ec2net-functions

#!/bin/bash

# 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

# Check if Predictable Network Interface Name is enabled
# and set the interface name prefix and default primary interface
if [[ $INTERFACE == eth* ]]; then
    PRIMARY_INTERFACE=eth0
    TYPE=eth
else
    PRIMARY_INTERFACE=ens3
    TYPE=ens
fi

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

metadata_base="http://169.254.169.254/latest/meta-data/network/interfaces/macs"
config_file="/etc/network/interfaces.d/if-${INTERFACE}.cfg"
dhclient_file="/etc/dhcp/dhclient-${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=60
  false
  while [ "${?}" -gt 0 ]; do
    if [ "${attempts}" -eq 0 ]; then
      logger --tag ec2net "[get_meta] Failed to get ${metadata_base}/${HWADDR}/${1}"
      return
    fi
    logger --tag ec2net "[get_meta] Trying to get ${metadata_base}/${HWADDR}/${1}"
    meta=$(curl -s -f ${metadata_base}/${HWADDR}/${1})
    if [ "${?}" -gt 0 ]; then
      let attempts--
      sleep 0.5
      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-
}

get_ipv6s() {
  /sbin/ip -6 addr list dev ${INTERFACE} scope global \
      | grep "inet6" \
      | awk '{print $2}' | cut -d/ -f1
}

get_ipv6_gateway() {
  # Because we start dhclient -6 immediately on interface
  # hotplug, it's possible we get a DHCP response before we
  # receive a router advertisement. The only immediate clue we
  # have about the gateway is the MAC address embedded in the
  # DHCP6 server ID. If that env var is passed to dhclient-script
  # we determine the router address from that; otherwise we wait
  # up to 10 seconds for an RA route to be added by the kernel.

  if echo "$new_dhcp6_server_id" | grep -q "^0:3:0:1:"; then
    logger --tag ec2net "[get_ipv6_gateway] Using DHCP6 environment variable"
    octets=($(echo "$new_dhcp6_server_id" | rev | cut -d : -f -6 | rev | tr : ' '))

    # The gateway's link local address is derived from the
    # hardware address by converting the MAC-48 to an EUI-64:
    #   00:00:5e  :  00:53:35
    #   ^^      ^^^^^ ff:fe is inserted in the middle
    #   first octet is xored with 0x2 (second LSB is flipped)
    # thus 02:00:5e:ff:fe:00:53:35.
    #
    # The EUI-64 is used as the last 64 bits in an fe80::/64
    # address, so fe80::200:5eff:fe00:5335.

    declare -A quibbles # quad nibbles
    quibbles[0]=$(( ((0x${octets[0]} ^ 2) << 8) + 0x${octets[1]} ))
    quibbles[1]=$(( 0x${octets[2]}ff ))
    quibbles[2]=$(( 0xfe00 + 0x${octets[3]} ))
    quibbles[3]=$(( (0x${octets[4]} << 8) + 0x${octets[5]} ))
    printf "fe80::%04x:%04x:%04x:%04x\n" ${quibbles[@]}
  else
    logger --tag ec2net "[get_ipv6_gateway] Waiting for IPv6 router advertisement"
    attempts=20
    while true; do
      if [ "${attempts}" -eq 0 ]; then
        logger --tag ec2net "[get_ipv6_gateway] Failed to receive router advertisement"
        return
      fi
      gateway6=$(/sbin/ip -6 route show dev "${INTERFACE}" | grep ^default | awk '{print $3}')
      if [ -n "${gateway6}" ]; then
        break
      else
        let attempts--
        sleep 0.5
      fi
    done
    echo "${gateway6}"
  fi
}

remove_primary() {
  if [ "${INTERFACE}" = "${PRIMARY_INTERFACE}" ]; then
    return
  fi
  logger --tag ec2net "[remove_primary] Removing configs for ${INTERFACE}"
  rm -f ${config_file}
  rm -f ${dhclient_file}
}

