ng_patch and 802.11Q

Gleb Smirnoff glebius at
Fri Nov 8 21:52:13 UTC 2013

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( and the 
B> example it given:
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
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.

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