Eclipse612 wrote:
Hi everyone,
I'm trying to develop a p2p module for NS2, and I've included a new header and packet type into it. These are the things I did:
1) I defined the new header in a couple of files ( a ".h" and a ".cc") using the struct and the mapping class as explained in tutorials, like this:
struct FakePayload
{
vector<string> payload_;
};
//C++ p2p Header Structure
struct hdr_p2p
{
string headerType_; // this is a p2p application packet
static int offset_; //offset of the p2p header first bit in the packet
string aduType_; // Could be: exploratory packet, location_info, resource_confirmation,application_data
string idFile_; //resource identifier, nonzero only if aduType_="application_data"
int idPart_; //part identifier, nonzero only if aduType_="application_data"
FakePayload fakePayload_; //dummy payload, used to insert info that shouldn't be in the header. We avoid using Appdata as recommended by Teerawat.
double timestamp_; // time of the packet forwarding
//header access methods
string& headerType() { return headerType_; }
inline static int& offset() { return offset_; }
string& aduType() { return aduType_; }
string& idFile() { return idFile_; }
int& idPart() { return idPart_; }
double& timestamp() { return timestamp_; }
FakePayload& fakePayload() {return fakePayload_;}
inline static hdr_p2p* access (const Packet* p)
{return (hdr_p2p*) p->access(offset_); }
};
int hdr_p2p::offset_;
// C++ Header Mapping Class
static class p2pHeaderClass : public PacketHeaderClass
{
public:
p2pHeaderClass(): PacketHeaderClass ("PacketHeader/p2p", sizeof(hdr_p2p))
{ bind_offset(&hdr_p2p::offset_); }
} class_p2phdr;
2) I edited packet.h and ns-packet.tcl that way:
Added
p2p #In use for p2p downloading time optimization experiments
to the "foreach prot" cycle in ns-packet.tcl;
Added
" static const packet_t PT_P2P = 62; "
just before the NTYPE, and
" name_[PT_P2P]="p2p"; "
to packet.h.
I verified - using some puts - that the p2p header is added to the packet header when I allocate a packet, being the first header with offset_ = 0.
The problem raises when, on a freshly allocated packet, I try to access the p2p header. The call to hdr_p2p::access(p) seems to be succesful, but when I try to get one of the data members of the hdr_p2p struct (by cout or by writing into them), I get a segmentation fault.
If I try to access one of the other protocol specific headers on the same packet, everything is right and working.
What did I do wrong? It looks like the allocation procedure just reserves space for the new header, but actually doesn't create any hdr_p2p object, thus causing the segmentation fault.
Thanks in advance for your help!
Stefano Vecchi
I tried some debugging and found out that segmentation fault is caused only by string types in the header. If I remove them, everything is right. Is there any restriction using strings in a new header struct?
I hope someone can help...thank you very much in advance.
