ec2net-functions

#!/bin/sh

# Copyright (C) 2012 Amazon.com, Inc. or its affiliates.
# All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License").
# You may not use this file except in compliance with the License.
# A copy of the License is located at
#
#    http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
# OF ANY KIND, either express or implied. See the License for the
# specific language governing permissions and limitations under the
# License.

# This file is not a stand-alone shell script; it provides functions
# to ec2 network scripts that source it.

# Set up a default search path.
PATH="/sbin:/usr/sbin:/bin:/usr/bin"
export PATH

# metadata query requires an interface and hardware address
if [ -z "${INTERFACE}" ]; then
  exit
fi
HWADDR=$(cat /sys/class/net/${INTERFACE}/address 2>/dev/null)
if [ -z "${HWADDR}" ] && [ "${ACTION}" != "remove" ]; then
  exit
fi
export HWADDR

# generate a routing table number
RTABLE=$(( ${INTERFACE#eth} + 10000 ))

metadata_base="http://169.254.169.254/latest/meta-data/network/interfaces/macs"
config_file="/etc/network/interfaces.d/${INTERFACE}.cfg"
dhclient_file="/etc/dhcp/dhclient-${INTERFACE}.conf"

# make no changes to unmanaged interfaces
if [ -s ${config_file} ]; then
  unmanaged=$(LANG=C grep -l "^[[:space:]]*EC2SYNC=no\([[:space:]#]\|$\)" $config_file)
  if [ "${config_file}" = "${unmanaged}" ]; then
    exit
  fi
fi

get_meta() {
  attempts=10
  false
  while [ "${?}" -gt 0 ]; do
    [ "${attempts}" -eq 0 ] && return
    meta=$(curl -s -f ${metadata_base}/${HWADDR}/${1})
    if [ "${?}" -gt 0 ]; then
      let attempts--
      sleep 3
      false
    fi
  done
  echo "${meta}"
}

get_cidr() {
  cidr=$(get_meta 'subnet-ipv4-cidr-block')
  echo "${cidr}"
}

get_ipv4s() {
  ipv4s=$(get_meta 'local-ipv4s')
  echo "${ipv4s}"
}

get_primary_ipv4() {
  printf '%s ' $(get_ipv4s) | cut -d' ' -f1
}

get_secondary_ipv4s() {
  printf '%s ' $(get_ipv4s) | cut -d' ' -f2-
}

remove_primary() {
  if [ "${INTERFACE}" = "eth0" ]; then
    return
  fi
  rm -f ${config_file}
  rm -f ${dhclient_file}
}

rewrite_primary() {
  if [ "${INTERFACE}" = "eth0" ]; then
    return
  fi
  cidr=$(get_cidr)
  if [ -z ${cidr} ]; then
    return
  fi
  network=$(echo ${cidr}|cut -d/ -f1)
  router=$(( $(echo ${network}|cut -d. -f4) + 1 ))
  gateway="$(echo ${network}|cut -d. -f1-3).${router}"
  cat <<- EOF > ${config_file}
# This file is automaticatically generated
# See https://github.com/jessecollier/ubuntu-ec2net for source
auto ${INTERFACE}
iface ${INTERFACE} inet dhcp
post-up ip route add default via ${gateway} dev ${INTERFACE} table ${RTABLE}
post-up ip route add default via ${gateway} dev ${INTERFACE} metric ${RTABLE}
EOF
  # Use broadcast address instead of unicast dhcp server address.
  # Works around an issue with two interfaces on the same subnet.
  # Unicast lease requests go out the first available interface,
  # and dhclient ignores the response. Broadcast requests go out
  # the expected interface, and dhclient accepts the lease offer.
  cat <<- EOF > ${dhclient_file}
	supersede dhcp-server-identifier 255.255.255.255;
EOF
}

remove_aliases() {
  /sbin/ip addr flush dev ${INTERFACE} secondary
}

rewrite_aliases() {
  aliases=$(get_secondary_ipv4s)
  if [ ${#aliases[*]} -eq 0 ]; then
    remove_aliases
    return
  fi
  # The network prefix can be provided in the environment by
  # e.g. DHCP, but if it's not available then we need it to
  # correctly configure secondary addresses.
  if [ -z "${PREFIX}" ]; then
    cidr=$(get_cidr)
    PREFIX=$(echo ${cidr}|cut -d/ -f2)
  fi
  [ -n "${PREFIX##*[!0-9]*}" ] || return
  # Retrieve a list of secondary IP addresses on the interface.
  # Treat this as the stale list. For each IP address obtained
  # from metadata, cross it off the stale list if present, or
  # add it to the interface otherwise. Then, remove any address
  # remaining in the stale list.
bash -s -- "${INTERFACE}" "${PREFIX}" $aliases <<\EOF
  INTERFACE="$1"; shift;
  PREFIX="$1"; shift;
  aliases=( "$@" )
  declare -A secondaries
  for secondary in $(/sbin/ip addr list dev ${INTERFACE} secondary \
                     |grep "inet .* secondary ${INTERFACE}" \
                     |awk '{print $2}'|cut -d/ -f1); do
    secondaries[${secondary}]=1
  done
  for alias in ${aliases}; do
    if [[ ${secondaries[${alias}]} ]]; then
      unset secondaries[${alias}]
    else
      /sbin/ip addr add ${alias}/${PREFIX} brd + dev ${INTERFACE}
    fi
  done
  for secondary in "${!secondaries[@]}"; do
    /sbin/ip addr del ${secondary}/${PREFIX} dev ${INTERFACE}
  done
EOF
}

remove_rules() {
  if [ "${INTERFACE}" = "eth0" ]; then
    return
  fi
  for rule in $(/sbin/ip rule list \
                |grep "from .* lookup ${RTABLE}" \
                |awk -F: '{print $1}'); do
    /sbin/ip rule delete pref "${rule}"
  done
}

rewrite_rules() {
  if [ "${INTERFACE}" = "eth0" ]; then
    return
  fi
  ips=$( get_ipv4s | xargs printf '%s ' )
  if [ "${#ips}" -eq 0 ]; then
    remove_rules
    return
  fi
# Could not figure out how to eliminate all these Bashisms but this script is
# sourced from a /bin/sh script so we have to wrap them.
bash -s -- "$RTABLE" $ips <<\EOF
  RTABLE="$1" ; shift
  ips=( "$@" )
  # Retrieve a list of IP rules for the route table that belongs
  # to this interface. Treat this as the stale list. For each IP
  # address obtained from metadata, cross the corresponding rule
  # off the stale list if present. Otherwise, add a rule sending
  # outbound traffic from that IP to the interface route table.
  # Then, remove all other rules found in the stale list.
  declare -A rules
  for rule in $( /sbin/ip rule list |
                 grep "from .* lookup ${RTABLE}" |
                 awk '{print $1$3}' ); do
    split=(${rule//:/ })
    rules[${split[1]}]=${split[0]}
  done
  for ip in "${ips[@]}"; do
    if [[ ${rules[${ip}]} ]]; then
      unset rules[${ip}]
    else
      /sbin/ip rule add from "${ip}" lookup ${RTABLE}
    fi
  done
  for rule in "${!rules[@]}"; do
    /sbin/ip rule delete pref "${rules[${rule}]}"
  done
EOF
}

plug_interface() {
    logger "ABOUT TO CALL REWRITE PRIMARY"
  rewrite_primary
}

unplug_interface() {
  remove_rules
  remove_aliases
  remove_primary
}

activate_primary() {
  /sbin/ifup ${INTERFACE}
}

deactivate_primary() {
  /sbin/ifdown ${INTERFACE}
}