#!/bin/sh
# PRECAUTIONS:
# You have to install
# -tcpdump
# -setleds
#
# If you haven't already to use this script!
# Read `man setleds` if your led does not work.
# It might not work, too, if you use another software
# to control the other leds (depends).
#
# LICENSE: artistic GPL, not included, because it
# is freely downloadable.
#
# AUTHOR : Sascha Wuestemann
# MAIL : sascha@killerhippy.de
# date : 20021210
# VERSION: 1.0
#
###################################################
# DESCRIPTION: #
# script for bootup or $HOME/.bash_login scripts, #
# to automagically highlight selected led over #
# all 8 ttys if we are online with our netgear- #
# router, else downlight them. #
###################################################
#
# Additionally, the online status is dumped to
# INFOFILE which contains "online with <internal-ip>"
# or "offline". Unfortunately, <internal-ip> _is_not_
# the ip you are using to walk the internet, but the
# ip the router uses at the inside. Nevertheless it
# indicates the online status.
#
# This script acts like a a deamon (is listed at ps).
# If you are worried about writing to your harddisk
# every 30 seconds, forget about that, Linux is
# aware about such and buffers it. If you don't
# believe in this, move the tempfiles to ramdisk
# yourself!
#
# TEMPFILE is needed to pass information and
# automatically deleted, while the script runs.
# If powerdown or else, del /tmp/onlinefile*
# /tmp/OnlineStatus
#
# You have to enable RIP with the direction "Both"
# or "Out Only" and the version RIP-1, RIP-2B or RIP-2M
# (only tested with these) to match against the script's
# logic. If your netgear-router only uses newer router
# information protocolls, send me a tcpdump.
#
# RIP-? sends router information every 30 seconds.
#
# A sample tcpdump:
#
# 18:46:06.374316 <netgear-ip>.520 > <three bytes net>.255.520:\
# RIPv1-resp &#91;items 2&#93;: {0.0.0.0}(1) {<actual internal ip>}(1) &#91;ttl 1&#93;
# user config starts here:
LED="caps" 			# can be "caps", "scroll", "num"
IFACE="eth1"			# networkinterface to watch
TEMPFILE="/tmp/onlinefile$$"
INFOFILE="/tmp/OnlineStatus"
NETWATCH="/usr/sbin/tcpdump"
SLEEPER="/bin/sleep 30s"	# how long to wait for RIP information
NETWATCH_OPTION_1="-q -c 1 -p -s0 -i $IFACE -n port 520 -w $TEMPFILE"
NETWATCH_OPTION_2="-r $TEMPFILE"
MATCH="port 520"
# user config has ended
#
# only script programmers should change things below
# subfunctions
leds ()
{
	&#91; "$1" = "online" &#93; && SCROLL_OPTION="+$LED" \
	|| SCROLL_OPTION="-$LED"
 local INITTY=/dev/tty&#91;1-8&#93;
 for TTY in $INITTY; do
 /usr/bin/setleds -L $SCROLL_OPTION <$TTY
 done
 echo "$1 with $ONLINE" > $INFOFILE
}
ledsreset ()
{
	INITTY=/dev/tty&#91;1-8&#93;
	for tty in $INITTY; do
 	 setleds -L < $tty
 	done
}
# catch aborts and clean
trap 'rm -f $TEMPFILE; rm -f $INFOFILE; \
ledsreset 1>/dev/null 2>&1; exit 32' 0
# simulate daemon
while true; do
 # send tcpdump into background and
	# save its pid
 $NETWATCH $NETWATCH_OPTION_1 &
	MYPID=$!
 # wait selected seconds (default 30)
 $SLEEPER
 # in case of, kill tcpdump with grace
	kill $MYPID >/dev/null 2>&1
 # read what we have recieved from tcpdump
 HIT=`$NETWATCH $NETWATCH_OPTION_2`
 # extract the second ip named "actual internal ip" above
 ONLINE=`echo $HIT | sed -n -e "s/^.*{//p"| sed -n -e "s/}.*$//p"`
 # test, if we recieved information at all
	if &#91; $ONLINE &#93;; then
 # ip is 0.0.0.0 if the router is offline
 if &#91; $ONLINE == 0\.0\.0\.0 &#93;; then
 leds offline
 else
 leds online
 fi
	else
	 leds offline
	fi
	# erase garbage tempfile
 rm $TEMPFILE
done