[Shell] Use ipfw to limit internet speed

limit

#!/bin/bash

# configuration
#host1 is for metadata, host2 is for data
host1="api.dropbox.com"
host2="api-content.dropbox.com"

# usage
if [ "$*" == "" ]; then
    echo "usage: $0 [restore|off|fast|medium|slow]"
    exit
fi

# remove any previous firewall rules
sudo ipfw list 10 > /dev/null 2>&1
if [ $? -eq 0 ]; then
    sudo ipfw delete 10 > /dev/null 2>&1
fi
sudo ipfw list 11 > /dev/null 2>&1
if [ $? -eq 0 ]; then
    sudo ipfw delete 11 > /dev/null 2>&1
fi
sudo ipfw list 12 > /dev/null 2>&1
if [ $? -eq 0 ]; then
    sudo ipfw delete 12 > /dev/null 2>&1
fi
sudo ipfw list 13 > /dev/null 2>&1
if [ $? -eq 0 ]; then
    sudo ipfw delete 12 > /dev/null 2>&1
fi

# process the command line option
if [ "$1" == "restore" ]; then
    echo "$host1 and $host2 are restored"
    exit
fi

if [ "$1" == "off" ]; then
    # add rules to deny any connections to configured host
    sudo ipfw add 10 deny tcp from $host1 to me
    sudo ipfw add 11 deny tcp from me to $host1
    sudo ipfw add 12 deny tcp from $host2 to me
    sudo ipfw add 13 deny tcp from me to $host2
    echo "$host1 and $host2 are denied"
else
    # create a pipe with limited bandwidth
    bw1="1Kbit"
    bw2="100Kbit"
    if [ "$1" == "fast" ]; then
        bw1="3Kbit"
        bw2="300Kbit"
    elif [ "$1" == "slow" ]; then
        bw1="10bit"
        bw2="1Kbit"
    fi
    sudo ipfw pipe 1 config bw $bw1
    sudo ipfw pipe 2 config bw $bw2

    # add rules to use bandwidth limited pipe 
    sudo ipfw add 10 pipe 1 tcp from $host1 to me
    sudo ipfw add 11 pipe 1 tcp from me to $host1
    sudo ipfw add 12 pipe 2 tcp from $host2 to me
    sudo ipfw add 13 pipe 2 tcp from me to $host2
    echo "$host1 and $host2 are limited to $bw1 and $bw2"
fi