Toggle masquerading as a domain, forwarding configurable port to 80 (OSX and Linux)

masquerade.sh

#!/bin/bash

PORT="8000"

usage() {
    cat << EOF
    usage: $0 host [port]
EOF
}

redirect() {
    if [ $OS = "Linux" ]; then
        sudo iptables -t nat -A OUTPUT -d $HOST -p tcp --dport 80 -j REDIRECT --to-ports $PORT
    else
        sudo ipfw add 100 fwd $HOST,$PORT tcp from any to any 80 in
    fi
    echo $cmd
}

flush() {
    if [ $OS = "Linux" ]; then
        sudo iptables -F
        sudo iptables -t nat -F
    else
        echo "y" | sudo ipfw flush
    fi
}

if [ -z "$1" ]; then
    usage
    exit 1
fi

if [ -n "$2" ]; then
    PORT="$2"
fi

HOST="$1"

if [ -f "/etc/hosts.masq" ]; then
    echo "Turning off masquerading for $HOST"
    sudo rm /etc/hosts.masq
    flush
    cat /etc/hosts |grep -v "127.0.0.1 $HOST" > /tmp/hosts
    sudo mv /tmp/hosts /etc/
else
    echo "Turning ON masquerading for $HOST"
    echo "127.0.0.1 $HOST" | sudo tee -a /etc/hosts > /dev/null
    redirect
    sudo touch /etc/hosts.masq
fi