support filtering of EAPOL parents based device-min-sens configuration

Filter EAPOL parents with DEVICE_MIN_SENS with CAND_PARENT_THRESHOLD and CAND_PARENT_HYSTERESIS configuration.

Only neighbours that have THRESHOLD + HYSTERESIS are accepted for EAPOL candidates.
If candidate signal level drops below the THRESHOLD - HYSTERESIS it is removed.

Change Parent list handling to be more consistent between functions

Author: Mika Tervonen

CHANGELOG.md

@@ -3,7 +3,7 @@
 ## Release vXX.X.X
 
 ### Features
-*
+* Filter EAPOL parents based on DEVICE_MIN_SENS configuration with Threshold and Hysteresis to prevent EAPOL failures caused by bad signal levels
 
 ### Changes
 * 

nanostack/ws_management_api.h

@@ -857,8 +857,10 @@ int ws_neighbor_info_get(
  *
  * Setting a value that is not suitable for Radio might prevent the device joining to the network.
  *
- * NOTE: Currently lower EAPOL parents are accepted if there is no parents higher than
- *       DEVICE_MIN_SENS + CAND_PARENT_THRESHOLD + CAND_PARENT_HYSTERESIS
+ * This configuration limits the EAPOL parents accepted for Authentication and device must hear signal
+ * level higher than device_min_sens + CAND_PARENT_THRESHOLD + CAND_PARENT_HYSTERESIS
+ * to start authentication.
+ *
  * NOTE: Currently not using this value to limit parents as it is only RECOMENDED in specification.
  *
  * \param interface_id Network interface ID.

source/6LoWPAN/ws/ws_bootstrap.c

@@ -1387,6 +1387,12 @@ static void ws_bootstrap_candidate_parent_store(parent_info_t *parent, const str
     parent->signal_dbm = data->signal_dbm;
     memcpy(parent->addr, data->SrcAddr, 8);
 
+    if (ws_neighbor_class_rsl_from_dbm_calculate(parent->signal_dbm) > (DEVICE_MIN_SENS + CAND_PARENT_THRESHOLD + CAND_PARENT_HYSTERISIS)) {
+        parent->link_acceptable = true;
+    }
+    if (ws_neighbor_class_rsl_from_dbm_calculate(parent->signal_dbm) < (DEVICE_MIN_SENS + CAND_PARENT_THRESHOLD - CAND_PARENT_HYSTERISIS)) {
+        parent->link_acceptable = false;
+    }
     parent->age = protocol_core_monotonic_time;
 }
 
@@ -1421,6 +1427,7 @@ static parent_info_t *ws_bootstrap_candidate_parent_allocate(protocol_interface_
     }
     if (entry) {
         entry->tx_fail = 0;
+        entry->link_acceptable = false;
     }
     return entry;
 }
@@ -1442,13 +1449,11 @@ static void ws_bootstrap_candidate_parent_mark_failure(protocol_interface_info_e
 {
     parent_info_t *entry = ws_bootstrap_candidate_parent_get(cur, addr, false);
     if (entry) {
-        ns_list_remove(&cur->ws_info->parent_list_reserved, entry);
         if (entry->tx_fail >= 2) {
+            ns_list_remove(&cur->ws_info->parent_list_reserved, entry);
             ns_list_add_to_end(&cur->ws_info->parent_list_free, entry);
         } else {
             entry->tx_fail++;
-            //New last
-            ns_list_add_to_end(&cur->ws_info->parent_list_reserved, entry);
             ws_bootstrap_candidate_parent_sort(cur, entry);
         }
 
@@ -1466,14 +1471,12 @@ static bool ws_bootstrap_candidate_parent_compare(parent_info_t *p1, parent_info
         return false;
     }
 
