feat(esp_netif): Support posting event on SNTP time update

components/esp_netif/include/esp_netif_sntp.h

@@ -17,6 +17,29 @@
 extern "C" {
 #endif
 
+/**
+ * @brief SNTP event base for esp-netif
+ */
+ESP_EVENT_DECLARE_BASE(NETIF_SNTP_EVENT);
+
+/**
+ * @brief Event IDs for NETIF_SNTP_EVENT
+ */
+typedef enum {
+    NETIF_SNTP_TIME_SYNC = 0,  /**< System time synchronized via SNTP */
+} esp_netif_sntp_event_t;
+
+/**
+ * @brief Event payload for NETIF_SNTP_TIME_SYNC
+ *
+ * The event data passed to handlers registered for
+ * `NETIF_SNTP_EVENT`/`NETIF_SNTP_TIME_SYNC` is a pointer to this struct.
+ */
+typedef struct esp_netif_sntp_time_sync {
+    struct timeval tv;  ///< Time of synchronization as reported by SNTP
+} esp_netif_sntp_time_sync_t;
+
+
 /**
  * @brief Time sync notification function
  */

components/esp_netif/lwip/esp_netif_sntp.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -19,6 +19,8 @@
 
 static const char *TAG = "esp_netif_sntp";
 
+ESP_EVENT_DEFINE_BASE(NETIF_SNTP_EVENT);
+
 typedef struct sntp_storage {
     esp_sntp_time_cb_t sync_cb;
     SemaphoreHandle_t sync_sem;
@@ -38,6 +40,14 @@ static void sync_time_cb(struct timeval *tv)
     if (s_storage && s_storage->sync_cb) {
         s_storage->sync_cb(tv);
     }
+    // Post event with the timeval payload
+    esp_netif_sntp_time_sync_t evt = {0};
+    if (tv) {
+        evt.tv = *tv;
+    }
+    if (esp_event_post(NETIF_SNTP_EVENT, NETIF_SNTP_TIME_SYNC, &evt, sizeof(evt), 0) != ESP_OK) {
+        ESP_LOGE(TAG, "Error posting SNTP time sync");
+    }
 }
 
 static esp_err_t sntp_init_api(void *ctx)

components/esp_netif/test_apps/test_app_esp_netif/main/esp_netif_test_lwip.c

@@ -9,6 +9,7 @@
 #include "unity_fixture.h"
 #include "esp_netif.h"
 #include "esp_netif_sntp.h"
+#include "esp_event.h"
 #include "esp_netif_net_stack.h"
 #include "esp_wifi.h"
 #include "nvs_flash.h"
@@ -18,8 +19,9 @@
 #include "memory_checks.h"
 #include "lwip/netif.h"
 #include "esp_netif_test.h"
-#include "esp_event.h"
+#include "freertos/FreeRTOS.h"
 #include "freertos/semphr.h"
+#include "sntp/sntp_get_set_time.h"
 
 TEST_GROUP(esp_netif);
 
@@ -68,6 +70,44 @@ TEST(esp_netif, init_and_destroy_sntp)
     esp_netif_sntp_deinit();
 }
 
