Synnefo » snf-ganeti

#!/bin/bash

#

# Copyright (C) 2014 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.

# This script is a hook called to configure new TAP network interfaces

# used for instance communication, and it should be called whenever a

# new instance is started.

#

# This script configures the new interface but it also performs

# maintenance on the network interfaces that have been configured

# before, by checking whether those TAP interfaces still exist, etc.

#

# This script also controls the DHCP server that leases IP address for

# instances, i.e., the NICs inside the instances, not the TAP

# interfaces.  The DHCP server is started and restarted (or reHUPed)

# as necessary and always with up-to-date configuration files.

#

# This script expects the following environment variables

#

#   INTERFACE: network interface name to be configured

#   MODE: networking mode for 'INTERFACE' (must be 'routed')

#   MAC: MAC address for 'INTERFACE'

#   IP: IP address for 'INTERFACE'

source @PKGLIBDIR@/net-common

readonly NETMASK=255.255.255.255

readonly DNSMASQ_CONF=/var/run/ganeti/dnsmasq.conf

readonly DNSMASQ_HOSTS=/var/run/ganeti/dnsmasq.hosts

readonly DNSMASQ_PID=/var/run/ganeti/dnsmasq.pid

# join intercalates a sequence of arguments using the given separator

function join {

  local IFS="$1"

  shift

  echo "$*"

}

# restart_dnsmasq restarts the DHCP server dnsmasq with the (possibly

# up-to-date) configuration file.

#

# If all instances have been terminated, which means there are no more

# TAP network interfaces to monitor or IP addresses to lease, the DHCP

# server is terminated through 'SIGTERM'.

#

# If there are still instances running, then:

#  - if the DHCP server is running, a 'SIGHUP' will be sent to the

#    dnsmasq process which will cause the configuration file to be

#    re-read, while keeping the process running

#  - if the DHCP server is not running, it will be started, and the

#    configuration file will be passed it

function restart_dnsmasq {

  SIGNAL=

  if [ -z "$ALIVE_INTERFACES" -o -z "$ALIVE_LEASES" ]

  then

      SIGNAL=TERM

  else

      SIGNAL=HUP

  fi

  RUNNING=

  if [ -f "$DNSMASQ_PID" ]

  then

      PID=$(cat $DNSMASQ_PID)

      if [ -n "$PID" ] && ps -p "$PID"

      then

	  RUNNING=yes

      fi

  fi

  KILLED=

  if [ "$RUNNING" = yes ]

  then

      kill -$SIGNAL $PID

      if [ "$SIGNAL" = TERM ]

      then

	  KILLED=yes

      fi

  fi

  if [ "$KILLED" = yes ]

  then

      rm -f $DNSMASQ_PID

  fi

  if [ "$RUNNING" != yes -o "$KILLED" == yes ]

  then

      if [ -n "$ALIVE_INTERFACES" -a -n "$ALIVE_LEASES" ]

      then

	  dnsmasq -C $DNSMASQ_CONF

      fi

  fi

  return 0

}

# Check that environment variable 'INTERFACE' exists.

#

# This environment variable holds the TAP network interface that

# should be configured by this script.  Ganeti always passes it,

# but... :)

if [ -z "$INTERFACE" ]

then

  echo kvm-vif-bridge: Failed to configure communication mechanism \

      interface because the \'INTERFACE\' environment variable was \

      not specified to the \'kvm-vif-bridge\' script

  exit 1

fi

# Check that environment variable 'MODE' exists.

#

# See comment about environment variable 'INTERFACE'.

if [ -z "$MODE" ]

then

  echo kvm-vif-bridge: Failed to configure communication mechanism \

      interface because the \'MODE\' environment variable was \

      not specified to the \'kvm-vif-bridge\' script

  exit 1

fi

# Check whether the interface being configured has instance

# communication enabled, otherwise exit this script.

if ! is_instance_communication_tap; then exit 0; fi

# Check that environment variable 'MAC' exists.

#

# See comment about environment variable 'INTERFACE'.

if [ -z "$MAC" ]

then

  echo kvm-vif-bridge: Failed to configure communication mechanism \

      interface because the \'MAC\' environment variable was \

      not specified to the \'kvm-vif-bridge\' script

  exit 1

fi

# Check that environment variable 'IP' exists.

#

# See comment about environment variable 'INTERFACE'.

if [ -z "$IP" ]

