After `openstack port set no-fixed-ip` command, the port's ip and mac's arp are still in qrouter without deletion

[liujinxin]

neutron branch: stable/victoria

Steps to reproduce the problem：

```

# openstack port show ba20b562-7320-4fb4-99f1-eae617720bf1
+-------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------+
| Field | Value |
+-------------------------+---------------------------------------------------------------------------------------------------------------------------------------------------+
| admin_state_up | UP |
| allowed_address_pairs | |
| binding_host_id | hci-002 |
| binding_profile | |
| binding_vif_details | bridge_name='br-int', connectivity='l2', datapath_type='system', ovs_hybrid_plug='False', port_filter='True' |
| binding_vif_type | ovs |
| binding_vnic_type | normal | |
| device_owner | compute:az-box-1 |
| extra_dhcp_opts | |
| fixed_ips | ip_address='192.168.1.43', subnet_id='f5acaafe-554e-47d4-9107-6566b5d50bb3' |
| id | ba20b562-7320-4fb4-99f1-eae617720bf1 |
| ip_allocation | None |
| mac_address | fa:16:3e:4c:fd:ce |
...

openstack port set ba20b562-7320-4fb4-99f1-eae617720bf1 --no-fixed-ip
openstack port set ba20b562-7320-4fb4-99f1-eae617720bf1 --fixed-ip ip-address=192.168.1.143

openstack port set ba20b562-7320-4fb4-99f1-eae617720bf1 --no-fixed-ip
openstack port set ba20b562-7320-4fb4-99f1-eae617720bf1 --fixed-ip ip-address=192.168.1.243

[root@hci-002 ~]# ip netns exec qrouter-ffd819cb-349e-4b31-845a-7b7d97461f32 arp -n |grep fa:16:3e:4c:fd:ce
192.168.1.43 ether fa:16:3e:4c:fd:ce CM qr-8ce629a5-03
192.168.1.143 ether fa:16:3e:4c:fd:ce CM qr-8ce629a5-03
192.168.1.243 ether fa:16:3e:4c:fd:ce CM qr-8ce629a5-03
```

[Brian Haley (brian-haley)]

I have not tried to reproduce this yet, but do you see it on the master branch?

Some other questions:

1) Is this affecting connectivity? Since the ARP entry for the new port IP is correct, communication should work, assuming the VM has re-done DHCP and configured the new address.

2) If another VM is booted and is assigned one of the "old" IP addresses, is the ARP entry updated?

There might simply be a bug removing the old ARP entry as changing the fixed IP of a port is an infrequent operation.

[Brian Haley (brian-haley)]

I could somewhat reproduce this on master branch using ML2/OVS, is that what you are using? I actually never saw ARP entries added when I changed IPs though, I had to reboot the VM to see that, and the original one was never marked Permanent (M flag).

10.0.0.24 ether fa:16:3e:63:04:d9 C qr-ed3c12f7-d4
10.0.0.25 ether fa:16:3e:63:04:d9 C qr-ed3c12f7-d4

The old one eventually went stale:

10.0.0.24 (incomplete) qr-ed3c12f7-d4
10.0.0.25 ether fa:16:3e:63:04:d9 C qr-ed3c12f7-d4

So I'm not sure why your entries were marked M.

[Rodolfo Alonso (rodolfo-alonso-hernandez)]

Hello Liu:

Are you using DVR? I'm asking this because DVR local qrouter namespaces (compute node namespaces) are the only places where we manually modify the ARP table. Can you confirm that? That could explain the "M" flag in the ARP table [1].

Regards.

[1]https://ipwithease.com/arp-timers-and-flag-types/

[Launchpad Janitor (janitor)]

[Expired for neutron because there has been no activity for 60 days.]