OpenWRT iPhone Watchdog with "ping passthrough"

watchdog.sh

#!/bin/sh
# A small script to make life with iPhone tethering less cumbersome on OpenWrt
# Petr Vyskocil, Apr 2020
# Modified by Hunter Fuller, Sep 2020
# Public domain
 
# After you successfully allow iPhone tethering, copy files with name like
# /var/lib/lockdown/12345678-9ABCDEF012345678.plist to /etc/lockdown/locks.
# That way, you won't have to set up trust again after router reboots.
if [ -e /etc/lockdown/locks ]; then
  mkdir -p /var/lib/lockdown
  cp /etc/lockdown/locks/* /var/lib/lockdown/
fi
 
# lockdown records restored, now we can launch usbmuxd. Don't launch it sooner!
/usr/sbin/usbmuxd
 
# We are up and running now. But unfortunately if your carrier signal is weak, iPhone will
# drop connection from time to time and you'd have to unplug and replug USB cable to start tethering
# again. Script below automates that activity.
 
# First wait a bit - we just brought the interface up by usbmuxd
sleep 20
 
# If we see iPhone ethernet interface, try to ping iPhone router's address (172.20.10.1).
# When the ping is unsuccessful, rebind iPhone ethernet USB driver and wait for things to settle down
while :
do
  #First do generic Internet test. If the Internet is down, stop responding to ping.
  ping -c 5 -w 10 4.2.2.1 > /dev/null
  if [ $? -ne 0 ]; then
    echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all
  else
    echo "0" > /proc/sys/net/ipv4/icmp_echo_ignore_all
  fi
  
  for i in /sys/bus/usb/drivers/ipheth/*:*; do
    test -e $i || continue
    ping -c 1 -w 1 172.20.10.1 > /dev/null
    if [ $? -ne 0 ]; then
      echo "${i##*/}" > "${i%/*}/unbind"
      echo "${i##*/}" > "${i%/*}/bind"
    fi
  done

  sleep 15
done