netdev - Re: [PATCH net-next 3/5] flow_offload: Reject matching on layer 2 miss

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Date: Fri, 19 May 2023 17:10:58 +0300
From: Ido Schimmel <idosch@...dia.com>
To: Simon Horman <simon.horman@...igine.com>, nbd@....name
Cc: netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
	davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
	edumazet@...gle.com, razor@...ckwall.org, roopa@...dia.com,
	taras.chornyi@...ision.eu, saeedm@...dia.com, leon@...nel.org,
	petrm@...dia.com, vladimir.oltean@....com, claudiu.manoil@....com,
	alexandre.belloni@...tlin.com, UNGLinuxDriver@...rochip.com,
	jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
	taspelund@...dia.com
Subject: Re: [PATCH net-next 3/5] flow_offload: Reject matching on layer 2
 miss

On Fri, May 19, 2023 at 01:33:00PM +0200, Simon Horman wrote:
> On Thu, May 18, 2023 at 02:33:26PM +0300, Ido Schimmel wrote:
> > Adjust drivers that support the 'FLOW_DISSECTOR_KEY_META' key to reject
> > filters that try to match on the newly added layer 2 miss option. Add an
> > extack message to clearly communicate the failure reason to user space.
> 
> Hi Ido,
> 
> FLOW_DISSECTOR_KEY_META is also used in the following.
> Perhaps they don't need updating. But perhaps it is worth mentioning why.

Good point.

> 
>  * drivers/net/ethernet/mediatek/mtk_ppe_offload.c

This driver does not seem to do anything with this key. TBH, I'm not
sure what is the purpose of this hunk:

if (flow_rule_match_key(rule, FLOW_DISSECTOR_KEY_META)) {
	struct flow_match_meta match;

	flow_rule_match_meta(rule, &match);
} else {
	return -EOPNOTSUPP;
}

Felix, can you comment?
Original patch:
https://lore.kernel.org/netdev/20230518113328.1952135-4-idosch@nvidia.com/

>  * drivers/net/ethernet/netronome/nfp/flower/conntrack.c

My understanding is that this code is for netfilter offload (not tc)
which does not use the new bit. Adding a check would therefore be dead
code. I don't mind adding a check or mentioning in the commit message
why I didn't add one. Let me know what you prefer.

Thanks