anchor.diff:  encode_protocol(fc)            -> 133;
   encode_protocol(divert)        -> 254.
   
  -payload_type(#ipv4{proto=P}) -> P.
  -payload(#ipv4{data=D}) -> D.
  +payload_type(#ipv4{proto=P}, _) -> P.
  +payload(#ipv4{data=D}, _) -> D.
  +default_options() -> [].
   
   
   %%====================================================================
  
positive.code: %% API
  -export([decode_addr/1, encode_addr/1
           ,pseudo_hdr/1
           ,decode/2
           ,encode/1, expand/1
           ,decode_protocol/1, encode_protocol/1
           ,header_checksum/1
           ,addr_len/0
           ,addr_to_list/1, list_to_addr/1
          ]).
  
  -export([payload/1, payload_type/1]).
  
  -include("enet_types.hrl").
  -define(IP_VERSION, 4).
  
negative.code:              src=SrcIP,
               dst=DestIP,
               options=Options,
               data=Data}, _)
    when is_integer(HLen), is_integer(DiffServ),
         is_integer(TotLen), is_integer(ID),
         is_bitstring(Flags), is_integer(FragOff), is_integer(TTL),
  