Comment 0 for bug 1891673

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.