netdev - Re: Why do we prefer skb->priority to tc filters?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 11 Mar 2015 11:25:40 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cong Wang <cwang@...pensource.com>
Cc:	netdev <netdev@...r.kernel.org>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	David Miller <davem@...emloft.net>
Subject: Re: Why do we prefer skb->priority to tc filters?

On Wed, 2015-03-11 at 11:08 -0700, Cong Wang wrote:
> On Wed, Mar 11, 2015 at 10:34 AM, Cong Wang <cwang@...pensource.com> wrote:
> >
> > Given that skb->priority can be specified in user-space, doesn't this
> > mean some application can always override our rules specified by tc
> > filters? I think we should always respect tc filters over any
> > application setting.
> >
> 
> Hmm, on the other hand, skb->priority can be changed in cgroup
> too, in this case the current behavior seems correct. :-/ Interesting.

Note that even HTB has the following code :

static struct htb_class *htb_classify(struct sk_buff *skb, struct Qdisc *sch,
                                      int *qerr)
{
        struct htb_sched *q = qdisc_priv(sch);
        struct htb_class *cl;
        struct tcf_result res;
        struct tcf_proto *tcf;
        int result;

        /* allow to select class by setting skb->priority to valid classid;
         * note that nfmark can be used too by attaching filter fw with no
         * rules in it
         */
        if (skb->priority == sch->handle)
                return HTB_DIRECT;      /* X:0 (direct flow) selected */
        cl = htb_find(skb->priority, sch);
        if (cl) {
                if (cl->level == 0)
                        return cl;
                /* Start with inner filter chain if a non-leaf class is selected */
                tcf = rcu_dereference_bh(cl->filter_list);
        } else {
                tcf = rcu_dereference_bh(q->filter_list);
        }


So if skb->priority happens to match sch->handle or any class handle,
we queue packet into a queue, without calling tc_classify()




--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html