nova compute fail to remove instance with port if network is broken

[George Shuklin]

If user was capable to create broken network configuration, instance become undeletable. Reason why user can create broken networking is under investigation (current hypothesis: if network (neutron) created in one tennant and instance in other, and user is admin in both tenants, it cause broken configuration).

But such instance deletetion cause trace on nova-compute:

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/nova/openstack/common/rpc/amqp.py", line 461, in _process_data
    **args)
  File "/usr/lib/python2.7/dist-packages/nova/openstack/common/rpc/dispatcher.py", line 172, in dispatch
    result = getattr(proxyobj, method)(ctxt, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 353, in decorated_function
    return function(self, context, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/exception.py", line 90, in wrapped
    payload)
  File "/usr/lib/python2.7/dist-packages/nova/exception.py", line 73, in wrapped
    return f(self, context, *args, **kw)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 243, in decorated_function
    pass
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 229, in decorated_function
    return function(self, context, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 294, in decorated_function
    function(self, context, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 271, in decorated_function
    e, sys.exc_info())
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 258, in decorated_function
    return function(self, context, *args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1792, in terminate_instance
    do_terminate_instance(instance, bdms)
  File "/usr/lib/python2.7/dist-packages/nova/openstack/common/lockutils.py", line 246, in inner
    return f(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1784, in do_terminate_instance
    reservations=reservations)
  File "/usr/lib/python2.7/dist-packages/nova/hooks.py", line 105, in inner
    rv = f(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1757, in _delete_instance
    user_id=user_id)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1729, in _delete_instance
    self._shutdown_instance(context, db_inst, bdms)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1639, in _shutdown_instance
    network_info = self._get_instance_nw_info(context, instance)
  File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 876, in _get_instance_nw_info
    instance)
  File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 455, in get_instance_nw_info
    result = self._get_instance_nw_info(context, instance, networks)
  File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 463, in _get_instance_nw_info
    nw_info = self._build_network_info_model(context, instance, networks)
  File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 1009, in _build_network_info_model
    subnets)
  File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 962, in _nw_info_build_network
    label=network_name,
UnboundLocalError: local variable 'network_name' referenced before assignment

The reason is following code :

    def _nw_info_build_network(self, port, networks, subnets):
        # NOTE(danms): This loop can't fail to find a network since we
        # filtered ports to only the ones matching networks in our parent
        for net in networks:
            if port['network_id'] == net['id']:
                network_name = net['name']
                break

(if no net found network_name become undefined).

Following patch should allow instance deletion in case of networking problems:

diff --git a/nova/network/neutronv2/api.py b/nova/network/neutronv2/api.py
index a41924d..8a44f99 100644
--- a/nova/network/neutronv2/api.py
+++ b/nova/network/neutronv2/api.py
@@ -939,6 +939,8 @@ class API(base.Base):
             if port['network_id'] == net['id']:
                 network_name = net['name']
                 break
+ else:
+ network_name = ""

         bridge = None
         ovs_interfaceid = None