Introduce new module for IP pool management

Add new library module lib/network.py.
Introduce new class: AddressPool.

AddressPool implements all operations needed for managing IPs
inside the IP pool.

Given a Network config object (nobj), the class:

 * initializes the corresponding IP pool object via
   network.AddressPool.InitializeNetwork(nobj)
 * obtains the corresponding IP pool object via
   network.AddressPool(nobj)
 * manipulates IPs inside the pool

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>

lib/errors.py

@@ -139,6 +139,12 @@ class ConfigVersionMismatch(ConfigurationError):
   pass
 
 
+class AddressPoolError(GenericError):
+  """Errors related to IP address pools.
+
+  """
+
+
 class ReservationError(GenericError):
   """Errors reserving a resource.
 

lib/network.py

+#
+#
+
+# Copyright (C) 2011 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 ganeti import errors
+
+class AddressPool(object):
+  """Address pool class, wrapping an objects.Network object
+
+  This class provides methods to manipulate address pools, backed by
+  L{objects.Network} objects.
+
+  """
+  def __init__(self, network):
+    """Initialize a new IPv4 address pool from an 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.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.net.reservations)
+    else:
+      self.reservations = bitarray(self.network.numhosts)
+      self.reservations.setall(False)
+
+    if self.net.ext_reservations:
+      self.ext_reservations = bitarray(self.net.ext_reservations)
+    else:
+      self.ext_reservations = bitarray(self.network.numhosts)
+      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"""
+    self.net.ext_reservations = self.ext_reservations.to01()
+    self.net.reservations = self.reservations.to01()
+
+  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 + external reservations."""
+    return (self.reservations | self.ext_reservations)
+
+  def Validate(self):
+    assert self.net.family == 4
+    assert len(self.reservations) == self._GetSize()
+    assert len(self.ext_reservations) == self._GetSize()
+    assert not (self.reservations & self.ext_reservations).any()
+
+    if self.gateway is not None:
+      assert self.net.family == self.gateway.version
+      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):
+    """Checks if the given IP is reserved"""
+    idx = self._GetAddrIndex(address)
+    return self.all_reservations[idx]
+
+  def Reserve(self, address, external=False):
+    """Mark an address as used."""
+    if self.IsReserved(address):
+      raise errors.AddressPoolError("%s is already reserved" % address)
+    self._Mark(address, external=external)
+
+  def Release(self, address, external=False):
+    """Release a given address reservation."""
+    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):
+    """A generator for free addresses."""
+    def _iter_free():
+      for idx in self.all_reservations.search("0", 64):
+        yield str(self.network[idx])
+
+    return _iter_free().next
+
+  def GetExternalReservations(self):
+    """Returns a list of all externally reserved addresses"""
+    idxs = self.ext_reservations.search("1")
+    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 IPs
+
+    """
+    obj = cls(net)
+    obj._Update()
+    for ip in [obj.network[0], obj.network[-1]]:
+      obj.Reserve(ip, external=True)
+    if obj.net.gateway is not None:
+      obj.Reserve(obj.net.gateway, external=True)
+    obj.Validate()
+    return obj