#!/bin/sh

# Version
version=0.05

# A simple script that checks for connectivity (including working DNS resolution)
# If no connectivity, reset tethering
# 
# Requires easytether-usb to be installed and already setup/working
# Manual (one time) setting of the USB device ID of the tether device (TETHERDEV).

# Find the tethering device with lsusb. Example (Samsung/Verizon kids tablet):
# Bus 001 Device 013: ID 04e8:6860 Samsung Electronics Co., Ltd Galaxy (MTP)
TETHERDEV=04e8:6860
# 04e8:6860 is for Samsung's USB identification (both Note 10 and kids tablet) 

# Some highly available website to check (www.google.com is backed by *lots* of servers)
CHECKWWW=www.google.com

# How long before we check again?
SLEEPITOFF=60

while true; do
	lsusb | grep $TETHERDEV > /dev/null  
	if (( $? )); then
		echo "Tethering device not found! Sleeping..."
		sleep 5s
	else
		echo "Tethering device present, continuing"
		break
	fi
done

while true; do
	curl --connect-timeout 10 $CHECKWWW > /dev/null 2>&1

	if [ $? != 0 ]; then
		# No internet
		echo "Network down, Houston we have a problem!" # FIXME: For debugging
		# Reset the USB device
		usbreset $TETHERDEV 
		# Wait a few seconds for device to be ready again
		sleep 5s
		# (re)start easytether-usb to make a connection
		easytether-usb 
	else
		# Internet working
		echo "Network up, all good in the hood!" # FIXME: For debugging
	fi
	sleep $SLEEPITOFF
done