[ovs-discuss] Questions about IPFIX

Ben Pfaff blp at ovn.org
Fri Jun 2 16:08:28 UTC 2017

ipfix_cache_entry_init() initializes the start and end to be the same:

        entry->flow_end_timestamp_usec = now.tv_usec + 1000000LL * now.tv_sec;
        entry->flow_start_timestamp_usec = entry->flow_end_timestamp_usec;

and then I don't see anything that ever updates the "end" time.  I guess
that's the issue.

On Fri, Jun 02, 2017 at 01:57:01PM +0200, Felix Konstantin Maurer wrote:
> I just took a look at the code, and I think it should work, as the the
> timestamps are properly updated in ipfix_cache_aggregate_entries.
> However, I don't know the code base well or C for that matter.
> Can you point me to where the time values are not properly set?
> Regards
> Felix
> On 05/31/2017 05:27 PM, Ben Pfaff wrote:
> > On Wed, May 31, 2017 at 03:05:45PM +0200, Felix Konstantin Maurer wrote:
> >> I'm currently trying to export flow statistics from an Openvswitch
> >> bridge with IPFIX. It works, however in almost all packets, the
> >> flowStartDeltaMicroseconds and the flowEndDeltaMicroseconds have the
> >> same value. Is that to be expected? Do I misunderstand something?
> >>
> >> I expected them to be different and to allow me to calculate over which
> >> time period the octetDeltaCount number of bytes of the flow had been sent.
> > 
> > The IPFIX code hard-codes the start and end times to the same value.
> > It's too bad--it would be nice to have this be more accurate.  I don't
> > know how difficult that would be.
> > 
> -- 
> RWTH Aachen University
> Communication and Distributed Systems
> http://www.comsys.rwth-aachen.de

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