anchor.diff:  check_link(DevAddr, FCnt) ->
       case mnesia:dirty_read(links, DevAddr) of
           [] ->
  -            lager:error("Unknown DevAddr ~s", [binary_to_hex(DevAddr)]),
  +            lager:warning("Unknown DevAddr ~s", [binary_to_hex(DevAddr)]),
               {error, {unknown_devaddr, DevAddr}};
           [L] ->
               case fcnt_gap(L#link.fcntup, FCnt) of
  
positive.code: 
      case mnesia:dirty_read(devices, DevEUI) of
          [] ->
              lager:error("Unknown DevEUI ~s", [binary_to_hex(DevEUI)]),
              {error, {unknown_deveui, DevEUI}};
          [D] ->
              case aes_cmac:aes_cmac(D#device.appkey, Msg, 4) of
  
negative.code:                     LastFCnt = (L#link.fcntup + N) band 16#FFFFFFFF,
                      {ok, L#link{fcntup = LastFCnt}};
                  BigN ->
                      lager:warning("~w has a large FCnt gap: last ~b, current ~b", [DevAddr, L#link.fcntup, FCnt]),
                      {error, {fcnt_gap_too_large, BigN}}
              end
      end.
  