libnm: refactor to_dbus_fcn() for "ipv6.dns" property

The goal is to get rid of gprop_to_dbus_fcn() uses.

Note that there is a change in behavior. The "dns" GPtrArray in
NMSettingIPConfig is never NULL (the default of the boxed property),
thus the previous code always serialized the property, even the
empty list.

Now, empty dns properties are omitted from D-Bus.

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

@@ -4101,6 +4101,12 @@ nm_setting_ip_config_clear_dns(NMSettingIPConfig *setting)
     }
 }
 
+GPtrArray *
+_nm_setting_ip_config_get_dns_array(NMSettingIPConfig *setting)
+{
+    return NM_SETTING_IP_CONFIG_GET_PRIVATE(setting)->dns;
+}
+
 /**
  * nm_setting_ip_config_get_num_dns_searches:
  * @setting: the #NMSettingIPConfig

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

@@ -10,6 +10,7 @@
 #include <arpa/inet.h>
 
 #include "nm-setting-private.h"
+#include "nm-utils-private.h"
 #include "nm-core-enum-types.h"
 #include "libnm-core-intern/nm-core-internal.h"
 
@@ -362,9 +363,21 @@ verify(NMSetting *setting, NMConnection *connection, GError **error)
 }
 
 static GVariant *
-ip6_dns_to_dbus(const GValue *prop_value)
+ip6_dns_to_dbus(const NMSettInfoSetting *               sett_info,
+                const NMSettInfoProperty *              property_info,
+                NMConnection *                          connection,
+                NMSetting *                             setting,
+                NMConnectionSerializationFlags          flags,
+                const NMConnectionSerializationOptions *options)
 {
-    return nm_utils_ip6_dns_to_variant(g_value_get_boxed(prop_value));
+    GPtrArray *dns;
+
+    dns = _nm_setting_ip_config_get_dns_array(NM_SETTING_IP_CONFIG(setting));
+
+    if (nm_g_ptr_array_len(dns) == 0)
+        return NULL;
+
+    return _nm_utils_ip6_dns_to_variant((const char *const *) dns->pdata, dns->len);
 }
 
 static void
@@ -1021,10 +1034,10 @@ nm_setting_ip6_config_class_init(NMSettingIP6ConfigClass *klass)
     _nm_properties_override_gobj(
         properties_override,
         g_object_class_find_property(G_OBJECT_CLASS(setting_class), NM_SETTING_IP_CONFIG_DNS),
-        NM_SETT_INFO_PROPERT_TYPE_GPROP(NM_G_VARIANT_TYPE("aay"),
+        NM_SETT_INFO_PROPERT_TYPE_DBUS(NM_G_VARIANT_TYPE("aay"),
                                        .compare_fcn = _nm_setting_property_compare_fcn_default,
-                                        .gprop_from_dbus_fcn = ip6_dns_from_dbus, ),
+                                       .to_dbus_fcn = ip6_dns_to_dbus,
-        .to_dbus_data.gprop_to_dbus_fcn = ip6_dns_to_dbus);
+                                       .gprop_from_dbus_fcn = ip6_dns_from_dbus, ));
 
     /* ---dbus---
      * property: addresses

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

@@ -65,4 +65,6 @@ GVariant *_nm_team_settings_property_to_dbus(const NMSettInfoSetting *
 
 void _nm_team_settings_property_from_dbus_link_watchers(GVariant *dbus_value, GValue *prop_value);
 
+GVariant *_nm_utils_ip6_dns_to_variant(const char *const *dns, gssize len);
+
 #endif

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

@@ -1592,20 +1592,30 @@ nm_utils_ip4_get_default_prefix(guint32 ip)
  **/
 GVariant *
 nm_utils_ip6_dns_to_variant(char **dns)
+{
+    return _nm_utils_ip6_dns_to_variant(NM_CAST_STRV_CC(dns), -1);
+}
+
+GVariant *
+_nm_utils_ip6_dns_to_variant(const char *const *dns, gssize len)
 {
     GVariantBuilder builder;
     gsize           i;
+    gsize           l;
+
+    if (len < 0)
+        l = NM_PTRARRAY_LEN(dns);
+    else
+        l = len;
 
     g_variant_builder_init(&builder, G_VARIANT_TYPE("aay"));
-    if (dns) {
+    for (i = 0; i < l; i++) {
-        for (i = 0; dns[i]; i++) {
         struct in6_addr ip;
 
         if (inet_pton(AF_INET6, dns[i], &ip) != 1)
             continue;
         g_variant_builder_add(&builder, "@ay", nm_g_variant_new_ay_in6addr(&ip));
     }
-    }
     return g_variant_builder_end(&builder);
 }
 

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

@@ -966,4 +966,6 @@ _nm_variant_attribute_spec_find_binary_search(const NMVariantAttributeSpec *cons
 
 gboolean _nm_ip_tunnel_mode_is_layer2(NMIPTunnelMode mode);
 
+GPtrArray *_nm_setting_ip_config_get_dns_array(NMSettingIPConfig *setting);
+
 #endif