[ovs-dev] [PATCHv6 2/3] ofproto-dpif-sflow: Add snaplen for sample action and sFlow.

[William Tu]

Hi Ben,
Thanks for the review.

> This changes the "wire format" of the NXAST_SAMPLE action, but we can't
> do that because it will break compatibility with older OpenFlow clients.
> Usually if we need a new feature in an action we add a new version that
> has that feature, e.g. NXAST_SAMPLE2.  The IPFIX enhancements that Benli
> Ye are working on already do that for another reason, so you should
> probably coordinate so that we don't end up with three versions of the
> sample action.

Sure, I will do that.

>
> I'm not sure why CHECK_TRUNC_USERSPACE exists, because I think that your
> patch implements the new action in userspace.

When translating sflow header config, only if it runs kernel datapath,
I will program truncate to sample's actions list, ex:
"sample(trunc(64), userspace(...))". If it runs userspace datapath,
then it falls back to original way "sample(userspace(...))" and let
sflow code cut the packet to 'header' size.

The sflow testcase in system-traffic.at is created only for kernel dp,
so CHECK_TRUNC_USERSPACE skips it when running in userspace.

Regards,
William