libnm: refactor to-dbus on the client skipping to serialize legacy properties

We have 4 legacy properties ("ipv[46].addresses", "ipv[46].routes") that
got replaced by newer variants ("ipv[46].address-data", "ipv[46].route-data").

When the client side of libnm (_nm_utils_is_manager_process) serializes
those properties, it must only serialize the newer version. That is so
that the forward/backward compatibility works as intended.

Previously, there was the NM_SETTING_PARAM_LEGACY GObject property flag.
That was fine, but not very clear.

For one, the legacy part of those properties is only about D-Bus. In
particular, they are not deprecated in libnm, keyfile, or nmcli. Thus
the name wasn't very clear.

Also, in the meantime we have more elaborate property meta data, that
goes beyond the meta data of the GObject property.

Move NM_SETTING_PARAM_LEGACY to NMSettInfoProperty.to_dbus_only_in_manager_process.
I think, this is a better name. It's also right at

```
     _nm_properties_override_gobj(
         properties_override,
         g_object_class_find_property(G_OBJECT_CLASS(setting_class), NM_SETTING_IP_CONFIG_ROUTES),
         NM_SETT_INFO_PROPERT_TYPE_DBUS(NM_G_VARIANT_TYPE("a(ayuayu)"),
                                        .to_dbus_fcn   = ip6_routes_to_dbus,
                                        .compare_fcn   = _nm_setting_ip_config_compare_fcn_routes,
                                        .from_dbus_fcn = ip6_routes_from_dbus, ),
         .to_dbus_only_in_manager_process = TRUE,
         .dbus_deprecated                 = TRUE, );
```

that is, directly at the place where we describe how the D-Bus property behaves.

src/libnm-core-impl/nm-setting-ip-config.c

@@ -6291,12 +6291,9 @@ nm_setting_ip_config_class_init(NMSettingIPConfigClass *klass)
                            "",
                            "",
                            G_TYPE_PTR_ARRAY,
-                           /* "addresses" is a legacy D-Bus property, because the
+                           /* On D-Bus, "addresses" is deprecated for "address-data". */
-                            * "addresses" GObject property normally gets set from
+                           G_PARAM_READWRITE | NM_SETTING_PARAM_INFERRABLE
-                            * the "address-data" D-Bus property...
+                               | NM_SETTING_PARAM_UNUSED1 | G_PARAM_STATIC_STRINGS);
-                            */
-                           G_PARAM_READWRITE | NM_SETTING_PARAM_INFERRABLE | NM_SETTING_PARAM_LEGACY
-                               | G_PARAM_STATIC_STRINGS);
 
     /**
      * NMSettingIPConfig:gateway:
@@ -6318,6 +6315,8 @@ nm_setting_ip_config_class_init(NMSettingIPConfigClass *klass)
         "",
         "",
         NULL,
+        /* On D-Bus, the legacy property "addresses" contains the gateway.
+         * This was replaced by "address-data" and "gateway". */
         G_PARAM_READWRITE | NM_SETTING_PARAM_INFERRABLE | G_PARAM_STATIC_STRINGS);
 
     /**
@@ -6330,9 +6329,9 @@ nm_setting_ip_config_class_init(NMSettingIPConfigClass *klass)
                            "",
                            "",
                            G_TYPE_PTR_ARRAY,
-                           G_PARAM_READWRITE | NM_SETTING_PARAM_INFERRABLE |
+                           /* On D-Bus, "routes" is deprecated for "route-data". */
-                               /* See :addresses above Re: LEGACY */
+                           G_PARAM_READWRITE | NM_SETTING_PARAM_INFERRABLE
-                               NM_SETTING_PARAM_LEGACY | G_PARAM_STATIC_STRINGS);
+                               | NM_SETTING_PARAM_UNUSED1 | G_PARAM_STATIC_STRINGS);
 
