add default features support

Change-Id: I0f0491180561aa75c43aac4a64acc9170622a6e6

config.yaml

@@ -196,3 +196,15 @@ options:
     description: |
         Apply system hardening. Supports a space-delimited list of modules
         to run. Supported modules currently include os, ssh, apache and mysql.
+  default-rbd-features:
+    default:
+    type: int
+    description: |
+      Restrict the rbd features used to the specified level. If set, this will
+      inform clients that they should set the config value `rbd default
+      features`, for example:
+      
+        rbd default features = 1
+
+      This needs to be set to 1 when deploying a cloud with the nova-lxd
+      hypervisor.

hooks/ceph_hooks.py

@@ -496,6 +496,8 @@ def client_relation_joined(relid=None):
             data = {'key': ceph.get_named_key(service_name),
                     'auth': config('auth-supported'),
                     'ceph-public-address': public_addr}
+            if config('rbd-features'):
+                data['rbd_features'] = config('rbd-features')
             relation_set(relation_id=relid,
                          relation_settings=data)
     else:

templates/ceph.conf

@@ -37,6 +37,10 @@ cluster addr = {{ cluster_addr }}
 {% endfor %}
 {% endif %}
 
+{% if rbd_features %}
+rbd default features = {{ rbd_features }}
+{% endif %}
+
 [mon]
 keyring = /var/lib/ceph/mon/$cluster-$id/keyring
 {% if mon -%}