ovs-fw does not reinstate GRE conntrack entry

[Shilla Saebi]

We have VMs running GRE tunnels between them with OVSFW and SG
  implemented along with GRE conntrack helper loaded on the hypervisor.
  GRE works as expected but the tunnel breaks whenever there is a
  neutron ovs agent event causing some exception like the below AMQP
  timeouts or OVSFW port not found :

AMQP Timeout:

2017-04-07 19:07:03.001 5275 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  MessagingTimeout: Timed out waiting for a reply to message ID
  4035644808d24ce9aae65a6ee567021c
  2017-04-07 19:07:03.001 5275 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  2017-04-07 19:07:03.003 5275 WARNING oslo.service.loopingcall [-]
  Function
  'neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent.OVSNeutronAgent._report_state'
  run outlasted interval by 120.01 sec
  2017-04-07 19:07:03.041 5275 INFO
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent [-]
  Agent has just been revived. Doing a full sync.
  2017-04-07 19:07:06.747 5275 INFO
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  [req-521c07b4-f53d-4665-b728-fc5f00191294 - - - - -] rpc_loop doing a
  full sync.
  2017-04-07 19:07:06.841 5275 INFO
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  [req-521c07b4-f53d-4665-b728-fc5f00191294 - - - - -] Agent out of sync
  with plugin!

OVSFWPortNOtFound:

2017-03-30 18:31:05.048 5160 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  self.firewall.prepare_port_filter(device)
  2017-03-30 18:31:05.048 5160 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent File
  "/openstack/venvs/neutron-14.0.5/lib/python2.7/site-packages/neutron/agent/linux/openvswitch_firewall/firewall.py",
  line 272, in prepare_port_filter
  2017-03-30 18:31:05.048 5160 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  of_port = self.get_or_create_ofport(port)
  2017-03-30 18:31:05.048 5160 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent File
  "/openstack/venvs/neutron-14.0.5/lib/python2.7/site-packages/neutron/agent/linux/openvswitch_firewall/firewall.py",
  line 246, in get_or_create_ofport
  2017-03-30 18:31:05.048 5160 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent raise
  OVSFWPortNotFound(port_id=port_id)
  2017-03-30 18:31:05.048 5160 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  OVSFWPortNotFound: Port 01f7c714-1828-4768-9810-a0ec25dd2b92 is not
  managed by this agent.
  2017-03-30 18:31:05.048 5160 ERROR
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  2017-03-30 18:31:05.072 5160 INFO
  neutron.plugins.ml2.drivers.openvswitch.agent.ovs_neutron_agent
  [req-db74f32b-5370-4a5f-86bf-935eba1490d0 - - - - -] Agent out of sync
  with plugin!

The agent throws out of sync messages and starts to initialize neutron
  ports once again along with fresh SG rules.

2017-04-07 19:07:07.110 5275 INFO neutron.agent.securitygroups_rpc
  [req-521c07b4-f53d-4665-b728-fc5f00191294 - - - - -] Preparing filters
  for devices set([u'4b14619f-3b9e-4103-b9d7-9c7e52c797d8'])
  2017-04-07 19:07:07.215 5275 ERROR
  neutron.agent.linux.openvswitch_firewall.firewall
  [req-521c07b4-f53d-4665-b728-fc5f00191294 - - - - -] Initializing port
  4b14619f-3b9e-4103-b9d7-9c7e52c797d8 that was already initialized.

During this process, when it prepares new filters for all ports, its
  marking the conntrack entry for certain GRE connection(high traffic)
  as invalid.

root@server:/var/log# conntrack -L -o extended -p gre -f ipv4
  ipv4 2 gre 47 178 src=1.1.1.203 dst=2.2.2.66 srckey=0x0 dstkey=0x0
  src=2.2.2.66 dst=1.1.1.203 srckey=0x0 dstkey=0x0 [ASSURED] mark=1
  zone=5 use=1
  ipv4 2 gre 47 179 src=5.5.5.104 dst=4.4.4.187 srckey=0x0 dstkey=0x0
  src=4.4.4.187 dst=5.5.5.104 srckey=0x0 dstkey=0x0 [ASSURED] mark=0
  zone=5 use=1

And that connection state remains invalid, unless someone reboots the
  VM, or flushes the connection directly on the conntrack or through
  OVS.

We have a blanket any protocol any port any IP SG rule during this
  scenario, we even tried adding specific rules to allow IP 47 for GRE.
  But nothing fixed this problem.

Was checking for ovs-conntrack helper specific bugs and came across
  patchwork.ozlabs.org/patch/755615/ - is this bug being
  triggered in the above scenario ? Is this a bug in the ovs-fw code or
  this something on the ovs-conntrack implementation.

OpenStack Version : Newton.
  Hypervisor OS : Ubuntu 16.04.2
  Kernel version : 4.4.0-70-generic
  OVS version : 2.6.1

please see: https://lists.gt.net/openstack/dev/62980 (original email from Aju Francis reporting this issue)

[Boden R (boden)]

Actually this bug is a dup of [1]; marking as such.

[1] https://bugs.launchpad.net/neutron/+bug/1708731