[OVS] Allow custom ethertype traffic in the ingress table

This patch is a partial revert of [1], reinstantiating the code merged
in [2]. This patch is the complementary to [1]: the traffic with
custom ethertypes is allowed in the ingress processing tables, same
as [1] is allowing all traffic from the virtual machine ports in this
host to leave the node. Both, this patch and [1], are bypassing the
OVS firewall just for the traffic with the configured allowed
ethertypes and just for/to the local ports and MAC addresses.

Any other traffic not coming from a local port or with destination
a local port, will be blocked as is now.

[1]https://review.opendev.org/c/openstack/neutron/+/678021
[2]https://review.opendev.org/c/openstack/neutron/+/668224/

Closes-Bug: #2009221
Related-Bug: #1832758
Change-Id: Ib8340d9430b946a446edf80886c49fbac729073c

doc/source/admin/config-ovsfwdriver.rst

@@ -175,6 +175,16 @@ the default ``_constants.AGENT_RES_PROCESSING_STEP``:
     # (6) Check the OVS agent restart time, checking the "iteration" time and
     #     number.
 
+Permitted ethertypes
+~~~~~~~~~~~~~~~~~~~~
+
+The OVS Firewall blocks traffic that does not have either the IPv4 or IPv6
+ethertypes at present. This is a behavior change compared to the
+"iptables_hybrid" firewall, which only operates on IP packets and thus does
+not address other ethertypes. With the configuration option
+``permitted_ethertypes`` it is possible to define a set of allowed ethertypes.
+Any traffic with these allowed ethertypes with destination to a local port or
+generated from a local port and MAC address, will be allowed.
 
 References
 ~~~~~~~~~~

neutron/agent/linux/openvswitch_firewall/firewall.py

@@ -1388,6 +1388,25 @@ class OVSFirewallDriver(firewall.FirewallDriver):
             actions='output:{:d}'.format(port.ofport)
         )
 
+        # Allow custom ethertypes
+        for permitted_ethertype in self.permitted_ethertypes:
+            if permitted_ethertype[:2] == '0x':
+                try:
+                    hex_ethertype = hex(int(permitted_ethertype, base=16))
+                    self._add_flow(
+                        table=ovs_consts.BASE_INGRESS_TABLE,
+                        priority=100,
+                        dl_type=hex_ethertype,
+                        reg_port=port.ofport,
+                        actions='output:{:d}'.format(port.ofport)
+                    )
+                    continue
+                except ValueError:
+                    pass
+            LOG.warning('Custom ethertype %(permitted_ethertype)s is not '
+                        'a hexadecimal number.',
+                        {'permitted_ethertype': permitted_ethertype})
+
         self._initialize_ingress_ipv6_icmp(port)
 
         # DHCP offers

neutron/tests/unit/agent/linux/openvswitch_firewall/test_firewall.py

@@ -31,6 +31,7 @@ from neutron.agent.linux.openvswitch_firewall import constants as ovsfw_consts
 from neutron.agent.linux.openvswitch_firewall import exceptions
 from neutron.agent.linux.openvswitch_firewall import firewall as ovsfw
 from neutron.conf.agent import securitygroups_rpc
+from neutron.conf.plugins.ml2.drivers import ovs_conf
 from neutron.plugins.ml2.drivers.openvswitch.agent.openflow.native \
     import ovs_bridge
 from neutron.tests import base
@@ -518,6 +519,7 @@ class FakeOVSPort(object):
 class TestOVSFirewallDriver(base.BaseTestCase):
     def setUp(self):
         super(TestOVSFirewallDriver, self).setUp()
+        ovs_conf.register_ovs_agent_opts(cfg=cfg.CONF)
         mock_bridge = mock.patch.object(
             ovs_lib, 'OVSBridge', autospec=True).start()
         securitygroups_rpc.register_securitygroups_opts()
@@ -844,6 +846,26 @@ class TestOVSFirewallDriver(base.BaseTestCase):
                                return_value={"vlan1": "br-vlan1"}):
             self.firewall.initialize_port_flows(port)
 
+    def test_initialize_port_flows_permitted_ethertypes(self):
+        self.firewall.permitted_ethertypes = ['0x1234', '0x5678']
+        port_dict = {'device': 'port-id',
+                     'security_groups': [1]}
+        of_port = create_ofport(port_dict,
+                                network_type=constants.TYPE_VLAN,
+                                physical_network='vlan1')
+        self.firewall.sg_port_map.ports[of_port.id] = of_port
+        port = self.firewall.get_or_create_ofport(port_dict)
+        with mock.patch.object(self.firewall, '_add_flow') as mock_add_flow:
+            self.firewall.initialize_port_flows(port)
+
+        calls = [mock.call(table=ovs_consts.BASE_INGRESS_TABLE,
+                           priority=100, dl_type='0x1234',
+                           reg_port=1, actions='output:1'),
+                 mock.call(table=ovs_consts.BASE_INGRESS_TABLE,
+                           priority=100, dl_type='0x5678',
+                           reg_port=1, actions='output:1')]
+        mock_add_flow.assert_has_calls(calls, any_order=True)
+
     def test_delete_all_port_flows(self):
         port_dict = {
             'device': 'port-id',