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[Corey Bryant <corey.bryant@xxxxxxxxxxxxx>]

** Also affects: cloud-archive/ocata
   Importance: Undecided
       Status: New

** No longer affects: cloud-archive/ocata

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https://bugs.launchpad.net/bugs/1722584

Title:
  [SRU] Return traffic from metadata service may get dropped by
  hypervisor due to wrong checksum

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 neutron:
  Fix Released

Bug description:
  [Impact]
  Prior addition of code to add checksum rules was found to cause problems with newer kernels. Patch subsequently reverted so this request is to backport those patches to the ubuntu archives.

  [Test Case]
  * deploy openstack (>= queens)
  * create router/network/instance (dvr=false,l3ha=false)
  * go to router ns on neutron-gateway and check that the following returns nothing
  sudo ip netns exec qrouter-<id> iptables -t mangle -S| grep '\--sport 9697 -j CHECKSUM --checksum-fill'

  [Regression Potential]
  None expected

  [Other Info]
  This revert patch does not remove rules added by the original patch so manual cleanup of those old rules is required.

  -----------------------------------------------------------------------------
  We have a problem with the metadata service not being responsive, when the proxied in the router namespace on some of our networking nodes after upgrading to Ocata (Running on CentOS 7.4, with the RDO packages).

  Instance routes traffic to 169.254.169.254 to it's default gateway.
  Default gateway is an OpenStack router in a namespace on a networking node.

  - Traffic gets sent from the guest,
  - to the router,
  - iptables routes it to the metadata proxy service,
  - response packet gets routed back, leaving the namespace
  - Hypervisor gets the packet in
  - Checksum of packet is wrong, and the packet gets dropped before putting it on the bridge

  Based on the following bug https://bugs.launchpad.net/openstack-
  ansible/+bug/1483603, we found that adding the following iptable rule
  in the router namespace made this work again: 'iptables -t mangle -I
  POSTROUTING -p tcp --sport 9697 -j CHECKSUM --checksum-fill'

  (NOTE: The rule from the 1st comment to the bug did solve access to
  the metadata service, but the lack of precision introduced other
  problems with the network)

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