Firewall mark classifier in tc(8)    Linux   Firewall mark classifier in tc(8)



NAME
       fw - fwmark traffic control filter

SYNOPSIS
       tc filter ... fw [ classid CLASSID ] [  action ACTION_SPEC ]

DESCRIPTION
       the fw filter allows one to classify packets based on a previously set
       fwmark by iptables.  If the masked value of the fwmark matches the
       filter's masked handle, the filter matches. By default, all 32 bits of
       the handle and the fwmark are masked.  iptables allows one to mark
       single packets with the MARK target, or whole connections using
       CONNMARK.  The benefit of using this filter instead of doing the heavy-
       lifting with tc itself is that on one hand it might be convenient to
       keep packet filtering and classification in one place, possibly having
       to match a packet just once, and on the other users familiar with
       iptables but not tc will have a less hard time adding QoS to their
       setups.

OPTIONS
       classid CLASSID
	      Push matching packets to the class identified by CLASSID.

       action ACTION_SPEC
	      Apply an action from the generic actions framework on matching
	      packets.

EXAMPLES
       Take e.g. the following tc filter statement:

	      tc filter add ... handle 6 fw classid 1:1

       will match if the packet's fwmark value is 6.  This is a sample
       iptables statement marking packets coming in on eth0:

	      iptables -t mangle -A PREROUTING -i eth0 -j MARK --set-mark 6

       Specific bits of the packet's fwmark can be set using the skbedit
       action. For example, to only set one bit of the fwmark without changing
       any other bit:

	      tc filter add ... action skbedit mark 0x8/0x8

       The fw filter can then be used to match on this bit by masking the
       handle:

	      tc filter add ... handle 0x8/0x8 fw action drop

       This is useful when different bits of the fwmark are assigned different
       meanings.

SEE ALSO
       tc(8), iptables(8), iptables-extensions(8), tc-skbedit(8)

iproute2			  21 Oct 2015
					     Firewall mark classifier in tc(8)