+static SemaphoreHandle_t s_sntp_evt_sem;
+static void sntp_event_handler(void *arg, esp_event_base_t base, int32_t id, void *data)
+{
+    (void)arg; (void)base; (void)id; (void)data;
+    if (s_sntp_evt_sem) {
+        xSemaphoreGive(s_sntp_evt_sem);
+    }
+}
+
+TEST(esp_netif, sntp_posts_time_sync_event)
+{
+    test_case_uses_tcpip();
+    TEST_ESP_OK(esp_event_loop_create_default());
+
+    // Register handler for NETIF_SNTP_EVENT
+    s_sntp_evt_sem = xSemaphoreCreateBinary();
+    TEST_ASSERT_NOT_NULL(s_sntp_evt_sem);
+    TEST_ESP_OK(esp_event_handler_register(NETIF_SNTP_EVENT, NETIF_SNTP_TIME_SYNC, &sntp_event_handler, NULL));
+
+    // Initialize esp-netif SNTP (no auto-start needed for this test)
+    esp_sntp_config_t config = ESP_NETIF_SNTP_DEFAULT_CONFIG("127.0.0.1");
+    config.start = false;
+    TEST_ESP_OK(esp_netif_sntp_init(&config));
+
+    // Trigger the SNTP time sync callback path artificially
+    sntp_set_system_time(1, 0);
+
+    // Wait for event to be posted
+    TEST_ASSERT_EQUAL(pdTRUE, xQueueSemaphoreTake(s_sntp_evt_sem, pdMS_TO_TICKS(1000)));
+
+    // Cleanup
+    esp_netif_sntp_deinit();
+    TEST_ESP_OK(esp_event_handler_unregister(NETIF_SNTP_EVENT, NETIF_SNTP_TIME_SYNC, &sntp_event_handler));
+    vSemaphoreDelete(s_sntp_evt_sem);
+    s_sntp_evt_sem = NULL;
+    TEST_ESP_OK(esp_event_loop_delete_default());
+}
+
 TEST(esp_netif, convert_ip_addresses)
 {
     const char *ipv4_src[] = {"127.168.1.1", "255.255.255.0", "305.500.721.801", "127.168.1..", "abc.def.***.ddd"};
@@ -666,6 +706,7 @@ TEST_GROUP_RUNNER(esp_netif)
      */
     RUN_TEST_CASE(esp_netif, init_and_destroy)
     RUN_TEST_CASE(esp_netif, init_and_destroy_sntp)
+    RUN_TEST_CASE(esp_netif, sntp_posts_time_sync_event)
     RUN_TEST_CASE(esp_netif, convert_ip_addresses)
     RUN_TEST_CASE(esp_netif, get_from_if_key)
     RUN_TEST_CASE(esp_netif, create_delete_multiple_netifs)

docs/en/api-reference/network/esp_netif_programming.rst

@@ -40,6 +40,31 @@ This section provides more details on specific use cases for the SNTP service, s
 3. Wait for the system time to synchronize using :cpp:func:`esp_netif_sntp_sync_wait()` (if required).
 4. Stop and destroy the service using :cpp:func:`esp_netif_sntp_deinit()`.
 
+Events
+^^^^^^
+
+The SNTP wrapper posts an event when the system time is synchronized:
+
+- Event base: ``NETIF_SNTP_EVENT``
+- Event ID: ``NETIF_SNTP_TIME_SYNC``
+- Event data: pointer to :cpp:type:`esp_netif_sntp_time_sync_t` with the synchronized ``timeval``
+
+Register a handler after creating the default event loop:
+
+.. code-block:: c
+
+    static void sntp_evt_handler(void *arg, esp_event_base_t base, int32_t id, void *data)
+    {
+        const esp_netif_sntp_time_sync_t *evt = (const esp_netif_sntp_time_sync_t *)data;
+        if (evt) {
+            ESP_LOGI("sntp", "time synchronized: %ld.%06ld", (long)evt->tv.tv_sec, (long)evt->tv.tv_usec);
+            // Optionally convert to human-readable time using localtime_r() or gmtime_r()
+        }
+    }
+
+    ESP_ERROR_CHECK(esp_event_loop_create_default());
+    ESP_ERROR_CHECK(esp_event_handler_register(NETIF_SNTP_EVENT, NETIF_SNTP_TIME_SYNC, &sntp_evt_handler, NULL));
+
 
 Basic Mode with Statically Defined Server(s)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

docs/en/api-reference/system/system_time.rst

@@ -105,7 +105,7 @@ To initialize a particular SNTP server and also start the SNTP service, simply c
     esp_sntp_config_t config = ESP_NETIF_SNTP_DEFAULT_CONFIG("pool.ntp.org");
     esp_netif_sntp_init(&config);
 
-This code automatically performs time synchronization once a reply from the SNTP server is received. Sometimes it is useful to wait until the time gets synchronized, :cpp:func:`esp_netif_sntp_sync_wait()` can be used for this purpose:
+This code automatically performs time synchronization once a reply from the SNTP server is received. Sometimes it is useful to wait until the time gets synchronized, :cpp:func:`esp_netif_sntp_sync_wait()` can be used for this purpose. Applications can also subscribe to an event posted when time is synchronized (``NETIF_SNTP_EVENT``, ID ``NETIF_SNTP_TIME_SYNC``). The event data is a pointer to :cpp:type:`esp_netif_sntp_time_sync_t` containing the synchronized ``timeval``:
 
