[Bug 1891673] Re: qrouter ns ip rules not deleted when fip removed from vm

[Edward Hope-Morley]

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

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

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

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

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

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

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

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https://bugs.launchpad.net/bugs/1891673

Title:
  qrouter ns ip rules not deleted when fip removed from vm

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:
  In Progress

Bug description:
  With Bionic Stein using dvr_snat if I add a floating ip to a vm then
  remove the floating ip, the corresponding ip rules in the associated
  qrouter ns local to the instance are not deleted which results in no
  longer being able to reach the external network because packets are
  still sent to the fip namespace (via rfp-/fpr-) e.g. in my compute
  host running a vm whose address is 192.168.21.28 for which i have
  removed the fip I still see:

  # ip netns exec qrouter-5e45608f-33d4-41bf-b3ba-915adf612e65 ip rule list
  0:      from all lookup local 
  32765:  from 192.168.21.28 lookup 16 
  32766:  from all lookup main 
  32767:  from all lookup default 
  3232240897:     from 192.168.21.1/24 lookup 3232240897 
  3232241231:     from 192.168.22.79/24 lookup 3232241231

  And table 16 leads to:

  # ip netns exec qrouter-5e45608f-33d4-41bf-b3ba-915adf612e65 ip route show table 16
  default via 169.254.109.249 dev rfp-5e45608f-3

  Which results in the instance no longer being able to reach the
  external network (packets are never sent to the snat- ns in my case).

  The workaround is to delete that ip rule but neutron should be taking
  care of this. Looks like the culprit is in
  neutron/agent/l3/dvr_local_router.py:floating_ip_removed_dist

  Note that the NAT rules were successfully removed from iptables so
  looks like it is just this bit that is left behind.

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