DD-WRT 4G WAN Failover Script

failover-service.sh

#!/bin/sh
INTERVAL=10
PACKETS=1
USINGWAN=0
WAN1=ppp0
WAN2=eth3

# We'll run this in the intervals given above
while sleep $INTERVAL
do
        WAN1GW=`nvram get wan_gateway`
        WAN2GW=192.168.8.1

        # Try to figure out the current route
        TARGET=`ip route | awk '/default via/ {print $3}'`

        # Set the variable, so let the script now which connection is it dealing with
        if [ "$WAN1GW" = "$TARGET" ]; then
                USINGWAN=1;
        else if [ "$WAN2GW" = "$TARGET" ]; then
                USINGWAN=2;
        fi;
        fi

        # We'll ping as many times the $PACKETS variable tells, and test if we have connection:
        RET=`ping -c $PACKETS $TARGET 2>/dev/null | awk '/packets received/ {print $4}'`
        echo "Result of pinging $TARGET: $RET packet(s) / $PACKETS"

        # If we don't have connection, change the active WAN port (If there is any loss with multiple packets, it should change as well)
        if [ "${RET:-0}" -ne "$PACKETS" ]; then
                if [ "$USINGWAN" = "1" ]; then
                        ip route delete default;
                        ip route add default via $WAN2GW dev $WAN2
                        USINGWAN=2
                        echo "Changed active WAN port to 2!"
                        logger "Changed active WAN port to 2!"
                else
                        ip route delete default;
                        ip route add default via $WAN1GW dev $WAN1
                        USINGWAN=1
                        echo "Changed active WAN port to 1!"
                        logger "Changed active WAN port to 1!"
                fi
        fi

        if [ "$USINGWAN" = "2" ]; then
                WAN1STAT=`ping -c $PACKETS $WAN1GW 2>/dev/null | awk '/packets received/ {print $4}'`
                echo "Result of pinging $WAN1GW: $WAN1STAT packet(s) / $PACKETS"
                if [ "${WAN1STAT:-0}" = "$PACKETS" ]; then
                        ip route delete default;
                        ip route add default via $WAN1GW dev $WAN1
                        USINGWAN=1
                        echo "Restored active WAN port to 1!"
                        logger "Restored active WAN port to 1!"
                fi
        fi
done;