# man > tc-cgroup(8)

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

## NAME
       cgroup - control group based traffic control filter

## SYNOPSIS
       **tc filter **... **cgroup **[ **match _**EMATCH_TREE_ ] [ **action _**ACTION_SPEC_ ]

## DESCRIPTION
       This  filter  serves  as a hint to **tc **that the assigned class ID of the net_cls control group
       the process the packet originates from belongs to should be used  for  classification.  Obvi‐
       ously, it is useful for locally generated packets only.

## OPTIONS
       **action _**ACTION_SPEC_
              Apply an action from the generic actions framework on matching packets.

       **match _**EMATCH_TREE_
              Match packets using the extended match infrastructure. See [**tc-ematch**(8)](https://www.chedong.com/phpMan.php/man/tc-ematch/8/markdown) for a detailed
              description of the allowed syntax in _EMATCH_TREE_.

## EXAMPLES
       In  order  to  use  this filter, a net_cls control group has to be created first and class as
       well as process ID(s) assigned to it. The following creates a net_cls cgroup named "foobar":

              modprobe cls_cgroup
              mkdir /sys/fs/cgroup/net_cls
              mount -t cgroup -onet_cls net_cls /sys/fs/cgroup/net_cls
              mkdir /sys/fs/cgroup/net_cls/foobar

       To assign a class ID to the created cgroup, a file named _net_cls.classid_ has  to  be  created
       which  contains  the  class  ID to be assigned as a hexadecimal, 64bit wide number. The upper
       32bits are reserved for the major handle, the remaining hold the minor. So a class ID of e.g.
       **ff:be **has to be written like so: **0xff00be **(leading zeroes may be omitted).  To  continue  the
       above example, the following assigns class ID 1:2 to foobar cgroup:

              echo 0x10002 > /sys/fs/cgroup/net_cls/foobar/net_cls.classid

       Finally some PIDs can be assigned to the given cgroup:

              echo 1234 > /sys/fs/cgroup/net_cls/foobar/tasks
              echo 5678 > /sys/fs/cgroup/net_cls/foobar/tasks

       Now  by  simply attaching a **cgroup **filter to a **qdisc **makes packets from PIDs 1234 and 5678 be
       pushed into class 1:2.


## SEE ALSO
       [**tc**(8)](https://www.chedong.com/phpMan.php/man/tc/8/markdown), [**tc-ematch**(8)](https://www.chedong.com/phpMan.php/man/tc-ematch/8/markdown),
       the file _Documentation/cgroups/net_cls.txt_ of the Linux kernel tree

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