cgroup - control group based traffic control filter tc " " filter " ... " cgroup " [ " match EMATCH_TREE " ] [ " action ACTION_SPEC " ]" 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.

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 .

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": 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: Finally some PIDs can be assigned to the given cgroup: Now by simply attaching a cgroup filter to a qdisc makes packets from PIDs 1234 and 5678 be pushed into class 1:2. tc (8), tc-ematch (8),

the file Documentation/cgroups/net_cls.txt of the Linux kernel tree