Fix segfault in json plugin

.gitignore

@@ -40,3 +40,4 @@ tools/__pycache__
 *.gcno
 *\.log
 .libs
+m4/

dmdynamicjson.c

@@ -702,7 +702,11 @@ static char *ubus_get_value(json_object *mapping_obj, int json_version, char *re
 		}
 
 		json_object_object_get_ex(res, buf, &arr_obj);
-		nbre_entries = (arr_obj) ? json_object_array_length(arr_obj) : 0;
+
+		if (arr_obj != NULL && json_object_is_type(arr_obj, json_type_array) == 1) {
+			nbre_entries = json_object_array_length(arr_obj);
+		}
+
 		dmasprintf(&value, "%d", nbre_entries);
 		goto end;
 	}

test/bbf_test/bbf_dm.c

@@ -99,8 +99,10 @@ int main(int argc, char *argv[])
 	}
 
 	ubus_ctx = ubus_connect(NULL);
-	if (ubus_ctx == NULL)
+	if (ubus_ctx == NULL) {
+		fprintf(stderr, "Failed to connect with ubus\n");
 		return -1;
+	}
 
 	dm_config_ubus(ubus_ctx);
 

test/files/etc/bbfdm/json/index.json

@@ -39,6 +39,28 @@
         }
       ]
     },
+    "MHubNumberOfEntries": {
+      "type": "int",
+      "version": "2.14",
+      "protocols": [
+        "cwmp",
+        "usp"
+      ],
+      "read": true,
+      "write": false,
+      "datatype": "int",
+      "mapping": [
+        {
+          "type": "ubus",
+          "ubus": {
+            "object": "proxd",
+            "method": "list",
+            "args": {},
+            "key": "numofdevices"
+          }
+        }
+      ]
+    },
     "Device.PD2.{i}.MiniHub.{i}.": {
       "type": "object",
       "version": "2.14",

test/files/tmp/proxd.data

@@ -2,5 +2,6 @@
 	"devices": [
 		{ "name": "one"},
 		{"name": "two"}
-	]
+	],
+	"numofdevices": "1"
 }