4.3. Scripting
If you don't want to have to type those commands in every time that you want to get the tunnel running, I've written a set of bash scripts that keep the tunnel up and running. You can download the package from here. Just download and uncompress it into /usr/local/vpn. Inside you'll find three files:
vpnd: The script that controls the tunnel connection.
check-vpnd: a script to be run by cron to check that vpnd is still up.
pty-redir: a small executable needed to initialize the tunnel.
You'll need to edit the vpnd script to set things like the client's username and the server's names. You may also need to modify the starttunnel section of the script to specify which networks you are using. Below is a copy of the script for your reading enjoyment. You'll note that you could put the script in a different directory, you just need to change the VPN_DIR variable.
#! /bin/bash
#
# vpnd: Monitor the tunnel, bring it up and down as necessary
#
USERNAME=vpn-username
IDENTITY=/root/.ssh/identity.vpn
VPN_DIR=/usr/local/vpn
LOCK_DIR=/var/run
VPN_EXTERNAL=vpn.mycompany.com
VPN_INTERNAL=vpn-internal.mycompany.com
PTY_REDIR=${VPN_DIR}/pty-redir
SSH=${VPN_DIR}/${VPN_EXTERNAL}
PPPD=/usr/sbin/pppd
ROUTE=/sbin/route
CRYPTO=blowfish
PPP_OPTIONS="noipdefault ipcp-accept-local ipcp-accept-remote local noauth nocrtscts lock nodefaultroute"
ORIG_SSH=/usr/bin/ssh
starttunnel () {
$PTY_REDIR $SSH -t -e none -o 'Batchmode yes' -c $CRYPTO -i $IDENTITY -l $USERNAME > /tmp/vpn-device
sleep 15
$PPPD `cat /tmp/vpn-device` $PPP_OPTIONS
sleep 15
# Add routes (modify these lines as necessary)
/sbin/route add -net 10.0.0.0 gw $VPN_INTERNAL netmask 255.0.0.0
/sbin/route add -net 172.16.0.0 gw $VPN_INTERNAL netmask 255.240.0.0
/sbin/route add -net 192.168.0.0 gw $VPN_INTERNAL netmask 255.255.0.0
}
stoptunnel () {
kill `ps ax | grep $SSH | grep -v grep | awk '{print $1}'`
}
resettunnel () {
echo "reseting tunnel."
date >> ${VPN_DIR}/restart.log
eval stoptunnel
sleep 5
eval starttunnel
}
checktunnel () {
ping -c 4 $VPN_EXTERNAL 2>/dev/null 1>/dev/null
if [ $? -eq 0 ]; then
ping -c 4 $VPN_INTERNAL 2>/dev/null 1>/dev/null
if [ $? -ne 0 ]; then
eval resettunnel
fi
fi
}
settraps () {
trap "eval stoptunnel; exit 0" INT TERM
trap "eval resettunnel" HUP
trap "eval checktunnel" USR1
}
runchecks () {
if [ -f ${LOCK_DIR}/tunnel.pid ]; then
OLD_PID=`cat ${LOCK_DIR}/vpnd.pid`
if [ -d /proc/${OLD_PID} ]; then
echo "vpnd is already running on process ${OLD_PID}."
exit 1
else
echo "removing stale pid file."
rm -rf ${LOCK_DIR}/vpnd.pid
echo $$ > ${LOCK_DIR}/vpnd.pid
echo "checking tunnel state."
eval checktunnel
fi
else
echo $$ > ${LOCK_DIR}/vpnd.pid
eval starttunnel
fi
}
case $1 in
check) if [ -d /proc/`cat ${LOCK_DIR}/vpnd.pid` ]; then
kill -USR1 `cat ${LOCK_DIR}/vpnd.pid`
exit 0
else
echo "vpnd is not running."
exit 1
fi ;;
reset) if [ -d /proc/`cat ${LOCK_DIR}/vpnd.pid` ]; then
kill -HUP `cat ${LOCK_DIR}/vpnd.pid`
exit 0
else
echo "vpnd is not running."
exit 1
fi ;;
--help | -h)
echo "Usage: vpnd [ check | reset ]"
echo "Options:"
echo " check Sends running vpnd a USR1 signal, telling it to check"
echo " the tunnel state, and restart if neccesary."
echo " reset Sends running vpnd a HUP signal, telling it to reset"
echo " it's tunnel connection." ;;
esac
ln -sf $ORIG_SSH $SSH
settraps
runchecks
while true; do
i=0
while [ $i -lt 600 ]; do
i=((i+1))
sleep 1
done
eval checktunnel
done
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