#!/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