 .. code-block:: c
 

docs/zh_CN/api-reference/system/system_time.rst

@@ -105,7 +105,7 @@ SNTP 时间同步
     esp_sntp_config_t config = ESP_NETIF_SNTP_DEFAULT_CONFIG("pool.ntp.org");
     esp_netif_sntp_init(&config);
 
-一旦收到 SNTP 服务器的响应，此代码会自动执行时间同步。有时等待时间同步很有意义，调用 :cpp:func:`esp_netif_sntp_sync_wait()` 可实现此目的：
+一旦收到 SNTP 服务器的响应，此代码会自动执行时间同步。有时等待时间同步很有意义，调用 :cpp:func:`esp_netif_sntp_sync_wait()` 可实现此目的。应用也可以订阅时间同步事件（事件基座 ``NETIF_SNTP_EVENT``，事件 ID ``NETIF_SNTP_TIME_SYNC``）：
 
 .. code-block:: c
 

examples/protocols/sntp/README.md

@@ -83,6 +83,15 @@ This example can use 3 time synchronization method:
 - `sntp_get_sync_status()` and `sntp_set_sync_status()` - get/set time synchronization status.
 - `sntp_get_sync_mode()` and `sntp_set_sync_mode()` - get/set the sync mode. Allowable two mode: `SNTP_SYNC_MODE_IMMED` and `SNTP_SYNC_MODE_SMOOTH`.
 
+## Events
+
+The esp-netif SNTP wrapper emits an event when the system time is synchronized:
+
+- Event base: `NETIF_SNTP_EVENT`
+- Event ID: `NETIF_SNTP_TIME_SYNC`
+
+Register a handler after creating the default event loop (the event data is a pointer to `esp_netif_sntp_time_sync_t` containing the synchronized `timeval`). You can convert the timeval to human-readable local time or UTC if desired using `localtime_r()`/`gmtime_r()`.
+
 ## Mode of update time
 
 `sntp_set_sync_mode()` - Set the sync mode of the system time. It has two mode:

examples/protocols/sntp/main/sntp_example_main.c

@@ -34,6 +34,22 @@ RTC_DATA_ATTR static int boot_count = 0;
 
 static void obtain_time(void);
 
+static void sntp_event_handler(void *arg, esp_event_base_t base, int32_t id, void *data)
+{
+    (void)arg; (void)base; (void)id;
+    const esp_netif_sntp_time_sync_t *evt = (const esp_netif_sntp_time_sync_t *)data;
+    if (evt) {
+        char ts[64];
+        time_t t = evt->tv.tv_sec;
+        struct tm tm_utc;
+        gmtime_r(&t, &tm_utc);
+        strftime(ts, sizeof(ts), "%Y-%m-%d %H:%M:%S", &tm_utc);
+        ESP_LOGI(TAG, "SNTP event: time synced (UTC): %s.%06ld", ts, (long)evt->tv.tv_usec);
+    } else {
+        ESP_LOGI(TAG, "SNTP event: time synced (no timeval provided)");
+    }
+}
+
 #ifdef CONFIG_SNTP_TIME_SYNC_METHOD_CUSTOM
 void sntp_sync_time(struct timeval *tv)
 {
@@ -140,6 +156,8 @@ static void obtain_time(void)
     ESP_ERROR_CHECK( nvs_flash_init() );
     ESP_ERROR_CHECK(esp_netif_init());
     ESP_ERROR_CHECK( esp_event_loop_create_default() );
+    // Register handler to log SNTP event with timeval payload
+    ESP_ERROR_CHECK(esp_event_handler_register(NETIF_SNTP_EVENT, NETIF_SNTP_TIME_SYNC, &sntp_event_handler, NULL));
 
 #if LWIP_DHCP_GET_NTP_SRV
     /**
@@ -223,4 +241,5 @@ static void obtain_time(void)
 
     ESP_ERROR_CHECK( example_disconnect() );
     esp_netif_sntp_deinit();
+    ESP_ERROR_CHECK(esp_event_handler_unregister(NETIF_SNTP_EVENT, NETIF_SNTP_TIME_SYNC, &sntp_event_handler));
 }