#!/bin/bash
#
# /etc/dhcp/dhclient-exit-hooks
#
# This file is sourced by /sbin/dhclient-script.
#
# dhcp option 121 is defined in RFC3442. The following is the link. 
# http://www.ietf.org/rfc/rfc3442.txt
#
# The code for this option is 121, and its minimum length is 5 bytes.
# This option can contain one or more static routes, each of which
# consists of a destination descriptor and the IP address of the router
# that should be used to reach that destination.
#
#    Code Len Destination 1    Router 1
#   +-----+---+----+-----+----+----+----+----+----+
#   | 121 | n | d1 | ... | dN | r1 | r2 | r3 | r4 |
#   +-----+---+----+-----+----+----+----+----+----+
#
#    Destination 2       Router 2
#   +----+-----+----+----+----+----+----+
#   | d1 | ... | dN | r1 | r2 | r3 | r4 |
#   +----+-----+----+----+----+----+----+
#
# In the above example, two static routes are specified.
#
# The following table contains some examples of how various subnet
# number/mask combinations can be encoded:
#
#   Subnet number   Subnet mask      Destination descriptor
#   0               0                0
#   10.0.0.0        255.0.0.0        8.10
#   10.0.0.0        255.255.255.0    24.10.0.0
#   10.17.0.0       255.255.0.0      16.10.17
#   10.27.129.0     255.255.255.0    24.10.27.129
#   10.229.0.128    255.255.255.128  25.10.229.0.128
#   10.198.122.47   255.255.255.255  32.10.198.122.47
#
# For metadata service, the following is a valid route from nova-api that
# the VM instance can uses to retrieve metadata.
#
#   32 169 254 169 254 128 224 149 201
#
# In the above example, mask length of destination descriptor is always 32,
# destination is always "169.254.169.254", and the gateway is a valid IP address.
#
# The add_routes function takes an array of unsigned integer 8, separated by spaces,
# parse them, and added each of the routes into routing table.
#

function add_routes() {
while [ $# -ne 0 ]; do
  mask=$1
  shift
 
  # Parse the arguments into a CIDR net/mask string
  if [ $mask -eq 32 ]; then
    destination="-host $1.$2.$3.$4"
    shift; shift; shift; shift
  elif [ $mask -gt 24 ]; then
    destination="-net $1.$2.$3.$4/$mask"
    shift; shift; shift; shift
  elif [ $mask -gt 16 ]; then
    destination="-net $1.$2.$3.0/$mask"
    shift; shift; shift
  elif [ $mask -gt 8 ]; then
    destination="-net $1.$2.0.0/$mask"
    shift; shift
  else
    destination="-net $1.0.0.0/$mask"
    shift
  fi
 
  # Read the gateway
  gateway="$1.$2.$3.$4"
  shift; shift; shift; shift

  # Add route into routing table
  route add $destination gw $gateway

  # Print it out if the route is added successfully
  if [ $? = 0 ]; then
    echo "Added route \"$destination gw $gateway\""
  fi
done
}

# Call add_routes to add routes
if [ "x$new_classless_static_routes" != x ]; then
  add_routes $new_classless_static_routes
fi