[nrf fromtree] net: mqtt: Add MQTT 5.0 support for CONNECT

Add support for CONNECT message specified in MQTT 5.0, along with
property encoders required to encode MQTT properties which is a new
concept in MQTT 5.0. Connect and will properties can be specified by the
application in the mqtt_client structure before connecting.

Introduce a helper function which allows to verify whether MQTT 5.0 is
used or not, so that it's still possible to use MQTT 3.1 even if MQTT
5.0 support is enabled in Kconfig.

Signed-off-by: Robert Lubos <[email protected]>
(cherry picked from commit 8fe2965)

Author: rlubos

include/zephyr/net/mqtt.h

@@ -84,7 +84,8 @@ enum mqtt_evt_type {
 /** @brief MQTT version protocol level. */
 enum mqtt_version {
 	MQTT_VERSION_3_1_0 = 3, /**< Protocol level for 3.1.0. */
-	MQTT_VERSION_3_1_1 = 4  /**< Protocol level for 3.1.1. */
+	MQTT_VERSION_3_1_1 = 4, /**< Protocol level for 3.1.1. */
+	MQTT_VERSION_5_0 = 5,   /**< Protocol level for 5.0. */
 };
 
 /** @brief MQTT Quality of Service types. */
@@ -185,6 +186,13 @@ struct mqtt_topic {
 	uint8_t qos;
 };
 
+/** @brief Abstracts MQTT UTF-8 encoded string pair.
+ */
+struct mqtt_utf8_pair {
+	struct mqtt_utf8 name;
+	struct mqtt_utf8 value;
+};
+
 /** @brief Parameters for a publish message. */
 struct mqtt_publish_message {
 	struct mqtt_topic topic;     /**< Topic on which data was published. */
@@ -523,6 +531,32 @@ struct mqtt_client {
 	 */
 	struct mqtt_utf8 *password;
 
+#if defined(CONFIG_MQTT_VERSION_5_0)
+	/** MQTT 5.0 Will properties. */
+	struct {
+		/** MQTT 5.0, chapter 3.1.3.2.8 User Property. */
+		struct mqtt_utf8_pair user_prop[CONFIG_MQTT_USER_PROPERTIES_MAX];
+
+		/** MQTT 5.0, chapter 3.1.3.2.5 Content Type. */
+		struct mqtt_utf8 content_type;
+
+		/** MQTT 5.0, chapter 3.1.3.2.6 Response Topic. */
+		struct mqtt_utf8 response_topic;
+
+		/** MQTT 5.0, chapter 3.1.3.2.7 Correlation Data. */
+		struct mqtt_binstr correlation_data;
+
+		/** MQTT 5.0, chapter 3.1.3.2.2 Will Delay Interval. */
+		uint32_t will_delay_interval;
+
+		/** MQTT 5.0, chapter 3.1.3.2.4 Message Expiry Interval. */
+		uint32_t message_expiry_interval;
+
+		/** MQTT 5.0, chapter 3.1.3.2.3 Payload Format Indicator. */
+		uint8_t payload_format_indicator;
+	} will_prop;
+#endif /* CONFIG_MQTT_VERSION_5_0 */
+
 	/** Will topic and QoS. Can be NULL. */
 	struct mqtt_topic *will_topic;
 
@@ -558,6 +592,35 @@ struct mqtt_client {
 	/** Unanswered PINGREQ count on this connection. */
 	int8_t unacked_ping;
 
+#if defined(CONFIG_MQTT_VERSION_5_0)
+	/** MQTT 5.0 properties. */
+	struct {
+		/** MQTT 5.0, chapter 3.1.2.11.8 User Property. */
+		struct mqtt_utf8_pair user_prop[CONFIG_MQTT_USER_PROPERTIES_MAX];
+
+		/** MQTT 5.0, chapter 3.1.2.11.9 Authentication Method. */
+		struct mqtt_utf8 auth_method;
+
+		/** MQTT 5.0, chapter 3.1.2.11.10 Authentication Data. */
+		struct mqtt_binstr auth_data;
+
+		/** MQTT 5.0, chapter 3.1.2.11.2 Session Expiry Interval. */
+		uint32_t session_expiry_interval;
+
+		/** MQTT 5.0, chapter 3.1.2.11.4 Maximum Packet Size. */
+		uint32_t maximum_packet_size;
+
+		/** MQTT 5.0, chapter 3.1.2.11.3 Receive Maximum. */
+		uint16_t receive_maximum;
+
+		/** MQTT 5.0, chapter 3.1.2.11.6 Request Response Information. */
+		bool request_response_info;
+
+		/** MQTT 5.0, chapter 3.1.2.11.7 Request Response Information. */
+		bool request_problem_info;
+	} prop;
+#endif /* CONFIG_MQTT_VERSION_5_0 */
+
 	/** Will retain flag, 1 if will message shall be retained persistently.
 	 */
 	uint8_t will_retain : 1;

subsys/net/lib/mqtt/Kconfig

@@ -81,4 +81,31 @@ config MQTT_CLEAN_SESSION
 	  the client. Setting this flag to 0 allows the client to create a
 	  persistent session.
 
+#if MQTT_VERSION_5_0
+
+config MQTT_USER_PROPERTIES_MAX
+	int "Maximum number of user properties in a packet"
+	default 1
+	range 1 $(UINT16_MAX)
+	help
+	  Maximum number of user properties that the client can include in a
+	  packet or parse on input.
+
+config MQTT_TOPIC_ALIAS_MAX
+	int "Maximum number of supported topic aliases"
+	default 5
+	range 0 $(UINT16_MAX)
+	help
+	  Maximum number of supported topic aliases used in PUBLISH packets.
+	  If set to 0, topic aliasing is disabled.
+
+config MQTT_TOPIC_ALIAS_STRING_MAX
+	int "The longest topic name that can be aliased"
+	default 64
+	range 8 $(UINT16_MAX)
+	help
+	  Specifies a size of a buffer for storing aliased topics.
+
+#endif # MQTT_VERSION_5_0
+
 endif # MQTT_LIB

subsys/net/lib/mqtt/mqtt.c

@@ -176,7 +176,8 @@ void mqtt_client_init(struct mqtt_client *client)
 	MQTT_STATE_INIT(client);
 	mqtt_mutex_init(client);
 
-	client->protocol_version = MQTT_VERSION_3_1_1;
+	client->protocol_version = IS_ENABLED(CONFIG_MQTT_VERSION_5_0) ?
+				   MQTT_VERSION_5_0 : MQTT_VERSION_3_1_1;
 	client->clean_session = MQTT_CLEAN_SESSION;
 	client->keepalive = MQTT_KEEPALIVE;
 }