netdev - Re: [PATCH net-next] net: sched: cls

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Date:	Mon, 28 Oct 2013 08:27:14 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Daniel Borkmann <dborkman@...hat.com>
Cc:	davem@...emloft.net, netdev@...r.kernel.org,
	Thomas Graf <tgraf@...g.ch>
Subject: Re: [PATCH net-next] net: sched: cls_bpf: add BPF-based classifier

On Mon, 2013-10-28 at 15:31 +0100, Daniel Borkmann wrote:

> I thought about this, I think this can partially be resolved by the
> user implementing one BPF program to match all possible flows for a
> class instead of implementing multiple BPF programs as mentioned in
> the commit, iow that's up to the user space. And the case you suggest,
> would be another option to further improve this, but would come with
> some difficulties in contrast to the notion 0: mismatch, !0: match.
> I think, this would need additional walk-through through all 'ret'
> opcodes to see if those classes actually exist. Then, we would need
> refcounting and call tcf_{un,}bind_filter() for each class that is
> related to this filter, and tcf_exts_exec() would either need to be
> i) understood in a "per-filter" notion, so as long as something
> matches (!0) exec the very same action/policy (which might not be
> what we want) or ii) could just not be implemented as multiple
> user-defined filters could be defined in iproute2 with different
> actions each, but in some paths return the same flowid. So I think
> this here seems the better trade-off.

I have no idea why you want to do all this.

classid are not checked at filter installation time, but at run time.

All you need to do is change :

+       list_for_each_entry(prog, &head->plist, link) {
+               if (SK_RUN_FILTER(prog->filter, skb) == 0)
+                       continue;
+
+               *res = prog->res;
+               ret = tcf_exts_exec(skb, &prog->exts, res);
+               if (ret < 0)
+                       continue;
+
+               return ret;
+       }

to

	list_for_each_entry(prog, &head->plist, link) {
		int filter_res = SK_RUN_FILTER(prog->filter, skb);

		if (!filter_res)
			continue;


               *res = prog->res;
		if (filter_res != -1)
			res->classid = filter_res;

               ret = tcf_exts_exec(skb, &prog->exts, res);
               if (ret < 0)
                       continue;

               return ret;
       }

(Reserving filter returns codes :
 0 : No match
 -1: select classid given in the "tc filter ...." command)
other values : flowid, overiding the default one.



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