bundles/systemd-networkd: generate unique mac address for vlan interfaces

bundles/systemd-networkd/files/template-iface-vlan.netdev

@@ -1,6 +1,7 @@
 [NetDev]
 Name=${interface}
 Kind=vlan
+MACAddress=${mac}
 
 [VLAN]
 Id=${vlan}

bundles/systemd-networkd/items.py

@@ -25,6 +25,9 @@ directories = {
     },
 }
 
+mac_host_prefix = '%04x' % (node.magic_number % 65534)
+generated_mac = f'52:54:00:{mac_host_prefix[0:2]}:{mac_host_prefix[2:4]}:{{}}'
+
 # Don't use .get() here. We might end up with a node without a network
 # config!
 for interface, config in node.metadata['interfaces'].items():
@@ -36,12 +39,15 @@ for interface, config in node.metadata['interfaces'].items():
         template = 'template-iface-nodhcp.network'
 
     if '.' in interface:
+        vlan_id = int(interface.split('.')[1])
+        vlan_hex = '%02x' % (vlan_id % 255)
         files[f'/etc/systemd/network/{interface}.netdev'] = {
             'source': 'template-iface-vlan.netdev',
             'content_type': 'mako',
             'context': {
                 'interface': interface,
-                'vlan': interface.split('.')[1],
+                'vlan': vlan_id,
+                'mac': generated_mac.format(vlan_hex)
             },
             'needed_by': {
                 'svc_systemd:systemd-networkd',