rewrite_primary() {
  if [ "${INTERFACE}" = "${PRIMARY_INTERFACE}" ]; 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/iget-master/ubuntu-ec2net for source
    auto ${INTERFACE}
    iface ${INTERFACE} inet dhcp
    iface ${INTERFACE} inet6 dhcp
    post-up ip route add default via ${gateway} dev ${INTERFACE} table ${RTABLE}
    post-up ip route add default via ${gateway} dev ${INTERFACE} metric ${RTABLE}
    post-up route add default gw ip-${gateway//./-} ${INTERFACE}
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() {
  logger --tag ec2net "[remove_aliases] Removing aliases of ${INTERFACE}"
  /sbin/ip addr flush dev ${INTERFACE} secondary
}

rewrite_aliases() {
  aliases=$(get_secondary_ipv4s)
  if [ ${#aliases[*]} -eq 0 ]; then
    remove_aliases
    return
  fi
  logger --tag ec2net "[rewrite_aliases] Rewriting aliases of ${INTERFACE}"
  # The network prefix can be provided in the environment by
  # e.g. DHCP, but if it's not available then we need it to
  # correctly configure secondary addresses.
  if [ -z "${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.
  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
}

remove_rules() {
  if [ "${INTERFACE}" == "${PRIMARY_INTERFACE}" ]; then
    return
  fi
  logger --tag ec2net "[remove_rules] Removing rules for ${INTERFACE}"
  for rule in $(/sbin/ip -4 rule list \
                |grep "from .* lookup ${RTABLE}" \
                |awk -F: '{print $1}'); do
    /sbin/ip -4 rule delete pref "${rule}"
  done
  for rule in $(/sbin/ip -6 rule list \
                |grep "from .* lookup ${RTABLE}" \
                |awk -F: '{print $1}'); do
    /sbin/ip -6 rule delete pref "${rule}"
  done
}

rewrite_rules() {
  if [ "${INTERFACE}" == "${PRIMARY_INTERFACE}" ]; then
    return
  fi
  ips=($(get_ipv4s))
  ip6s=($(get_ipv6s))
  if [ ${#ips[*]} -eq 0 ]; then
    remove_rules
    return
  fi
  # This is the part we would do in rewrite_primary() if we knew
  # the gateway address.
  if [ ${#ip6s[*]} -gt 0 -a -z "$(/sbin/ip -6 route show table ${RTABLE})" ]; then
    gateway6=$(get_ipv6_gateway)
    # Manually add the route, then add it to ${route6_file} so it
    # gets brought down with the rest of the interface.
    /sbin/ip -6 route add default via ${gateway6} dev ${INTERFACE} table ${RTABLE}
    cat <<- EOF > ${route6_file}
	default via ${gateway6} dev ${INTERFACE} table ${RTABLE}
EOF
  fi
  logger --tag ec2net "[rewrite_rules] Rewriting rules for ${INTERFACE}"
  # 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 -4 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 -4 rule add from ${ip} lookup ${RTABLE}
    fi
  done
  for rule in "${!rules[@]}"; do
    /sbin/ip -4 rule delete pref "${rules[${rule}]}"
  done
  # Now do the same, but for IPv6
  declare -A rules6
  for rule in $(/sbin/ip -6 rule list \
                |grep "from .* lookup ${RTABLE}" \
                |awk '{print $1$3}'); do
    split=(${rule/:/ }) # take care to only replace the first :
    rules6[${split[1]}]=${split[0]}
  done
  for ip in ${ip6s[@]}; do
    if [[ ${rules6[${ip}]} ]]; then
      unset rules6[${ip}]
    else
      /sbin/ip -6 rule add from ${ip} lookup ${RTABLE}
    fi
  done
  for rule in "${!rules6[@]}"; do
    /sbin/ip -6 rule delete pref "${rules6[${rule}]}"
  done
}

plug_interface() {
  logger --tag ec2net "[plug_interface] ${INTERFACE} plugged"
  rewrite_primary
}

unplug_interface() {
  logger --tag ec2net "[unplug_interface] ${INTERFACE} unplugged"
  remove_rules
  remove_aliases
  remove_primary
}

activate_primary() {
  logger --tag ec2net "[activate_primary] Activating ${INTERFACE}"
  /sbin/ifup ${INTERFACE}
}

deactivate_primary() {
  logger --tag ec2net "[deactivate_primary] Deactivating ${INTERFACE}"
  /sbin/ifdown ${INTERFACE}
}