Add (dangerous) feature : use layer 2 acks instead of NUD in the IPv6 layer.

(Decrease packet numbers but dangerous if neighbors change their ips (not a problem in standard RPL with EUI-64 based addresses))

core/net/uip-ds6.c

@@ -369,6 +369,24 @@ uip_ds6_nbr_lookup(uip_ipaddr_t *ipaddr)
   return NULL;
 }
 
+/*---------------------------------------------------------------------------*/
+uip_ds6_nbr_t *
+uip_ds6_nbr_ll_lookup(uip_lladdr_t *lladdr)
+{
+  uip_ds6_nbr_t *fin;
+
+  for( locnbr=uip_ds6_nbr_cache, fin=locnbr + UIP_DS6_NBR_NB;
+       locnbr<fin;
+       ++locnbr) {
+    if(locnbr->isused) {
+      if(!memcmp(lladdr,&locnbr->lladdr,UIP_LLADDR_LEN)) {
+        return locnbr;
+      }
+    }
+  }
+  return NULL;
+}
+
 /*---------------------------------------------------------------------------*/
 uip_ds6_defrt_t *
 uip_ds6_defrt_add(uip_ipaddr_t *ipaddr, unsigned long interval)