[OVN][Migration] Enable settings backup subnet for NFS clients

If the BACKUP_MIGRATION_IP is set to a different IP outside of
the default nets[1] set in the “openstack overcloud backup”
playbook setup_nfs role[2]. Then the NFS will fail to mount
directories during the backup, because they will not be
reachable | permitted.
This change simply adds a new variable
BACKUP_MIGRATION_CTL_PLANE_CIDRS into the ovn_migration script
to allow the user to overwrite the extra-var used for
Openstack overcloud backup --setup-nfs command.

[1] https://opendev.org/openstack/tripleo-ansible/src/commit/e281ae7624774d71f22fbb993af967ed1ec08780/tripleo_ansible/roles/backup_and_restore/defaults/main.yml#L47
[2] https://opendev.org/openstack/tripleo-ansible/src/commit/e281ae7624774d71f22fbb993af967ed1ec08780/tripleo_ansible/roles/backup_and_restore/tasks/setup_nfs.yml#L127

Change-Id: I160dfc4e893b93ac7a40e19b3dd6b89750dac57d
(cherry picked from commit b677d65)

doc/source/ovn/migration.rst

@@ -155,6 +155,12 @@ Perform the following steps in the undercloud
      server that will be used as a NFS server to store the backup.
      Default: 192.168.24.1
 
+   * BACKUP_MIGRATION_CTL_PLANE_CIDRS - Only used if CREATE_BACKUP is enabled.
+     A comma separated string of control plane subnets in CIDR notation for the
+     controllers being backed up. The specified subnets will be used to enable
+     NFS remote clients connections.
+     Default: 192.168.24.0/24
+
    .. warning::
 
       Please note that VALIDATE_MIGRATION requires enough quota (2

tools/ovn_migration/tripleo_environment/ovn_migration.sh

@@ -42,7 +42,8 @@ LANG=C
 : ${VALIDATE_MIGRATION:=False}
 : ${DHCP_RENEWAL_TIME:=30}
 : ${CREATE_BACKUP:=True}
-: ${BACKUP_MIGRATION_IP:=192.168.24.1} # TODO: Document this new var
+: ${BACKUP_MIGRATION_IP:=192.168.24.1}
+: ${BACKUP_MIGRATION_CTL_PLANE_CIDRS:=192.168.24.0/24}
 
 
 check_for_necessary_files() {
@@ -328,6 +329,7 @@ start_migration() {
     -e overcloudrc=$OVERCLOUDRC_FILE \
     -e stackrc=$STACKRC_FILE \
     -e backup_migration_ip=$BACKUP_MIGRATION_IP \
+    -e backup_migration_ctl_plane_cidrs=$BACKUP_MIGRATION_CTL_PLANE_CIDRS \
     -e create_backup=$CREATE_BACKUP \
     -e ansible_inventory=$inventory_file \
     -e validate_migration=$VALIDATE_MIGRATION $*

tools/ovn_migration/tripleo_environment/playbooks/roles/recovery-backup/tasks/main.yml

@@ -36,6 +36,7 @@
         --setup-nfs \
         --extra-vars '{
                 "tripleo_backup_and_restore_server": {{ backup_migration_ip }},
+                "tripleo_backup_and_restore_clients_nets": {{ backup_migration_ctl_plane_cidrs.split(',') }},
                 "nfs_server_group_name": {{ revert_preparation_server_name }}
               }'