Network throttling for OSX

throttle

#!/bin/bash
#
# Throttles your Mac OS X internet connection on one port.
# Handy for testing

set -e

RATE=15KByte/s
PORT=80
PIPE_NUMBER=1
ACTION=

function usage()
{
    echo $1
    echo
    echo "Usage: `basename "$0"` <action> [options]"
    echo "  Action:"
    echo "     on"
    echo "     off"
    echo
    echo "  Options:"
    echo "  --rate <rate>"
    echo "      Example: --rate 100KByte/s"
    echo "  --port <port> (default is 80 if you don't specify --port)"
    echo "      Example: --port 80"
    exit 1
}

function turn_throttling_off()
{
    echo "Turning off network throttling"
    sudo ipfw delete $PIPE_NUMBER || echo "Is it already turned off?"
}

function turn_throttling_on()
{
    echo "Throttling traffic to port $PORT: $RATE"
    sudo ipfw pipe $PIPE_NUMBER config bw $RATE >/dev/null
    sudo ipfw add $PIPE_NUMBER pipe $PIPE_NUMBER src-port $PORT >/dev/null
    sudo ipfw add $PIPE_NUMBER pipe $PIPE_NUMBER dst-port $PORT >/dev/null
}

# Grab command line args:
while [ -n "$1" ]; do
  case $1 in
    --rate)
      shift
      RATE=$1
      ;;
    --port)
      shift
      PORT=$1
      ;;
    *)
      ACTION=$1
  esac
  shift
done

[ -n "$ACTION" ] || usage "Error: no action specified"

case $ACTION in
  on)
    turn_throttling_off >/dev/null 2>&1 # in case it's already on, clear out the old one
    turn_throttling_on
    ;;
  off)
    turn_throttling_off
    ;;
  *)
    usage "Error: Bad action specified"
    ;;
esac