From 2dd322a64291c20da33f28fd5c302ff27e70eae4 Mon Sep 17 00:00:00 2001
From: esberglu <esberglu@us.ibm.com>
Date: Wed, 31 Jan 2018 16:29:57 -0600
Subject: [PATCH] Use dict.get() when accessing capabilities dict

Many compute drivers override the driver capabilities dict [1]. The
code should be using dict.get() to avoid throwing KeyErrors if the
overriding dictionaries do not have the corresponding keys. If the
key is not found it will be assumed the the capability is not supported
and default to false. This ensures that no drivers are broken because
they are missing a capability.

[1] https://github.com/openstack/nova/blob/5251f18d87/nova/virt/driver.py#L124-L134

Change-Id: I1fa04fa110f2c65e10c065c61f2f0f58c1fad646
Closes-Bug: #1746608
---
 nova/compute/manager.py   | 16 ++++++++++------
 nova/virt/block_device.py |  3 ++-
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index 819f32065c43..adeef57c1ed9 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -1794,7 +1794,8 @@ class ComputeManager(manager.Manager):
                     tagging_requested = True
                     break
         if (tagging_requested and
-                not self.driver.capabilities.get('supports_device_tagging')):
+                not self.driver.capabilities.get('supports_device_tagging',
+                                                 False)):
             raise exception.BuildAbortException('Attempt to boot guest with '
                                                 'tagged devices on host that '
                                                 'does not support tagging.')
@@ -2964,7 +2965,7 @@ class ComputeManager(manager.Manager):
                 hints = self._get_scheduler_hints({}, request_spec)
                 self._validate_instance_group_policy(context, instance, hints)
 
-            if not self.driver.capabilities["supports_recreate"]:
+            if not self.driver.capabilities.get("supports_recreate", False):
                 raise exception.InstanceRecreateNotSupported
 
             self._check_instance_exists(context, instance)
@@ -4061,7 +4062,8 @@ class ComputeManager(manager.Manager):
         # if the flavor IDs match, it's migrate; otherwise resize
         if same_host and instance_type.id == instance['instance_type_id']:
             # check driver whether support migrate to same host
-            if not self.driver.capabilities['supports_migrate_to_same_host']:
+            if not self.driver.capabilities.get(
+                    'supports_migrate_to_same_host', False):
                 raise exception.UnableToMigrateToSelf(
                     instance_id=instance.uuid, host=self.host)
 
@@ -5406,7 +5408,8 @@ class ComputeManager(manager.Manager):
             # TODO(mriedem): This is copied from DriverVolumeBlockDevice
             # and should be consolidated into some common code at some point.
             vol_multiattach = new_volume.get('multiattach', False)
-            virt_multiattach = self.driver.capabilities['supports_multiattach']
+            virt_multiattach = self.driver.capabilities.get(
+                'supports_multiattach', False)
             if vol_multiattach and not virt_multiattach:
                 raise exception.MultiattachNotSupportedByVirtDriver(
                     volume_id=new_volume_id)
@@ -5660,7 +5663,8 @@ class ComputeManager(manager.Manager):
     def attach_interface(self, context, instance, network_id, port_id,
                          requested_ip, tag):
         """Use hotplug to add an network adapter to an instance."""
-        if not self.driver.capabilities['supports_attach_interface']:
+        if not self.driver.capabilities.get('supports_attach_interface',
+                                            False):
             raise exception.AttachInterfaceNotSupported(
                 instance_uuid=instance.uuid)
         if (tag and not
@@ -7593,7 +7597,7 @@ class ComputeManager(manager.Manager):
     def _run_image_cache_manager_pass(self, context):
         """Run a single pass of the image cache manager."""
 
-        if not self.driver.capabilities["has_imagecache"]:
+        if not self.driver.capabilities.get("has_imagecache", False):
             return
 
         # Determine what other nodes use this storage
diff --git a/nova/virt/block_device.py b/nova/virt/block_device.py
index de317f2c7678..4adbc72e59a3 100644
--- a/nova/virt/block_device.py
+++ b/nova/virt/block_device.py
@@ -496,7 +496,8 @@ class DriverVolumeBlockDevice(DriverBlockDevice):
             self.volume_size = volume.get('size')
 
         vol_multiattach = volume.get('multiattach', False)
-        virt_multiattach = virt_driver.capabilities['supports_multiattach']
+        virt_multiattach = virt_driver.capabilities.get(
+            'supports_multiattach', False)
 
         if vol_multiattach and not virt_multiattach:
             raise exception.MultiattachNotSupportedByVirtDriver(