Scripting

VPN HOWTO
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# 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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