wwan_iface_watchdog/wwan-iface-watchdog

#!/bin/sh /etc/rc.common

# write wwan-iface-watchdog.sh script
function write_script() {
  [ -d /root/scripts ] || mkdir -p /root/scripts
  if [ ! -e /root/scripts/wwan-iface-watchdog.sh ]; then
    echo '#!/bin/sh' > /root/scripts/wwan-iface-watchdog.sh
    echo '' >> /root/scripts/wwan-iface-watchdog.sh
    echo 'while true; do' >> /root/scripts/wwan-iface-watchdog.sh
    echo '    tries=0' >> /root/scripts/wwan-iface-watchdog.sh
    echo '    while [[ $tries -lt 5 ]]; do' >> /root/scripts/wwan-iface-watchdog.sh
    echo '        /bin/ping -q -c 1 8.8.8.8 && sleep 5 && continue 2' >> /root/scripts/wwan-iface-watchdog.sh
    echo '        tries=$((tries+1))' >> /root/scripts/wwan-iface-watchdog.sh
    echo '    done' >> /root/scripts/wwan-iface-watchdog.sh
    echo '    logger "Interface disconnected, restarting wwan..."' >> /root/scripts/wwan-iface-watchdog.sh
    echo '    /sbin/ifup wwan' >> /root/scripts/wwan-iface-watchdog.sh
    echo '    sleep 60' >> /root/scripts/wwan-iface-watchdog.sh
    echo 'done' >> /root/scripts/wwan-iface-watchdog.sh
    chmod +x /root/scripts/wwan-iface-watchdog.sh
  fi
}

START=99
PIDDIR=/var/pids
PIDFILE=/var/pids/wwan-iface-watchdog

# init functions
start() {
  logger "Starting wwan iface watchdog"
  write_script
  [ -d $PIDDIR ] || mkdir -p $PIDDIR
  [ -f $PIDFILE ] && exit 1
  /root/scripts/wwan-iface-watchdog.sh > /dev/null 2>&1 &
  echo $! > $PIDFILE
}

stop() {
  logger "Stopping wwan iface watchdog"
  kill `cat $PIDFILE`
  rm $PIDFILE
}       

restart() {
  logger "Restarting wwan iface watchdog"
  kill `cat $PIDFILE`
  rm $PIDFILE
  write_script
  /root/scripts/wwan-iface-watchdog.sh > /dev/null 2>&1 &
  echo $! > $PIDFILE
}