anchor.diff:  
   adjust_status(IF, operstate, A, B) ->
       {adjust_operstate(A, IF), adjust_operstate(B, IF)};
  -adjust_status(_, A, B) ->
  +adjust_status(_, _, A, B) ->
       {A, B}.
   
   adjust_operstate(undefined,  _) -> down;
  
positive.code:                   undefined
            end,
      Interfaces = get_interfaces(),
      {ok, #st{ifs = Interfaces,
               poll_ref = Ref}}.
  
  
negative.code: get_interfaces() ->
      case inet:getifaddrs() of
          {ok, IFs} ->
              [if_entry(I) || {_Name, _Flags} = I <- IFs];
          Error ->
              ?error("getifaddrs() -> ~p", [Error]),
              []
  