netdev - Re: [patch net-next] tc: introduce OpenFlow classifier

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Date:	Thu, 26 Mar 2015 21:39:11 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, jhs@...atatu.com,
	tgraf@...g.ch, jesse@...ira.com
Subject: Re: [patch net-next] tc: introduce OpenFlow classifier

On Thu, Mar 26, 2015, at 16:29, Jiri Pirko wrote:
> Thu, Mar 26, 2015 at 03:23:56PM CET, hannes@...essinduktion.org wrote:
> >> +static int of_classify(struct sk_buff *skb, const struct tcf_proto *tp,
> >> +		       struct tcf_result *res)
> >> +{
> >> +	struct cls_of_head *head = rcu_dereference_bh(tp->root);
> >> +	struct cls_of_filter *f;
> >> +	struct of_flow_key skb_key;
> >> +	int ret;
> >> +
> >> +	of_extract_key(skb, &skb_key);
> >> +
> >> +	list_for_each_entry_rcu(f, &head->filters, list) {
> >> +		if (!of_match(&skb_key, f))
> >> +			continue;
> >
> >This seems very limited to me, do you have plans to extend this?
> 
> What do you have in mind?

We have the possibility to make the order of the matches matter easily
here (like a decision tree).
Maybe this would give a benefit over simple full match with mask, so
user space can align the most
significant matches first thus creating less churn in the caches and
make the lookup time shorter?
I understand, if you want build a simples openvswitch replacement a hash
table would be good to go,
too.

Just a proposal, maybe we can add more benefit to this kind of
classifier.

Albeit it looks a bit like cls_bpf could do that more easily.

What do you think?

Bye,
Hannes
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