Traffic shaping with tc

Sometimes it's necessary to limit traffic bandwidth from and to a container. You can do it using ordinary tc tool.

Very nice post, good luck! ;-)

Limiting outgoing bandwidth

We can limit container outgoing bandwidth by setting the tc filter on eth0.

DEV=eth0
tc qdisc del dev $DEV root
tc qdisc add dev $DEV root handle 1: cbq avpkt 1000 bandwidth 100mbit
tc class add dev $DEV parent 1: classid 1:1 cbq rate 256kbit allot 1500 prio 5 bounded isolated
tc filter add dev $DEV parent 1: protocol ip prio 16 u32 match ip src X.X.X.X flowid 1:1
tc qdisc add dev $DEV parent 1:1 sfq perturb 10

X.X.X.X is an IP address of container.

Limiting incoming bandwidth

This can be done by setting the tc filter on venet0:

DEV=venet0
tc qdisc del dev $DEV root
tc qdisc add dev $DEV root handle 1: cbq avpkt 1000 bandwidth 100mbit
tc class add dev $DEV parent 1: classid 1:1 cbq rate 256kbit allot 1500 prio 5 bounded isolated
tc filter add dev $DEV parent 1: protocol ip prio 16 u32 match ip dst X.X.X.X flowid 1:1
tc qdisc add dev $DEV parent 1:1 sfq perturb 10

Note that X.X.X.X is an IP address of container.

Limiting CT to HN talks

As you can see, two filters above don't limit container to HN talks. I mean a container can emit as much traffic as it wishes. To make such a limitation from the HN, it is necessary to use tc police on venet0:

DEV=venet0
tc filter add dev $DEV parent 1: protocol ip prio 20 u32 match u32 1 0x0000 police rate 2kbit buffer 10k drop flowid :1

Limiting packets per second rate from container

To prevent dos atacks from the container you can limit packets per second rate using iptables.

DEV=eth0
iptables -I FORWARD 1 -o $DEV -s X.X.X.X -m limit --limit 200/sec -j ACCEPT
iptables -I FORWARD 2 -o $DEV -s X.X.X.X -j DROP

Here X.X.X.X is an IP address of container.

An alternate approch using HTB

For details refer to the HTB Home Page

#!/bin/sh
#
# Incoming traffic control
#
CT_IP1=$1
CT_IP2=$2
DEV=venet0
#
tc qdisc del dev $DEV root
#
tc qdisc add dev $DEV root handle 1: htb default 10
#
tc class add dev $DEV parent 1: classid 1:1 htb rate 100mbit burst 15k
tc class add dev $DEV parent 1:1 classid 1:10 htb rate 10mbit ceil 10mbit burst 15k
tc class add dev $DEV parent 1:1 classid 1:20 htb rate 20mbit ceil 20mbit burst 15k
tc class add dev $DEV parent 1:1 classid 1:30 htb rate 30mbit ceil 30mbit burst 15k
#
tc qdisc add dev $DEV parent 1:10 handle 10: sfq perturb 10
tc qdisc add dev $DEV parent 1:20 handle 20: sfq perturb 10
tc qdisc add dev $DEV parent 1:30 handle 30: sfq perturb 10
#
if [ ! -z $CT_IP1 ]; then
    tc filter add dev $DEV protocol ip parent 1:0 prio 1 u32 match ip dst "$CT_IP1" flowid 1:20 
fi
if [ ! -z $CT_IP2 ]; then
    tc filter add dev $DEV protocol ip parent 1:0 prio 1 u32 match ip dst "$CT_IP2" flowid 1:30 
fi
#
echo;echo "tc configuration for $DEV:"
tc qdisc show dev $DEV
tc class show dev $DEV
tc filter show dev $DEV
#
# Outgoing traffic control
#
DEV=eth0
#
tc qdisc del dev $DEV root
#
tc qdisc add dev $DEV root handle 1: htb default 10
#
tc class add dev $DEV parent 1: classid 1:1 htb rate 100mbit burst 15k
tc class add dev $DEV parent 1:1 classid 1:10 htb rate 10mbit ceil 10mbit burst 15k
tc class add dev $DEV parent 1:1 classid 1:20 htb rate 20mbit ceil 20mbit burst 15k
tc class add dev $DEV parent 1:1 classid 1:30 htb rate 30mbit ceil 30mbit burst 15k
#
tc qdisc add dev $DEV parent 1:10 handle 10: sfq perturb 10
tc qdisc add dev $DEV parent 1:20 handle 20: sfq perturb 10
tc qdisc add dev $DEV parent 1:30 handle 30: sfq perturb 10
#
if [ ! -z $CT_IP1 ]; then
    tc filter add dev $DEV protocol ip parent 1:0 prio 1 u32 match ip src "$CT_IP1" flowid 1:20
fi
if [ ! -z $CT_IP2 ]; then
    tc filter add dev $DEV protocol ip parent 1:0 prio 1 u32 match ip src "$CT_IP2" flowid 1:30
fi
#
echo;echo "tc configuration for $DEV:"
tc qdisc show dev $DEV
tc class show dev $DEV
tc filter show dev $DEV

External links

• Linux Advanced Routing & Traffic Control HOWTO