	# find the process invoke path who invoke dhcp-client start
	pid=`ps ww | grep "start dhcp-client" | grep -v "grep" | head -n 1 | awk '{print $1}'`
	while [ $pid -gt 0 ]; do
		cmdline="`cat /proc/$pid/cmdline`"
		/usr/bin/logger -t dhcp-client -p err "parent pid = [$pid], cmdline = [$cmdline]" || true
		pid=`cat /proc/$pid/status | grep PPid | awk '{print $2}'`
	done

	# start record packet
	mkdir -p /var/log/dhcp-client
	PCAP_FILE="/var/log/dhcp-client/$IFACE-$(/bin/date +"%y-%m-%d-%H-%M-%S").pcap"
	/usr/sbin/tcpdump -i $IFACE port 67 or port 68 -w $PCAP_FILE &

