From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bhanu CV Subject: How does iptables classify change skb priority Date: Tue, 1 Feb 2011 08:31:50 -0800 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: netfilter-devel@vger.kernel.org Return-path: Received: from mail-fx0-f66.google.com ([209.85.161.66]:37117 "EHLO mail-fx0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751521Ab1BAQbz (ORCPT ); Tue, 1 Feb 2011 11:31:55 -0500 Received: by fxm14 with SMTP id 14so1495425fxm.1 for ; Tue, 01 Feb 2011 08:31:53 -0800 (PST) Sender: netfilter-devel-owner@vger.kernel.org List-ID: Hi, I am trying to change the skb priority of the packets going out to a particular destination. Then I use vlan set_egress_map to change the vlan priority of the packet. This works as I want it to, the confusing part is I do not know why it works! I use the following two commands: change the skb->priority (?) for the packets that I am interested in to 3: iptables -t mangle -A POSTROUTING -d 192.168.10.75 -j CLASSIFY --set-class 0:3 change the vlan priority of the packet leaving over the vlan vconfig set_egress_map eth4.2 3 3 This does send a packet on the wire with MAC layer priority of 3, which is what I want. What I am trying to understand is the action that iptables is taking. I do not have any class under the root qdisc on eth4. The root qdisc has handle 0: It would be great if someone could explain how iptables is classifying the packet in a way which changes the skb->priority of the packet. I had posted this same message on netfilter user mailing list but did not get any responses. I am now posting it here hoping that the folks on this mailing list would be able to help better. Thanks in advance, Bhanu