[Bug 1869808] Re: reboot neutron-ovs-agent introduces a short interrupt of vlan traffic

[Trent Lloyd]

Attaching revised SRU patch for Ubuntu Bionic, no code content changes
but fixed the changelog to list all 3 bug numbers correctly.

** Patch added: "neutron SRU patch for Ubuntu Bionic (new version)"
   https://bugs.launchpad.net/neutron/+bug/1869808/+attachment/5464699/+files/lp1869808-bionic.debdiff

** Patch removed: "debdiff for ubuntu cloud archive (queens)"
   https://bugs.launchpad.net/neutron/+bug/1869808/+attachment/5464416/+files/lp1869808-queens.debdiff

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Title:
  reboot neutron-ovs-agent introduces a short interrupt of vlan traffic

Status in Ubuntu Cloud Archive:
  New
Status in Ubuntu Cloud Archive queens series:
  New
Status in Ubuntu Cloud Archive rocky series:
  New
Status in Ubuntu Cloud Archive stein series:
  New
Status in Ubuntu Cloud Archive train series:
  New
Status in Ubuntu Cloud Archive ussuri series:
  New
Status in Ubuntu Cloud Archive victoria series:
  New
Status in neutron:
  Fix Released
Status in neutron package in Ubuntu:
  New
Status in neutron source package in Bionic:
  New
Status in neutron source package in Focal:
  New
Status in neutron source package in Groovy:
  New
Status in neutron source package in Hirsute:
  New

Bug description:
  We are using Openstack Neutron 13.0.6 and it is deployed using
  OpenStack-helm.

  I test ping servers in the same vlan while rebooting neutron-ovs-
  agent. The result shows

  root at mgt01:~# openstack server list
  +--------------------------------------+-----------------+--------+------------------------------------------+------------------------------+-----------+
  | ID                                   | Name            | Status | Networks                                 | Image                        | Flavor    |
  +--------------------------------------+-----------------+--------+------------------------------------------+------------------------------+-----------+
  | 22d55077-b1b5-452e-8eba-cbcd2d1514a8 | test-1-1        | ACTIVE | vlan105=172.31.10.4                      | Cirros 0.4.0 64-bit          | m1.tiny   |
  | 726bc888-7767-44bc-b68a-7a1f3a6babf1 | test-1-2        | ACTIVE | vlan105=172.31.10.18                     | Cirros 0.4.0 64-bit          | m1.tiny   |

  $ ping 172.31.10.4
  PING 172.31.10.4 (172.31.10.4): 56 data bytes
  ......
  64 bytes from 172.31.10.4: seq=59 ttl=64 time=0.465 ms
  64 bytes from 172.31.10.4: seq=60 ttl=64 time=0.510 ms <--------
  64 bytes from 172.31.10.4: seq=61 ttl=64 time=0.446 ms
  64 bytes from 172.31.10.4: seq=63 ttl=64 time=0.744 ms
  64 bytes from 172.31.10.4: seq=64 ttl=64 time=0.477 ms
  64 bytes from 172.31.10.4: seq=65 ttl=64 time=0.441 ms
  64 bytes from 172.31.10.4: seq=66 ttl=64 time=0.376 ms
  64 bytes from 172.31.10.4: seq=67 ttl=64 time=0.481 ms

  As one can see, packet seq 62 is lost, I believe, during rebooting ovs
  agent.

  Right now, I am suspecting
  https://github.com/openstack/neutron/blob/6d619ea7c13e89ec575295f04c63ae316759c50a/neutron/plugins/ml2/drivers/openvswitch/agent/openflow/native/ofswitch.py#L229
  this code is refreshing flow table rules even though it is not
  necessary.

  Because when I dump flows on phys bridge, I can see duration is
  rewinding to 0 which suggests flow has been deleted and created again

  """       duration=secs
                The  time,  in  seconds,  that  the entry has been in the table.
                secs includes as much precision as the switch provides, possibly
                to nanosecond resolution.
  """

  root at compute01:~# ovs-ofctl dump-flows br-floating
  ...
   cookie=0x673522f560f5ca4f, duration=323.852s, table=2, n_packets=1100, n_bytes=103409, 
                              ^------ this value resets
  priority=4,in_port="phy-br-floating",dl_vlan=2 actions=mod_vlan_vid:105,NORMAL
  ...

  IMO, rebooting ovs-agent should not affecting data plane.

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