Bluetooth: Mesh: restore ttl in Time model after unsolicited statuses

Commit fixes the known issue when the Time model changes
the configured publishing ttl after sending any
unsolicited Time status.

Signed-off-by: Aleksandr Khromykh <[email protected]>

doc/nrf/releases_and_maturity/releases/release-notes-changelog.rst

@@ -85,6 +85,7 @@ Bluetooth Mesh
   * :ref:`bt_mesh_ug_reserved_ids` with model ID and opcodes for the new :ref:`bt_mesh_le_pair_resp_readme` model.
   * :ref:`bt_mesh_light_ctrl_readme` APIs to match new Sensor APIs.
   * :ref:`ug_bt_mesh_configuring` with the recommendation on how to configure persistent storage to increase performance.
+  * Fixed an issue when the Time Server model rewrites TTL to zero forever during the unsolicited Time Status publication.
 
 Matter
 ------

include/bluetooth/mesh/time_srv.h

@@ -107,6 +107,11 @@ struct bt_mesh_time_srv {
 	struct bt_mesh_time_srv_data data;
 	/** Delayable work to randomize status relaying. */
 	struct k_work_delayable status_delay;
+	/** Property whether the Time status was unsolicited. */
+	bool is_unsolicited;
+	/** Cached publishing TTL while server is sending the unsolicited Time Status with zero TTL.
+	 */
+	uint8_t cached_ttl;
 
 	/** @brief Update callback.
 	 *

subsys/bluetooth/mesh/time_srv.c

@@ -416,6 +416,8 @@ static int bt_mesh_time_srv_init(const struct bt_mesh_model *model)
 	srv->model = model;
 	srv->data.timestamp = -STATUS_INTERVAL_MIN;
 	net_buf_simple_init(srv->pub.msg, 0);
+	srv->is_unsolicited = false;
+	srv->cached_ttl = 0;
 
 	k_work_init_delayable(&srv->status_delay, time_status_send_after_delay);
 
@@ -429,6 +431,8 @@ static void bt_mesh_time_srv_reset(const struct bt_mesh_model *model)
 
 	srv->data = data;
 	net_buf_simple_reset(srv->pub.msg);
+	srv->is_unsolicited = false;
+	srv->cached_ttl = 0;
 	(void)k_work_cancel_delayable(&srv->status_delay);
 
 	if (IS_ENABLED(CONFIG_BT_SETTINGS)) {
@@ -489,6 +493,7 @@ const struct bt_mesh_model_cb _bt_mesh_time_setup_srv_cb = {
 int _bt_mesh_time_srv_update_handler(const struct bt_mesh_model *model)
 {
 	struct bt_mesh_time_srv *srv = model->rt->user_data;
+	struct bt_mesh_model_pub *pub = srv->model->pub;
 	struct bt_mesh_time_status status;
 	int64_t uptime;
 	int err;
@@ -504,6 +509,15 @@ int _bt_mesh_time_srv_update_handler(const struct bt_mesh_model *model)
 		return err;
 	}
 
+	/* If sent as an unsolicited message, the Time Status message shall be sent
+	 * with TTL=0 to avoid building up cumulative time errors resulting from delays
+	 * in processing the messages by relays.
+	 */
+	if (!bt_mesh_model_pub_is_retransmission(pub->mod) && srv->is_unsolicited) {
+		pub->ttl = srv->cached_ttl;
+		srv->is_unsolicited = false;
+	}
+
 	srv->data.timestamp = uptime;
 	/* Account for delay in TX processing: */
 	status.uncertainty += CONFIG_BT_MESH_TIME_MESH_HOP_UNCERTAINTY;
@@ -517,6 +531,7 @@ int _bt_mesh_time_srv_update_handler(const struct bt_mesh_model *model)
 int bt_mesh_time_srv_time_status_send(struct bt_mesh_time_srv *srv,
 				      struct bt_mesh_msg_ctx *ctx)
 {
+	struct bt_mesh_model_pub *pub = srv->model->pub;
 	int64_t uptime = k_uptime_get();
 	int err;
 
