Add a timer for scan responses

This ensures that the callback will be called within the configured time (in ms) when devices fail to respond to a scan response request within that time.

Author: h2zero

src/NimBLEAdvertisedDevice.h

@@ -162,7 +162,9 @@ class NimBLEAdvertisedDevice {
     int8_t        m_rssi{};
     uint8_t       m_callbackSent{};
     uint8_t       m_advLength{};
-
+# if CONFIG_NIMBLE_CPP_SCAN_RSP_TIMEOUT
+    ble_npl_time_t m_time{};
+# endif
 # if CONFIG_BT_NIMBLE_EXT_ADV
     bool     m_isLegacyAdv{};
     uint8_t  m_sid{};

src/NimBLEScan.cpp

@@ -22,12 +22,85 @@
 # include "NimBLEDevice.h"
 # include "NimBLELog.h"
 
+# if defined(CONFIG_NIMBLE_CPP_IDF)
+#  include "nimble/nimble_port.h"
+# else
+#  include "nimble/porting/nimble/include/nimble/nimble_port.h"
+# endif
+
 # include <string>
 # include <climits>
 
+# define SR_TIMEOUT CONFIG_NIMBLE_CPP_SCAN_RSP_TIMEOUT
+
 static const char*         LOG_TAG = "NimBLEScan";
 static NimBLEScanCallbacks defaultScanCallbacks;
 
+# if SR_TIMEOUT
+static ble_npl_event     dummySrTimerEvent;
+static ble_gap_disc_desc dummyDesc{
+    .event_type = BLE_HCI_ADV_RPT_EVTYPE_SCAN_RSP, .length_data = 0, .addr{}, .rssi = 127, .data = nullptr, .direct_addr{}};
+
+extern "C" void ble_gap_rx_adv_report(ble_gap_disc_desc* desc);
+
+/**
+ * @brief Sends dummy (null) scan response data to the scan event handler in order to
+ * provide the scan result to the callbacks when a device hasn't responded to the
+ * scan request in time. This is called by the host task from the default event queue.
+ */
+static void sendDummyScanResponse(ble_npl_event* ev) {
+    (void)ev;
+    ble_gap_rx_adv_report(&dummyDesc);
+}
+
+/**
+ * @brief This will schedule an event to run in the host task that will call sendDummyScanResponse
+ * which will send a null data scan response to the scan event handler if the device
+ * hasn't responded to a scan response request within the timeout period.
+ */
+void NimBLEScan::srTimerCb(ble_npl_event* event) {
+    NimBLEScan*             pScan   = (NimBLEScan*)ble_npl_event_get_arg(event);
+    NimBLEAdvertisedDevice* curDev  = nullptr;
+    NimBLEAdvertisedDevice* nextDev = nullptr;
+    ble_npl_time_t          now     = ble_npl_time_get();
+
+    for (auto& dev : pScan->m_scanResults.m_deviceVec) {
+        if (dev->m_callbackSent < 2 && dev->isScannable()) {
+            if (!curDev || (now - dev->m_time > now - curDev->m_time)) {
+                nextDev = curDev;
+                curDev  = dev;
+                continue;
+            }
+
+            if (!nextDev || now - dev->m_time > now - nextDev->m_time) {
+                nextDev = dev;
+            }
+        }
+    }
+
+    // Add the event to the host queue
+    if (curDev) {
+        memcpy(&dummyDesc.addr, curDev->getAddress().getBase(), sizeof(dummyDesc.addr));
+        NIMBLE_LOGI(LOG_TAG, "Scan response timeout for: %s", curDev->getAddress().toString().c_str());
+        ble_npl_eventq_put(nimble_port_get_dflt_eventq(), &dummySrTimerEvent);
+    }
+
+    // Restart the timer for the next device that we are expecting a scan response from
+    if (nextDev) {
+        auto nextTime = now - nextDev->m_time;
+        if (nextTime >= SR_TIMEOUT) {
+            nextTime = 1;
+        } else {
+            nextTime = SR_TIMEOUT - nextTime;
+        }
+
+        ble_npl_time_t ticks;
+        ble_npl_time_ms_to_ticks(nextTime, &ticks);
+        ble_npl_callout_reset(&pScan->m_srTimer, ticks);
+    }
+}
+# endif
+
 /**
  * @brief Scan constructor.
  */
@@ -36,13 +109,22 @@ NimBLEScan::NimBLEScan()
       // default interval + window, no whitelist scan filter,not limited scan, no scan response, filter_duplicates
       m_scanParams{0, 0, BLE_HCI_SCAN_FILT_NO_WL, 0, 1, 1},
       m_pTaskData{nullptr},
-      m_maxResults{0xFF} {}
+      m_maxResults{0xFF} {
+# if SR_TIMEOUT
+    ble_npl_callout_init(&m_srTimer, nimble_port_get_dflt_eventq(), NimBLEScan::srTimerCb, this);
+    ble_npl_event_init(&dummySrTimerEvent, sendDummyScanResponse, NULL);
+# endif
+}
 
