man > tc-fw(8)

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 us‐
       ing 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)