Симулятор плохой сети

Понадобилось симулировать плохой канал связи, с потерями пакетов, задержками, в общем GPRS. Быстро нашлось решение: http://www.uponmyshoulder.com/blog/2013/simulating-bad-network-conditions-on-linux/

Пригодится ещё.

#!/bin/bash

#

# tc uses the following units when passed as a parameter.

# kbps: Kilobytes per second

# mbps: Megabytes per second

# kbit: Kilobits per second

# mbit: Megabits per second

# bps: Bytes per second

# Amounts of data can be specified in:

# kb or k: Kilobytes

# mb or m: Megabytes

# mbit: Megabits

# kbit: Kilobits

# To get the byte figure from bits, divide the number by 8 bit

#

#

# Name of the traffic control command.

TC=/sbin/tc

# The network interface we're planning on limiting bandwidth.

IF=eth0 # Interface

# Latency

LAT_1=200ms # Base latency

LAT_2=50ms # Plus or minus

LAT_3=25% # Based on previous packet %

# Dropping packets

DROP_1=5% # Base probability

DROP_2=25% # Based on previous packet %

# Bandwidth

DNLD=50kbps # DOWNLOAD Limit

UPLD=50kbps # UPLOAD Limit

# IP address of the machine we are controlling

IP=192.168.122.33 # Host IP

# Filter options for limiting the intended interface.

U32="$TC filter add dev $IF protocol ip parent 1:0 prio 1 u32"

start() {

# We'll use Hierarchical Token Bucket (HTB) to shape bandwidth.

# For detailed configuration options, please consult Linux man

# page.

$TC qdisc add dev $IF root handle 2: netem delay $LAT_1 $LAT_2 $LAT_3 loss $DROP_1 $DROP_2

$TC qdisc add dev $IF parent 2: handle 1: htb default 30

$TC class add dev $IF parent 1: classid 1:1 htb rate $DNLD

$TC class add dev $IF parent 1: classid 1:2 htb rate $UPLD

$U32 match ip dst $IP/32 flowid 1:1

$U32 match ip src $IP/32 flowid 1:2

# The first line creates the root qdisc, and the next three lines

# create three child qdisc that are to be used to shape download

# and upload bandwidth.

#

# The 5th and 6th line creates the filter to match the interface.

# The 'dst' IP address is used to limit download speed, and the

# 'src' IP address is used to limit upload speed.

}

stop() {

# Stop the bandwidth shaping.

$TC qdisc del dev $IF root

}

restart() {

# Self-explanatory.

stop

sleep 1

start

}

show() {

# Display status of traffic control status.

$TC -s qdisc ls dev $IF

}

case "$1" in

start)

echo -n "Starting bandwidth shaping: "

start

echo "done"

;;

stop)

echo -n "Stopping bandwidth shaping: "

stop

echo "done"

;;

restart)

echo -n "Restarting bandwidth shaping: "

restart

echo "done"

;;

show)

echo "Bandwidth shaping status for $IF:"

show

echo ""

;;

*)

pwd=$(pwd)

echo "Usage: tc.bash {start|stop|restart|show}"

;;

esac

exit 0