#!/bin/bash

chan=$1
chan_pre=$chan'_pre'
chan_forward=$chan'_forward'
chan_post=$chan'_post'
from=$2
from_port=$3
to=$4
to_port=$5

if ! [ -n "$1" ]; then
  echo "iptable chan not found" >&1
  exit 1
fi

if ! [ -n "$2" ]; then
  echo "from host not found" >&1
  exit 1
fi
if ! [ -n "$3" ]; then
  echo "from port not found" >&1
  exit 1
fi

if ! [ -n "$4" ]; then
  echo "destination host not found" >&1
  exit 1
fi

if ! [ -n "$5" ]; then
  echo "destination port not found" >&1
  exit 1
fi

echo "redirect ${from}:${from_port} to ${to}:${to_port}"

## 清空 引用
sudo iptables -t nat  -nvL PREROUTING --line-number | awk -F ' ' 'BEGIN{c=0} /'${chan_pre}'/ {printf "%s %s %s\n",c, $1,$4;system("sudo iptables -t nat -D PREROUTING "$1-c);c++}'
sudo iptables -t filter  -nvL FORWARD --line-number | awk -F ' ' 'BEGIN{c=0} /'${chan_forward}'/ {printf "%s %s %s\n",c, $1,$4;system("sudo iptables -t filter -D FORWARD "$1-c);c++}'
sudo iptables -t nat  -nvL POSTROUTING --line-number | awk -F ' ' 'BEGIN{c=0} /'${chan_post}'/ {printf "%s %s %s\n",c, $1,$4;system("sudo iptables -t nat -D POSTROUTING "$1-c);c++}'

## 清空自定义链
sudo iptables -t nat -F $chan_pre
sudo iptables -t filter -F $chan_forward
sudo iptables -t nat -F $chan_post
## 删除自定义链
sudo iptables -t nat -X $chan_pre
sudo iptables -t filter -X $chan_forward
sudo iptables -t nat -X $chan_post

## 创建自定义链
sudo iptables -t nat -N $chan_pre
sudo iptables -t filter -N $chan_forward
sudo iptables -t nat -N $chan_post

sudo iptables -t nat -p tcp -d $from --dport $from_port -j DNAT --to $to:$to_port -I $chan_pre
sudo iptables -t nat -p udp -d $from --dport $from_port -j DNAT --to $to:$to_port -I $chan_pre

sudo iptables -t filter -d $to -j ACCEPT -I $chan_forward

sudo iptables -t nat -p tcp -d $to --dport $to_port -j SNAT --to $from -I $chan_post
sudo iptables -t nat -p udp -d $to --dport $to_port -j SNAT --to $from -I $chan_post

## 引用新链
sudo iptables -t nat -I PREROUTING -j $chan_pre
sudo iptables -t filter -I FORWARD -j $chan_forward
sudo iptables -t nat -I POSTROUTING -j $chan_post

#iptables -L
sudo iptables -t nat  -nvL $chan_pre --line-number
sudo iptables -t nat -nvL PREROUTING --line-number
echo "\n\n"
sudo iptables -t filter  -nvL $chan_forward --line-number
sudo iptables -t filter  -nvL FORWARD --line-number
echo "\n\n"
sudo iptables -t nat  -nvL $chan_post --line-number
sudo iptables -t nat -nvL POSTROUTING  --line-number