#!/bin/sh
# Antonio Ávila for Fon Technology (GPL)

crontab_file="/etc/crontabs/root"
ntp_file="/etc/config/ntpservers"

#Flush previous ntp servers...
cat /etc/crontabs/root | grep -v ntp > /etc/crontabs/root

randline=$(expr `head -c1 /dev/urandom | hexdump -d | sed 's/\ //g' | sed 's/^0*//' | head -n1` % `wc -l $ntp_file | sed 's/^\ [ \t]*//' | cut -d" " -f1`)

ntpserver=$(head -n$randline $ntp_file | tail -n1)

case "$1" in
	"stop")
		cat $crontab_file | grep -v "ntp" > $crontab_file
		crontab -l
		echo stop
		return
		;;
	*)
		;;
esac

randminute=$(expr `head -c2 /dev/urandom | hexdump -d | sed 's/\ //g' | sed 's/^0*//' | head -n1` % 60)
randhour=$(expr `head -c2 /dev/urandom | hexdump -d | sed 's/\ //g' | sed 's/^0*//' | head -n1` % 24)
echo "$randminute $randhour * * * ntpclient -s -h $ntpserver" >> $crontab_file
ntpclient -s -h $ntpserver &
crontab -l