failover.sw by JMVS

#!/bin/sh
ME="$(basename $0)" #Get name of the actual running script
logger "$ME: Starting Failover Dual-Wan script..."
RUNNING="$(ps | awk '/'"$ME"'/ {++x}; END {print x+0}')" #Check if there's another instance running
if [ "$RUNNING" -gt 3 ]; then
    echo "Another instance of \"$ME\" is running" #Another intance running, abort.
    logger "$ME: Another instance of the Failover Dual-Wan script is already running, aborting..."
    exit 1
fi
### CONFIG START ################################################
INT=25 #Interval to check connection in seconds (default: 25secs)
PCK=1 #Number of packets to ping (default: 1 packet)
### CONFIG END ##################################################
WAN1NM="$(nvram get wan_ifname)" #Get WAN 1 interface
WAN2NM="$(nvram get wan2_ifname)" #Get WAN 2 interface
WAN1GW="$(nvram get wan_gateway)" #Get WAN 1 gateway
WAN2GW="$(nvram get wan2_gateway)" #Get WAN 2 gateway
RWAN="$(ip route | awk '/default via/ {print $3}')" #Get active running gateway
WARNBAK=0 #Variable set so we can output to the log only once per incident
### SCRIPT START ################################################
gpio enable 2 #Turns off WPS LED (WRT310N v2)
if [ "$WAN1GW" = "$RWAN" ]; then #Find out which WAN is active and running
    AWANNM=$WAN1NM #Define active WAN 1 as connection
    AWANGW=$WAN1GW
    gpio disable 4 #Turn on blue LED (WRT310N v2)
    gpio enable 2
else
    AWANNM=$WAN2NM #Define active WAN 2 as connection
    AWANGW=$WAN2GW
    gpio disable 4 #Turn on violet LED (WRT310N v2)
fi
logger "$ME: WAN1 - Interface: $WAN1NM / Gateway: $WAN1GW"
logger "$ME: WAN2 - Interface: $WAN2NM / Gateway: $WAN2GW"
logger "$ME: $AWANNM active via $AWANGW"

while [ 1 = 1 ] #Endless loop
do
    CHK="$(ping -c $PCK $AWANGW 2>/dev/null | awk '/packets received/ {print $4}')"
    if [ "$CHK" -ne "$PCK" ]; then #Check if the connection is working
        logger "$ME: $AWANNM interface not responding, switching..." #Connection down
        ip route delete default #Delete actual routing
        if [ "$AWANNM" = "$WAN1NM" ]; then
            AWANNM=$WAN2NM
            AWANGW=$WAN2GW
            gpio disable 2 #Turn on violet LED
        else
            AWANNM=$WAN1NM
            AWANGW=$WAN1GW
            gpio enable 2 #Turn on blue LED
        fi
        ip route add default via $AWANGW dev $AWANNM #Establish new routing
    fi
    if [ "$AWANNM" = "$WAN2NM" ]; then
        CHKWAN1="$(ping -c $PCK $WAN1GW 2>/dev/null | awk '/packets received/ {print $4}')"
        if [ $WARNBAK = 0 ]; then
            logger "$ME WARNING: Using backup interface"
            $WARNBAK=1
        fi
        if [ "$CHKWAN1" = "$PCK" ]; then
            logger "$ME: $WAN1NM interface working again, switching..."
            $WARNBAK=0
            ip route delete default #Delete actual routing
            ip route add default via $WAN1GW dev $WAN1NM #Establish new routing
            AWANNM=$WAN1NM #Define new active connection
            gpio enable 2 #Turn on blue LED
        fi
    fi
sleep $INT
done;
logger "$ME ERROR: Script terminated abnormaly."