#!/bin/sh /etc/rc.common
# Copyright (c) 2009 OpenWrt.org
# Copyright (c) 2009 Stefan Katerkamp <s@katerkamp.de>

START=99

NTPSERVER=pool.ntp.org
NTPPORT=0
INTERVALMINUTES=10
COUNT=5

unset SNUM
unset SPOS
unset NTPSERVERS
unset NTPPORTS

create_config_ntpclient() {
	uci_set_default ntpclient <<-EOR
	config ntpserver
		option hostname $NTPSERVER
		option port     $NTPPORT
	config ntpclient
		option interval	$(($INTERVALMINUTES * 60))
		option count    $COUNT
	EOR
	
	config_load ntpclient
}

ntpcommand() {
	if [ "$NTPPORT" == "0" ]; then
		echo /usr/sbin/ntpclient -s -h $NTPSERVER
	else
		echo /usr/sbin/ntpclient -s -p $NTPPORT -h $NTPSERVER
	fi
}

cron_clean() {
	crontab -l >&- 2>&-
	if [ $? -eq 0 ]; then
		crontab -l | sed -e /ntpclient/d | crontab -
	fi
}

cron_seed() {
	local cronstuff='*/'"$INTERVALMINUTES"' * * * *'
	local reset="/etc/init.d/ntpclient restart"
	
	cron_clean

	crontab -l >&- 2>&-
	if [ $? -eq 0 ]; then
		crontab -l | sed -e '$a\'"$cronstuff $(ntpcommand) || $reset" | crontab -
	else
		echo "$cronstuff $(ntpcommand) || $reset" | crontab -
	fi
	[ -L /var/spool/cron/crontabs ] || /etc/init.d/cron restart >&- 2>&-
}

pick_server() {
	local rand
	
	[ -n "${NTPSERVERS// /}" ] || {
		NTPSERVERS="$NTPSERVER"
		NTPPORTS="$NTPPORT"
	}
	set -- $NTPSERVERS
	SNUM=$#
	rand=$(hexdump -e\"%u\" -n1 /dev/urandom)
	[ "$rand" == '*' ] && rand=0
	SPOS=$(($rand % $SNUM))
	SPOS=$(($SPOS + 1))
	eval NTPSERVER=\${$SPOS}
	
	set -- $NTPPORTS
	eval NTPPORT=\${$SPOS}
}

load_ntpservers() {
	local hostname
	local port
	config_get hostname $1 hostname
	config_get port $1 port
	[ -n "$hostname" ] && {
		NTPSERVERS="$NTPSERVERS $hostname"
		if [ -n "$port" ]; then
			NTPPORTS="$NTPPORTS $port"
		else
			NTPPORTS="$NTPPORTS 0"
		fi
	}
}

load_ntpvalues() {
	local interval
	local count
	config_get interval $1 interval
	[ -n "$interval" ] && INTERVALMINUTES=$(($interval / 60))
	[ "$INTERVALMINUTES" == "0" ] && INTERVALMINUTES=1
	config_get count $1 count
	[ -n "$count" ] && COUNT=$count
	[ "$COUNT" == "0" ] && COUNT=1
}

eager_clockadjust() {
	local i=0
	while [ $i -lt $COUNT ]; do
		i=$(($i + 1))
		eval $(ntpcommand) >&- 2>&-
		if [ $? -eq 0 ]; then
			logger "Successful NTP clock adjust ($NTPSERVER)."
			return
		fi
		logger NTP $NTPSERVER failed.
		pick_server
	done
	logger NTP eager clock adjust failed.
}

start() {
	config_load ntpclient
	[ "$?" != "0" ] && create_config_ntpclient
	config_foreach load_ntpvalues ntpclient
	config_foreach load_ntpservers ntpserver
	pick_server
	eager_clockadjust
	cron_seed
}

restart() {
	start
	logger "Restarted ntpclient. NTP server #$SPOS of $SNUM."
}

stop() {
	cron_clean
	logger "Stopped ntpclient."
}