libnm: treat missing NMSettingVlan:flags property as old default value

We changed the default value of MSettingVlan:flags from 0 to
1 (NM_VLAN_FLAG_REORDER_HEADERS). That means, that old libnm
clients will not serialize 0 (their default).
This change broke the D-Bus API. The D-Bus API allows to omit a value
when meaning the default value. That means, we cannot change the
default value (in the D-Bus API!) without breaking previous assumptions.

A newer libnm version should treat a missing flags argument as the
old default value and thus preserve the original default value (in the
D-Bus API).

This has the downside that for the future we will continue to treat a missing
value as the old default value (0), and in order to get the new default
value (1), the client must explicitly set the flags.

We also must restore the original default value in libnm-glib.
libnm-glib does not support _nm_setting_class_override_property()
and thus it must keep thinking that the default value for the GObject
property continues to be 0. Otherwise, it would not serialize a 1, which
a new libnm would now interpret as 0.

https://bugzilla.redhat.com/show_bug.cgi?id=1250225

Fixes: 687b6515980c08cdbb9734bd112a594166c4d6dd

diff --git a/libnm-core/nm-setting-vlan.c b/libnm-core/nm-setting-vlan.c
index 6fd4e33..99e4336 100644 (file)
--- a/libnm-core/nm-setting-vlan.c
+++ b/libnm-core/nm-setting-vlan.c
@@ -564,6 +564,18 @@ _override_flags_get (NMSetting *setting, const char *property)
        return g_variant_new_uint32 (nm_setting_vlan_get_flags ((NMSettingVlan *) setting));
 }
 
+static void
+_override_flags_not_set (NMSetting *setting,
+                          GVariant *connection_dict,
+                          const char *property)
+{
+       /* we changed the default value for FLAGS. When an older client
+        * doesn't serialize the property, we assume it is the old default. */
+       g_object_set (G_OBJECT (setting),
+                     NM_SETTING_VLAN_FLAGS, (NMVlanFlags) 0,
+                     NULL);
+}
+
 static GSList *
 priority_strv_to_maplist (NMVlanPriorityMap map, char **strv)
 {
@@ -742,6 +754,11 @@ nm_setting_vlan_class_init (NMSettingVlanClass *setting_class)
         * output packet headers), %NM_VLAN_FLAG_GVRP (use of the GVRP protocol),
         * and %NM_VLAN_FLAG_LOOSE_BINDING (loose binding of the interface to its
         * master device's operating state).
+        *
+        * The default value of this property is NM_VLAN_FLAG_REORDER_HEADERS,
+        * but it used to be 0. To preserve backward compatibility, the default-value
+        * in the D-Bus API continues to be 0 and a missing property on D-Bus
+        * is still considered as 0.
         **/
        /* ---ifcfg-rh---
         * property: flags
@@ -763,7 +780,7 @@ nm_setting_vlan_class_init (NMSettingVlanClass *setting_class)
                                             NULL,
                                             _override_flags_get,
                                             NULL,
-                                            NULL);
+                                            _override_flags_not_set);
 
        /**
         * NMSettingVlan:ingress-priority-map:

diff --git a/libnm-util/nm-setting-vlan.c b/libnm-util/nm-setting-vlan.c
index c3d4bb5..52676d4 100644 (file)
--- a/libnm-util/nm-setting-vlan.c
+++ b/libnm-util/nm-setting-vlan.c
@@ -805,7 +805,7 @@ nm_setting_vlan_class_init (NMSettingVlanClass *setting_class)
        g_object_class_install_property
                (object_class, PROP_FLAGS,
                 g_param_spec_uint (NM_SETTING_VLAN_FLAGS, "", "",
-                                   0, G_MAXUINT32, NM_VLAN_FLAG_REORDER_HEADERS,
+                                   0, G_MAXUINT32, 0,
                                    G_PARAM_READWRITE |
                                    G_PARAM_CONSTRUCT |
                                    NM_SETTING_PARAM_INFERRABLE |