     /**
      * NMSettingIPConfig:route-metric:

src/libnm-core-impl/nm-setting-ip4-config.c

@@ -1001,7 +1001,8 @@ nm_setting_ip4_config_class_init(NMSettingIP4ConfigClass *klass)
                                        .to_dbus_fcn   = ip4_addresses_to_dbus,
                                        .compare_fcn   = _nm_setting_ip_config_compare_fcn_addresses,
                                        .from_dbus_fcn = ip4_addresses_from_dbus, ),
-        .dbus_deprecated = TRUE, );
+        .to_dbus_only_in_manager_process = TRUE,
+        .dbus_deprecated                 = TRUE, );
     _nm_properties_override_dbus(
         properties_override,
         "address-labels",
@@ -1139,7 +1140,8 @@ nm_setting_ip4_config_class_init(NMSettingIP4ConfigClass *klass)
                                        .to_dbus_fcn   = ip4_routes_to_dbus,
                                        .compare_fcn   = _nm_setting_ip_config_compare_fcn_routes,
                                        .from_dbus_fcn = ip4_routes_from_dbus, ),
-        .dbus_deprecated = TRUE, );
+        .to_dbus_only_in_manager_process = TRUE,
+        .dbus_deprecated                 = TRUE, );
 
     /* ---dbus---
      * property: route-data

src/libnm-core-impl/nm-setting-ip6-config.c

@@ -1010,7 +1010,8 @@ nm_setting_ip6_config_class_init(NMSettingIP6ConfigClass *klass)
                                        .to_dbus_fcn   = ip6_addresses_to_dbus,
                                        .compare_fcn   = _nm_setting_ip_config_compare_fcn_addresses,
                                        .from_dbus_fcn = ip6_addresses_from_dbus, ),
-        .dbus_deprecated = TRUE, );
+        .to_dbus_only_in_manager_process = TRUE,
+        .dbus_deprecated                 = TRUE, );
 
     /* ---dbus---
      * property: address-data
@@ -1129,7 +1130,8 @@ nm_setting_ip6_config_class_init(NMSettingIP6ConfigClass *klass)
                                        .to_dbus_fcn   = ip6_routes_to_dbus,
                                        .compare_fcn   = _nm_setting_ip_config_compare_fcn_routes,
                                        .from_dbus_fcn = ip6_routes_from_dbus, ),
-        .dbus_deprecated = TRUE, );
+        .to_dbus_only_in_manager_process = TRUE,
+        .dbus_deprecated                 = TRUE, );
 
     /* ---dbus---
      * property: route-data

src/libnm-core-impl/nm-setting-private.h

@@ -318,8 +318,9 @@ typedef struct {
  */
 #define NM_SETTING_PARAM_INFERRABLE (1 << (4 + G_PARAM_USER_SHIFT))
 
-/* This is a legacy property, which clients should not send to the daemon. */
+/* This flag has no meaning (anymore). It's only kept, because we used it
-#define NM_SETTING_PARAM_LEGACY (1 << (5 + G_PARAM_USER_SHIFT))
+ * on some older versions of libnm. */
+#define NM_SETTING_PARAM_UNUSED1 (1 << (5 + G_PARAM_USER_SHIFT))
 
 /* When a connection is active and gets modified, usually the change
  * to the settings-connection does not propagate automatically to the

src/libnm-core-impl/nm-setting.c

@@ -1737,12 +1737,11 @@ property_to_dbus(const NMSettInfoSetting                *sett_info,
               || NM_FLAGS_HAS(property_info->param_spec->flags, G_PARAM_WRITABLE)
               || property_info->property_type == &nm_sett_info_propert_type_setting_name);
 
+    if (property_info->to_dbus_only_in_manager_process && !_nm_utils_is_manager_process)
+        return NULL;
+
     if (property_info->param_spec && !ignore_flags
         && !NM_FLAGS_HAS(property_info->param_spec->flags, NM_SETTING_PARAM_TO_DBUS_IGNORE_FLAGS)) {
-        if (NM_FLAGS_HAS(property_info->param_spec->flags, NM_SETTING_PARAM_LEGACY)
-            && !_nm_utils_is_manager_process)
-            return NULL;
-
         if (NM_FLAGS_HAS(property_info->param_spec->flags, NM_SETTING_PARAM_SECRET)) {
             NMSettingSecretFlags f = NM_SETTING_SECRET_FLAG_NONE;
 

src/libnm-core-intern/nm-core-internal.h

@@ -827,6 +827,13 @@ struct _NMSettInfoProperty {
      * is the default. */
     bool to_dbus_including_default : 1;
 
+    /* This indicates, that the property is deprecated (on D-Bus) for another property.
+     * See also _nm_setting_use_legacy_property() how that works.
+     *
+     * The to_dbus_fcn() will be skipped for such properties, if _nm_utils_is_manager_process
+     * is FALSE. */
+    bool to_dbus_only_in_manager_process : 1;
+
     /* Whether the property is deprecated.
      *
      * Note that we have various representations of profiles, e.g. on D-Bus, keyfile,