#!/bin/bash

# Frequenza in secondi con cui fare il check delle connessioni
SLEEPTIME=10

# IP o host esterno da pingare per effettuare le prove
TESTIP=www.google.com

# Timeout del ping in secondi
TIMEOUT=2

# Interfacce
EXTIF1=eth1
EXTIF2=eth2

# Indirizzi IP delle interfacce
IP1=192.168.1.7
IP2=192.168.0.7

# Gateway delle interfacce
GW1=192.168.1.1
GW2=192.168.0.1

# Weights del router. Nella mia guida erano entrami ad 1 per fare il round robin delle connessioni:
# Guarda questa riga: ip route add default scope global nexthop via $P1 dev $IF1 weight 1 nexthop via $P2 dev $IF2 weight 1
# Presente nell'articolo http://ideafactory.it/debian/iproute-load-balance-verso-2-gateway.html
W1=1
W2=1

# Nome dei provider utilizzati
NAME1=ngi
NAME2=fastweb

# Numero di ripetizioni di successo o di fallimento prima di cambiare lo stato alla connessione
SUCCESSREPEATCOUNT=4
FAILUREREPEATCOUNT=1

### NON MODIFICARE DA QUI IN GIU'

# Ultimo stato del link di connessione. NON MODIFICARE!
LLS1=1
LLS2=1

# Esito dell'ultimo ping. NON MODIFICARE!
LPS1=1
LPS2=1

# Esito del ping corrente. NON MODIFICARE!
CPS1=1
CPS2=1

# Variabili che mi servono per sapere se devo cambiare il routing. NON MODIFICARE!
CLS1=1
CLS2=1

# Contatori. NON MODIFICARE!
COUNT1=0
COUNT2=0

while : ; do
        ping -W $TIMEOUT -I $IP1 -c 1 $TESTIP > /dev/null  2>&1
        RETVAL=$?

        if [ $RETVAL -ne 0 ]; then
                echo $NAME1 Down
                CPS1=1
        else
                CPS1=0
        fi

        if [ $LPS1 -ne $CPS1 ]; then
                echo Ping status changed for $NAME1 from $LPS1 to $CPS1
                COUNT1=1
        else
                if [ $LPS1 -ne $LLS1 ]; then
                        COUNT1=`expr $COUNT1 + 1`
                fi
        fi

        if [[ $COUNT1 -ge $SUCCESSREPEATCOUNT || ($LLS1 -eq 0 && $COUNT1 -ge $FAILUREREPEATCOUNT) ]]; then
                echo Uptime status will be changed for $NAME1 from $LLS1
                CLS1=0
                COUNT1=0
                if [ $LLS1 -eq 1 ]; then
                        LLS1=0
                else
                        LLS1=1
                fi
        else
                CLS1=1
        fi

        LPS1=$CPS1

        ping -W $TIMEOUT -I $IP2 -c 1 $TESTIP > /dev/null  2>&1
        RETVAL=$?


        if [ $RETVAL -ne 0 ]; then
                echo $NAME2 Down
                CPS2=1
        else
                CPS2=0
        fi

        if [ $LPS2 -ne $CPS2 ]; then
                echo Ping status changed for $NAME2 from $LPS2 to $CPS2
                COUNT2=1
        else
                if [ $LPS2 -ne $LLS2 ]; then
                        COUNT2=`expr $COUNT2 + 1`
                fi
        fi

        if [[ $COUNT2 -ge $SUCCESSREPEATCOUNT || ($LLS2 -eq 0 && $COUNT2 -ge $FAILUREREPEATCOUNT) ]]; then
                echo Uptime status will be changed for $NAME2 from $LLS2
                CLS2=0
                COUNT2=0
                if [ $LLS2 -eq 1 ]; then
                        LLS2=0
                else
                        LLS2=1
                fi
        else
                CLS2=1
        fi

        LPS2=$CPS2

        if [[ $CLS1 -eq 0 || $CLS2 -eq 0 ]]; then
                if [[ $LLS1 -eq 1 && $LLS2 -eq 0 ]]; then
                        echo Switching to $NAME2
                        ip route replace default scope global via $GW2 dev $EXTIF2
                elif [[ $LLS1 -eq 0 && $LLS2 -eq 1 ]]; then
                        echo Switching to $NAME1
                        ip route replace default scope global via $GW1 dev $EXTIF1
                elif [[ $LLS1 -eq 0 && $LLS2 -eq 0 ]]; then
                        echo Restoring default load balancing
                        ip route replace default scope global nexthop via $GW1 dev $EXTIF1 weight $W1 nexthop via $GW2 dev $EXTIF2 weight $W2
                fi
        fi
        sleep $SLEEPTIME
done