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#

#

# Copyright (C) 2011, 2012 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.

"""IP address pool management functions.

"""

import ipaddr

from bitarray import bitarray

from base64 import b64encode

from base64 import b64decode

from ganeti import errors

def _ComputeIpv4NumHosts(network_size):

  """Derives the number of hosts in an IPv4 network from the size.

  """

  return 2 ** (32 - network_size)

IPV4_NETWORK_MIN_SIZE = 30

# FIXME: This limit is for performance reasons. Remove when refactoring

# for performance tuning was successful.

IPV4_NETWORK_MAX_SIZE = 16

IPV4_NETWORK_MIN_NUM_HOSTS = _ComputeIpv4NumHosts(IPV4_NETWORK_MIN_SIZE)

IPV4_NETWORK_MAX_NUM_HOSTS = _ComputeIpv4NumHosts(IPV4_NETWORK_MAX_SIZE)

class AddressPool(object):

  """Address pool class, wrapping an C{objects.Network} object.

  This class provides methods to manipulate address pools, backed by

  L{objects.Network} objects.

  """

  FREE = bitarray("0")

  RESERVED = bitarray("1")

  def __init__(self, network):

    """Initialize a new IPv4 address pool from an L{objects.Network} object.

    @type network: L{objects.Network}

    @param network: the network object from which the pool will be generated

    """

    self.network = None

    self.gateway = None

    self.network6 = None

    self.gateway6 = None

    self.net = network

    self.network = ipaddr.IPNetwork(self.net.network)

    if self.network.numhosts > IPV4_NETWORK_MAX_NUM_HOSTS:

      raise errors.AddressPoolError("A big network with %s host(s) is currently"

                                    " not supported. please specify at most a"

                                    " /%s network" %

                                    (str(self.network.numhosts),

                                     IPV4_NETWORK_MAX_SIZE))

    if self.network.numhosts < IPV4_NETWORK_MIN_NUM_HOSTS:

      raise errors.AddressPoolError("A network with only %s host(s) is too"

                                    " small, please specify at least a /%s"

                                    " network" %

                                    (str(self.network.numhosts),

                                     IPV4_NETWORK_MIN_SIZE))

    if self.net.gateway:

      self.gateway = ipaddr.IPAddress(self.net.gateway)

    if self.net.network6:

      self.network6 = ipaddr.IPv6Network(self.net.network6)

    if self.net.gateway6:

      self.gateway6 = ipaddr.IPv6Address(self.net.gateway6)

    if self.net.reservations:

      self.reservations = bitarray()

      self.reservations.frombytes(b64decode(self.net.reservations))

    else:

      self.reservations = bitarray(self.network.numhosts)

      # pylint: disable=E1103

      self.reservations.setall(False)

    if self.net.ext_reservations:

      self.ext_reservations = bitarray()

      self.ext_reservations.frombytes(b64decode(self.net.ext_reservations))

    else:

      self.ext_reservations = bitarray(self.network.numhosts)

      # pylint: disable=E1103

      self.ext_reservations.setall(False)

    assert len(self.reservations) == self.network.numhosts

    assert len(self.ext_reservations) == self.network.numhosts

  def Contains(self, address):

    if address is None:

      return False

    addr = ipaddr.IPAddress(address)

    return addr in self.network

  def _GetAddrIndex(self, address):

    addr = ipaddr.IPAddress(address)

    if not addr in self.network:

      raise errors.AddressPoolError("%s does not contain %s" %

                                    (self.network, addr))

    return int(addr) - int(self.network.network)

  def Update(self):

    """Write address pools back to the network object.

    """

    # pylint: disable=E1103

    self.net.ext_reservations = b64encode(self.ext_reservations.tobytes())

    self.net.reservations = b64encode(self.reservations.tobytes())

  def _Mark(self, address, value=True, external=False):

    idx = self._GetAddrIndex(address)

    if external:

      self.ext_reservations[idx] = value

    else:

      self.reservations[idx] = value

    self.Update()

  def _GetSize(self):

    return 2 ** (32 - self.network.prefixlen)

  @property

  def all_reservations(self):

    """Return a combined map of internal and external reservations.

    """

    return (self.reservations | self.ext_reservations)

  def Validate(self):

    assert len(self.reservations) == self._GetSize()

    assert len(self.ext_reservations) == self._GetSize()

    all_res = self.reservations & self.ext_reservations

    if self.gateway is not None:

      assert self.gateway in self.network

    if self.network6 and self.gateway6:

      assert self.gateway6 in self.network6

    return True

  def IsFull(self):

    """Check whether the network is full.

    """

    return self.all_reservations.all()

  def GetReservedCount(self):

    """Get the count of reserved addresses.

    """

    return self.all_reservations.count(True)

  def GetFreeCount(self):

    """Get the count of unused addresses.

    """

    return self.all_reservations.count(False)

  def GetMap(self):

    """Return a textual representation of the network's occupation status.

    """

    return self.all_reservations.to01().replace("1", "X").replace("0", ".")

  def IsReserved(self, address, external=False):

    """Checks if the given IP is reserved.

    """

    idx = self._GetAddrIndex(address)

    if external:

      return self.ext_reservations[idx]

    else:

      return self.reservations[idx]

  def Reserve(self, address, external=False):

    """Mark an address as used.

    """

    if self.IsReserved(address, external):

      if external:

        msg = "IP %s is already externally reserved" % address

      else:

        msg = "IP %s is already used by an instance" % address

      raise errors.AddressPoolError(msg)

    self._Mark(address, external=external)

  def Release(self, address, external=False):

    """Release a given address reservation.

    """

    if not self.IsReserved(address, external):

      if external:

        msg = "IP %s is not externally reserved" % address

      else:

        msg = "IP %s is not used by an instance" % address

      raise errors.AddressPoolError(msg)

    self._Mark(address, value=False, external=external)

  def GetFreeAddress(self):

    """Returns the first available address.

    """

    if self.IsFull():

      raise errors.AddressPoolError("%s is full" % self.network)

    idx = self.all_reservations.index(False)

    address = str(self.network[idx])

    self.Reserve(address)

    return address

  def GenerateFree(self):

    """Returns the first free address of the network.

    @raise errors.AddressPoolError: Pool is full

    """

    idx = self.all_reservations.search(self.FREE, 1)

    if idx:

      return str(self.network[idx[0]])

    else:

      raise errors.AddressPoolError("%s is full" % self.network)

  def GetExternalReservations(self):

    """Returns a list of all externally reserved addresses.

    """

    # pylint: disable=E1103

    idxs = self.ext_reservations.search(self.RESERVED)

    return [str(self.network[idx]) for idx in idxs]

  @classmethod

  def InitializeNetwork(cls, net):

    """Initialize an L{objects.Network} object.

    Reserve the network, broadcast and gateway IP addresses.

    """

    obj = cls(net)

    obj.Update()

    for ip in [obj.network[0], obj.network[-1]]:

      obj.Reserve(ip, external=True)

    obj.Validate()

    return obj