Adding some sanity-checking to configdb.json parsing logic

src/sonic-config-engine/sonic-cfggen

@@ -78,6 +78,87 @@ def unique_name(l):
             new_list.append(item)
     return new_list
 
+def valid_config(data):
+    """Verifies that proposed config-state (data) is semantically
+    correct/consistent.
+
+    Args:
+    data: config-data in dictionary form
+
+    Returns:
+    'true' if valid configuration, 'false' otherwise
+    """
+
+    # Verifies that there is a valid entry in PORT table for every entry
+    # present in INTERFACE table. See that there's no need to verify the
+    # opposite direction as it's perfectly valid to have PORT entries with
+    # no matching entry in INTERFACE table.
+    #
+    #  "INTERFACE": {
+    #     "Ethernet112|10.1.2.2/24": {},
+    #     "Ethernet112|fc00:1:2::2/64": {},
+    #  }
+    #
+    if 'INTERFACE' in data and 'PORT' in data:
+        interface_table = data['INTERFACE']
+
+        for key in interface_table:
+            if key[0] not in data['PORT']:
+                print("Interface", key[0], "not found in PORT table.")
+                return False
+
+    # Verifies that VLAN_INTERFACE entries are relying on existing VLAN entities.
+    #
+    #  "VLAN_INTERFACE": {
+    #      "Vlan100|172.18.1.1/24": {
+    #      "scope": "global",
+    #      }
+    #   }
+    if 'VLAN_INTERFACE' in data and 'VLAN' in data:
+        vlan_interface_table = data['VLAN_INTERFACE']
+
+        for key in vlan_interface_table:
+            if key[0] not in data['VLAN']:
+                print("Vlan interface", key[0], "not found in VLAN table.")
+                return False
+
+    # Verifies that VLAN table holds members that are present in PORT table.
+    #
+    #  "VLAN": {
+    #      "Vlan100": {
+    #      ...
+    #      "members": [
+    #           "Ethernet16",
+    #           "Ethernet17"
+    #       }
+    #   }
+    if 'VLAN' in data and 'PORT' in data:
+        vlan_table = data['VLAN']
+
+        for key, value in vlan_table.iteritems():
+            for member in value['members']:
+                if member not in data['PORT']:
+                    print("VLAN member", member, "not found in PORT table.")
+                    return False
+
+    # Verifies that each DEVICE_NEIGHBOR key matches a valid entry in PORT table.
+    #
+    #  "DEVICE_NEIGHBOR": {
+    #      "Ethernet112": {
+    #      "name": "lnos-x1-a-csw01",
+    #      "port": "Ethernet1"
+    #      }
+    #   }
+    if 'DEVICE_NEIGHBOR' in data and 'PORT' in data:
+        devnbr_table = data['DEVICE_NEIGHBOR']
+
+        for key in devnbr_table:
+            if key not in data['PORT']:
+                print("DEVICE_NEIGHBOR port", key, "not found in PORT table.")
+                return False
+
+    return True
+
 
 class FormatConverter:
     """Convert config DB based schema to legacy minigraph based schema for backward capability.
@@ -154,6 +235,7 @@ def main():
     group.add_argument("-t", "--template", help="render the data with the template file")
     group.add_argument("-v", "--var", help="print the value of a variable, support jinja2 expression")
     group.add_argument("--var-json", help="print the value of a variable, in json format")
+    group.add_argument("--check-json", help="check passed config -- to be used with -j", action='store_true')
     group.add_argument("--write-to-db", help="write config into configdb", action='store_true')
     group.add_argument("--print-data", help="print all data", action='store_true')
     args = parser.parse_args()
@@ -241,6 +323,11 @@ def main():
         configdb.connect(False)
         configdb.mod_config(FormatConverter.output_to_db(data))
 
+    if args.check_json:
+        if valid_config(FormatConverter.output_to_db(data)) == False:
+            print("\nInvalid configuration detected. No configuration changes processed. Exiting...\n")
+            sys.exit(1)
+
     if args.print_data:
         print(json.dumps(FormatConverter.to_serialized(data), indent=4, cls=minigraph_encoder))