@@ -528,7 +543,14 @@ int bt_mesh_time_srv_time_status_send(struct bt_mesh_time_srv *srv,
 		return -EOPNOTSUPP;
 	}
 
-	srv->model->pub->ttl = 0;
+	if (ctx) {
+		ctx->send_ttl = 0;
+		ctx->rnd_delay = false;
+	} else {
+		srv->cached_ttl = srv->is_unsolicited ? srv->cached_ttl : pub->ttl;
+		srv->is_unsolicited = true;
+		pub->ttl = 0;
+	}
 
 	err = send_time_status(srv->model, ctx, uptime);
 	if (!err) {

tests/subsys/bluetooth/mesh/time_model/src/main.c

@@ -40,6 +40,7 @@ static struct bt_mesh_time_status expected_status;
 static uint32_t time_status_rx_number;
 static bool is_randomized;
 static bool is_unsolicited;
+static bool is_skipped;
 
 static void tc_setup(void *f)
 {
@@ -50,7 +51,12 @@ static void tc_setup(void *f)
 		.tm_hour = 0,   .tm_min = 0, .tm_sec = 0,
 	};
 
+	is_randomized = false;
+	is_unsolicited = false;
+	is_skipped = false;
 	time_status_rx_number = 0;
+	mock_elem[0].models->pub->mod = mock_elem[0].models;
+	mock_elem[0].models->pub->ttl = 10;
 	zassert_not_null(_bt_mesh_time_srv_cb.init, "Init cb is null");
 	_bt_mesh_time_srv_cb.init(mock_elem[0].models);
 
@@ -91,6 +97,10 @@ int bt_mesh_msg_send(const struct bt_mesh_model *model, struct bt_mesh_msg_ctx *
 
 	zassert_equal_ptr(time_srv.model, model);
 
+	if (is_skipped) {
+		return 0;
+	}
+
 	if (is_randomized) {
 		zassert_is_null(ctx);
 	} else {
@@ -185,7 +195,6 @@ ZTEST(time_model, test_time_set_timing)
 {
 	int64_t start_time = k_uptime_get();
 
-	is_randomized = false;
 	is_unsolicited = true;
 
 	while (k_uptime_get() - start_time < TEST_TIME) {
@@ -247,4 +256,36 @@ ZTEST(time_model, test_time_periodic_pub_status_mix)
 	zassert_equal(TEST_TIME / STATUS_INTERVAL_MIN, time_status_rx_number);
 }
 
+/** Test scenario: update handler of the Time model is called once
+ *  (emulation of publication by timer). TTL should be equal configured value.
+ *  Unsolicited Time Status is published. TTL should be 0.
+ *  Unsolicited Time Status is published again. TTL is still 0.
+ *  Update handler is called. TTL should go back to the configured value.
+ *  Update handler is called again. TTL should be still equal the configured value.
+ */
+ZTEST(time_model, test_time_pub_ttl)
+{
+	struct bt_mesh_model_pub *pub = mock_elem[0].models->pub;
+
+	is_skipped = true;
+
+	zassert_equal(10, pub->ttl);
+	zassert_ok(_bt_mesh_time_srv_update_handler(mock_elem[0].models));
+	zassert_equal(10, pub->ttl);
+
+	net_buf_simple_reset(pub->msg);
+	zassert_ok(bt_mesh_time_srv_time_status_send(&time_srv, NULL));
+	zassert_equal(0, pub->ttl);
+	net_buf_simple_reset(pub->msg);
+	zassert_ok(bt_mesh_time_srv_time_status_send(&time_srv, NULL));
+	zassert_equal(0, pub->ttl);
+
+	net_buf_simple_reset(pub->msg);
+	zassert_ok(_bt_mesh_time_srv_update_handler(mock_elem[0].models));
+	zassert_equal(10, pub->ttl);
+	net_buf_simple_reset(pub->msg);
+	zassert_ok(_bt_mesh_time_srv_update_handler(mock_elem[0].models));
+	zassert_equal(10, pub->ttl);
+}
+
 ZTEST_SUITE(time_model, NULL, NULL, tc_setup, tc_teardown, NULL);