Configure VM interfaces in macvtap passthrough mode

Tenks currently uses macvtap interfaces in 'VEPA' mode for the VMs. If the VMs
run any virtual networking internally, typically this will use a different MAC
address, which will not be reachable from outside due to the macvtap MAC
filtering.

This change uses macvtap 'passthrough' mode, such that all traffic is passed.

Change-Id: I0077c7001b2b419a94ea420833fa6dd3e8a3a967
Story: 2004906
Task: 29256

ansible/filter_plugins/tenks.py

@@ -70,9 +70,12 @@ def set_libvirt_interfaces(context, node):
     """
     node['interfaces'] = []
     for physnet in node.get('physical_networks', []):
+        # Use macvtap 'passthrough' mode, since this does not filter packets
+        # based on MAC address of the interface.
         node['interfaces'].append(
             {'type': 'direct',
-             'source': {'dev': source_link_name(context, node, physnet)}}
+             'source': {'dev': source_link_name(context, node, physnet),
+                        'mode': 'passthrough'}}
         )
     return node
 

releasenotes/notes/macvtap-passthrough-adfecbce7dcd8474.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes an issue where deployed VMs can't be reached on a different MAC
+    address than the one originally assigned. See `story 2004906
+    <https://storyboard.openstack.org/#!/story/2004906>`__ for details.