Public bug reported:
Description: Ubuntu 16.04.3 LTS
Linux 4.4.0-96-generic on AMD64
Neutron 2:10.0.4-0ubuntu2~cloud0 from Cloud Archive xenial-updates/ocata
OpenVSwitch 2.6.1-0ubuntu5.2~cloud0 from Cloud Archive xenial-upates/ocata
In an environment with three bare-metal Neutron deployments, hosting
upward of 300 routers, with approximately the same number of instances,
typically one router per instance, packet loss on instances accessed via
floating IPs, including complete connectivity loss, is experienced. The
problem is exacerbated by enabling L3HA, likely due to the increase in
router namespaces to be scheduled and managed, and the additional
scheduling work of bringing up keepalived and monitoring the keepalived
Reducing the number of routers and rescheduling routers on new hosts,
causing the routers to undergo a full recreation of namespace, iptables
rules, and replugging of interfaces into OVS will correct packet loss or
connectivity loss on impacted routers.
On Neutron hosts in this environment, we have used systemtap to trace
calls to kfree_skb which reveals the majority of dropped packets occur
in the openvswitch module, notably on the br-int bridge. Inspecting the
state of OVS shows many qtap interfaces which are no longer present on
the Neutron host which are still plugged in to OVS.
Diagnostic outputs in following comments.
** Affects: neutron
** Affects: openvswitch (Ubuntu)
** Also affects: neutron
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Neutron integrated with OpenVSwitch drops packets and fails to
plug/unplug interfaces from OVS on router interfaces at scale
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