Neutron with NSX plugin generates an error when adding of interface to external network to tenants router

[Igor Zinovik]

Neutron server with NSX core plugin throws UnboundLocalError when operator tries
to add interface to router into external network.

Scenario for reproduction:
1. Create External network and subnet for it
$ neutron net-create --router:external --provider:network_type flat --provider:physical_network network-222 External
$ neutron subnet-create --name ExtSubnet --allocation-pool start=172.16.0.128,end=172.16.0.250 --gateway 172.16.0.1 --disable-dhcp External 172.16.0.0/24

2. Create tenant router and add interface to it in External network
$ neutron router-create Admin-router --router_type shared
$ neutron router-interface-add Admin-router ExternSubnet
Request Failed: internal server error while processing your request

Nevertheless Horizon 'Network topology' view shows that router is connected to External network.

Environment: vCenter 5.5, NSX 6.1.4, Neutron NSX plugin tag 2015.1.2 (3de8db42e331500381b68852af1679cc53c3ab09)

Neutron log shows a traceback
2015-10-08 11:32:59.876 25187 INFO neutron.wsgi [-] (25187) accepted ('192.168.0.2', 45302)
2015-10-08 11:32:59.880 25187 INFO neutron.wsgi [-] 192.168.0.2 - - [08/Oct/2015 11:32:59] "OPTIONS / HTTP/1.0" 200 262 0.001621
2015-10-08 11:33:00.214 25188 ERROR neutron.api.v2.resource [req-47743236-f1f6-4a90-8df2-2dfc0ef81431 ] add_router_interface failed
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource Traceback (most recent call last):
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource File "/usr/lib/python2.7/dist-packages/neutron/api/v2/resource.py", line 83, in resource
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource result = method(request=request, **args)
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource File "/usr/lib/python2.7/dist-packages/oslo_db/api.py", line 131, in wrapper
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource return f(*args, **kwargs)
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource File "/usr/lib/python2.7/dist-packages/neutron/api/v2/base.py", line 209, in _handle_action
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource return getattr(self._plugin, name)(*arg_list, **kwargs)
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource File "/usr/lib/python2.7/dist-packages/vmware_nsx/neutron/plugins/vmware/plugins/nsx_v.py", line 1413, in add_router_interface
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource context, router_id, interface_info)
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource File "/usr/lib/python2.7/dist-packages/vmware_nsx/neutron/plugins/vmware/plugins/nsx_v_drivers/shared_router_driver.py", line 553
, in add_router_interface
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource network_id, address_groups)
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource File "/usr/lib/python2.7/dist-packages/vmware_nsx/neutron/plugins/vmware/vshield/edge_utils.py", line 1301, in update_internal_in
terface
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource 'net_moref': vcns_network_id})
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource UnboundLocalError: local variable 'vcns_network_id' referenced before assignment
2015-10-08 11:33:00.214 25188 TRACE neutron.api.v2.resource

[Igor Zinovik (izinovik)]

Neutron server reports itself as
root@node-1:~# neutron-server --version
neutron-server 2015.1.1