#!/bin/sh
#
# Read in the LVS configuration file.
. /etc/lvs.conf

reset_lvs() {
  # Reset the LVS virtual server tables.
  $IPVSADM --clear
}


configure_networking() {
  # Turn off all relevant ICMP redirects. $LVS_IF is the network
  # interface used for LVS traffic on the director.
  echo "0" > /proc/sys/net/ipv4/conf/all/send_redirects
  echo "0" > /proc/sys/net/ipv4/conf/default/send_redirects
  echo "0" > /proc/sys/net/ipv4/conf/$LVS_IF/send_redirects

  # Turn on the IP forwarding flag
  echo "1" >/proc/sys/net/ipv4/ip_forward

  # Add interface and routing for the VIP interface.
  /sbin/ifconfig $VIP_IF $VIP netmask 255.255.248.0 broadcast 156.141.63.255
  /sbin/route add -host $VIP dev $VIP_IF
}


remove_interface() {
  # Remove the VIP network interface.
  [ -n "$(ifconfig | grep ^$VIP_IF)" ] && /sbin/ifconfig $VIP_IF down
}


add_services() {
  # For each TCP service listed in the configuration, add the service
  # and add the Real-servers that provide the service.
  for TPORT in $TPORTS; do

    # -A = Add service; -t = Service uses TCP
    # $VIP:$TPORTS = Virtual IP Address of new service, and the port
    # number of the service being presented on this interface.
    # -s = scheduling method (rr = Round Robin)
    $IPVSADM -A -t $VIP:$TPORT -s rr

    # Add real-servers into the LVS cluster for the above service.
    #
    # -a = Add real-server;  -t = Service uses TCP
    # 156.141.59.63:telnet = Virtual IP Address of new service,
    # and the port number of the service being presented on this interface.
    # -r <host>:<port> = hostname/IP Address of the real-server and port
    # number of the service on the real-server.
    # -m = use Masquerading (aka Network Address Translation)
    # -w = Weight of the real-server in the pool. Can be used to direct traffic
    # to more powerful servers in the pool.
    for RIP in $RIPS; do
      $IPVSADM -a -t $VIP:$TPORT -r $RIP:$TPORT -m -w 1
    done
  done

  # For each UDP service listed in the configuration, add the service
  # and add the Real-servers that provide the service.
  for UPORT in $UPORTS; do

    # -A = Add service; -u = Service uses UDP
    # $VIP:$UPORTS = Virtual IP Address of new service, and the port
    # number of the service being presented on this interface.
    # -s = scheduling method (rr = Round Robin)
    $IPVSADM -A -u $VIP:$UPORT -s rr

    # Add real-servers into the LVS cluster for the above service.
    #
    # -a = Add real-server;  -t = Service uses TCP
    # 156.141.59.63:telnet = Virtual IP Address of new service,
    # and the port number of the service being presented on this interface.
    # -r <host>:<port> = hostname/IP Address of the real-server and port
    # number of the service on the real-server.
    # -m = use Masquerading (aka Network Address Translation)
    # -w = Weight of the real-server in the pool. Can be used to direct traffic
    # to more powerful servers in the pool.
    for RIP in $RIPS; do
      $IPVSADM -a -u $VIP:$UPORT -r $RIP:$UPORT -m -w 1
    done
  done
}


poll_servers() {
  # Ping each host in the cluster to verify whether or not they are
  # alive. Systems which do not respond should be removed from the
  # ipvs table.
  for RIP in $RIPS; do
    # In order to be reduce dependencies, assume that fping is
    # unavailable, and use the less efficient system ping command. In
    # order to accommodate network latency, systems that do not
    # respond will be polled again, up to a maximum of $SEEK
    # iterations.
    SEEK=4
    while [ $SEEK -gt 0 ]; do
      [ -z "`ping -c 1 $RIP | grep 100%`" ] && SEEK=-1 || SEEK=$(($SEEK-1))
    done

    # If SEEK is "-1" then a positive result was obtained and the host
    # is available to the network. Now check to see if the host is in
    # the LVS table -- if it is not, then add the host to the
    # configuration.
    if [ "$SEEK" = "-1" ]; then
      # Check to see if the host is already in the configuration. If
      # it is not, then add it.
      if [ -z "$($IPVSADM -l | grep $RIP)" ]; then
	for TPORT in $TPORTS; do
	  $IPVSADM -a -t $VIP:$TPORT -r $RIP:$TPORT -m -w 1
	done
	for UPORT in $UPORTS; do
          $IPVSADM -a -u $VIP:$UPORT -r $RIP:$UPORT -m -w 1
	done
        mail -s "[LVS WARNING] Login Node Added" malcolm_cowe@xxxxxxxxxxx <<EOF
$RIP added to LVS login cluster.
EOF
      fi
    else
      # If the value of SEEK is not -1, then the host was not found on
      # the network. If this is the case, the host is removed from the
      # active LVS configuration.
      if [ ! -z "$($IPVSADM -l | grep $RIP)" ]; then
	for TPORT in $TPORTS; do
          $IPVSADM -d -t $VIP:$TPORT -r $RIP:$TPORT
	done
	for UPORT in $UPORTS; do
          $IPVSADM -d -u $VIP:$UPORT -r $RIP:$UPORT
	done
        mail -s "[LVS WARNING] Login Node Removed" malcolm_cowe@xxxxxxxxxxx <<EOF
$RIP removed from LVS login cluster. Possible node failure.
EOF
      fi
    fi
  done
}


lock_file() {
  case "$1" in
    add)
      touch /var/lock/subsys/lvs-director
      ;;
    remove)
      rm -f /var/lock/subsys/lvs-director
      ;;
  esac
}


usage() {
    echo $"Usage: $0 {start|stop|reload|status|update}"
}


#
# Start of the main iteration
#

case "$1" in
  start)
    if [ -f /var/lock/subsys/lvs-director ]; then
      echo "LVS Already running"
      exit 1
    fi
    reset_lvs
    configure_networking
    add_services
    lock_file add
    ;;
  stop)
    reset_lvs
    remove_interface
    lock_file remove
    ;;
  reload)
    reset_lvs
    add_services
    ;;
  status)
    $IPVSADM -L
    ;;
  update)
    if [ ! -f /var/lock/subsys/lvs-director ]; then
      echo "LVS is not running. Cannot update service."
      exit 1
    fi
    poll_servers
    ;;
  *)
    usage
    ;;
esac