#!/bin/bash
# This script is meant to be called automatically by dnsmasq's dhcp-script directive 
# but it can also be used to manage the manual insertion and deletion of nodes. 
# Make sure dnsmasq doesn't come an play against you though.

MODULESPATH=%%MODULESPATH
BEEPS=%%BEEPS

beeps(){
	### Beeps:
	PAUSE=20
	START=200
	STOP=2000
	STEP=200
	BEEP_add="$(for I in `seq $START $STEP $STOP`; do echo -n " -f $I -l $PAUSE -r 1 -n"; done)"
	BEEP_del="$(for I in `seq $STOP -$STEP $START`; do echo -n " -f $I -l $PAUSE -r 1 -n"; done)"
	BEEP_add="beep ${BEEP_add%%-n}"
	BEEP_del="beep ${BEEP_del%%-n}"
	eval \$BEEP_$COMMAND
}

run_modules(){
	for I in ${MODULESPATH}/*-${COMMAND}
	do
		$I $@ $DNSMASQ_USER_CLASS0
	done
	[[ $BEEPS == "true" ]] && beeps
}

# Yes, it's crude but we'll elaborate later on something more functionnal
# ...say something based on Avahi with live beakons
node_is_alive(){
	ping -c 1 -w 1 $HNAME
	return $?
}

# Nodes can either be added or removed. For a thorough description of the mechanism, see
# dnsmasq's manpage section concerning dhcp-script
old_node(){
	shift
	if [[ node_is_alive  ]]; then
		$0 add $*
	else
		$0 del $*
	fi
}

usage(){
	echo "$0 is called as follows:"
	echo "$0 <add|del> <MAC address> <IP address> <hostname> <processor count> [number of processors]"
	echo "If [number of processors] is not set, the default one is used from the clustering config file when needed."
}

##### Variables #######
COMMAND=$1
MACADDR=$2
IP=$3
HNAME=$4


##### Variables END ###

if [[ $COMMAND == "del" ]]; then
	run_modules $@
else
	# we background this since it performs a ping with a 1 second timeout
	# on a 256 node system, those seconds add up...
	if [[ $# -lt 5 ]]; then
		# We ignore calls made with only 4 args as we're missing the processor count.
		# This can be caused by dnsmasq reloading or dnsmasq not setting DNSMASQ_USER_CLASS0 
		# as the incoming request is either only a "renewal/rebind" request which doesnt trigger
		# DHCPDISCOVER
		exit 0
	elif [[ $COMMAND == "old" ]]; then
		old_node $@ &
	else # COMMAND == add 
		run_modules $@
	fi
fi

exit 0