[ovs-dev] bug in flow stats for VLAN acceleration?

Motonori Shindo motonori at shin.do
Wed Jan 7 04:20:28 UTC 2015


Ben,

Thanks for addressing this issue. I found that it was just merged into
master. I will verify the new behavior first and then start working on
fixing NetFlow part. Will keep you posted.

Regards,

---
Motonori Shindo

2015-01-01 1:48 GMT+09:00 Ben Pfaff <blp at nicira.com>:

> I sent out a patch that should fix this:
>         http://openvswitch.org/pipermail/dev/2014-December/049972.html
>
> It will take some time, probably a few days, for it to get into the
> kernel and the OVS tree's kernel module.  After that, I think you'll be
> ready to go.  (However, the buggy behavior will still be present if a
> user upgrades userspace without upgrading their kernel module.  I doubt
> that that is really a big deal though.)
>
> On Thu, Dec 11, 2014 at 12:36:51AM +0900, Motonori Shindo wrote:
> > Ben and Jesse,
> >
> > Thanks for picking this issue up.
> >
> > Although current behavior is not consistent in VLAN and no-VLAN cases,
> as far as NetFlow concerns it doesn’t matter in fact because NetFlow only
> counts L3 packet size anyway.
> >
> > Here’s the story. First, I wanted to fix an issue that OVS currently
> reports L2 packet size, not L3 packet size in NetFlow flow records (NetFlow
> should report L3 packet size). I thought the easiest way to fix this
> problem was to subtract the ethernet header length when reporting a NetFlow
> flow record. Then, I realized that I should also take VLAN header into
> account if it is present. I checked how NetFlow behaves in VLAN case and
> no-VLAN case and found out that OVS reports the same packet size in NetFlow
> regardless to the presence of VLAN header.
> >
> > Once this packet size issue related to VLAN header gets solved by
> someone else (as this is probably beyond of my understanding of the
> relevant code), I will work on fixing the L2 vs L3 packet size issue
> specifically in NetFlow.
> >
> > Regards,
> >
> > On 2014/12/09 3:22, "Jesse Gross" <jesse at nicira.com <mailto:
> jesse at nicira.com>> wrote:
> >
> > On Mon, Dec 8, 2014 at 9:58 AM, Ben Pfaff <blp at nicira.com <mailto:
> blp at nicira.com>> wrote:
> > Motonori Shindo (CCed) reported to me recently that NetFlow does not
> > include VLAN headers in the byte counts that it exports.  Taking a
> > look at the kernel datapath code, I see that ovs_flow_stats_update()
> > accounts raw skb->len to byte counters.  I suspect that it should add
> > 4 if a VLAN header was present but removed by VLAN acceleration.
> >
> > Presumably we should also do this for port stats as well to be
> consistent.
> >
> >
> >
> > ---
> > Motonori Shindo
>



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