When creating a network, so far no size constraints were checked.
We now limit the size of a network to a /30 or bigger, although
tecnically, the ipaddr library supports even /32 networks.

Signed-off-by: Helga Velroyen <helgav@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Signed-off-by: Iustin Pop <iustin@google.com>
[iustin@google.com: slightly improved code flow]
Reviewed-by: Iustin Pop <iustin@google.com>

- Quote characters
- Docstrings

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Reviewed-by: Iustin Pop <iustin@google.com>

GenerateFree now returns the first available IP in the network
or raises AddressPoolError if it is full.

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Reviewed-by: Iustin Pop <iustin@google.com>

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Reviewed-by: Iustin Pop <iustin@google.com>

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Reviewed-by: Iustin Pop <iustin@google.com>

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Reviewed-by: Iustin Pop <iustin@google.com>

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: Apollon Oikonomopoulos <apollon@noc.grnet.gr>
Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Reviewed-by: Iustin Pop <iustin@google.com>