bluetooth: add api for changing rpa timeout in runtime

Added a new Bluetooth API and Kconfig option for overriding the RPA
timeout in runtime.

Signed-off-by: Kamil Piszczek <Kamil.Piszczek@nordicsemi.no>

include/zephyr/bluetooth/bluetooth.h

@@ -2021,6 +2021,26 @@ static inline int bt_le_whitelist_clear(void)
  */
 int bt_le_set_chan_map(uint8_t chan_map[5]);
 
+/**
+ * @brief Set the Resolvable Private Address timeout in runtime
+ *
+ * The new RPA timeout value will be used for the next RPA rotation
+ * and all subsequent rotations until another override is scheduled
+ * with this API.
+ *
+ * Initially, the if @kconfig{CONFIG_BT_RPA_TIMEOUT} is used as the
+ * RPA timeout.
+ *
+ * This symbol is linkable if @kconfig{CONFIG_BT_RPA_TIMEOUT_DYNAMIC}
+ * is enabled.
+ *
+ * @param new_rpa_timeout Resolvable Private Address timeout in seconds
+ *
+ * @retval 0 Success.
+ * @retval -EINVAL RPA timeout value is invalid. Valid range is 1s - 3600s.
+ */
+int bt_le_set_rpa_timeout(uint16_t new_rpa_timeout);
+
 /**
  * @brief Helper for parsing advertising (or EIR or OOB) data.
  *

subsys/bluetooth/host/Kconfig

@@ -350,6 +350,13 @@ config BT_RPA_TIMEOUT
 	  This option defines how often resolvable private address is rotated.
 	  Value is provided in seconds and defaults to 900 seconds (15 minutes).
 
+config BT_RPA_TIMEOUT_DYNAMIC
+	bool "Support setting the Resolvable Private Address timeout at runtime"
+	depends on BT_PRIVACY
+	help
+	  This option allows the user to override the default value of
+	  the Resolvable Private Address timeout using dedicated APIs.
+
 config BT_SIGNING
 	bool "Data signing support"
 	help

subsys/bluetooth/host/conn.c

@@ -2492,7 +2492,7 @@ static bool create_param_validate(const struct bt_conn_le_create_param *param)
 {
 #if defined(CONFIG_BT_PRIVACY)
 	/* Initiation timeout cannot be greater than the RPA timeout */
-	const uint32_t timeout_max = (MSEC_PER_SEC / 10) * CONFIG_BT_RPA_TIMEOUT;
+	const uint32_t timeout_max = (MSEC_PER_SEC / 10) * bt_dev.rpa_timeout;
 
 	if (param->timeout > timeout_max) {
 		return false;

subsys/bluetooth/host/hci_core.c

@@ -76,6 +76,9 @@ static void init_work(struct k_work *work);
 
 struct bt_dev bt_dev = {
 	.init          = Z_WORK_INITIALIZER(init_work),
+#if defined(CONFIG_BT_PRIVACY)
+	.rpa_timeout   = CONFIG_BT_RPA_TIMEOUT,
+#endif
 #if defined(CONFIG_BT_DEVICE_APPEARANCE_DYNAMIC)
 	.appearance = CONFIG_BT_DEVICE_APPEARANCE,
 #endif
@@ -2975,7 +2978,7 @@ static int le_init(void)
 		}
 
 		cp = net_buf_add(buf, sizeof(*cp));
-		cp->rpa_timeout = sys_cpu_to_le16(CONFIG_BT_RPA_TIMEOUT);
+		cp->rpa_timeout = sys_cpu_to_le16(bt_dev.rpa_timeout);
 		err = bt_hci_cmd_send_sync(BT_HCI_OP_LE_SET_RPA_TIMEOUT, buf,
 					   NULL);
 		if (err) {
@@ -3933,6 +3936,24 @@ int bt_le_set_chan_map(uint8_t chan_map[5])
 				    buf, NULL);
 }
 
