OpenWRT/LEDE procd service to check/reconnect stalled/disconnected wan interface

iface_watchdog.sh

#!/bin/sh /etc/rc.common
# https://joost.oostdijk.net/articles/service-configuration-with-procd/
# runs until first stall/disconnect of recovery taking longer than 60 seconds
INTERNET_ADDRESS=8.8.8.8
IFACE="${1:-LTE}"
SECONDS=${2:-10}
[ -z "${IFACE}" ] && {
  /bin/echo -e "Usage: iface_watchdog <interface> [poll_each_seconds]\nChecks+reconnects stalled/disconnected interface" | /usr/bin/logger -s
  exit 1
}

USE_PROCD=1
START=99
SERVICE_DAEMONIZE=1
SERVICE_WRITE_PID=1
SERVICE_PID_FILE=/var/run/${IFACE}_watchdog.pid
SERVICE_QUIET=0
STOP=10

log() {
  /usr/bin/logger -t WATCHDOG "$@"
}

start_service() {
  log -s "Starting iface_watchdog ${IFACE} ${SECONDS}"
  procd_open_instance "${IFACE}_watchdog"
  procd_set_param command /bin/sh -c ". /etc/init.d/iface_watchdog ${IFACE} ${SECONDS}; watchdog"
  procd_set_param respawn
  procd_set_param pidfile "${SERVICE_PID_FILE}"
  procd_close_instance
}

ppid() {        # PID
  /usr/bin/awk '{print $4}' < "/proc/$1/stat"
}

stop() {
  DIR="$(/bin/pwd)" && cd /var/run
  for pid in `/usr/bin/pgrep sleep`; do
    ppid=`ppid $pid`
    PID_FILE=`/bin/egrep -l "^$ppid"'$' *_watchdog.pid` && /usr/bin/tr '\0' '\n' < "/proc/$ppid/cmdline" | /bin/egrep -q "/etc/init.d/iface_watchdog\s${PID_FILE%%_watchdog.pid}" && {
      log -s "Stopping iface_watchdog ${PID_FILE%%_watchdog.pid}"
      /bin/kill $ppid $pid
      /bin/sleep 1
      cd "$DIR"
      return
    }
  done
  cd "$DIR"
  log -s 'WARNING: no matching process found, repeat your attempt!'
}

rxBytes() {     # device
  /bin/cat "/sys/class/net/$1/statistics/rx_bytes"
}

zeroBytesReceived() {   # device
  BYTES=`rxBytes "$1"`
  DIFF=$((${BYTES} - ${RX_BYTES:-0}))
  RX_BYTES=${BYTES}
  return ${DIFF}
}

pause() {       # seconds
  /bin/sleep "$1" && return
  /usr/bin/pgrep -qf 'iface_watchdog\sstop' && {
    log "${IFACE}: Exit requested"
    exit 0
  }
}

watchdog() {
  . /lib/functions/network.sh
  for sig in INT TERM ; do
    trap "log '${IFACE}: Exiting on SIG$sig'; exit 0" $sig
  done 
  log "${IFACE}: Started"
  network_get_device DEV "${IFACE}" || [ -n "${DEV}" ] || {
    log "${IFACE}: Unable to map to device, assuming boot => delaying reboot for 5 minutes"
    pause 300
    network_flush_cache
  }

  while network_get_device DEV "${IFACE}" && [ -n "${DEV}" ] && [ `/sbin/logread | egrep -o 'lease of .* obtained, lease time.*' | uniq -c | awk 'END {print $1}'` -le 3 ]; do
    zeroBytesReceived "${DEV}" && {
      /bin/ping -c ${SECONDS} -w ${SECONDS} "${INTERNET_ADDRESS}"
      zeroBytesReceived "${DEV}" && {
        log "${IFACE}: Interface stalled at "`rxBytes "${DEV}"`" RX bytes, restarting device ${DEV}"
        /usr/bin/env -i /sbin/ifup "${IFACE}" 2>&1 | /usr/bin/logger
        log "${IFACE}: Waiting 60 seconds for device ${DEV} to come up"
        pause $((60 - ${SECONDS}))
        network_flush_cache
      }
    }
    pause ${SECONDS}
  done
  log "${IFACE}: Unable to map to device, rebooting"
  /sbin/reboot
}