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

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Message-ID: <1426104582.11398.61.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 11 Mar 2015 13:09:42 -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 12:18 -0700, Cong Wang wrote:
> This is exactly why I am asking, kernel respects user's choice so much
> that it could override even both cgroup prio and tc filters, I don't know
> what is the reason behind, but this means our tc filters can not work
> with an application which sets skb->priority. For example, our tc filters
> classify the packets from this socket into flow 1:1, but application
> sets 1:2 by itself...

Application cannot set whatever skb->priority, unless it really knows
better than kernel.

        case SO_PRIORITY:
                if ((val >= 0 && val <= 6) ||
                    ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
                        sk->sk_priority = val;
                else
                        ret = -EPERM;
                break;



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