+#if defined(CONFIG_BT_RPA_TIMEOUT_DYNAMIC)
+int bt_le_set_rpa_timeout(uint16_t new_rpa_timeout)
+{
+	if ((new_rpa_timeout == 0) || (new_rpa_timeout > 3600)) {
+		return -EINVAL;
+	}
+
+	if (new_rpa_timeout == bt_dev.rpa_timeout) {
+		return 0;
+	}
+
+	bt_dev.rpa_timeout = new_rpa_timeout;
+	atomic_set_bit(bt_dev.flags, BT_DEV_RPA_TIMEOUT_CHANGED);
+
+	return 0;
+}
+#endif
+
 void bt_data_parse(struct net_buf_simple *ad,
 		   bool (*func)(struct bt_data *data, void *user_data),
 		   void *user_data)

subsys/bluetooth/host/hci_core.h

@@ -44,6 +44,7 @@ enum {
 	BT_DEV_INITIATING,
 
 	BT_DEV_RPA_VALID,
+	BT_DEV_RPA_TIMEOUT_CHANGED,
 
 	BT_DEV_ID_PENDING,
 	BT_DEV_STORE_ID,
@@ -358,6 +359,9 @@ struct bt_dev {
 
 	/* Work used for RPA rotation */
 	struct k_work_delayable rpa_update;
+
+	/* The RPA timeout value. */
+	uint16_t rpa_timeout;
 #endif
 
 	/* Local Name */

subsys/bluetooth/host/id.c

@@ -6,6 +6,7 @@
  */
 
 #include <zephyr/settings/settings.h>
+#include <zephyr/sys/byteorder.h>
 
 #include <zephyr/bluetooth/bluetooth.h>
 #include <zephyr/bluetooth/hci_vs.h>
@@ -204,9 +205,47 @@ static void le_rpa_invalidate(void)
 }
 
 #if defined(CONFIG_BT_PRIVACY)
+
+#if defined(CONFIG_BT_RPA_TIMEOUT_DYNAMIC)
+static void le_rpa_timeout_update(void)
+{
+	int err = 0;
+
+	if (atomic_test_and_clear_bit(bt_dev.flags, BT_DEV_RPA_TIMEOUT_CHANGED)) {
+		struct net_buf *buf;
+		struct bt_hci_cp_le_set_rpa_timeout *cp;
+
+		buf = bt_hci_cmd_create(BT_HCI_OP_LE_SET_RPA_TIMEOUT,
+					sizeof(*cp));
+		if (!buf) {
+			BT_ERR("Failed to create HCI RPA timeout command");
+			err = -ENOBUFS;
+			goto submit;
+		}
+
+		cp = net_buf_add(buf, sizeof(*cp));
+		cp->rpa_timeout = sys_cpu_to_le16(bt_dev.rpa_timeout);
+		err = bt_hci_cmd_send_sync(BT_HCI_OP_LE_SET_RPA_TIMEOUT, buf, NULL);
+		if (err) {
+			BT_ERR("Failed to send HCI RPA timeout command");
+			goto submit;
+		}
+	}
+
+submit:
+	if (err) {
+		atomic_set_bit(bt_dev.flags, BT_DEV_RPA_TIMEOUT_CHANGED);
+	}
+}
+#endif
+
 static void le_rpa_timeout_submit(void)
 {
-	(void)k_work_schedule(&bt_dev.rpa_update, RPA_TIMEOUT);
+#if defined(CONFIG_BT_RPA_TIMEOUT_DYNAMIC)
+	le_rpa_timeout_update();
+#endif
+
+	(void)k_work_schedule(&bt_dev.rpa_update, K_SECONDS(bt_dev.rpa_timeout));
 }
 
 /* this function sets new RPA only if current one is no longer valid */

subsys/bluetooth/host/id.h

@@ -5,8 +5,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-#define RPA_TIMEOUT_MS       (CONFIG_BT_RPA_TIMEOUT * MSEC_PER_SEC)
-#define RPA_TIMEOUT          K_MSEC(RPA_TIMEOUT_MS)
+#define RPA_TIMEOUT_MS(_rpa_timeout) (_rpa_timeout * MSEC_PER_SEC)
 
 static inline bool bt_id_rpa_is_new(void)
 {
@@ -16,7 +15,7 @@ static inline bool bt_id_rpa_is_new(void)
 	/* RPA is considered new if there is less than half a second since the
 	 * timeout was started.
 	 */
-	return remaining_ms > (RPA_TIMEOUT_MS - 500);
+	return remaining_ms > (RPA_TIMEOUT_MS(bt_dev.rpa_timeout) - 500);
 #else
 	return false;
 #endif