net: lib: mqtt_helper: Allow to bind with specific network interface

Allow the mqtt_helper library to bind with a specific network interface
so that the application can control which interface is used for
communication in an environment with multiple network interfaces.

Signed-off-by: Robert Lubos <[email protected]>

Author: rlubos

include/net/mqtt_helper.h

@@ -88,6 +88,11 @@ struct mqtt_helper_conn_params {
 	struct mqtt_helper_buf device_id;
 	struct mqtt_helper_buf user_name;
 	struct mqtt_helper_buf password;
+
+	/** Name of the interface that the MQTT helper should be bound to.
+	 *  Leave as NULL if not specified.
+	 */
+	const char *if_name;
 };
 
 /** @brief Initialize the MQTT helper.

subsys/net/lib/mqtt_helper/mqtt_helper.c

@@ -483,6 +483,7 @@ static int client_connect(struct mqtt_helper_conn_params *conn_params)
 	mqtt_client.will_message = &last_will_message;
 #endif
 
+	mqtt_client.transport.if_name = conn_params->if_name;
 #if defined(CONFIG_MQTT_LIB_TLS)
 	mqtt_client.transport.type      = MQTT_TRANSPORT_SECURE;
 #else