tc-cgroup(8) — Linux manual page

Cgroup classifier in tc(8)        Linux        Cgroup classifier in tc(8)

NAME         top

       cgroup - control group based traffic control filter

SYNOPSIS         top

       tc filter ... cgroup [ match EMATCH_TREE ] [ action ACTION_SPEC ]

DESCRIPTION         top

       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. Obviously, it is
       useful for locally generated packets only.

OPTIONS         top

       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) for a detailed description of the allowed
              syntax in EMATCH_TREE.

EXAMPLES         top

       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         top

       tc(8), tc-ematch(8),
       the file Documentation/cgroups/net_cls.txt of the Linux kernel
       tree

COLOPHON         top

       This page is part of the iproute2 (utilities for controlling
       TCP/IP networking and traffic) project.  Information about the
       project can be found at 
       ⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
       If you have a bug report for this manual page, send it to
       netdev@vger.kernel.org, shemminger@osdl.org.  This page was
       obtained from the project's upstream Git repository
       ⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
       2025-08-11.  (At that time, the date of the most recent commit
       that was found in the repository was 2025-08-08.)  If you discover
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       COLOPHON (which is not part of the original manual page), send a
       mail to man-pages@man7.org

iproute2                        21 Oct 2015    Cgroup classifier in tc(8)

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