1 =========================
2 Network classifier cgroup
3 =========================
4 
5 The Network classifier cgroup provides an interface to
6 tag network packets with a class identifier (classid).
7 
8 The Traffic Controller (tc) can be used to assign
9 different priorities to packets from different cgroups.
10 Also, Netfilter (iptables) can use this tag to perform
11 actions on such packets.
12 
13 Creating a net_cls cgroups instance creates a net_cls.classid file.
14 This net_cls.classid value is initialized to 0.
15 
16 You can write hexadecimal values to net_cls.classid; the format for these
17 values is 0xAAAABBBB; AAAA is the major handle number and BBBB
18 is the minor handle number.
19 Reading net_cls.classid yields a decimal result.
20 
21 Example::
22 
23 	mkdir /sys/fs/cgroup/net_cls
24 	mount -t cgroup -onet_cls net_cls /sys/fs/cgroup/net_cls
25 	mkdir /sys/fs/cgroup/net_cls/0
26 	echo 0x100001 >  /sys/fs/cgroup/net_cls/0/net_cls.classid
27 
28 - setting a 10:1 handle::
29 
30 	cat /sys/fs/cgroup/net_cls/0/net_cls.classid
31 	1048577
32 
33 - configuring tc::
34 
35 	tc qdisc add dev eth0 root handle 10: htb
36 	tc class add dev eth0 parent 10: classid 10:1 htb rate 40mbit
37 
38 - creating traffic class 10:1::
39 
40 	tc filter add dev eth0 parent 10: protocol ip prio 10 handle 1: cgroup
41 
42 configuring iptables, basic example::
43 
44 	iptables -A OUTPUT -m cgroup ! --cgroup 0x100001 -j DROP
45