-    if (ws_neighbor_class_rsl_from_dbm_calculate(p1->signal_dbm) < (DEVICE_MIN_SENS + CAND_PARENT_THRESHOLD + CAND_PARENT_HYSTERISIS) &&
-            ws_neighbor_class_rsl_from_dbm_calculate(p2->signal_dbm) > (DEVICE_MIN_SENS + CAND_PARENT_THRESHOLD + CAND_PARENT_HYSTERISIS)) {
-        // above threshold is always better than not.
+    if (p1->link_acceptable && !p2->link_acceptable) {
+        // Link acceptable is always better than not
         return true;
     }
-    if (ws_neighbor_class_rsl_from_dbm_calculate(p2->signal_dbm) < (DEVICE_MIN_SENS + CAND_PARENT_THRESHOLD + CAND_PARENT_HYSTERISIS) &&
-            ws_neighbor_class_rsl_from_dbm_calculate(p1->signal_dbm) > (DEVICE_MIN_SENS + CAND_PARENT_THRESHOLD + CAND_PARENT_HYSTERISIS)) {
-        // P2 is less than threshold and P1 is larger so P1 is always better.
+    if (!p1->link_acceptable && p2->link_acceptable) {
+        // Link acceptable is always better than not
         return false;
     }
 
@@ -1498,6 +1501,7 @@ static void ws_bootstrap_candidate_list_clean(struct protocol_interface_info_ent
     int pan_count = 0;
 
     ns_list_foreach_safe(parent_info_t, entry, &cur->ws_info->parent_list_reserved) {
+
         if ((current_time - entry->age) > WS_PARENT_LIST_MAX_AGE) {
             ns_list_remove(&cur->ws_info->parent_list_reserved, entry);
             ns_list_add_to_end(&cur->ws_info->parent_list_free, entry);
@@ -1534,6 +1538,9 @@ static void ws_bootstrap_candidate_parent_sort(struct protocol_interface_info_en
             return;
         }
     }
+    // This is the last entry
+    ns_list_remove(&cur->ws_info->parent_list_reserved, new_entry);
+    ns_list_add_to_end(&cur->ws_info->parent_list_reserved, new_entry);
 }
 
 static void ws_bootstrap_pan_information_store(struct protocol_interface_info_entry *cur, const struct mcps_data_ind_s *data, ws_utt_ie_t *ws_utt, ws_us_ie_t *ws_us, ws_pan_information_t *pan_information)
@@ -1560,6 +1567,14 @@ static void ws_bootstrap_pan_information_store(struct protocol_interface_info_en
     }
     // Safe the information
     ws_bootstrap_candidate_parent_store(new_entry, data, ws_utt, ws_us, pan_information);
+    if (!new_entry->link_acceptable) {
+        // This entry is either poor quality or changed to poor quality link so we will remove this
+        // Todo in future possibility to try poor link parents if we have not found any good link parents
+        tr_info("neighbour not accepted: addr:%s panid:%x rsl:%d device_min_sens: %d", trace_array(new_entry->addr, 8), new_entry->pan_id, ws_neighbor_class_rsl_from_dbm_calculate(new_entry->signal_dbm), DEVICE_MIN_SENS);
+        ns_list_remove(&cur->ws_info->parent_list_reserved, new_entry);
+        ns_list_add_to_end(&cur->ws_info->parent_list_free, new_entry);
+        return;
+    }
     // set to the correct place in list
     ws_bootstrap_candidate_parent_sort(cur, new_entry);
 

source/6LoWPAN/ws/ws_common.h

@@ -47,9 +47,10 @@ typedef struct parent_info_s {
     ws_pan_information_t pan_information;
     ws_utt_ie_t          ws_utt;
     ws_us_ie_t           ws_us;
-    uint32_t             timestamp;          /**< Timestamp when packet was received */
-    uint32_t             age;          /**< Age of entry in 100ms ticks */
-    uint8_t              excluded_channel_data[32]; //Channel mask Max length and it accept 8 different range
+    uint32_t             timestamp;                 /**< Timestamp when packet was received */
+    uint32_t             age;                       /**< Age of entry in 100ms ticks */
+    uint8_t              excluded_channel_data[32]; /**< Channel mask Max length and it accept 8 different range*/
+    bool                 link_acceptable: 1;        /**< True when Link quality is in acceptable level*/
     ns_list_link_t       link;
 } parent_info_t;