Limit allowed network size

Limit the size of networks that users can create, since big IP
pools can have negative impact on performance. Allowed network
size is controled by 'MAX_CIDR_BLOCK' setting.

snf-cyclades-app/synnefo/api/networks.py

@@ -44,9 +44,10 @@ from synnefo.api import util
 from synnefo.api.actions import network_actions
 from synnefo.api.common import method_not_allowed
 from synnefo.api.faults import (BadRequest, Unauthorized,
-                                NetworkInUse)
+                                NetworkInUse, OverLimit)
 from synnefo.db.models import Network
 from synnefo.logic import backend
+from synnefo.settings import MAX_CIDR_BLOCK
 
 
 log = getLogger('synnefo.api')
@@ -168,6 +169,10 @@ def create_network(request):
     if type == 'PUBLIC_ROUTED':
         raise Unauthorized('Can not create a public network.')
 
+    cidr_block = int(subnet.split('/')[1])
+    if cidr_block <= MAX_CIDR_BLOCK:
+        raise OverLimit("Network size is to big. Please specify a network"
+                        " smaller than /" + str(MAX_CIDR_BLOCK) + '.')
 
     link, mac_prefix = util.network_specs_from_type(type)
     if not link:

snf-cyclades-app/synnefo/app_settings/default/api.py

@@ -21,6 +21,8 @@ POLL_LIMIT = 3600
 # Network Configuration
 #
 
+# Maximum allowed network size for private networks.
+MAX_CIDR_BLOCK = 22
 # Name of the network in Ganeti corresponding to the default public network.
 # All created VMs will obtain an IP from this network.
 GANETI_PUBLIC_NETWORK = 'snf-net-1'