mdns: Add support for registering custom netif

* Original commit: espressif/esp-idf@bec42ff85d

examples/protocols/mdns/main/Kconfig.projbuild

@@ -48,4 +48,13 @@ menu "Example Configuration"
         help
             Set the GPIO number used as mDNS test button
 
+    config MDNS_ADD_CUSTOM_NETIF
+        bool "Add user netif to mdns service"
+        default n
+        help
+            If enabled, we try to add a custom netif to mdns service.
+            Note that for using with common connection example code, we have to disable
+            all predefined interfaces in mdns component setup (since we're adding one
+            of the default interfaces)
+
 endmenu

examples/protocols/mdns/main/mdns_example_main.c

@@ -266,6 +266,14 @@ void app_main(void)
      */
     ESP_ERROR_CHECK(example_connect());
 
+#if defined(CONFIG_MDNS_ADD_CUSTOM_NETIF) && !defined(CONFIG_MDNS_PREDEF_NETIF_STA) && !defined(CONFIG_MDNS_PREDEF_NETIF_ETH)
+    /* Demonstration of adding a custom netif to mdns service, but we're adding the default example one,
+     * so we must disable all predefined interfaces (PREDEF_NETIF_STA, AP and ETH) first
+     */
+    ESP_ERROR_CHECK(mdns_add_custom_netif(EXAMPLE_INTERFACE));
+    ESP_ERROR_CHECK(mdns_post_custom_action(EXAMPLE_INTERFACE, MDNS_EVENT_ENABLE_IP4));
+    ESP_ERROR_CHECK(mdns_post_custom_action(EXAMPLE_INTERFACE, MDNS_EVENT_ANNOUNCE_IP4));
+#endif
     initialise_button();
     xTaskCreate(&mdns_example_task, "mdns_example_task", 2048, NULL, 5, NULL);
 }