netdev - Re: TC stats / hw offload question

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Date:   Fri, 8 Feb 2019 10:26:52 +0000
From:   Edward Cree <ecree@...arflare.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>,
        netdev <netdev@...r.kernel.org>
CC:     Jiri Pirko <jiri@...nulli.us>, Cong Wang <xiyou.wangcong@...il.com>
Subject: Re: TC stats / hw offload question

On 06/02/19 02:20, Jamal Hadi Salim wrote:
> The classifiers dont mod the packets. The actions do. And they
> maintain stats on the size on "entry" i.e pre-edit. 
Thank you for clearing that up.

> Each action keeps its own counters. If you did something like:
>
> tc match using flower blah \
> action vlan push tag ... \
> action redirect to egress of eth0
>
> And you submited a packet of size x bytes,
> then the "match" would record x bytes.
Sorry, where would it record that?  I can't find any stats counters on
 the "match" either in the software path or the offload API.

> the "vlan action" would record x bytes.
> the "redirect" would record size x+vlaninfo bytes
> the egress of eth0 would  recorr x+vlaninfo bytes
Am I right in thinking that offloaded counters don't do that?  As far
 as I can tell, the drivers with flower offload all use
 tcf_exts_stats_update() which takes a single 'bytes' count and adds
 it to all the actions.  (Presumably this is pre-edit length.)

-Ed