Add RSL check for ETX Calculation for RPL parent selection

Separate Wi-SUN ETX function so that all ETX checks have same validation
Remove all direct calls to etx_local_etx_read function and replace with
Wi-SUN version.

Remove check for 0 ack from etx_local_etx_read as it is ok to run the
ETX Calculation through even if first probe fails

Author: Mika Tervonen

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Release vXX.X.X
 
 ### Features
+* Filter RPL parents based on DEVICE_MIN_SENS configuration with Threshold and Hysteresis.
 * 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

@@ -861,7 +861,9 @@ int ws_neighbor_info_get(
  * 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.
+ * ETX Calculation gives a maximum ETX if two way EWMA RSL is less than
+ * device_min_sens + CAND_PARENT_THRESHOLD + CAND_PARENT_HYSTERESIS to
+ * prevent selecting parents with poor signal quality
  *
  * \param interface_id Network interface ID.
  * \param device_min_sens value used in the parent selections.

source/6LoWPAN/ws/ws_bootstrap.c

@@ -909,17 +909,17 @@ static void ws_bootstrap_ll_address_validate(struct protocol_interface_info_entr
  * \return 0x0000 address unknown or other error
  * \return 0x0001 no ETX statistics on this interface
  */
-uint16_t ws_etx_read(protocol_interface_info_entry_t *interface, addrtype_t addr_type, const uint8_t *addr_ptr)
+uint16_t ws_local_etx_read(protocol_interface_info_entry_t *interface, addrtype_t addr_type, const uint8_t *mac_adddress)
 {
     uint16_t etx;
 
-    if (!addr_ptr || !interface) {
+    if (!mac_adddress || !interface) {
         return 0;
     }
 
     uint8_t attribute_index;
 
-    mac_neighbor_table_entry_t *mac_neighbor = mac_neighbor_table_address_discover(mac_neighbor_info(interface), addr_ptr + PAN_ID_LEN, addr_type);
+    mac_neighbor_table_entry_t *mac_neighbor = mac_neighbor_table_address_discover(mac_neighbor_info(interface), mac_adddress, addr_type);
     if (!mac_neighbor) {
         return 0xffff;
     }
@@ -933,6 +933,12 @@ uint16_t ws_etx_read(protocol_interface_info_entry_t *interface, addrtype_t addr
 
     etx = etx_local_etx_read(interface->id, attribute_index);
 
+    // if we have a measurement ready then we will check the RSL validity
+    if (etx != 0xffff && !ws_neighbour->candidate_parent) {
+        // RSL value measured is lower than acceptable ETX will be given as MAX
+        return WS_ETX_MAX << 1; // We use 8 bit fraction and ETX is usually 7 bit fraction
+    }
+
     // If we dont have valid ETX for children we assume good ETX.
     // After enough packets is sent to children real calculated ETX is given.
     // This might result in ICMP source route errors returned to Border router causing secondary route uses
@@ -942,6 +948,15 @@ uint16_t ws_etx_read(protocol_interface_info_entry_t *interface, addrtype_t addr
 
     return etx;
 }
+
+uint16_t ws_etx_read(protocol_interface_info_entry_t *interface, addrtype_t addr_type, const uint8_t *addr_ptr)
+{
+    if (!addr_ptr || !interface) {
+        return 0;
+    }
+    return ws_local_etx_read(interface, addr_type, addr_ptr + PAN_ID_LEN);
+}
+
 bool ws_bootstrap_nd_ns_transmit(protocol_interface_info_entry_t *cur, ipv6_neighbour_t *entry,  bool unicast, uint8_t seq)
 {
     (void)cur;
@@ -3001,17 +3016,17 @@ static bool ws_rpl_new_parent_callback(uint8_t *ll_parent_address, void *handle,
             return false;
         }
         // +2 Is for PAN ID space
-        memcpy(mac64 + 2, replacing + 8, 8);
-        mac64[2] ^= 2;
+        memcpy(mac64, replacing + 8, 8);
+        mac64[0] ^= 2;
 
-        if (ws_etx_read(cur, ADDR_802_15_4_LONG, mac64) == 0xffff) {
-            //Not proped yet because ETX is 0xffff
+        if (ws_local_etx_read(cur, ADDR_802_15_4_LONG, mac64) == 0xffff) {
+            //Not probed yet because ETX is 0xffff
             return false;
         }
 
         uint16_t etx = 0;
         if (neigh_buffer.neighbor) {
-            etx = etx_local_etx_read(cur->id, neigh_buffer.neighbor->index);
+            etx = ws_local_etx_read(cur, ADDR_802_15_4_LONG, neigh_buffer.neighbor->mac64);
         }
 
         // Accept now only better one's when max candidates selected and max candidate list size is reached
@@ -3554,7 +3569,7 @@ static uint16_t ws_bootstrap_routing_cost_calculate(protocol_interface_info_entr
         return 0xffff;
     }
 
-    uint16_t etx = etx_local_etx_read(cur->id, mac_neighbor->index);
+    uint16_t etx = ws_local_etx_read(cur, ADDR_802_15_4_LONG, mac_neighbor->mac64);
     if (etx == 0) {
         etx = WS_ETX_MAX; //SET maximum value here if ETX is unknown
     } else {
@@ -4254,7 +4269,7 @@ int ws_bootstrap_neighbor_info_get(protocol_interface_info_entry_t *cur, ws_neig
             neighbor_ptr[count].rsl_out = ws_neighbor_class_rsl_out_get(ws_neighbor);
 
             // ETX is shown calculated as 8 bit integer, but more common way is to use 7 bit such that 128 means ETX:1.0
-            neighbor_ptr[count].etx = etx_local_etx_read(cur->id, mac_entry->index);
+            neighbor_ptr[count].etx = ws_local_etx_read(cur, ADDR_802_15_4_LONG, mac_entry->mac64);
             if (neighbor_ptr[count].etx != 0xffff) {
                 neighbor_ptr[count].etx = neighbor_ptr[count].etx >> 1;
             }

source/Service_Libs/etx/etx.c

@@ -439,11 +439,6 @@ uint16_t etx_local_etx_read(int8_t interface_id, uint8_t attribute_index)
     }
 
     if (etx_info.cache_sample_requested && entry->etx_samples < etx_info.init_etx_sample_count) {
-        etx_sample_storage_t *storage = etx_info.etx_cache_storage_list + attribute_index;
-        if (storage->received_acks == 0 && storage->attempts_count) {
-            //No ack so return max value
-            return etx_info.max_etx;
-        }
         //Not ready yet
         return 0xffff;
     }