Re: IP Header Size is always 5

[Shameem Ahamed <shameem.ahamed () hotmail com>]

Hello Sebastian,

Thanks for the reply.


In that case also, we should be able to get the source and destination IP address from the below code

printf("Source IP: %s \n",inet_ntoa(ipHeader->ip_src));

For me it gives me Segmentation Fault.

Also, i am not able to access the tcp header details.


printf("Transport Protocaol Used : %s \n", prototoname(ipHeader->ip_p));
printf("Source IP: %s \n",inet_ntoa(ipHeader->ip_src));
//
tcpHeader=(struct tcphdr *)(packet +ETHER_SIZE+size_ip);

printf("====================TCP Header Details================\n");
size_tcp=tcpHeader->doff;
printf("TCP Header Size is: %d \n",size_tcp);



Regards,
Shameem

> Date: Wed, 1 Apr 2009 11:22:55 -0400
> From: Sebastien.Roy () Sun COM
> Subject: Re: [tcpdump-workers] IP Header Size is always 5
> To: tcpdump-workers () lists tcpdump org
>
> On Wed, 2009-04-01 at 20:42 +0530, Shameem Ahamed wrote:
> > I was trying to create a function (for testing purpose) which displays
> > the header information for Ethernet, IP and TCP using a Linux machine.
> > The problem i am having is, whenever i read any packet from the saved
> > pcap file, it displays the IP header size (ip->ip_hl) is 5 (some times
> > less than 5).
>
> The header length field in an IPv4 header is the length of the header in
> 32-bit words (not in bytes).  See RFC 791.
>
> -Seb
>
>
> -
> This is the tcpdump-workers list.
> Visit https://cod.sandelman.ca/ to unsubscribe.

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