[ovn][migration] Support migration to OVN from iptables firewall

Before this patch, when migrating from ML2/OVS to ML2/OVN, we
removed the VIF details that are not used by OVN. However, this
changes how the VIFs are plugged if the hybrid iptables firewall
was used.

In order to not break the migration, we want to keep whatever
plugging was used in ML2/OVS. For this reason, this patch is
leaving the VIF details untouched.

The consequence is that, after migration, whatever workloads
used the hybrid plugging will remain like that. Newly created
VIFs will be plugged to the OVS bridge directly. As a result,
the migration to OVN won't require moving to the OVS firewall
first while in ML2/OVS.

This patch is also removing the constraint that prevented the
migration if the hybrid firewall was used.

Signed-off-by: Daniel Alvarez Sanchez <[email protected]>
Change-Id: Iad4fae7af54cc502ac0ba02a911cdd4fefa13535
(cherry picked from commit 5f2eaad)

Author: cubeek

neutron/plugins/ml2/drivers/ovn/db_migration.py

@@ -30,17 +30,17 @@
 LOG = logging.getLogger(__name__)
 
 VIF_DETAILS_TO_REMOVE = (
-    pb_api.OVS_HYBRID_PLUG,
-    pb_api.VIF_DETAILS_BRIDGE_NAME)
+    pb_api.VIF_DETAILS_BRIDGE_NAME,
+)
 
 
 def migrate_neutron_database_to_ovn():
     """Change DB content from OVS to OVN mech driver.
 
      - Changes vxlan network type to Geneve and updates Geneve allocations.
-     - Removes unnecessary settings from port binding vif details, such as
-       connectivity, bridge_name and ovs_hybrid_plug, as they are not used by
-       OVN.
+     - Removes bridge name from port binding vif details to support operations
+       on instances with a trunk bridge.
+     - Updates the port profile for trunk ports.
     """
     ctx = n_context.get_admin_context()
     with db_api.CONTEXT_WRITER.using(ctx) as session:

neutron/tests/unit/plugins/ml2/drivers/ovn/test_db_migration.py

@@ -152,6 +152,7 @@ def test_db_migration(self):
         ]
         expected_vif_details = [
             {pb.CAP_PORT_FILTER: "true",
+             pb.OVS_HYBRID_PLUG: "true",
              pb.VIF_DETAILS_CONNECTIVITY: pb.CONNECTIVITY_L2},
             {pb.CAP_PORT_FILTER: "true"},
             {"foo": "bar"},

tools/ovn_migration/tripleo_environment/playbooks/ovn-migration.yml

@@ -14,14 +14,6 @@
     - pre-migration
 
 
-- name: Pre migration checks in the OVN controllers
-  hosts: ovn-controllers
-  roles:
-    - pre-checks/ovn-controllers
-  tags:
-    - pre-migration
-
-
 #
 # This step is executed before migration, and will backup some config
 # files related to containers before those get lost.