validator: Validate duplicate interface names

The current interface state is using the name property as an unique
key. Passing in duplicate interfaces names causes a failure only at the
verification step (if it is executed), making it hard to understand the
problem.

This change adds a validation for duplicate interface names, raising an
error early on.

Signed-off-by: Edward Haas <edwardh@redhat.com>

libnmstate/netapplier.py

@@ -59,6 +59,7 @@ def apply(desired_state, verify_change=True, commit=True, rollback_timeout=60):
     desired_state = copy.deepcopy(desired_state)
     validator.validate(desired_state)
     validator.validate_capabilities(desired_state, netinfo.capabilities())
+    validator.validate_unique_interface_name(desired_state)
     validator.validate_dhcp(desired_state)
     validator.validate_dns(desired_state)
     validator.validate_vxlan(desired_state)

libnmstate/validator.py

@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2018-2019 Red Hat, Inc.
+# Copyright (c) 2018-2020 Red Hat, Inc.
 #
 # This file is part of nmstate
 #
@@ -48,6 +48,10 @@ class NmstateRouteWithNoIPInterfaceError(NmstateValueError):
     pass
 
 
+class NmstateDuplicateInterfaceNameError(NmstateValueError):
+    pass
+
+
 def validate(data, validation_schema=schema.ifaces_schema):
     data = copy.deepcopy(data)
     for ifstate in data.get(schema.Interface.KEY, ()):
@@ -109,6 +113,17 @@ def validate_link_aggregation_state(desired_state, current_state):
                 specified_slaves |= slaves
 
 
+def validate_unique_interface_name(state):
+    ifaces_names = [
+        ifstate[schema.Interface.NAME]
+        for ifstate in state.get(schema.Interface.KEY, [])
+    ]
+    if len(ifaces_names) != len(set(ifaces_names)):
+        raise NmstateDuplicateInterfaceNameError(
+            f"Duplicate interfaces names detected: {sorted(ifaces_names)}"
+        )
+
+
 def validate_dhcp(state):
     for iface_state in state[Constants.INTERFACES]:
         for family in ("ipv4", "ipv6"):

tests/lib/validator_test.py

@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2018-2019 Red Hat, Inc.
+# Copyright (c) 2018-2020 Red Hat, Inc.
 #
 # This file is part of nmstate
 #
@@ -154,6 +154,18 @@ def test_dns_three_nameservers():
     )
 
 
+def test_unique_interface_name():
+    with pytest.raises(validator.NmstateDuplicateInterfaceNameError):
+        libnmstate.validator.validate_unique_interface_name(
+            {
+                schema.Interface.KEY: [
+                    {schema.Interface.NAME: "foo0"},
+                    {schema.Interface.NAME: "foo0"},
+                ]
+            }
+        )
+
+
 def empty_state():
     return state.State({})