Consider all router ports for dvr arp updates

[Christoph Manns]

If you have a subnet with 2 routers and you create and then delete
a VM it may happen that an old ARP entry may persist. If you create
another VM with the same IP and the ARP update goes to the other
router you have a VM which isn't reachable via one router since the
ARP entry is wrong.

A solution would be to update all router ports and not just one.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/605434

[Swaminathan Vasudevan (swaminathan-vasudevan)]

Can you explain your use case here for a subnet with two routers.
As per the initial design if the VM is deleted a port delete event should be sent to neutron and neutron server will send an rpc message to the agent to remove the ARP entry for invalid entries or for deleted VMs.

So not sure if the delete is not removing the ARP entries.
We need to fix that first.

[Christoph Manns (christoph-manns)]

We have multiple external networks and since multiple interfaces on one VM are a bit hard to handle we have one subnet with multiple routers. This works quite well, the only problem is that ARP entries may persist. The l3 agent gets a delete request but only for one router, so the other routers keep their ARP entries.

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

Bug closed due to lack of activity, please feel free to reopen if needed.

[OpenStack Infra (hudson-openstack)]

Change abandoned by "Rodolfo Alonso <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/neutron/+/605434