用Linux系统自身做一个L2TP的VPN服务器

#!/bin/sh
#
# xl2tpd This shell script takes care of starting and stopping l2tpd.
#
# chkconfig: - 80 30
# description: Layer 2 Tunnelling Protocol Daemon (RFC 2661)
#
# processname: xl2tpd
# config: /etc/xl2tpd/xl2tpd.conf
# pidfile: /var/run/xl2tpd.pid

#Servicename
SERVICE=xl2tpd

# Source function library.
. /etc/rc.d/init.d/functions

# Source networking configuration.
. /etc/sysconfig/network

if [ ${NETWORKING} = "no" ]
then
exit 0
fi

[ -x /usr/sbin/$SERVICE ] || exit 0

RETVAL=0

start() {
echo -n "Starting $SERVICE: "
if [ ! -d /var/run/xl2tpd ]
then
mkdir /var/run/xl2tpd
fi
daemon $SERVICE
RETVAL=$?
[ $RETVAL -eq 0 ] && touch /var/lock/subsys/$SERVICE
echo ""
return $RETVAL
}

stop() {
echo -n "Stopping $SERVICE: "
killproc $SERVICE
RETVAL=$?
echo
[ $RETVAL -eq 0 ] && rm -f /var/lock/subsys/$SERVICE
return $RETVAL
}

restart() {
stop
start
}

# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
status)
status $SERVICE
RETVAL=$?
;;
restart|reload)
restart
;;
condrestart)
[ -f /var/lock/subsys/$SERVICE ] && restart || :
;;
*)
echo "Usage: $SERVICE {start|stop|status|restart|reload|condrestart}"
exit 1
esac