[ovs-discuss] Inaccurate statistics in flow_removed struct using OpenvSwitch

kk yap yapkke at stanford.edu
Wed May 18 00:55:51 UTC 2011


We are using OVS as a software switch, with last commit

When a flow of ten pings is sent across the switch, OVS counted 19
packets instead.  The setup is
           veth1 ---- veth0 --- OVS --- eth1

IP address is assigned to veth1.  The attached pcap file is capture
with the any interface, i.e., each ICMP packet will appear thrice (at
veth1, veth0 and eth1).  The controller is local and at port 6633.
Looking at the control traffic, packet 777 and 779  are flow removed
for the ICMP flows, and they both shows packet count of 19 despite of
having only ten packets in the flows.

Looking at the code, ovs-openflowd returns facet + stat as packet
count for the flow removed.  The number recorded by facet is correct,
but the sum of the value exceed the real value.  This occurs at the
facet_update_stats function.  What is the purpose of the addition?
Can we expect accurate statistics from OVS?


KK and TY
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