[Click] No network header/Segmentation fault

[Beyers Cronje]

Hi,

You have to use either MarkIPHeader of CheckIPHeader elements to set the IP
header annotations.

Beyers

On Fri, Jul 4, 2008 at 5:06 PM, Tushar Soni <omega_marines at yahoo.com> wrote:

> Hi everyone,
>
> I have a scenario where coding some packets at the access point and
> decoding the packets at receiver side using click. Now when i decode the
> packet and use Print() element, the packet structure and ip header looks ok.
> But when i use IPPrint it gives me segmentation fault. When i try to get the
> ip header(Packet::ip_header()) or the udp header(Packet::udp_header()) it
> returns null (so this is the reason why IPPrint does not work). The
> commented code should explain better about what i am doing and the problems
> i am facing. I would be glad if someone could help me figure out what i am
> doing wrong. Thanks.
>
> Tushar
>
> For coding i combine a certain number of packets, from ip header onwards(ip
> header included). So when i decode i should have a packet from ipheader
> onwards.
>
> void
> Decoder::check_uncoded(Packet *p) //p is the coded packet
> {
>    FoundPacketsList found_pkts_list;// this is typedef of type :
> Vector<Packet *>
>    WritablePacket *wp = p->uniqueify();
>   xor_header *xor_h_cod = (xor_header *)wp->data();//i have created my own
> header
>    int entries_cod = xor_h_cod->get_entries();
>    int coded_hlen = xor_header::get_header_length(entries_cod);
>    for( int i = 0; i < entries_cod; i++)
>    {
>        //_ddhq is a type if queue and here i am basically checking if the
> ipid of the unocoded packet
>       //is present in the coded header that i created
>        int location =  _ddhq.is_present(xor_h_cod->get_entry_ipid(i));
>        if( location >= 0 )
>        {
>                //if the id is in the coded header i add it to a list
>            found_pkts_list.push_back(_ddhq.packet(location));
>        }
>    }
>    if(found_pkts_list.size() > 0)
>    {
>
>        bool decodable = false;
>        //this is the condition for decodability
>        if( entries_cod - found_pkts_list.size() == 1)
>        {
>            decodable = true;
>        }
>        //remove my header
>        wp->pull(coded_hlen);
>        FoundPacketsList::iterator x = found_pkts_list.begin();
>        //here i combine the packets in the list with the coded packet to
> decode it
>        while( x < found_pkts_list.end())
>        {
>            Packet *p_i = (*x);
>            unsigned char *xored_data = (unsigned char *)wp->data();
>            unsigned char *data = (unsigned char *)(p_i->ip_header());
>            int len = p_i->length();
>            for (int i = 0; i < len; i++) {
>                xored_data[i] ^= data[i];
>            }
>            x++;
>        }
>        if(decodable)
>        {
>            //wp = wp->uniqueify();
>            click_chatter("WOOHOO Packet Decoded");
>            click_chatter("Length: %u", wp->length());
>
>            click_ip *iph = wp->ip_header();
>            //PROBLEM IS HERE ip_header() returns nothing
>            if(!iph)
>                click_chatter("Shitty packet"); // this is always called
> because the iph is never created
>            else
>            {
>                click_udp *udph = wp->udp_header();
>                if(!udph)
>                    click_chatter("UDP header not found");
>            }
>                //here i push the packet to the higher layers
>                //i use a tun element for this and when i run it gives: no
> network header as the error
>            output(1).push(wp);
>        }
>
>    }
>    else
>    {
>        click_chatter("None of the packets found in uncoded queue.");
>        _codedq.push(0,p);
>    }
> }
>
>
>
>
>  Tºüçhé §übt!é
>
>
>
>
>
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