anchor.diff:  publish(Pid, EthAddr, IpAddr) ->
       gen_server:call(Pid, {publish, EthAddr, IpAddr}).
   
  +get_cache(Pid) ->
  +    gen_server:call(Pid, get_cache).
  +
   arp_filter({enet, _, {rx, _, #eth{type=arp}}}) -> true;
   arp_filter(_) -> false.
   
  
positive.code:     {ok, #state{cache = enet_arp_cache:new()}}.
  
  %% @private
  handle_call({publish, EthAddr, IpAddr}, _From,
              State = #state{cache = OldCache}) ->
      NewCache = enet_arp_cache:publish(EthAddr, IpAddr, OldCache),
  
negative.code:          ,ip_addr/2
           ,arp_filter/1
           ,publish/3
           ,get_cache/1
           ]).
  
  %% gen_server callbacks
  