[Bug 1967718] Re: Traffic sent to LRP port recirculate until TTL=0

[nikhil kshirsagar]

I tried backporting the 481f25b784896eec07fedc77631992a009bcdada patch
to 22.03, which needed 27a92cc272 and a42c808f30, and then some other
commits too like 4dc4bc7fdb and ee20c48c2f5ce9d512adfcbea3ee300f8bb09625
for 22.03.

Unfortunately I encountered a lot of build failures on 22.03. I was able
to build on 22.09.1 with the order of 481f25b784896eec07fed +
27a92cc272, a42c808f30 , but ended up with a lot of failing unit tests,
so that wasn't entirely successful either.

My attempts are detailed at https://pastebin.ubuntu.com/p/zf85J63RxY/
and https://pastebin.ubuntu.com/p/m2qvwKwMGR/ and this email
communication to the ovn mailing list
https://mail.openvswitch.org/pipermail/ovs-dev/2023-August/406940.html

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https://bugs.launchpad.net/bugs/1967718

Title:
  Traffic sent to LRP port recirculate until TTL=0

Status in ovn package in Ubuntu:
  Fix Released

Bug description:
  When TCP/UDP traffic is sent to the address of an LRP port and at the
  same time is not part of any SNAT/DNAT conversation, it will keep
  recirculating in the OVS data plane until TTL is 0.

  When the packet eventually drops, you might get this message logged:

  [   58.586597] openvswitch: ovs-system: deferred action limit reached,
  drop recirc action

  This behavior is problematic because it wastes resources and could
  also trigger other potential problems in the data plane quite quickly
  [0]. For any internet connected system it is also highly likely to
  occur.

  As mentioned above the LRP address is used for both SNAT return
  traffic and DNAT forwarding, so we would need to allow that traffic to
  pass and at the same time install flows to prevent this from
  happening.

  0: https://mail.openvswitch.org/pipermail/ovs-
  discuss/2022-March/051780.html

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