vpn

#!/bin/bash

####################
# Variables
####################
## How many seconds to wait for the ppp to come up each try
TIMEOUT=120
## How many seconds to wait for l2tpd to restart
L2TPD_TIMEOUT=10
## LAC name in config file
L2TPD_LAC=zju

L2TPD_CONTROL_DIR=/var/run/xl2tpd
L2TPD_CONTROL_FILE=$L2TPD_CONTROL_DIR/l2tp-control
L2TPD_INIT_FILE=/etc/init.d/xl2tpd
L2TPD_CFG_FILE=/etc/xl2tpd/xl2tpd.conf
CHAP_SECRET_FILE=/etc/ppp/chap-secrets
PPP_OPT_FILE=/etc/xl2tpd/options

LNS=10.5.1.9

## Global variables set by function
GW=0.0.0.0
PPP=ppp0

####################
# Commands
####################
function usage
{
  echo "$0: A utility for ZJU school L2TP VPN."
  echo "Usage: $0 [ACTION]"
  echo
  echo "Actions: "
  echo "      Default             Connect."
  echo "      -d                  Disconnect."
  echo "      -r                  Reconnect."
  echo "      -c                  Configure."
  echo "      -h                  Show this information."
  echo
}

function connect
{
  if ppp_alive ; then
    echo "[MSG] VPN already connected."
  else
    restart_l2tpd && bring_up_ppp && setup_route
  fi
}

function disconnect
{
  echo -n "[MSG] Disconnecting VPN ... "
  echo "d $L2TPD_LAC" > $L2TPD_CONTROL_FILE
  sleep 1
  echo "Done!"
  return 0
}

function reconnect
{
  disconnect && restart_l2tpd && bring_up_ppp && setup_route
}

function configure
{
  echo "Configure L2TP VPN for ZJU.";
  read_param && write_settings && free_param && reconnect
}


####################
# Internal utility functions
####################
function init
{
  GW=$(ip route get $LNS 2>/dev/null |grep "$LNS"|awk {'print $3'})
  if [ -z "$GW" ];then
    echo "[ERR] Network is not available"
    exit 1
  fi
  if [ $(expr length "$GW") -ge 6 ]; then
    PPP=ppp0
  else
    PPP=ppp1
    GW=$(ip add show "$GW"| grep inet|awk {'print $2'})
  fi
}

function super_user
{
  if [ "$UID" = "0" ]; then
    return 0         # Yes, super user
  else
    return 1
  fi
}

function read_param
{
  read -p "Username: " username
  read -s -p "Password: " password
  echo
}

function write_settings
{
  if [ -e $L2TPD_CFG_FILE ]; then
    mv $L2TPD_CFG_FILE $L2TPD_CFG_FILE.old
  fi

  cat>$L2TPD_CFG_FILE<<EOF
[global]                    ; Global parameters:
port = 1701                 ; * Bind to port 1701
access control = yes        ; * Refuse connections without IP match
rand source = dev           ; Source for entropy for random

[lac zju]
lns = $LNS                  ; * Who is our LNS?
redial = yes                ; * Redial if disconnected?
redial timeout = 3          ; * Wait n seconds between redials
max redials = 999           ; * Give up after n consecutive failures
require chap = yes          ; * Require CHAP auth. by peer
refuse pap = yes            ; * Refuse PAP authentication
require authentication = no     ; * Require peer to authenticate
ppp debug = yes                    ; * Turn on PPP debugging
pppoptfile = $PPP_OPT_FILE  ; * ppp options file for this lac
name = $username
EOF

  if [ -e $PPP_OPT_FILE ]; then
    mv $PPP_OPT_FILE $PPP_OPT_FILE.old
  fi

  cat>$PPP_OPT_FILE<<EOF
asyncmap 0
noauth
crtscts
lock
hide-password
modem
netmask 255.255.255.0
proxyarp
lcp-echo-failure 4
lcp-echo-interval 30
ipcp-accept-local
ipcp-accept-remote
noipx
defaultroute
mru 1400
mtu 1400
EOF

  sed -i /$username/d $CHAP_SECRET_FILE
  echo "$username  *  $password  *" >> $CHAP_SECRET_FILE
  chmod 600 $CHAP_SECRET_FILE

  return 0
}

function free_param
{
  unset username
  unset password
  return 0
}

function ppp_alive
{
  if ip addr show | grep "inet.*$PPP" > /dev/null; then
    return 0         # Yes, connected
  else
    return 1
  fi
}

function bring_up_ppp
{
  [ -d $L2TPD_CONTROL_DIR ] || mkdir $L2TPD_CONTROL_DIR
  if [ ! -e $L2TPD_CONTROL_FILE ]; then
    echo "[MSG] L2tpd daemon not running!"
    if ! restart_l2tpd ; then
      return 1        # l2tpd not started
    fi
  fi
  echo "c $L2TPD_LAC" > $L2TPD_CONTROL_FILE
  for i in $(seq 0 $TIMEOUT)
  do
    if ppp_alive; then
      echo " Done!"
      return 0     # Yes, brought up!
    fi
    echo -n -e "\\r[MSG] Trying to bring up vpn... $i secs..."
    sleep 1
  done
  echo
  echo "[ERR] Failed to bring up vpn!"
  return 1
}

function setup_route
{
  echo "[MSG] Detected gateway: $GW, PPP device: $PPP ."
  echo -n "[MSG] Setting up route table...  "

  ip route add 10.0.0.0/8 metric 10 via $GW 2>/dev/null
  ip route add 210.32.0.0/20 metric 10 via $GW 2>/dev/null
  ip route add 210.32.128.0/18 metric 10 via $GW 2>/dev/null
  ip route add 222.205.0.0/16 metric 10 via $GW 2>/dev/null
  ip route del default 2>/dev/null
  ip route add default dev $PPP 2>/dev/null
  echo "Done!"
}

function restart_l2tpd
{
  echo "[MSG] Restarting l2tpd... "
  $L2TPD_INIT_FILE restart
  for i in $(seq $L2TPD_TIMEOUT)
  do
    if [ -e $L2TPD_CONTROL_FILE ]; then
      echo "[MSG] Done!"
      return 0         # Successfully restarted!
    fi
    sleep 1
  done
  echo "[ERR] Failed to restart l2tpd!"
  return 1         # Failed to restart l2tpd
}

####################
# Main
####################
if ! super_user ; then
  echo "[ERR] You must be super user to run this utility!"
  exit 1
fi

init ## Get $GW and $PPP

if [ $# -lt 1 ]; then
  connect
elif [ "$1" = "-d" ]; then
  disconnect
elif [ "$1" = "-r" ]; then
  reconnect
elif [ "$1" = "-c" ]; then
  configure
elif [ "$1" = "-h" ]; then
  usage
else
  echo "[ERR] Unknown parameter.";
fi