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

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Date:   Mon, 2 Mar 2020 14:58:49 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Pablo Neira Ayuso <pablo@...filter.org>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        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, ecree@...arflare.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

Mon, Mar 02, 2020 at 02:20:16PM CET, pablo@...filter.org wrote:
>On Sun, Mar 01, 2020 at 09:44:43AM +0100, Jiri Pirko wrote:
>> Sat, Feb 29, 2020 at 08:29:47PM CET, pablo@...filter.org wrote:
>> >On Fri, Feb 28, 2020 at 06:24:54PM +0100, Jiri Pirko wrote:
>[...]
>> >> diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
>> >> index 4e864c34a1b0..eee1cbc5db3c 100644
>> >> --- a/include/net/flow_offload.h
>> >> +++ b/include/net/flow_offload.h
>> >> @@ -154,6 +154,10 @@ enum flow_action_mangle_base {
>> >>  	FLOW_ACT_MANGLE_HDR_TYPE_UDP,
>> >>  };
>> >>  
>> >> +enum flow_action_hw_stats_type {
>> >> +	FLOW_ACTION_HW_STATS_TYPE_ANY,
>> >> +};
>> >> +
>> >>  typedef void (*action_destr)(void *priv);
>> >>  
>> >>  struct flow_action_cookie {
>> >> @@ -168,6 +172,7 @@ void flow_action_cookie_destroy(struct flow_action_cookie *cookie);
>> >>  
>> >>  struct flow_action_entry {
>> >>  	enum flow_action_id		id;
>> >> +	enum flow_action_hw_stats_type	hw_stats_type;
>> >>  	action_destr			destructor;
>> >>  	void				*destructor_priv;
>> >>  	union {
>> >> @@ -228,6 +233,7 @@ struct flow_action_entry {
>> >>  };
>> >>  
>> >>  struct flow_action {
>> >> +	bool				mixed_hw_stats_types;
>> >
>> >Why do you want to place this built-in into the struct flow_action as
>> >a boolean?
>> 
>> Because it is convenient for the driver to know if multiple hw_stats_type
>> values are used for multiple actions.
>> 
>> >You can express the same thing through a new FLOW_ACTION_COUNTER.
>[...]
>> >Please, explain me why it would be a problem from the driver side to
>> >provide a separated counter action.
>> 
>> I don't see any point in doing that. The action itself implies that has
>> stats, you don't need a separate action for that for the flow_offload
>> abstraction layer. What you would end up with is:
>> counter_action1, actual_action1, counter_action2, actual_action2,...
>> 
>> What is the point of that?
>
>Yes, it's a bit more work for tc to generate counter action + actual
>action.
>
>However, netfilter has two ways to use counters:
>
>1) per-rule counter, in this case the counter is updated after rule
>   matching, right before calling the action. This is the legacy mode.
>
>2) explicit counter action, in this case the user specifies explicitly
>   that it needs a counter in a given position of the rule. This
>   counter might come before or after the actual action.
>
>ethtool does not have counters yet. Now there is a netlink interface
>for it, there might be counters there at some point.
>
>I'm suggesting a model that would work for the existing front-ends
>using the flow_action API.

I see. I'm interested in 1) now. If you ever want to implement 2), I see
no problem in doing it.