#!/bin/sh
# http://tomatousb.org/forum/t-454177/wan-dhcp-issues
# modified by Xruptor

#run this script only once on router reset, sometimes it runs multiple times for some reason
chkFile="/tmp/CHECKWAN"

if [ -f "$chkFile" ]
then
   logger -p NOTICE -t CHECKWAN "CHECKWAN already initialized, exiting."
   exit
fi

#create the tmp file so that we don't run this more than once
touch $chkFile

# No of times to check each host before trying next
TRIES=1
# How often to check in seconds if OK
TCHECK=20
# How long to wait if all hosts fail
TFAIL=10
# How many fails before restarting dhcp
NFAIL=3

#don't touch this
notice=1

# defaults don't touch
GATEWAY="0.0.0.0"
UP=0
HSTS="8.8.8.8 8.8.4.4"
chk=0
dn=0

DNSCHK(){
    cnt=0
    chk=0
    while [ $cnt -lt $TRIES ]; do
         if /bin/ping -c 1 -W 5 -w 5 $@  >/dev/null; then
            chk=1
            break
        else
            let cnt=cnt+1
        fi
    done
}

PINGCHK(){
    chk=0
    if /bin/ping -c 1 -W 5 -w 5 8.8.8.8  >/dev/null; then
       chk=1
    fi
}

GETGATEWAY() {
    GATEWAY=`nvram get wan_gateway`
    if [ -z "$GATEWAY" ]; then
        GATEWAY="0.0.0.0"
    fi
    if [ $GATEWAY != "0.0.0.0" ]; then
        HSTS="$GATEWAY 8.8.8.8 8.8.4.4"
    else
    HSTS="8.8.8.8 8.8.4.4"
    fi
}

while [ true ]; do

    sleep 15

    if [ $notice -lt 2 ]; then
            let notice=notice+1
        logger -p NOTICE -t CHECKWAN "CHECKWAN has initialized."
    fi

    dn=0
    GETGATEWAY

    while [ $dn -lt $NFAIL ]; do
        for h in $HSTS; do
            UP=0;
            DNSCHK $h
            if [ $chk -gt 0 ]; then
                UP=1
                break
            else
                logger -p NOTICE -t CHECKWAN "WAN Ping check failed on host $h"
            fi
        done

        if [ $UP -gt 0 ]; then
            dn=0
            sleep $TCHECK
        else
            let dn=dn+1
            logger -p NOTICE -t CHECKWAN "WAN Check Failure # $dn"
            sleep $TFAIL
        fi
    done

    logger -p NOTICE -t CHECKWAN "Releasing DHCP for forced renewal"

    #reset chk for PING check, JUST IN CASE!!
    chk=0

    #reset DHCP by using Kill command first
    #-----------------------------
    killall -SIGUSR1 udhcpc
    #-----------------------------

    logger -p NOTICE -t CHECKWAN "Attemping to renew the DHCP."

        #grab new IP address, try restarting the wan
        service restart_wan
    #sleep 5

    #do a ping check until WAN is back up
    while [ $chk -lt 1 ]; do
        sleep 15
        PINGCHK
    done

    logger -p NOTICE -t CHECKWAN "WAN DHCP has been renewed."

done