vxlan: T5668: add CLI knob to enable ARP/ND suppression

In order to minimize the flooding of ARP and ND messages in the VXLAN network,
EVPN includes provisions [1] that allow participating VTEPs to suppress such
messages in case they know the MAC-IP binding and can reply on behalf of the
remote host. In Linux, the above is implemented in the bridge driver using a
per-port option called "neigh_suppress" that was added in kernel version 4.15.

[1] https://www.rfc-editor.org/rfc/rfc7432#section-10

interface-definitions/interfaces-vxlan.xml.in

@@ -89,6 +89,12 @@
                   <valueless/>
                 </properties>
               </leafNode>
+              <leafNode name="neighbor-suppress">
+                <properties>
+                  <help>Enable neighbor discovery (ARP and ND) suppression</help>
+                  <valueless/>
+                </properties>
+              </leafNode>
             </children>
           </node>
           #include <include/port-number.xml.i>

python/vyos/ifconfig/vxlan.py

@@ -56,6 +56,10 @@ class VXLANIf(Interface):
     }
 
     _command_set = {**Interface._command_set, **{
+        'neigh_suppress': {
+            'validate': lambda v: assert_list(v, ['on', 'off']),
+            'shellcmd': 'bridge link set dev {ifname} neigh_suppress {value}',
+        },
         'vlan_tunnel': {
             'validate': lambda v: assert_list(v, ['on', 'off']),
             'shellcmd': 'bridge link set dev {ifname} vlan_tunnel {value}',
@@ -113,6 +117,19 @@ def _create(self):
                        'port {port} dev {ifname}'
                 self._cmd(cmd.format(**self.config))
 
+    def set_neigh_suppress(self, state):
+        """
+        Controls whether neigh discovery (arp and nd) proxy and suppression
+        is enabled on the port. By default this flag is off.
+        """
+
+        # Determine current OS Kernel neigh_suppress setting - only adjust when needed
+        tmp = get_interface_config(self.ifname)
+        cur_state = 'on' if dict_search(f'linkinfo.info_slave_data.neigh_suppress', tmp) == True else 'off'
+        new_state = 'on' if state else 'off'
+        if cur_state != new_state:
+            self.set_interface('neigh_suppress', state)
+
     def set_vlan_vni_mapping(self, state):
         """
         Controls whether vlan to tunnel mapping is enabled on the port.
@@ -163,3 +180,9 @@ def update(self, config):
         # Enable/Disable VLAN tunnel mapping
         # This is only possible after the interface was assigned to the bridge
         self.set_vlan_vni_mapping(dict_search('vlan_to_vni', config) != None)
+
+        # Enable/Disable neighbor suppression, there is no need to explicitly
+        # "disable" it, as VXLAN interface will be recreated if anything
+        # under "parameters" changes.
+        if dict_search('parameters.neighbor_suppress', config) != None:
+            self.set_neigh_suppress('on')

smoketest/scripts/cli/test_interfaces_vxlan.py

@@ -177,11 +177,48 @@ def test_vxlan_vlan_vni_mapping(self):
 
         tmp = get_interface_config(interface)
         self.assertEqual(tmp['master'], bridge)
+        self.assertFalse(tmp['linkinfo']['info_slave_data']['neigh_suppress'])
 
         tmp = get_vxlan_vlan_tunnels('vxlan0')
         self.assertEqual(tmp, list(vlan_to_vni))
 
         self.cli_delete(['interfaces', 'bridge', bridge])
 
+    def test_vxlan_neighbor_suppress(self):
+        bridge = 'br555'
+        interface = 'vxlan555'
+        source_interface = 'eth0'
+
+        self.cli_set(self._base_path + [interface, 'external'])
+        self.cli_set(self._base_path + [interface, 'source-interface', source_interface])
+
+        self.cli_set(self._base_path + [interface, 'parameters', 'neighbor-suppress'])
+
+        # This must fail as this VXLAN interface is not associated with any bridge
+        with self.assertRaises(ConfigSessionError):
+            self.cli_commit()
+        self.cli_set(['interfaces', 'bridge', bridge, 'member', 'interface', interface])
+
+        # commit configuration
+        self.cli_commit()
+
+        self.assertTrue(interface_exists(bridge))
+        self.assertTrue(interface_exists(interface))
+
+        tmp = get_interface_config(interface)
+        self.assertEqual(tmp['master'], bridge)
+        self.assertTrue(tmp['linkinfo']['info_slave_data']['neigh_suppress'])
+
+        # Remove neighbor suppress configuration and re-test
+        self.cli_delete(self._base_path + [interface, 'parameters', 'neighbor-suppress'])
+        # commit configuration
+        self.cli_commit()
+
+        tmp = get_interface_config(interface)
+        self.assertEqual(tmp['master'], bridge)
+        self.assertFalse(tmp['linkinfo']['info_slave_data']['neigh_suppress'])
+
+        self.cli_delete(['interfaces', 'bridge', bridge])
+
 if __name__ == '__main__':
     unittest.main(verbosity=2)

src/conf_mode/interfaces-vxlan.py

@@ -34,6 +34,7 @@
 from vyos.ifconfig import Interface
 from vyos.ifconfig import VXLANIf
 from vyos.template import is_ipv6
+from vyos.utils.dict import dict_search
 from vyos import ConfigError
 from vyos import airbag
 airbag.enable()
@@ -164,6 +165,11 @@ def verify(vxlan):
                 raise ConfigError(f'VNI "{vni}" is already assigned to a different VLAN!')
             vnis_used.append(vni)
 
+    if dict_search('parameters.neighbor_suppress', vxlan):
+        if 'is_bridge_member' not in vxlan:
+            raise ConfigError('Neighbor suppression requires that VXLAN interface '\
+                              'is member of a bridge interface!')
+
     verify_mtu_ipv6(vxlan)
     verify_address(vxlan)
     verify_bond_bridge_member(vxlan)