Port forwarding for incoming port using iptables

iptables-nat-multiport.sh

#!/bin/bash
# The MIT License (MIT)
#
# Copyright (c) 2016 Faizal Sadri
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

CMD="$(dirname $0)/$(basename $0)"
HOST_IP=10.0.2.146
MULTIPORT=80,443
HOST_ETH=eth0
REMOTE_IP=10.0.2.169

# iptables -t nat -A PREROUTING -p tcp -m multiport --dports 80,443 -j DNAT --to-destination 192.168.1.175

RULE1=`iptables -t nat -C POSTROUTING -j MASQUERADE >/dev/null 2>&1`
RULE2=`iptables -t nat -C PREROUTING -p tcp -i $HOST_ETH -d $HOST_IP -m multiport --dports $MULTIPORT -j DNAT --to-destination $REMOTE_IP >/dev/null 2>&1`
FLAG=`echo $?`

function port() {
    case $1 in
        'enable')
            echo 1 > /proc/sys/net/ipv4/ip_forward

            if [ $FLAG -ne 0 ]; then
                iptables -t nat -A POSTROUTING -j MASQUERADE
                iptables -t nat -A PREROUTING -p tcp -i $HOST_ETH -d $HOST_IP -m multiport --dports $MULTIPORT -j DNAT --to-destination $REMOTE_IP 
                echo "Port $MULTIPORT enabled for remote port."
            else
                echo "Rule Exist"
            fi
            ;;
        'disable')
            echo 0 > /proc/sys/net/ipv4/ip_forward
            if [ $FLAG -eq 0 ]; then
                iptables -t nat -D POSTROUTING -j MASQUERADE
                iptables -t nat -D PREROUTING -p tcp -i $HOST_ETH -d $HOST_IP -m multiport --dports $MULTIPORT -j DNAT --to-destination $REMOTE_IP 
                echo "Port $MULTIPORT removed."
            fi
            ;;
        'status')
                STATUS=`iptables -t nat -L | grep DNAT`

                if [ -z "$STATUS" ]
                then
                    echo "Port $MULTIPORT not enabled."
                else
                    echo $STATUS
                fi
            ;;
        *)
            echo -e "Argument not found :\n Wrong syntax < $CMD $1 >"
            ;;
    esac
}

if [ $# -ne 1 ]; then
    echo "$CMD enable|disable"
else
    port $1
fi

iptables-nat.sh

#!/bin/bash
# The MIT License (MIT)
#
# Copyright (c) 2016 Faizal Sadri
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

CMD="$(dirname $0)/$(basename $0)"
HOST_IP=192.168.1.20
HOST_PORT=9432
HOST_ETH=eth0
REMOTE_IP=192.168.1.24
REMOTE_PORT=5432

RULE1=`iptables -t nat -C POSTROUTING -j MASQUERADE >/dev/null 2>&1`
RULE2=`iptables -t nat -C PREROUTING -p tcp -i $HOST_ETH -d $HOST_IP --dport $HOST_PORT -j DNAT --to $REMOTE_IP:$REMOTE_PORT >/dev/null 2>&1`
FLAG=`echo $?`

function port() {
    case $1 in
        'enable')
            echo 1 > /proc/sys/net/ipv4/ip_forward

            if [ $FLAG -ne 0 ]; then
                iptables -t nat -A POSTROUTING -j MASQUERADE
                iptables -t nat -A PREROUTING -p tcp -i $HOST_ETH -d $HOST_IP --dport $HOST_PORT -j DNAT --to $REMOTE_IP:$REMOTE_PORT
                echo "Port $HOST_PORT enabled for remote port."
            else
                echo "Rule Exist"
            fi
            ;;
        'disable')
            echo 0 > /proc/sys/net/ipv4/ip_forward
            if [ $FLAG -eq 0 ]; then
                iptables -t nat -D POSTROUTING -j MASQUERADE
                iptables -t nat -D PREROUTING -p tcp -i $HOST_ETH -d $HOST_IP --dport $HOST_PORT -j DNAT --to $REMOTE_IP:$REMOTE_PORT
                echo "Port $HOST_PORT removed."
            fi
            ;;
        *)
            echo -e "Argument not found :\n Wrong syntax < $CMD $1 >"
            ;;
    esac
}

if [ $# -ne 1 ]; then
    echo "$CMD enable|disable"
else
    port $1
fi

localport-forward-external.sh

#!/bin/bash
# The MIT License (MIT)
#
# Copyright (c) 2016 Faizal Sadri
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

CMD="$(dirname $0)/$(basename $0)"
HOST_IP=127.0.0.1
HOST_PORT=5432
HOST_ETH=lo
REMOTE_IP=10.0.2.170
REMOTE_PORT=5432

RULE1=`iptables -t nat -C POSTROUTING -j MASQUERADE >/dev/null 2>&1`
RULE2=`iptables -t nat -C OUTPUT -p tcp -o $HOST_ETH -d $HOST_IP --dport $HOST_PORT -j DNAT --to-destination $REMOTE_IP:$REMOTE_PORT >/dev/null 2>&1`
FLAG=`echo $?`

function port() {
    case $1 in
        'enable')
            sysctl -w net.ipv4.ip_forward=1
            sysctl -w net.ipv4.conf.all.route_localnet=1
            if [ $FLAG -ne 0 ]; then
                iptables -t nat -A POSTROUTING -j MASQUERADE
                iptables -t nat -A OUTPUT -p tcp -o $HOST_ETH -d $HOST_IP --dport $HOST_PORT -j DNAT --to-destination $REMOTE_IP:$REMOTE_PORT
                echo "Port $HOST_PORT enabled for remote port."
            else
                echo "Rule Exist"
            fi
            ;;
        'disable')
            sysctl -w net.ipv4.ip_forward=0
            sysctl -w net.ipv4.conf.all.route_localnet=0
            if [ $FLAG -eq 0 ]; then
                iptables -t nat -D POSTROUTING -j MASQUERADE
                iptables -t nat -D OUTPUT -p tcp -o $HOST_ETH -d $HOST_IP --dport $HOST_PORT -j DNAT --to-destination $REMOTE_IP:$REMOTE_PORT
                echo "Port $HOST_PORT removed."
            fi
            ;;
        'status')
            iptables -t nat -L | grep DNAT
            ;;
        *)
            echo -e "Argument not found :\n Wrong syntax < $CMD $1 >"
            ;;
    esac
}

if [ $# -ne 1 ]; then
    echo "$CMD enable|disable|status"
else
    port $1
fi