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

[Hannes Frederic Sowa <hannes@stressinduktion.org>]

On Thu, Mar 26, 2015, at 16:29, Jiri Pirko wrote:
> Thu, Mar 26, 2015 at 03:23:56PM CET, hannes@stressinduktion.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