Primer prototipo LoadBalancer con IPtables

El siguiente script en bash es el primer prototipo de LoadBalancer para un servicio TCP en dos o mas servidores simultaneamente utilizando iptables.

#!/bin/bash
local_ip="10.10.50.81"

ip1="10.10.96.50"
ip2="10.10.50.106"
tcp_port="80"


#Se valida que los servicios esten disponibles
nmap $ip1 -p $tcp_port | grep -i open >> /dev/null
service1=$?
nmap $ip2 -p $tcp_port | grep -i open >> /dev/null
service2=$?
let status=$service1+$service2
echo "Valor: $status"
let remakerules=10

while [ 0 -eq 0 ]; do

        if [ "$remakerules" != "$status" ]; then
                # You need these system settings.
                echo 1 > /proc/sys/net/ipv4/ip_forward
                for f in /proc/sys/net/ipv4/conf/*/rp_filter ; do echo 1 > $f ; done

                # Clear iptables/netfilter settings.
                iptables -F
                iptables -X
                iptables -t nat -F
                iptables -t nat -X
                iptables -t filter -F
                iptables -t filter -X
                iptables -t mangle -F
                iptables -t mangle -X


                iptables -P INPUT ACCEPT
                iptables -P OUTPUT ACCEPT
                iptables -P FORWARD ACCEPT
                iptables -t nat -P PREROUTING ACCEPT
                iptables -t nat -P POSTROUTING ACCEPT

                if [ "$service1" == "0" -a "$service2" == "0" ]; then
                        #Los dos servicios estan disponibles
                        iptables -t nat -A PREROUTING -p tcp -d $local_ip --dport $tcp_port -m state --state NEW -m statistic --mode random --probability .5 -j DNAT --to $ip1:$tcp_port
                        iptables -t nat -A PREROUTING -p tcp -d $local_ip --dport $tcp_port -m state --state NEW -m statistic --mode random --probability .5 -j DNAT --to $ip2:$tcp_port
                else
                        if [ "$service2" == "0" ]; then
                                #Unicamente el servicio2 esta arriba
                                iptables -t nat -A PREROUTING -p tcp -d $local_ip --dport $tcp_port -m state --state NEW -m statistic --mode nth --every 1 --packet 0 -j DNAT --to $ip2:$tcp_port
                        else
                                if [ "$service1" == "0" ]; then
                                        #Unicamente el servicio1 esta arriba
                                        iptables -t nat -A PREROUTING -p tcp -d $local_ip --dport $tcp_port -m state --state NEW -m statistic --mode nth --every 1 --packet 0 -j DNAT --to $ip1:$tcp_port
                                else
                                        echo "CRITICAL: Los dos Servicios estan abajo"
                                fi
                        fi
                fi


                iptables -A INPUT -j ACCEPT
                iptables -A OUTPUT -j ACCEPT
                iptables -A FORWARD -j ACCEPT
                iptables -A INPUT -j LOG --log-prefix "iptables: " --log-level 4
                iptables -A OUTPUT -j LOG --log-prefix "iptables: " --log-level 4
                iptables -A FORWARD -j LOG --log-prefix "iptables: " --log-level 4

                iptables -t nat -A POSTROUTING  -j MASQUERADE
                echo "Cambio de reglas..."
        fi

        #sleep 1200
        sleep 1

        #Se valida que los servicios esten disponibles
        nmap $ip1 -p $tcp_port | grep -i open >> /dev/null
        service1=$?
        nmap $ip2 -p $tcp_port | grep -i open >> /dev/null
        service2=$?
        let remakerules=$status
        let status=$service1+$service2
        echo "Valor: $status"

done