netdev - Re: [patch net-next v2 01/12] flow_offload: Introduce offload of HW stats type

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Date:   Tue, 3 Mar 2020 21:27:39 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Edward Cree <ecree@...arflare.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, Jiri Pirko <jiri@...nulli.us>,
        netdev@...r.kernel.org, davem@...emloft.net, saeedm@...lanox.com,
        leon@...nel.org, michael.chan@...adcom.com, vishal@...lsio.com,
        jeffrey.t.kirsher@...el.com, idosch@...lanox.com,
        aelior@...vell.com, peppe.cavallaro@...com,
        alexandre.torgue@...com, jhs@...atatu.com,
        xiyou.wangcong@...il.com, mlxsw@...lanox.com,
        netfilter-devel@...r.kernel.org
Subject: Re: [patch net-next v2 01/12] flow_offload: Introduce offload of HW
 stats type

On Tue, Mar 03, 2020 at 06:55:54PM +0000, Edward Cree wrote:
> On 02/03/2020 22:49, Jakub Kicinski wrote:
> > On Mon, 2 Mar 2020 22:46:59 +0100 Pablo Neira Ayuso wrote:
> >> On Mon, Mar 02, 2020 at 12:18:52PM -0800, Jakub Kicinski wrote:
> >>> On Mon, 2 Mar 2020 20:24:37 +0100 Pablo Neira Ayuso wrote:  
> >>>> It looks to me that you want to restrict the API to tc for no good
> >>>> _technical_ reason.  
> 
> The technical reason is that having two ways to do things where one would
>  suffice means more code to be written, tested, debugged.  So if you want
>  to add this you need to convince us that the existing way (a) doesn't
>  meet your needs and (b) can't be extended to cover them.

One single unified way to express the hardware offload for _every_
supported frontend is the way to go. The flow_offload API provides a
framework to model all hardware offloads for each existing front-end.

I understand your motivation might be a specific front-end of your
choice, that's fair enough.

> > Also neither proposal addresses the problem of reporting _different_
> > counter values at different stages in the pipeline, i.e. moving from
> > stats per flow to per action. But nobody seems to be willing to work 
> > on that.
> For the record, I produced a patch series[1] to support that, but it
>  wasn't acceptable because none of the in-tree drivers implemented the
>  facility.  My hope is that we'll be upstreaming our new driver Real
>  Soon Now™, at which point I'll rebase and repost those changes.
> Alternatively if any other vendor wants to support it in their driver
>  they could use those patches as a base.

Great, I am very much looking forward to reviewing your upstream code.

Just keep in my mind that whatever proposal you make must work for
netfilter too.

Thank you.