Comment 0 for bug 1557909

Stale snat namespace on the controller after recovery of dead l3 agent.

Note: Only on Stable/LIBERTY Branch:

Setup:
Multiple controller (DVR_SNAT) setup.

Steps:
1) Create tenant network, subnet and router.
 2) Create a external network
 3) Attached internal & external network to a router
 4) Create VM on above tenant network.
 5) Make sure VM can reach outside using CSNAT.
 6) Find router hosting l3 agent and stop the l3 agent.
 7) Manually move router to other controller (dvr_snat mode). SNAT namespace should be create on new controller node.
 8) Start the l3 agent on the controller (the one that stopped in step6)
 9) Notice that snat namespace is now available on 2 controller and it is not getting deleted from the agent which is not hosting it.

Example:
| cfa97c12-b975-4515-86c3-9710c9b88d76 | L3 agent | vm2-ctl2-936 | :-) | True | neutron-l3-agent |
| df4ca7c5-9bae-4cfb-bc83-216612b2b378 | L3 agent | vm1-ctl1-936 | :-) | True | neutron-l3-agent |

mysql> select * from csnat_l3_agent_bindings;
+--------------------------------------+--------------------------------------+---------+------------------+
| router_id | l3_agent_id | host_id | csnat_gw_port_id |
+--------------------------------------+--------------------------------------+---------+------------------+
| 0fb68420-9e69-41bb-8a88-8ab53b0faabb | cfa97c12-b975-4515-86c3-9710c9b88d76 | NULL | NULL |
+--------------------------------------+--------------------------------------+---------+------------------+

On vm1-ctl1-936

Stale SNAT namespace on Initially hosting controller.

ubuntu@vm1-ctl1-936:~/devstack$ sudo ip netns
snat-0fb68420-9e69-41bb-8a88-8ab53b0faabb
qrouter-0fb68420-9e69-41bb-8a88-8ab53b0faabb

On vm2-ctl2-936 (2nd Controller)

ubuntu@vm2-ctl2-936:~$ ip netns
snat-0fb68420-9e69-41bb-8a88-8ab53b0faabb
qrouter-0fb68420-9e69-41bb-8a88-8ab53b0faabb