Fix Child NUD with long ARO registrations

NUD was not sent to children if they had long ARO registrations
This should affect interoperability with devices that dont use
ARO as keep alive

Author: Mika Tervonen

source/6LoWPAN/ws/ws_bootstrap.c

@@ -2191,6 +2191,8 @@ static bool ws_neighbor_entry_nud_notify(mac_neighbor_table_entry_t *entry_ptr,
     uint8_t ll_address[16];
     bool nud_proces = false;
     bool activate_nud = false;
+    bool child;
+    bool candidate_parent;
     protocol_interface_info_entry_t *cur = user_data;
 
     ws_neighbor_class_entry_t *ws_neighbor = ws_neighbor_class_entry_get(&cur->ws_info->neighbor_storage, entry_ptr->index);
@@ -2204,12 +2206,17 @@ static bool ws_neighbor_entry_nud_notify(mac_neighbor_table_entry_t *entry_ptr,
 
     if (time_from_start > WS_NEIGHBOR_NUD_TIMEOUT) {
 
+        child = ipv6_neighbour_has_registered_by_eui64(&cur->ipv6_neighbour_cache, entry_ptr->mac64);
+        candidate_parent = rpl_control_is_dodag_parent_candidate(cur, ll_address, cur->ws_info->cfg->gen.rpl_parent_candidate_max);
         /* For parents ARO registration is sent in link timeout times
          * For candidate parents NUD is needed
          * For children NUD is sent only at very close to end
          */
-        if (ipv6_neighbour_has_registered_by_eui64(&cur->ipv6_neighbour_cache, entry_ptr->mac64) &&
-                (time_from_start < WS_NEIGHBOR_NUD_TIMEOUT * 1.8)) {
+        if (!child && !candidate_parent) {
+            // No need for keep alive
+            return false;
+        }
+        if (child && (time_from_start < WS_NEIGHBOR_NUD_TIMEOUT * 1.8)) {
             /* This is our child with valid ARO registration send NUD if we are close to delete
              *
              * if ARO was received link is considered active so this is only in case of very long ARO registration times
@@ -2220,11 +2227,6 @@ static bool ws_neighbor_entry_nud_notify(mac_neighbor_table_entry_t *entry_ptr,
             return false;
         }
 
-        if (!rpl_control_is_dodag_parent_candidate(cur, ll_address, cur->ws_info->cfg->gen.rpl_parent_candidate_max)) {
-            //NUD Not needed for if neighbour is not parent candidate
-            return false;
-        }
-
         if (time_from_start > WS_NEIGHBOR_NUD_TIMEOUT * 1.5) {
             activate_nud = true;
         } else {