Fix missing RPL Prefix Slaac delete handler.

Change-Id: Ifaaaaa15c09c8d26e33285fa23dace75601924c8

Author: Juha Heiskanen

source/6LoWPAN/ws/ws_bootstrap.c

@@ -1859,16 +1859,21 @@ static void ws_rpl_prefix_callback(prefix_entry_t *prefix, void *handle, uint8_t
      * from a prefix advertised by a parent.
      */
     if (prefix->options & PIO_A) {
-        if (icmpv6_slaac_prefix_update(cur, prefix->prefix, prefix->prefix_len, prefix->lifetime, prefix->preftime) != 0) {
-            ipv6_interface_slaac_handler(cur, prefix->prefix, prefix->prefix_len, prefix->lifetime, prefix->preftime);
-            /*
-             * Give SLAAC addresses a different label and low precedence to indicate that
-             * they probably shouldn't be used for external traffic. SLAAC use in Wi-SUN is non-standard,
-             * and we use it for mesh-local traffic we should prefer any DHCP-assigned addresses
-             * for talking to the outside world
-             *
-             */
-            addr_policy_table_add_entry(prefix->prefix, prefix->prefix_len, 2, WS_NON_PREFFRED_LABEL);
+
+        if (parent_link_local) {
+            if (icmpv6_slaac_prefix_update(cur, prefix->prefix, prefix->prefix_len, prefix->lifetime, prefix->preftime) != 0) {
+                ipv6_interface_slaac_handler(cur, prefix->prefix, prefix->prefix_len, prefix->lifetime, prefix->preftime);
+                /*
+                 * Give SLAAC addresses a different label and low precedence to indicate that
+                 * they probably shouldn't be used for external traffic. SLAAC use in Wi-SUN is non-standard,
+                 * and we use it for mesh-local traffic we should prefer any DHCP-assigned addresses
+                 * for talking to the outside world
+                 *
+                 */
+                addr_policy_table_add_entry(prefix->prefix, prefix->prefix_len, 2, WS_NON_PREFFRED_LABEL);
+            }
+        } else {
+            icmpv6_slaac_prefix_update(cur, prefix->prefix, prefix->prefix_len, 0, 0);
         }
     } else if (prefix->prefix_len) {
         // Create new address using DHCP