How are gratuitous ARP requests and replies sent in neutron upon live-migration in Red Hat OpenStack Platform

Solution In Progress - Updated -

Issue

When a VM live-migrates in a OVS-DVR scenario, the FIP namespace sends out a gratuitous ARP reply and request to update the ARP cache of devices in the network:

  283 204.501910 fa:16:3e:60:2d:76 ff:ff:ff:ff:ff:ff fa:16:3e:60:2d:76 → Broadcast      ARP 56 Gratuitous ARP for 10.10.73.111 (Request) (duplicate use of 10.10.73.111 detected!)
  284 204.569800 fa:16:3e:60:2d:76 ff:ff:ff:ff:ff:ff fa:16:3e:60:2d:76 → Broadcast      ARP 56 Gratuitous ARP for 10.10.73.111 (Reply) (duplicate use of 10.10.73.111 detected!)
  285 206.604594 fa:16:3e:60:2d:76 ff:ff:ff:ff:ff:ff fa:16:3e:60:2d:76 → Broadcast      ARP 56 Gratuitous ARP for 10.10.73.111 (Request) (duplicate use of 10.10.73.111 detected!)
  286 206.636691 fa:16:3e:60:2d:76 ff:ff:ff:ff:ff:ff fa:16:3e:60:2d:76 → Broadcast      ARP 56 Gratuitous ARP for 10.10.73.111 (Reply) (duplicate use of 10.10.73.111 detected!)
  287 208.671387 fa:16:3e:60:2d:76 ff:ff:ff:ff:ff:ff fa:16:3e:60:2d:76 → Broadcast      ARP 56 Gratuitous ARP for 10.10.73.111 (Request) (duplicate use of 10.10.73.111 detected!)
  288 208.704282 fa:16:3e:60:2d:76 ff:ff:ff:ff:ff:ff fa:16:3e:60:2d:76 → Broadcast      ARP 56 Gratuitous ARP for 10.10.73.111 (Reply) (duplicate use of 10.10.73.111 detected!)

Where 10.10.73.111 is the floating IP and 10.10.73.117 is the host's IP address inside the floating IP namespace:

[root@compute-0 ~]# ip netns exec fip-0134457a-6c52-4193-bc61-5bf2cd9af7dd ip a
(...)
44: fg-ea52c8cd-de: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1    000
    link/ether fa:16:3e:60:2d:76 brd ff:ff:ff:ff:ff:ff
    inet 10.10.73.117/27 brd 10.10.73.127 scope global fg-ea52c8cd-de
       valid_lft forever preferred_lft forever
    inet6 fe80::f816:3eff:fe60:2d76/64 scope link
       valid_lft forever preferred_lft forever

These request and reply messages are spaced out by ca. 2 seconds each. How does this work?

Environment

Red Hat OpenStack Platform 13

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