vxlan: T5753: add support for VNI filtering

In a service provider network a service provider typically supports multiple
bridge domains with overlapping vlans. One bridge domain per customer. Vlans in
each bridge domain are mapped to globally unique VXLAN VNI ranges assigned to
each customer.

Without the ability of VNI filtering, we can not provide VXLAN tunnels
with multiple tenants all requiring e.g. VLAN 10.

To Test:

set interfaces vxlan vxlan987 parameters external
set interfaces vxlan vxlan987 source-interface eth0
set interfaces vxlan vxlan987 parameters vni-filter
set interfaces vxlan vxlan987 vlan-to-vni 50 vni 10050
set interfaces vxlan vxlan987 vlan-to-vni 51 vni 10051
set interfaces vxlan vxlan987 vlan-to-vni 52 vni 10052
set interfaces vxlan vxlan987 vlan-to-vni 53 vni 10053
set interfaces vxlan vxlan987 vlan-to-vni 54 vni 10054
set interfaces vxlan vxlan987 vlan-to-vni 60 vni 10060
set interfaces vxlan vxlan987 vlan-to-vni 69 vni 10069
set interfaces bridge br0 member interface vxlan987

Add new op-mode command: show bridge vni

Interface    VNI
-----------  -----------
vxlan987     10050-10054
vxlan987     10060
vxlan987     10069

1 files changed, 29 insertions, 6 deletions

diff --git a/src/conf_mode/interfaces-vxlan.py b/src/conf_mode/interfaces-vxlan.py
index 6bf3227d5..4251e611b 100755
--- a/src/conf_mode/interfaces-vxlan.py
+++ b/src/conf_mode/interfaces-vxlan.py
@@ -60,8 +60,14 @@ def get_config(config=None):
             vxlan.update({'rebuild_required': {}})
             break
 
+    # When dealing with VNI filtering we need to know what VNI was actually removed,
+    # so build up a dict matching the vlan_to_vni structure but with removed values.
     tmp = node_changed(conf, base + [ifname, 'vlan-to-vni'], recursive=True)
-    if tmp: vxlan.update({'vlan_to_vni_removed': tmp})
+    if tmp:
+        vxlan.update({'vlan_to_vni_removed': {}})
+        for vlan in tmp:
+            vni = leaf_node_changed(conf, base + [ifname, 'vlan-to-vni', vlan, 'vni'])
+            vxlan['vlan_to_vni_removed'].update({vlan : {'vni' : vni[0]}})
 
     # We need to verify that no other VXLAN tunnel is configured when external
     # mode is in use - Linux Kernel limitation
@@ -98,14 +104,31 @@ def verify(vxlan):
     if 'vni' not in vxlan and dict_search('parameters.external', vxlan) == None:
         raise ConfigError('Must either configure VXLAN "vni" or use "external" CLI option!')
 
-    if dict_search('parameters.external', vxlan):
+    if dict_search('parameters.external', vxlan) != None:
         if 'vni' in vxlan:
             raise ConfigError('Can not specify both "external" and "VNI"!')
 
         if 'other_tunnels' in 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}')
+            # When multiple VXLAN interfaces are defined and "external" is used,
+            # all VXLAN interfaces need to have vni-filter enabled!
+            # See Linux Kernel commit f9c4bb0b245cee35ef66f75bf409c9573d934cf9
+            other_vni_filter = False
+            for tunnel, tunnel_config in vxlan['other_tunnels'].items():
+                if dict_search('parameters.vni_filter', tunnel_config) != None:
+                    other_vni_filter = True
+                    break
+            # eqivalent of the C foo ? 'a' : 'b' statement
+            vni_filter = True and (dict_search('parameters.vni_filter', vxlan) != None) or False
+            # If either one is enabled, so must be the other. Both can be off and both can be on
+            if (vni_filter and not other_vni_filter) or (not vni_filter and other_vni_filter):
+                raise ConfigError(f'Using multiple VXLAN interfaces with "external" '\
+                    'requires all VXLAN interfaces to have "vni-filter" configured!')
+
+            if not vni_filter and not other_vni_filter:
+                other_tunnels = ', '.join(vxlan['other_tunnels'])
+                raise ConfigError(f'Only one VXLAN tunnel is supported when "external" '\
+                                f'CLI option is used and "vni-filter" is unset. '\
+                                f'Additional tunnels: {other_tunnels}')
 
     if 'gpe' in vxlan and 'external' not in vxlan:
         raise ConfigError(f'VXLAN-GPE is only supported when "external" '\
@@ -165,7 +188,7 @@ 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 dict_search('parameters.neighbor_suppress', vxlan) != None:
         if 'is_bridge_member' not in vxlan:
             raise ConfigError('Neighbor suppression requires that VXLAN interface '\
                               'is member of a bridge interface!')