# man > tc-fw(8)

_Firewall_ _mark_ _classifier_ _in_ [_tc_(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)               Linux              _Firewall_ _mark_ _classifier_ _in_ [_tc_(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)

## 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)](https://www.chedong.com/phpMan.php/man/tc/8/markdown), [**iptables**(8)](https://www.chedong.com/phpMan.php/man/iptables/8/markdown), [**iptables-extensions**(8)](https://www.chedong.com/phpMan.php/man/iptables-extensions/8/markdown), [**tc-skbedit**(8)](https://www.chedong.com/phpMan.php/man/tc-skbedit/8/markdown)

iproute2                                     21 Oct 2015           _Firewall_ _mark_ _classifier_ _in_ [_tc_(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown)