Workaround for TCP checksum issue with ovs-dpdk and veth pair

The need for this change stems from following issues:
1) When ovs_use_veth = False with ovs-dpdk issue with ovs
was observed - after vswitch restart interface is not comming up.
Meaning ovs-dpdk uses ovs internal ports and it is not able to bring
them up on restart.
2) When ovs_use_veth = True and ovs-dpkd is used, packets sent with
incorrect checksum due to the fact that ovs-dpdk does not do checksum
calculations for veth interface.

This commit allows to use second option and resolve checksum issue by
disabling checksum offload.

Closes-Bug: #1832021
Related-Bug: #1831935

Change-Id: Iecce8d2c6c2c46718cc1020c6e8f914cd4560e4b

etc/neutron/rootwrap.d/dhcp.filters

@@ -10,6 +10,7 @@
 
 # dhcp-agent
 dnsmasq: CommandFilter, dnsmasq, root
+ethtool: CommandFilter, ethtool, root
 # dhcp-agent uses kill as well, that's handled by the generic KillFilter
 # it looks like these are the only signals needed, per
 # neutron/agent/linux/dhcp.py

etc/neutron/rootwrap.d/l3.filters

@@ -12,6 +12,7 @@
 arping: CommandFilter, arping, root
 
 # l3_agent
+ethtool: CommandFilter, ethtool, root
 sysctl: CommandFilter, sysctl, root
 route: CommandFilter, route, root
 radvd: CommandFilter, radvd, root

neutron/agent/linux/ethtool.py

@@ -0,0 +1,34 @@
+# Copyright 2020 OpenStack Foundation
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+from neutron.agent.linux import ip_lib
+
+
+class Ethtool(object):
+
+    COMMAND = 'ethtool'
+
+    @staticmethod
+    def _cmd(cmd, namespace, **kwargs):
+        ip_wrapper = ip_lib.IPWrapper(namespace)
+        return ip_wrapper.netns.execute(cmd, run_as_root=True, **kwargs)
+
+    @classmethod
+    def offload(cls, device, rx, tx, namespace=None):
+        rx = 'on' if rx else 'off'
+        tx = 'on' if tx else 'off'
+        cmd = ['--offload', device, 'rx', rx, 'tx', tx]
+        cmd = [cls.COMMAND] + cmd
+        cls._cmd(cmd, namespace)

neutron/agent/linux/interface.py

@@ -25,8 +25,12 @@ from pyroute2.netlink import exceptions as pyroute2_exc
 import six
 
 from neutron.agent.common import ovs_lib
+from neutron.agent.linux import ethtool
 from neutron.agent.linux import ip_lib
 from neutron.common import utils
+from neutron.conf.plugins.ml2.drivers import ovs_conf
+from neutron.plugins.ml2.drivers.openvswitch.agent.common \
+    import constants as ovs_const
 
 LOG = logging.getLogger(__name__)
 
@@ -317,6 +321,7 @@ class OVSInterfaceDriver(LinuxInterfaceDriver):
 
     def __init__(self, conf, **kwargs):
         super(OVSInterfaceDriver, self).__init__(conf, **kwargs)
+        ovs_conf.register_ovs_agent_opts(self.conf)
         if self.conf.ovs_use_veth:
             self.DEV_NAME_PREFIX = 'ns-'
 
@@ -402,6 +407,11 @@ class OVSInterfaceDriver(LinuxInterfaceDriver):
 
         ns_dev.link.set_up()
         if self.conf.ovs_use_veth:
+            # ovs-dpdk does not do checksum calculations for veth interface
+            # (bug 1832021)
+            if self.conf.OVS.datapath_type == ovs_const.OVS_DATAPATH_NETDEV:
+                ethtool.Ethtool.offload(ns_dev.name, rx=False, tx=False,
+                                        namespace=namespace)
             root_dev.link.set_up()
 
     def unplug(self, device_name, bridge=None, namespace=None, prefix=None):

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

@@ -19,11 +19,14 @@ from oslo_utils import excutils
 from pyroute2.netlink import exceptions as pyroute2_exc
 
 from neutron.agent.common import ovs_lib
+from neutron.agent.linux import ethtool
 from neutron.agent.linux import interface
 from neutron.agent.linux import ip_lib
 from neutron.common import utils
 from neutron.conf.agent import common as config
 from neutron.conf.plugins.ml2.drivers import ovs_conf
+from neutron.plugins.ml2.drivers.openvswitch.agent.common \
+    import constants as ovs_const
 from neutron.tests import base
 
 
@@ -63,6 +66,8 @@ class TestBase(base.BaseTestCase):
         self.conf = config.setup_conf()
         ovs_conf.register_ovs_opts(self.conf)
         config.register_interface_opts(self.conf)
+        self.eth_tool_p = mock.patch.object(ethtool, 'Ethtool')
+        self.eth_tool = self.eth_tool_p.start()
         self.ip_dev_p = mock.patch.object(ip_lib, 'IPDevice')
         self.ip_dev = self.ip_dev_p.start()
         self.ip_p = mock.patch.object(ip_lib, 'IPWrapper')
@@ -507,7 +512,12 @@ class TestOVSInterfaceDriverWithVeth(TestOVSInterfaceDriver):
 
     def setUp(self):
         super(TestOVSInterfaceDriverWithVeth, self).setUp()
+        ovs_conf.register_ovs_agent_opts(self.conf)
         self.conf.set_override('ovs_use_veth', True)
+        self.conf.set_override(
+            'datapath_type',
+            ovs_const.OVS_DATAPATH_NETDEV,
+            group='OVS')
 
     def test_get_device_name(self):
         br = interface.OVSInterfaceDriver(self.conf)
@@ -538,6 +548,7 @@ class TestOVSInterfaceDriverWithVeth(TestOVSInterfaceDriver):
             mock.patch.object(
                 interface, '_get_veth',
                 return_value=(root_dev, ns_dev)).start()
+            ns_dev.name = devname
 
             expected = [mock.call(),
                         mock.call().add_veth('tap0', devname,
@@ -568,6 +579,9 @@ class TestOVSInterfaceDriverWithVeth(TestOVSInterfaceDriver):
             self.ip.assert_has_calls(expected)
             root_dev.assert_has_calls([mock.call.link.set_up()])
             ns_dev.assert_has_calls([mock.call.link.set_up()])
+            self.eth_tool.assert_has_calls([mock.call.offload(
+                                            devname, rx=False,
+                                            tx=False, namespace=namespace)])
 
     def test_plug_new(self):
         # The purpose of test_plug_new in parent class(TestOVSInterfaceDriver)