.TH "Cgroup classifier in tc" 8 " 21 Oct 2015" "iproute2" "Linux"

.SH NAME

cgroup \- control group based traffic control filter

.SH SYNOPSIS

.in +8

.ti -8

.BR tc " " filter " ... " cgroup " [ " match

.IR EMATCH_TREE " ] [ "

.B action

.IR ACTION_SPEC " ]"

.SH DESCRIPTION

This filter serves as a hint to

.B 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.

.SH OPTIONS

.TP

.BI action " ACTION_SPEC"

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

.TP

.BI match " EMATCH_TREE"

Match packets using the extended match infrastructure. See

.BR tc-ematch (8)

for a detailed description of the allowed syntax in

.IR EMATCH_TREE .

.SH 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":

.RS

.EX

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

.EE

.RE

To assign a class ID to the created cgroup, a file named

.I 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.

.B ff:be

has to be written like so:

.B 0xff00be

(leading zeroes may be omitted). To continue the above example, the following

assigns class ID 1:2 to foobar cgroup:

.RS

.EX

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

.EE

.RE

Finally some PIDs can be assigned to the given cgroup:

.RS

.EX

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

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

.EE

.RE

Now by simply attaching a

.B cgroup

filter to a

.B qdisc

makes packets from PIDs 1234 and 5678 be pushed into class 1:2.

.SH SEE ALSO

.BR tc (8),

.BR tc-ematch (8),

.br

the file

.I Documentation/cgroups/net_cls.txt

of the Linux kernel tree