feat: Add custom transport configuration

Today there is no way to add a new transport without applying
modifications to the transport list. This impose limitations on the
client usage. Adding the custom configuration we enable user defined
transports.

host_test/main/test_mqtt_client.cpp

@@ -3,6 +3,7 @@
  *
  * SPDX-License-Identifier: Apache-2.0
  */
+#include "esp_transport.h"
 #define CATCH_CONFIG_MAIN  // This tells the catch header to generate a main
 #include "catch.hpp"
 
@@ -60,6 +61,7 @@ struct ClientInitializedFixture {
         esp_read_mac_IgnoreAndReturn(ESP_OK);
         esp_read_mac_ReturnThruPtr_mac(mac);
         esp_transport_list_destroy_IgnoreAndReturn(ESP_OK);
+        esp_transport_destroy_IgnoreAndReturn(ESP_OK);
         vEventGroupDelete_Ignore();
         vQueueDelete_Ignore();
 

include/mqtt_client.h

@@ -12,6 +12,7 @@
 #include <string.h>
 #include "esp_err.h"
 #include "esp_event.h"
+#include "esp_transport.h"
 #ifdef CONFIG_MQTT_PROTOCOL_5
 #include "mqtt5_client.h"
 #endif
@@ -329,6 +330,7 @@ typedef struct esp_mqtt_client_config_t {
         int refresh_connection_after_ms; /*!< Refresh connection after this value (in milliseconds) */
         bool disable_auto_reconnect;     /*!< Client will reconnect to server (when errors/disconnect). Set
                                  `disable_auto_reconnect=true` to disable */
+        esp_transport_handle_t transport; /*!< Custom transport handle to use. Warning: The transport should be valid during the client lifetime and is destroyed when esp_mqtt_client_destroy is called. */
     } network; /*!< Network configuration */
     /**
      * Client task configuration

lib/include/mqtt_client_priv.h

@@ -91,6 +91,7 @@ typedef struct {
     bool use_secure_element;
     void *ds_data;
     int message_retransmit_timeout;
+    esp_transport_handle_t transport;
 } mqtt_config_storage_t;
 
 typedef enum {

mqtt_client.c

@@ -1,4 +1,5 @@
 #include "mqtt_client.h"
+#include "esp_transport.h"
 #include "mqtt_client_priv.h"
 #include "esp_log.h"
 #include <stdint.h>
@@ -475,6 +476,9 @@ esp_err_t esp_mqtt_set_config(esp_mqtt_client_handle_t client, const esp_mqtt_cl
     } else {
         client->config->reconnect_timeout_ms = MQTT_RECON_DEFAULT_MS;
     }
+    if (config->network.transport) {
+        client->config->transport = config->network.transport;
+    }
 
     if (config->broker.verification.alpn_protos) {
         for (int i = 0; i < client->config->num_alpn_protos; i++) {
@@ -592,6 +596,7 @@ void esp_mqtt_destroy_config(esp_mqtt_client_handle_t client)
         esp_event_loop_delete(client->config->event_loop_handle);
     }
 #endif
+    esp_transport_destroy(client->config->transport);
     memset(client->config, 0, sizeof(mqtt_config_storage_t));
     free(client->config);
     client->config = NULL;
@@ -1513,18 +1518,6 @@ static void esp_mqtt_task(void *pv)
     outbox_tick_t msg_tick = 0;
     client->run = true;
 
-    //get transport by scheme
-    client->transport = esp_transport_list_get_transport(client->transport_list, client->config->scheme);
-
-    if (client->transport == NULL) {
-        ESP_LOGE(TAG, "There are no transports valid, stop mqtt client, config scheme = %s", client->config->scheme);
-        client->run = false;
-    }
-    //default port
-    if (client->config->port == 0) {
-        client->config->port = esp_transport_get_default_port(client->transport);
-    }
-
     client->state = MQTT_STATE_INIT;
     xEventGroupClearBits(client->status_bits, STOPPED_BIT);
     while (client->run) {
@@ -1538,10 +1531,29 @@ static void esp_mqtt_task(void *pv)
             client->event.event_id = MQTT_EVENT_BEFORE_CONNECT;
             esp_mqtt_dispatch_event_with_msgid(client);
 
-            if (client->transport == NULL) {
-                ESP_LOGE(TAG, "There is no transport");
-                client->run = false;
+
+            client->transport = client->config->transport;
+            if (!client->transport) {
+
+                if (esp_mqtt_client_create_transport(client) != ESP_OK) {
+                    ESP_LOGE(TAG, "Failed to create transport list");
+                    client->run = false;
+                    break;
+                }
+                //get transport by scheme
+                client->transport = esp_transport_list_get_transport(client->transport_list, client->config->scheme);
+
+                if (client->transport == NULL) {
+                    ESP_LOGE(TAG, "There are no transports valid, stop mqtt client, config scheme = %s", client->config->scheme);
+                    client->run = false;
+                    break;
+                }
             }
+            //default port
+            if (client->config->port == 0) {
+                client->config->port = esp_transport_get_default_port(client->transport);
+            }
+
 #if MQTT_ENABLE_SSL
             esp_mqtt_set_ssl_transport_properties(client->transport_list, client->config);
 #endif
@@ -1667,11 +1679,6 @@ esp_err_t esp_mqtt_client_start(esp_mqtt_client_handle_t client)
         MQTT_API_UNLOCK(client);
         return ESP_FAIL;
     }
-    if (esp_mqtt_client_create_transport(client) != ESP_OK) {
-        ESP_LOGE(TAG, "Failed to create transport list");
-        MQTT_API_UNLOCK(client);
-        return ESP_FAIL;
-    }
     esp_err_t err = ESP_OK;
 #if MQTT_CORE_SELECTION_ENABLED
     ESP_LOGD(TAG, "Core selection enabled on %u", MQTT_TASK_CORE);