Add qos rule validation for network

Minimum bandwidth QoS rule is only applicable for the network
which is backed by physical networks.
When updating network policy on network without port
will raise exception.

Partial-Bug: #1913180
Change-Id: I6b57f7ce6d411be388c63b87f2c75f2de703cc97

neutron_lib/exceptions/qos.py

@@ -69,6 +69,11 @@ class QosRuleNotSupported(e.Conflict):
     message = _("Rule %(rule_type)s is not supported by port %(port_id)s")
 
 
+class QosRuleNotSupportedByNetwork(e.Conflict):
+    message = _("Rule %(rule_type)s is not supported "
+                "by network %(network_id)s")
+
+
 class QoSRuleParameterConflict(e.Conflict):
     message = _("Unable to add the rule with value %(rule_value)s to the "
                 "policy %(policy_id)s as the existing rule of type "

neutron_lib/services/qos/base.py

@@ -109,6 +109,17 @@ class DriverBase(object):
         """
         return True
 
+    def validate_rule_for_network(self, context, rule, network_id):
+        """Return True/False for valid/invalid.
+
+        This is only meant to be used when a rule is compatible
+        with some networks but not with others (depending on
+        network properties).
+
+        Returns True by default for backwards compatibility.
+        """
+        return True
+
     def create_policy(self, context, policy):
         """Create policy invocation.