feat: Add TCP keepalive configuration

Author: bogdankolendovskyy

include/mqtt_client.h

@@ -341,6 +341,7 @@ 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_keep_alive_t tcp_keep_alive_cfg;  /*!< Transport keep-alive config*/
         esp_transport_handle_t transport; /*!< Custom transport handle to use, leave it NULL to allow MQTT client create or recreate its own. Warning: The transport should be valid during the client lifetime and is destroyed when esp_mqtt_client_destroy is called. */
         struct ifreq * if_name; /*!< The name of interface for data to go through. Use the default interface without setting */
     } network; /*!< Network configuration */

lib/include/mqtt_client_priv.h

@@ -100,6 +100,7 @@ typedef struct {
     uint64_t outbox_limit;
     esp_transport_handle_t transport;
     struct ifreq * if_name;
+    esp_transport_keep_alive_t tcp_keep_alive_cfg;
 } mqtt_config_storage_t;
 
 typedef enum {

mqtt_client.c

@@ -429,6 +429,10 @@ esp_err_t esp_mqtt_set_config(esp_mqtt_client_handle_t client, const esp_mqtt_cl
         client->config->port = config->broker.address.port;
     }
 
+    if (config->network.tcp_keep_alive_cfg.keep_alive_enable) {
+        client->config->tcp_keep_alive_cfg = config->network.tcp_keep_alive_cfg;
+    }
+
     err = ESP_ERR_NO_MEM;
     ESP_MEM_CHECK(TAG, esp_mqtt_set_if_config(config->broker.address.hostname, &client->config->host), goto _mqtt_set_config_failed);
     ESP_MEM_CHECK(TAG, esp_mqtt_set_if_config(config->broker.address.path, &client->config->path), goto _mqtt_set_config_failed);
@@ -521,7 +525,7 @@ 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;
     }
-    
+
     client->config->transport = config->network.transport;
 
     if (config->network.if_name) {
@@ -1608,6 +1612,10 @@ static void esp_mqtt_task(void *pv)
             esp_mqtt_set_ssl_transport_properties(client->transport_list, client->config);
 #endif
 
+            if(client->config->tcp_keep_alive_cfg.keep_alive_enable) {
+                esp_transport_tcp_set_keep_alive(client->transport, &client->config->tcp_keep_alive_cfg);
+            }
+
             client->event.event_id = MQTT_EVENT_BEFORE_CONNECT;
             esp_mqtt_dispatch_event_with_msgid(client);