vxlan: T3700: add support for external controlled FDB

Background information [1]. Specifies whether an external control plane
(e.g. ip route encap/EVPN) or the internal FDB should be used.

[1]: https://legacy.netdevconf.info/2.2/slides/prabhu-linuxbridge-tutorial.pdf

1 files changed, 22 insertions, 2 deletions

diff --git a/src/conf_mode/interfaces-vxlan.py b/src/conf_mode/interfaces-vxlan.py
index 804f2d14f..b197d08a6 100755
--- a/src/conf_mode/interfaces-vxlan.py
+++ b/src/conf_mode/interfaces-vxlan.py
@@ -44,6 +44,20 @@ def get_config(config=None):
     base = ['interfaces', 'vxlan']
     vxlan = get_interface_dict(conf, base)
 
+    # We need to verify that no other VXLAN tunnel is configured when external
+    # mode is in use - Linux Kernel limitation
+    conf.set_level(base)
+    vxlan['other_tunnels'] = conf.get_config_dict([], key_mangling=('-', '_'),
+                                                  get_first_key=True,
+                                                  no_tag_node_value_mangle=True)
+
+    # This if-clause is just to be sure - it will always evaluate to true
+    ifname = vxlan['ifname']
+    if ifname in vxlan['other_tunnels']:
+        del vxlan['other_tunnels'][ifname]
+        if len(vxlan['other_tunnels']) == 0:
+            del vxlan['other_tunnels']
+
     return vxlan
 
 def verify(vxlan):
@@ -63,8 +77,14 @@ def verify(vxlan):
     if not any(tmp in ['group', 'remote', 'source_address'] for tmp in vxlan):
         raise ConfigError('Group, remote or source-address must be configured')
 
-    if 'vni' not in vxlan:
-        raise ConfigError('Must configure VNI for VXLAN')
+    if 'vni' not in vxlan and 'external' not in vxlan:
+        raise ConfigError(
+            'Must either configure VXLAN "vni" or use "external" CLI option!')
+
+    if {'external', 'other_tunnels'} <= set(vxlan):
+        other_tunnels = ', '.join(vxlan['other_tunnels'])
+        raise ConfigError(f'Only one VXLAN tunnel is supported when "external" '\
+                          f'CLI option is used. Additional tunnels: {other_tunnels}')
 
     if 'source_interface' in vxlan:
         # VXLAN adds at least an overhead of 50 byte - we need to check the