With ecmp_nexthop_monitor_enable=true, ovn-controller flushes the
conntrack entries of an ecmp-symmetric-reply next-hop when the next-hop
goes away. We found two ways in which entries of a removed next-hop
survive the flush:
1/2: The flush message is built before ofctrl_put() checks
ofctrl_can_put(), and the next-hop is forgotten at once. If ofctrl
cannot send in that run, the message is deleted and never built
again. We hit this intermittently while removing members of an
ecmp-symmetric-reply route under load.
2/2: The flush is sent before the flow bundle that removes the next-hop,
so a packet handled in between can commit a new entry towards the
removed next-hop.
The test added in 1/2 stops ovs-vswitchd and fills the OpenFlow
connection before removing a next-hop; 2/2 adds an ordering check to
it. Each check fails without its change.
Tested on top of main 7d16edb88: checkpatch clean, build with
--enable-Werror, "make check" 1216 passed, 175 skipped, 0 failed. Both
patches also apply to branch-26.09 and branch-26.03; we run them on top
of v26.03.3.
Bekei Park (2):
controller: Do not lose ECMP next-hop conntrack flushes.
controller: Flush ECMP next-hop conntrack after the flow bundle.
controller/ecmp-next-hop-monitor.c | 53 ++++++++++++++----
controller/ecmp-next-hop-monitor.h | 9 ++--
controller/ofctrl.c | 26 +++++----
tests/ovn.at | 86 ++++++++++++++++++++++++++++++
4 files changed, 150 insertions(+), 24 deletions(-)
--
2.43.0
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