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.
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