iptables_redirect.sh

#!/bin/bash
#===============================================================================
#
# FILE: iptable_redirect_port.sh
#
# USAGE: ./iptable_redirect_port.sh PROTOCOL SERVER_PORT DHOST DPORT [-d]
#
# DESCRIPTION: Redirect traffic to another server.
#
# OPTIONS: —
# REQUIREMENTS: —
# BUGS: —
# NOTES: —
# AUTHOR: Zhang Guangtong <zhgt123@gmail.com>
# ORGANIZATION:
# CREATED: 2015年08月05日 10:07
# REVISION: —
#===============================================================================

# example:
#iptables -t nat -A PREROUTING -p tcp –dport 1111 -j DNAT –to-destination 192.168.1.10:8022
#iptables -t nat -A POSTROUTING -d 192.168.1.10 -p tcp –dport 8022 -j MASQUERADE

redirect_port()
{
PROTOCOL=$1
SERVER_PORT=$2
DHOST=$3
DPORT=$4
iptables -t nat -A PREROUTING -p $PROTOCOL –-dport $SERVER_PORT -j DNAT –to-destination $DHOST:$DPORT
iptables -I FORWARD -d $DHOST -p $PROTOCOL –-dport $DPORT -j ACCEPT
iptables -I FORWARD -s $DHOST -p $PROTOCOL –-sport $DPORT -j ACCEPT
iptables -t nat -A POSTROUTING -d $DHOST -p $PROTOCOL –-dport $DPORT -j MASQUERADE
}
clean_redirect_port()
{
PROTOCOL=$1
SERVER_PORT=$2
DHOST=$3
DPORT=$4
iptables -t nat -D PREROUTING -p $PROTOCOL –-dport $SERVER_PORT -j DNAT –to-destination $DHOST:$DPORT
iptables -D FORWARD -d $DHOST -p $PROTOCOL –-dport $DPORT -j ACCEPT
iptables -D FORWARD -s $DHOST -p $PROTOCOL –-sport $DPORT -j ACCEPT
iptables -t nat -D POSTROUTING -d $DHOST -p $PROTOCOL –-dport $DPORT -j MASQUERADE
}
usage()
{
echo "Usage: $0 PROTOCOL SERVER_PORT DHOST DPORT [-d]"
echo ""
echo "example1:"
echo " $0 tcp 443 192.168.1.20 8043"
echo " Visit this host on port 443 equal vist 192.168.1.20:443"
echo "example2:"
echo " $0 tcp 443 192.168.1.20 8043 -d"
echo " Clean previous rules"
echo "Notes: please make sure net.ipv4.ip_forward=1 in /etc/sysctl.conf and run \"sysctl -p\" to apply changes"
}

if [ $# -lt 4 ]; then
usage
exit
fi
if [ "$5" == "-d" ]; then
clean_redirect_port "$@"
else
redirect_port "$@"
fi