anchor.diff:     method Action readPacketBuff(Bit#(16) addr);
      method Action writePacketBuff(Bit#(16) addr, Bit#(64) data);
      method Action freePacketBuff(Bit#(32) id);
  +   method Action writePacketData(Vector#(2, Bit#(64)) data, Vector#(2, Bit#(8)) mask, Bit#(1) sop, Bit#(1) eop);
   endinterface
   
   interface TbTop;
  
positive.code:       method Action freePacketBuff(Bit#(32) id);
  
        endmethod
     endinterface
  endmodule: mkTbTop
  
  
negative.code: import MemServerIndication::*;
  import MMUIndication::*;
  import SharedBuff::*;
  import Ethernet::*;
  import PacketBuffer::*;
  
  import Malloc::*;
  
  