+        for port in ports.values():
             self._remove_chain(port, INGRESS_DIRECTION)
             self._remove_chain(port, EGRESS_DIRECTION)
             self._remove_chain(port, IP_SPOOF_FILTER)
@@ -307,10 +317,18 @@ class IptablesFirewallDriver(firewall.FirewallDriver):
             '%s%s' % (CHAIN_NAME_PREFIX[direction], port['device'][3:]))
 
     def filter_defer_apply_on(self):
-        self.iptables.defer_apply_on()
+        if not self._defer_apply:
+            self.iptables.defer_apply_on()
+            self._pre_defer_filtered_ports = dict(self.filtered_ports)
+            self._defer_apply = True
 
     def filter_defer_apply_off(self):
-        self.iptables.defer_apply_off()
+        if self._defer_apply:
+            self._defer_apply = False
+            self._remove_chains_apply(self._pre_defer_filtered_ports)
+            self._pre_defer_filtered_ports = None
+            self._setup_chains_apply(self.filtered_ports)
+            self.iptables.defer_apply_off()
 
 
 class OVSHybridIptablesFirewallDriver(IptablesFirewallDriver):

neutron/tests/unit/test_iptables_firewall.py

@@ -15,6 +15,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
+import copy
+
 import mock
 from mock import call
 from oslo.config import cfg
@@ -935,6 +937,70 @@ class IptablesFirewallTestCase(base.BaseTestCase):
         self.iptables_inst.assert_has_calls([call.defer_apply_on(),
                                              call.defer_apply_off()])
 
+    def _mock_chain_applies(self):
+        class CopyingMock(mock.MagicMock):
+            """Copies arguments so mutable arguments can be asserted on.
+
+            Copied verbatim from unittest.mock documentation.
+            """
+            def __call__(self, *args, **kwargs):
+                args = copy.deepcopy(args)
+                kwargs = copy.deepcopy(kwargs)
+                return super(CopyingMock, self).__call__(*args, **kwargs)
+        # Need to use CopyingMock because _{setup,remove}_chains_apply are
+        # usually called with that's modified between calls (i.e.,
+        # self.firewall.filtered_ports).
+        chain_applies = CopyingMock()
+        self.firewall._setup_chains_apply = chain_applies.setup
+        self.firewall._remove_chains_apply = chain_applies.remove
+        return chain_applies
+
+    def test_mock_chain_applies(self):
+        chain_applies = self._mock_chain_applies()
+        port_prepare = {'device': 'd1', 'mac_address': 'prepare'}
+        port_update = {'device': 'd1', 'mac_address': 'update'}
+        self.firewall.prepare_port_filter(port_prepare)
+        self.firewall.update_port_filter(port_update)
+        self.firewall.remove_port_filter(port_update)
+        chain_applies.assert_has_calls([call.remove({}),
+                                        call.setup({'d1': port_prepare}),
+                                        call.remove({'d1': port_prepare}),
+                                        call.setup({'d1': port_update}),
+                                        call.remove({'d1': port_update}),
+                                        call.setup({})])
+
+    def test_defer_chain_apply_need_pre_defer_copy(self):
+        chain_applies = self._mock_chain_applies()
+        port = self._fake_port()
+        device2port = {port['device']: port}
+        self.firewall.prepare_port_filter(port)
+        with self.firewall.defer_apply():
+            self.firewall.remove_port_filter(port)
+        chain_applies.assert_has_calls([call.remove({}),
+                                        call.setup(device2port),
+                                        call.remove(device2port),
+                                        call.setup({})])
+
+    def test_defer_chain_apply_coalesce_simple(self):
+        chain_applies = self._mock_chain_applies()
+        port = self._fake_port()
+        with self.firewall.defer_apply():
+            self.firewall.prepare_port_filter(port)
+            self.firewall.update_port_filter(port)
+            self.firewall.remove_port_filter(port)
+        chain_applies.assert_has_calls([call.remove({}), call.setup({})])
+
+    def test_defer_chain_apply_coalesce_multiple_ports(self):
+        chain_applies = self._mock_chain_applies()
+        port1 = {'device': 'd1', 'mac_address': 'mac1'}
+        port2 = {'device': 'd2', 'mac_address': 'mac2'}
+        device2port = {'d1': port1, 'd2': port2}
+        with self.firewall.defer_apply():
+            self.firewall.prepare_port_filter(port1)
+            self.firewall.prepare_port_filter(port2)
+        chain_applies.assert_has_calls([call.remove({}),
+                                        call.setup(device2port)])
+
     def test_ip_spoofing_filter_with_multiple_ips(self):
         port = {'device': 'tapfake_dev',
                 'mac_address': 'ff:ff:ff:ff',