then

  echo kvm-vif-bridge: Failed to configure communication mechanism \

      interface because the \'IP\' environment variable was \

      not specified to the \'kvm-vif-bridge\' script

  exit 1

fi

# Configure the TAP interface

#

# Ganeti defers the configuration of instance network interfaces to

# hooks, therefore, we must configure the interface's network address,

# netmask, and IP address.

#

# The TAP network interface, which is used by the instance

# communication, is part of the network 169.254.0.0/16 and has the IP

# 169.254.169.254.  Because all network interfaces used in the

# instance communication have the same IP, the routing table must also

# be configured, and that is done at a later step.

#

# Note the interface must be marked as up before configuring the

# routing table and before starting/restarting the DHCP server.

#

# Note also that we don't have to check whether the interface is

# already configured because reconfiguring the interface with the same

# parameters does not produce an error.

ifconfig $INTERFACE 169.254.169.254 netmask $NETMASK up

# Configure the routing table

#

# Given that all TAP network interfaces in the instance communication

# have the same IP address, the routing table must be configured in

# order to properly route traffic from the host to the guests.

#

# Note that we must first check if a duplicate routing rule has

# already been added to the routing table, as this operation will fail

# if we try to add a routing rule that already exists.

ACTIVE_IP=$(ip route | grep "dev $INTERFACE" | awk '{ print $1 }')

if [ -z "$ACTIVE_IP" -o "$ACTIVE_IP" != "$IP" ]

then

  route add -host $IP dev $INTERFACE

fi

# Ensure the DHCP server configuration files exist

touch $DNSMASQ_CONF

chmod 0644 $DNSMASQ_CONF

touch $DNSMASQ_HOSTS

chmod 0644 $DNSMASQ_HOSTS

# Determine dnsmasq operational mode.

#

# The DHCP server dnsmasq can run in different modes.  In this version

# of the script, only the mode 'bind-dynamic' is supported.  Please

# refer to the dnsmasq FAQ for a detailed of each mode.

#

# Note that dnsmasq might already be running, therefore, we don't need

# to determine which modes are supported by this DHCP server.

# Instead, we just read the current mode from the configuration file.

DNSMASQ_MODE=$(head -n 1 $DNSMASQ_CONF)

if [ -z "$DNSMASQ_MODE" ]

then

  BIND_DYNAMIC=$(dnsmasq --help | grep -e --bind-dynamic)

  if [ -z "$BIND_DYNAMIC" ]

  then

    echo kvm-vif-bridge: dnsmasq mode \"bind-dynamic\" is not supported

    exit 1

  fi

  DNSMASQ_MODE=bind-dynamic

fi

# Determine the interfaces that should go in the configuration file.

#

# The TAP network interfaces used by the instance communication are

# named after the following pattern

#

#  gnt.com.%d

#

# where '%d' is a unique number within the host.  Fortunately, dnsmasq

# supports binding to specific network interfaces via a pattern.

ALIVE_INTERFACES=${GANETI_TAP}.*

# Determine which of the leases are not duplicated and should go in

# the new configuration file for the DHCP server.

#

# Given that instances come and go, it is possible that we offer more

# leases that necessary and, worse, that we have duplicate leases,

# that is, the same IP address for the same/different MAC addresses.

# Duplicate leases must be eliminated before being written to the

# configuration file.

CONF_LEASES=$(cat $DNSMASQ_HOSTS)

CONF_LEASES=$(join $'\n' $CONF_LEASES | sort -u)

ALIVE_LEASES=( $MAC,$IP )

for i in $CONF_LEASES

do

  LEASE_MAC=$(echo $i | cut -d "," -f 1)

  LEASE_IP=$(echo $i | cut -d "," -f 2)

  if [ "$LEASE_MAC" != "$MAC" -a "$LEASE_IP" != "$IP" ]

  then

      ALIVE_LEASES=( ${ALIVE_LEASES[@]} $i )

  fi

done

ALIVE_LEASES=$(echo ${ALIVE_LEASES[@]} | sort -u)

# Update dnsmasq configuration.

#

# Write the parameters we have collected before into the new dnsmasq

# configuration file.  Also, write the new leases into the new dnsmasq

# hosts file.  Finally, restart dnsmasq with the new configuration

# files.

cat > $DNSMASQ_CONF <<EOF

$DNSMASQ_MODE

dhcp-authoritative

dhcp-hostsfile=$DNSMASQ_HOSTS

dhcp-range=169.254.0.0,static,255.255.0.0

except-interface=eth*

except-interface=lo

leasefile-ro

no-hosts

no-ping

no-resolv

pid-file=$DNSMASQ_PID

port=0

strict-order

EOF

for i in $ALIVE_INTERFACES; do echo interface=$i >> $DNSMASQ_CONF; done

echo -n > $DNSMASQ_HOSTS

for i in $ALIVE_LEASES; do echo $i >> $DNSMASQ_HOSTS; done

restart_dnsmasq