cyclades: Setting for max NICs per Ganeti instance

Add new 'GANETI_MAX_NICS_PER_INSTANCE' setting which represents the
maximum number of NICs that is allowed for each Ganeti instance. The
value of this setting must be less than 'max:nic-count` option of
Ganeti's ipolicy.

snf-cyclades-app/conf/20-snf-cyclades-app-backend.conf

@@ -41,3 +41,7 @@
 #BACKEND_ALLOCATOR_MODULE = "synnefo.logic.allocators.default_allocator"
 ## Refresh backend statistics timeout, in minutes, used in backend allocation
 #BACKEND_REFRESH_MIN = 15
+#
+## Maximum number of NICs per Ganeti instance. This value must be less or equal
+## than 'max:nic-count' option of Ganeti's ipolicy.
+#GANETI_MAX_NICS_PER_INSTANCE = 8

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

@@ -41,3 +41,7 @@ GANETI_USE_OPPORTUNISTIC_LOCKING = True
 BACKEND_ALLOCATOR_MODULE = "synnefo.logic.allocators.default_allocator"
 # Refresh backend statistics timeout, in minutes, used in backend allocation
 BACKEND_REFRESH_MIN = 15
+
+# Maximum number of NICs per Ganeti instance. This value must be less or equal
+# than 'max:nic-count' option of Ganeti's ipolicy.
+GANETI_MAX_NICS_PER_INSTANCE = 8

snf-cyclades-app/synnefo/logic/servers.py

@@ -422,6 +422,12 @@ def rename(server, new_name):
 
 @transaction.commit_on_success
 def create_port(*args, **kwargs):
+    vm = kwargs.get("machine", None)
+    if vm is None and len(args) >= 3:
+        vm = args[2]
+    if vm is not None:
+        if vm.nics.count() == settings.GANETI_MAX_NICS_PER_INSTANCE:
+            raise faults.BadRequest("Maximum ports per server limit reached")
     return _create_port(*args, **kwargs)
 
 
@@ -551,7 +557,10 @@ def create_instance_ports(user_id, networks=None):
     else:
         # Else just connect to the networks that the user defined
         ports = create_ports_for_request(user_id, networks)
-    return forced_ports + ports
+    total_ports = forced_ports + ports
+    if len(total_ports) > settings.GANETI_MAX_NICS_PER_INSTANCE:
+        raise faults.BadRequest("Maximum ports per server limit reached")
+    return total_ports
 
 
 def create_ports_for_setting(user_id, category):