 /**
  * @brief Scan destructor, release any allocated resources.
  */
 NimBLEScan::~NimBLEScan() {
     clearResults();
+# if SR_TIMEOUT
+    ble_npl_callout_deinit(&m_srTimer);
+    ble_npl_event_deinit(&dummySrTimerEvent);
+# endif
 }
 
 /**
@@ -114,6 +196,9 @@ int NimBLEScan::handleGapEvent(ble_gap_event* event, void* arg) {
                 advertisedDevice = new NimBLEAdvertisedDevice(event, event_type);
                 pScan->m_scanResults.m_deviceVec.push_back(advertisedDevice);
                 NIMBLE_LOGI(LOG_TAG, "New advertiser: %s", advertisedAddress.toString().c_str());
+# if SR_TIMEOUT
+                advertisedDevice->m_time = ble_npl_time_get();
+# endif
             } else {
                 advertisedDevice->update(event, event_type);
                 if (isLegacyAdv && event_type == BLE_HCI_ADV_RPT_EVTYPE_SCAN_RSP) {
@@ -137,6 +222,13 @@ int NimBLEScan::handleGapEvent(ble_gap_event* event, void* arg) {
                 advertisedDevice->m_callbackSent++;
                 // got the scan response report the full data.
                 pScan->m_pScanCallbacks->onResult(advertisedDevice);
+# if SR_TIMEOUT
+            } else if (isLegacyAdv && !ble_npl_callout_is_active(&pScan->m_srTimer)) {
+                // Start the timer to wait for the scan response.
+                ble_npl_time_t ticks;
+                ble_npl_time_ms_to_ticks(SR_TIMEOUT, &ticks);
+                ble_npl_callout_reset(&pScan->m_srTimer, ticks);
+# endif
             }
 
             // If not storing results and we have invoked the callback, delete the device.
@@ -149,13 +241,15 @@ int NimBLEScan::handleGapEvent(ble_gap_event* event, void* arg) {
 
         case BLE_GAP_EVENT_DISC_COMPLETE: {
             NIMBLE_LOGD(LOG_TAG, "discovery complete; reason=%d", event->disc_complete.reason);
+# if SR_TIMEOUT
+            ble_npl_callout_stop(&pScan->m_srTimer);
+# endif
+            pScan->m_pScanCallbacks->onScanEnd(pScan->m_scanResults, event->disc_complete.reason);
 
             if (pScan->m_maxResults == 0) {
                 pScan->clearResults();
             }
 
-            pScan->m_pScanCallbacks->onScanEnd(pScan->m_scanResults, event->disc_complete.reason);
-
             if (pScan->m_pTaskData != nullptr) {
                 NimBLEUtils::taskRelease(*pScan->m_pTaskData, event->disc_complete.reason);
             }
@@ -384,6 +478,10 @@ bool NimBLEScan::stop() {
         return false;
     }
 
+# if SR_TIMEOUT
+    ble_npl_callout_stop(&m_srTimer);
+# endif
+
     if (m_maxResults == 0) {
         clearResults();
     }

src/NimBLEScan.h

@@ -97,11 +97,18 @@ class NimBLEScan {
     static int handleGapEvent(ble_gap_event* event, void* arg);
     void       onHostSync();
 
+# if CONFIG_NIMBLE_CPP_SCAN_RSP_TIMEOUT
+    static void srTimerCb(ble_npl_event* event);
+# endif
+
     NimBLEScanCallbacks* m_pScanCallbacks;
     ble_gap_disc_params  m_scanParams;
     NimBLEScanResults    m_scanResults;
     NimBLETaskData*      m_pTaskData;
     uint8_t              m_maxResults;
+# if CONFIG_NIMBLE_CPP_SCAN_RSP_TIMEOUT
+    ble_npl_callout m_srTimer{};
+# endif
 
 # if CONFIG_BT_NIMBLE_EXT_ADV
     uint8_t  m_phy{SCAN_ALL};

src/nimconfig.h

@@ -176,6 +176,14 @@
  */
 // #define CONFIG_BT_NIMBLE_CRYPTO_STACK_MBEDTLS 1
 
+/**
+ * @brief Un-comment to change the timeout, in milliseconds.
+ * @details This is the time to wait for a scan response before calling the onResult scan callback,
+ * lower values increase callback rates but will lose data more often, higher values give full data more
+ * often. Setting this to 0 will disable the scan response timeout.
+ */
+ // #define CONFIG_NIMBLE_CPP_SCAN_RSP_TIMEOUT (30)
+
 /**********************************
  End Arduino user-config
 **********************************/
@@ -255,6 +263,10 @@
 #define CONFIG_NIMBLE_STACK_USE_MEM_POOLS 0
 #endif
 
+#ifndef CONFIG_NIMBLE_CPP_SCAN_RSP_TIMEOUT
+#define CONFIG_NIMBLE_CPP_SCAN_RSP_TIMEOUT (30)
+#endif
+
 /** @brief Set if CCCD's and bond data should be stored in NVS */
 #define CONFIG_BT_NIMBLE_NVS_PERSIST 1