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Date: Sat, 9 Nov 2013 01:52:10 +0400
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: Bear <jilingshu@gmail.com>
Subject: Re: ng_patch and 802.11Q
Message-ID: <20131108215210.GH7577@FreeBSD.org>
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On Fri, Nov 08, 2013 at 02:11:49AM -0330, Bear wrote:
B> Hi all,
B> I want to modify VLAN priority by ng_patch. After reading the manpage of 
B> ng_patch(http://www.freebsd.org/cgi/man.cgi?query=ng_patch) and the 
B> example it given:
B> 
B>  >  /usr/sbin/ngctl -f- <<-SEQ
B>  > 	 mkpeer ipfw: patch 200 in
B>  > 	 name ipfw:200 ttl_add
B>  > 	 msg ttl_add: setconfig { count=1 csum_flags=1 ops=[	 \
B>  > 		 { mode=2 value=3 length=1 offset=8 } ] }
B>  >  SEQ
B>  >  /sbin/ipfw add 150 netgraph 200 ip from any to simplex.remote.net
B> 
B> It seems ng_patch can only modify IP header. However, the position of 
B> VLAN header is before IP header and after Ethernet header. How can I 
B> modify it?

ipfw allows you to intercept packets at IP layer. Tp modify VLAN header,
you need to capture them earlier. May be ng_ether(4) will help you.

-- 
Totus tuus, Glebius.