Comment 17 for bug 1696125

Looking in the neutron L2 agent logs, I see the tap device is attached/added here:

http://logs.openstack.org/94/471494/2/check/gate-tempest-dsvm-neutron-linuxbridge-ubuntu-xenial/e0332b9/logs/screen-q-agt.txt.gz#_Jun_12_22_19_30_156456

Jun 12 22:19:30.156456 ubuntu-xenial-internap-mtl01-9270284 neutron-linuxbridge-agent[18735]: DEBUG neutron.plugins.ml2.drivers.agent._common_agent [None req-2b21118e-0da6-4c4a-a9d5-5d0e2cf4ccf8 None None] Port tapb2bdb0c0-62 added {{(pid=18735) _process_device_if_exists /opt/stack/new/neutron/neutron/plugins/ml2/drivers/agent/_common_agent.py:236}}
...
Jun 12 22:19:30.240016 ubuntu-xenial-internap-mtl01-9270284 neutron-linuxbridge-agent[18735]: DEBUG neutron.plugins.ml2.drivers.linuxbridge.agent.linuxbridge_neutron_agent [None req-2b21118e-0da6-4c4a-a9d5-5d0e2cf4ccf8 None None] Adding device tapb2bdb0c0-62 to bridge brq8bb2148d-ee {{(pid=18735) _add_tap_interface /opt/stack/new/neutron/neutron/plugins/ml2/drivers/linuxbridge/agent/linuxbridge_neutron_agent.py:532}}

Then it's removed here:

Jun 12 22:19:31.745781 ubuntu-xenial-internap-mtl01-9270284 neutron-linuxbridge-agent[18735]: DEBUG neutron.plugins.ml2.drivers.agent._common_agent [None req-2b21118e-0da6-4c4a-a9d5-5d0e2cf4ccf8 None None] Agent loop found changes! {'current': set(['tap3578cb80-7a', 'tape6c02d6c-e4', 'tap8b6dc92f-75', 'tapb7c1b8db-1e', 'tap999bcb19-81', 'tap839063fe-6d', 'tap3a6b0b5c-cb', 'tap14bcf3bb-af', 'tap0f5cf6b7-63']), 'timestamps': {'tap3578cb80-7a': 9, 'tape6c02d6c-e4': 483, 'tap8b6dc92f-75': 6, 'tapb7c1b8db-1e': 10, 'tap999bcb19-81': 478, 'tap839063fe-6d': 484, 'tap3a6b0b5c-cb': 480, 'tap14bcf3bb-af': 479, 'tap0f5cf6b7-63': 11}, 'removed': set(['tapb2bdb0c0-62']), 'added': set([]), 'updated': set([])} {{(pid=18735) daemon_loop /opt/stack/new/neutron/neutron/plugins/ml2/drivers/agent/_common_agent.py:452}}
...
Jun 12 22:19:31.840782 ubuntu-xenial-internap-mtl01-9270284 neutron-linuxbridge-agent[18735]: INFO neutron.agent.securitygroups_rpc [None req-2b21118e-0da6-4c4a-a9d5-5d0e2cf4ccf8 None None] Remove device filter for set(['tapb2bdb0c0-62'])
...
Jun 12 22:19:31.901327 ubuntu-xenial-internap-mtl01-9270284 neutron-linuxbridge-agent[18735]: INFO neutron.plugins.ml2.drivers.agent._common_agent [None req-2b21118e-0da6-4c4a-a9d5-5d0e2cf4ccf8 None None] Attachment tapb2bdb0c0-62 removed