#!/bin/bash
#

# Copyright (C) 2011 Google Inc.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.

set -e -u

USAGE_MSG="Usage: $0 {start|stop}"
PATH=$PATH:/sbin:/usr/sbin:/usr/local/sbin

FPING_PACKET_COUNT=5
FPING_PACKET_INTERVAL_MS=200

# Start the master IP
start() {
  case $CLUSTER_IP_VERSION in
    4)
      ARP_COMMAND="arping -q -U -c 3 -I $MASTER_NETDEV -s $MASTER_IP $MASTER_IP"
      ;;
    6)
      ARP_COMMAND="ndisc6 -q r 3 $MASTER_IP $MASTER_NETDEV"
      ;;
    *)
      echo "Invalid cluster IP version specified: $CLUSTER_IP_VERSION" >&2
      exit 1
      ;;
  esac

  # Check if the master IP address is already configured on this machine
  if fping -c $FPING_PACKET_COUNT -p $FPING_PACKET_INTERVAL_MS \
      -S 127.0.0.1 $MASTER_IP >/dev/null 2>&1; then
    echo "Master IP address already configured on this machine. Doing nothing."
    exit 0
  fi

  # Check if the master IP address is already configured on another machine
  if fping -c $FPING_PACKET_COUNT -p $FPING_PACKET_INTERVAL_MS \
      $MASTER_IP >/dev/null 2>&1; then
    echo "Error: master IP address configured on another machine." >&2
    exit 1
  fi

  if ! ip addr add $MASTER_IP/$MASTER_NETMASK \
     dev $MASTER_NETDEV label $MASTER_NETDEV:0; then
    echo "Error during the activation of the master IP address" >&2
    exit 1
  fi

  # Send gratuituous ARP to update neighbours' ARP cache
  $ARP_COMMAND || :
}

# Stop the master IP
stop() {
  # Check if the master IP address is still configured on this machine
  if ! ip addr show dev $MASTER_NETDEV | \
     grep -F " $MASTER_IP/$MASTER_NETMASK" >/dev/null 2>&1; then
    # Check if the master IP address is configured on a wrong device
    if fping -c $FPING_PACKET_COUNT -p $FPING_PACKET_INTERVAL_MS \
        -S 127.0.0.1 $MASTER_IP >/dev/null 2>&1; then
      echo "Error: master IP address configured on wrong device," \
           "can't shut it down." >&2
      exit 1
    else
      echo "Master IP address not configured on this machine. Doing nothing."
      exit 0
    fi
  fi

  if ! ip addr del $MASTER_IP/$MASTER_NETMASK dev $MASTER_NETDEV; then
    echo "Error during the deactivation of the master IP address" >&2
    exit 1
  fi
}

if (( $# < 1 )); then
  echo $USAGE_MSG >&2
  exit 1
fi

case "$1" in
  start)
    start
    ;;
  stop)
    stop
    ;;
  *)
    echo $USAGE_MSG >&2
    exit 1
    ;;
esac

exit 0