---
name: "tc-cgroup"
section: "8"
platform: "linux"
package: "iproute2"
version: "7.3.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/tc-cgroup"
---

# tc-cgroup(8)

control group based traffic control filter

## 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. Obviously, 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)](/tc-ematch/8.md) 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)](/tc/8.md), [**tc-ematch**(8)](/tc-ematch/8.md),\
 the file *Documentation/cgroups/net\_cls.txt* of the Linux kernel tree