keyfile: ensure all-default VLAN setting is read correctly

Settings with all-default values are not written to reduce
complexity of the keyfile (and be more human-readable friendly)
and that includes VLAN settings with a VLAN ID of zero.  So
when reading this file back, if there is no 'base type' setting
(eg, the setting specified by the connection::type property)
then just add that setting.  nm_connection_verify() will catch
cases where an empty 'base type' setting is invalid.

src/settings/plugins/keyfile/reader.c

@@ -1195,15 +1195,23 @@ nm_keyfile_plugin_connection_from_file (const char *filename, GError **error)
 
 	/* Make sure that we have the base device type setting even if
 	 * the keyfile didn't include it, which can happen when the base
-	 * device type setting is all default values (like ethernet).
+	 * device type setting is all default values (like ethernet where
+	 * the MAC address isn't given, or VLAN when the VLAN ID is zero).
 	 */
 	s_con = nm_connection_get_setting_connection (connection);
 	if (s_con) {
 		ctype = nm_setting_connection_get_connection_type (s_con);
 		setting = nm_connection_get_setting_by_name (connection, ctype);
-		if (ctype) {
+		if (ctype && !setting) {
-			if (!setting && !strcmp (ctype, NM_SETTING_WIRED_SETTING_NAME))
+			NMSetting *base_setting;
-				nm_connection_add_setting (connection, nm_setting_wired_new ());
+			GType base_setting_type;
+
+			base_setting_type = nm_connection_lookup_setting_type (ctype);
+			if (base_setting_type != G_TYPE_INVALID) {
+				base_setting = (NMSetting *) g_object_new (base_setting_type, NULL);
+				g_assert (base_setting);
+				nm_connection_add_setting (connection, base_setting);
+			}
 		}
 	}
 

src/settings/plugins/keyfile/tests/keyfiles/Makefile.am

@@ -18,7 +18,8 @@ KEYFILES = \
 	Test_Bridge_Main \
 	Test_Bridge_Component \
 	Test_New_Wired_Group_Name \
-	Test_New_Wireless_Group_Names
+	Test_New_Wireless_Group_Names \
+	Test_Missing_Vlan_Setting
 
 CERTS = \
 	test-ca-cert.pem \

src/settings/plugins/keyfile/tests/keyfiles/Test_Missing_Vlan_Setting

@@ -0,0 +1,11 @@
+# Settings with all default values are not written, including
+# VLAN settings with a VLAN ID of 0, which is the default value.
+
+[connection]
+id=Test Missing Vlan Setting
+uuid=4e80a56d-c99f-4aad-a6dd-b449bc398c57
+type=vlan
+autoconnect=true
+
+[802-3-ethernet]
+mac-address=00:11:22:33:44:55

src/settings/plugins/keyfile/tests/test-keyfile.c

@@ -3247,6 +3247,28 @@ test_write_new_wireless_group_names (void)
 	g_object_unref (connection);
 }
 
+static void
+test_read_missing_vlan_setting (void)
+{
+	NMConnection *connection;
+	NMSettingVlan *s_vlan;
+	GError *error = NULL;
+	gboolean success;
+
+	connection = nm_keyfile_plugin_connection_from_file (TEST_KEYFILES_DIR"/Test_Missing_Vlan_Setting", &error);
+	g_assert_no_error (error);
+	g_assert (connection);
+	success = nm_connection_verify (connection, &error);
+	g_assert_no_error (error);
+	g_assert (success);
+
+	/* Ensure the VLAN setting exists */
+	s_vlan = nm_connection_get_setting_vlan (connection);
+	g_assert (s_vlan);
+	g_assert_cmpint (nm_setting_vlan_get_id (s_vlan), ==, 0);
+
+	g_object_unref (connection);
+}
 
 int main (int argc, char **argv)
 {
@@ -3309,6 +3331,8 @@ int main (int argc, char **argv)
 	test_read_new_wireless_group_names ();
 	test_write_new_wireless_group_names ();
 
+	test_read_missing_vlan_setting ();
+
 	base = g_path_get_basename (argv[0]);
 	fprintf (stdout, "%s: SUCCESS\n", base);
 	g_free (base);