[ns] Adding a new header.

["Jingyi" <eehjy@ust.hk>]

Dear fellows,

I want to add a new simple header without associating it with a new agent, i.e., a header like the common header. 
However, I don't want to modified the common header. So I did the following:

--------- file: header-df.h ---------
#include "packet.h"

struct hdr_df { 
 u_int8_t numdf_; 

 static int offset_;
 inline static int& offset() { return offset_; }
 inline static hdr_df* access(const Packet* p) {
  return (hdr_df*) p->access(offset_);
 }

 /* per-field member functions */
 u_int8_t& numdf() { return numdf_; }
};

--------- file: header-df.cc ---------
#include "header-df.h"

int hdr_df::offset_;

static class DfHeaderClass : public PacketHeaderClass {
public: 
        DfHeaderClass() : PacketHeaderClass("PacketHeader/Df",
          sizeof(hdr_df)) {
  bind_offset(&hdr_df::offset_);
 }

 void export_offsets() {
  field_offset("numdf_", OFFSET(hdr_df, numdf_));
 }
} class_dfhdr;

------------------------------------
I modified "ns-packet.tcl" accordingly. 
Since there's no new agent, I didn't modify the "packet.h".
------------------------------------
I used the header in my classifier file "classifier-deflect.cc" as follows:
    int num = hdr_df::access(p)->numdf();
and got the following error message:

classifier-deflect.cc: In method `int DeflectClassifier::classify (Packet *, Handler *)':
classifier-deflect.cc:503: `hdr_df' undeclared (first use this
function)
classifier-deflect.cc:503: (Each undeclared identifier is reported only once for each function it appears in.)
classifier-deflect.cc:503: parse error before `::'
classifier-deflect.cc:513: parse error before `::'
make: *** [classifier-deflect.o] Error 1

---------------------------------
Could someone help me out? 
Thanks a lot!

Jingyi