Create proxies in iptables

proxy

#!/bin/bash
#
# Copyright Thom Seddon 2015
# MIT
#

if [ "$1" == "" ] || [ "$1" == "help" ]; then
  echo "Usage: ~/.proxy <option>"
  echo
  echo "  Options: "
  echo "    create: <inport> <outport> [protocol=tcp]"
  echo "    delete: <num>"
  echo "    help"
  echo "    show"
  exit 1
fi

if [ "$(id -u)" != "0" ]; then
  echo "Must run with sudo"
  exit 1
fi

if [ "$1" == "create" ]; then
  if [ "$3" == "" ]; then
    echo "Wrong params"
    exit 1
  fi  

  if [ "$4" == "" ]; then
    proto=tcp
  else
    proto=$4
  fi  

  inip=127.0.0.1
  inport=$2
  outip=127.0.0.1
  outport=$3

  #iptables -t nat -A PREROUTING --dst $inip -p tcp --dport $inport -j DNAT --to-destination $outip:$outport
  #iptables -t nat -A POSTROUTING -p tcp --dst $outip --dport $outport -j SNAT --to-source $inip
  #iptables -t nat -A OUTPUT --dst $inip -p tcp --dport $inport -j DNAT --to-destination $outip:$outport

  iptables -t nat -A PREROUTING -p $proto --dport $inport -j DNAT --to-destination $outip:$outport
  iptables -t nat -A POSTROUTING -p $proto --dst $outip --dport $outport -j SNAT --to-source $inip
  iptables -t nat -A OUTPUT -p $proto --dport $inport -j DNAT --to-destination $outip:$outport
fi

if [ "$1" == "delete" ]; then
  if [ "$2" == "" ]; then
    echo "Wrong params"
    exit 1
  fi  

  iptables -t nat -D PREROUTING $2
  iptables -t nat -D POSTROUTING $2
  iptables -t nat -D OUTPUT $2
fi

if [ "$1" == "show" ]; then
  iptables -t nat -vnL --line-numbers
fi