README.md

slow

This bash script offers quick shortcuts to simulate slower network connections. It is useful when you need to simulate a wireless network on a Linux network server, especially when you are using a virtual machine guest on your local machine or in the cloud.

slow 3G                   # Slow network on default eth0 down to 3G wireless speeds
slow 3G -l 600ms -p 10%   # slow network on eth0 and setup latency to 600ms packetloss to 10%
slow reset                # Reset connection for default eth0 to normal
slow vsat --latency=500ms # Simulate satellite internet  with a high latency
slow dsl -b 1mbps         # Simulate DSL with a slower speed than the default
slow modem-56k -d eth0    # Simulate a 56k modem on the eth1 device. eth0 is unchanged.

Credits

Richard Bullington-McGuire [email protected] wrote the script inspired by a UI suggestion from Mike Schwartz [email protected].

Stack Overflow and Superuser questions that helped:

• http://stackoverflow.com/questions/402377/using-getopts-in-bash-shell-script-to-get-long-and-short-command-line-options/7680682#7680682
• http://superuser.com/questions/147156/simulating-a-low-bandwidth-high-latency-network-connection-on-linux

An Aptivate blog post lent some inspiration, as did this script for throttling bandwidth.

*fork version add implementation packet loss

license.txt

Copyright 2012 Modus Create, Inc.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

slow

#!/bin/bash
#
# slow
#
# Simulates a low bandwidth, high-latency network connection
#
# Requires a Linux operating system with the 'tc' traffic control tool
#
# Author: Richard Bullington-McGuire <[email protected]>
# Author: Mike Schwartz <[email protected]>
#
# Copyright 2012 Modus Create, Inc.
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject
# to the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
# Version Change
# 0.1 first version
# 0.2 implementation packet loss by aloysius
VERSION=0.2
device=eth0
bandwidth=100kbit
latency=350ms
packetloss=0%
command=slow
retcode=0
PATH=/sbin:/bin:/usr/sbin:/usr/bin

echorun() {
  echo -E '#' "$@"
  "$@"
}

if ! which tc > /dev/null; then
  echo "Aborting: No 'tc' iptables firewall traffic conditioner found" 1>&2
  echo "This requires the Linux iptables firewall." 1>&2
  exit 1
fi

if [ $EUID -ne 0 ]; then
  echo "Aborting: you must run this as root."
  exit 2
fi


# Option processing courtesy of Stack Overflow question
# http://stackoverflow.com/questions/402377/using-getopts-in-bash-shell-script-to-get-long-and-short-command-line-options/7680682#7680682
# Questioner: gagneet http://stackoverflow.com/users/35416/gagneet
# Answer: http://stackoverflow.com/a/9899366
# Answerer:  http://stackoverflow.com/users/375889/jakesandlund


while test $# -gt 0
do
  case $1 in

  # Normal option processing
    -h | --help)
      # usage and help
      command=help
      break
      ;;
    -v | --version)
      command=version
      break
      ;;
    -d | --device)
      shift
      device=$1
      ;;
    -b | --bandwidth)
      shift
      bandwidth=$1
      ;;
    -l | --latency)
      shift
      latency=$1
      ;;
    -p | --packetloss)
      shift
      packetloss=$1
      ;;
  # ...

  # Special cases
    --)
      break
      ;;
    --*)
      # error unknown (long) option $1
      ;;
    -?)
      # error unknown (short) option $1
      ;;
   # 
   # Shortcuts
       AMPS|amps)
         command=slow
         bandwidth=14kbit
         latency=250ms
         ;;
       EDGE|edge|2.5G|GPRS|gprs)
         command=slow
         bandwidth=50kbit
         latency=200ms
         ;;
       3G|3g)
         command=slow
         bandwidth=1000kbit
         latency=200ms
         ;;
       4G|4g)
         command=slow
         bandwidth=10000kbit
         latency=100ms
         ;;
       modem-0.1k|modem-110)
         command=slow
         bandwidth=110bps
         latency=350ms
         ;;
       modem-0.3k|modem-300)
         command=slow
         bandwidth=300bps
         latency=300ms
         ;;
       modem-1.2k|modem-1200)
         command=slow
         bandwidth=1200bps
         latency=280ms
         ;;
       modem-2.4k|modem-2400)
         command=slow
         bandwidth=2400bps
         latency=250ms
         ;;
       modem-9.6k|modem-9600)
         command=slow
         bandwidth=9600bps
         latency=200ms
         ;;
       modem-14.4k|modem-14400)
         command=slow
         bandwidth=14400bps
         latency=150ms
         ;;
       modem-28.8k|modem-28800)
         command=slow
         bandwidth=28800bps
         latency=150ms
         ;;
       modem-56k|modem-56000)
         command=slow
         bandwidth=56kbit
         latency=120ms
         ;;
       56k)
         command=slow
         bandwidth=56kbit
         latency=40ms
         ;;
       T1|t1)
         command=slow
         bandwidth=1500kbit
         latency=20ms
         ;;
       T3|t3)
         command=slow
         bandwidth=45mbps
         latency=10ms
         ;;
       DSL|dsl)
         command=slow
         bandwidth=2mbps
         latency=40ms
         ;;
       cablemodem)
         command=slow
         bandwidth=10mbps
         latency=20ms
         ;;
       wifi-a|wifi-g)
         command=slow
         bandwidth=54mbps
         latency=5ms
         ;;
       wifi-b)
         command=slow
         bandwidth=11mbps
         latency=10ms
         ;; 
       wifi-n)
         command=slow
         bandwidth=110mbps
         latency=2ms
         ;;
       vsat)
         command=slow
         bandwidth=5mbps
         latency=500ms
         ;;
       clear|reset)
         command=clear
         ;;
       status)
         command=status
         break
         ;;


  # FUN STUFF HERE:
  # Split apart combined short options
    -*)
      split=$1
      shift
      set -- $(echo "$split" | cut -c 2- | sed 's/./-& /g') "$@"
      continue
      ;;

  # Done with options
    *)
      break
      ;;
  esac

  # for testing purposes:
  echo "param $1"

  shift
done

echo "command=$command"
echo "bandwidth=$bandwidth"
echo "latency=$latency"

case $command in
  help)
    echo $0
    echo 'Usage: slow <network-type> [-d device] [-b bandwidth] [-l latency] [-p drop]'
    echo '       slow reset'
    echo '       slow status'
    echo
    echo '"network-type" type can be:'
    echo '  GPRS'
    echo '  GSM'
    echo '  EDGE'
    echo '  2.5G'
    echo '  GPRS'
    echo '  3G'
    echo '  4G'
    echo '  modem-2.4k'
    echo '  modem-9.6k'
    echo '  modem-14.4k'
    echo '  modem-28.8k'
    echo '  modem-56k'
    echo '  56k'
    echo '  T1'
    echo '  T3'
    echo '  DSL'
    echo '  cablemodem'
    echo '  wifi-a'
    echo '  wifi-b'
    echo '  wifi-g'
    echo '  wifi-n'
    echo '  eth-10'
    echo '  eth-100'
    echo '  eth-1000'
    echo '  vsat'
    echo '  vsat-busy'
    ;;
  version)
    # version info
    echo "slow version $VERSION"
    echo "Copyright (c) 2012 Modus Create"
    ;;
  slow)
    # Credit to Superuser for the basic commands that run this 
    # Question: http://superuser.com/questions/147156/simulating-a-low-bandwidth-high-latency-network-connection-on-linux
    # Author: Justin L. http://superuser.com/users/38740/justin-l
    # Answer: http://superuser.com/a/147434/159810
    if  tc qdisc show dev $device | fgrep -q "qdisc htb 1: root"; then
      verb=change
      echo "Changing existing queuing discipline"
    else
      verb=add
      echo "Adding new queuing discipline"
      echorun tc qdisc $verb dev $device root handle 1: htb default 12
    fi
    if ! lsmod | fgrep -q "sch_netem"; then
      modprobe sch_netem
    fi
    echorun tc class $verb dev $device parent 1:1 classid 1:12 htb rate $bandwidth ceil $bandwidth  &&
    echorun tc qdisc $verb dev $device parent 1:12 netem delay $latency loss $packetloss
    retcode=$?
    ;;
  clear)
    echo resetting queueing discipline
    echorun tc qdisc del dev $device root
    retcode=$?
    ;;
  status)
    echorun tc qdisc
    retcode=$?
    ;;
esac

exit $retcode