Is there a struct for the options field of tcp_header?
On 7/9/05, rootclown <[EMAIL PROTECTED]> wrote:
> dear Thinh Ho:
> get tcp header with the following way
>
> struct ethhdr *eth;
> struct iphdr *ip;
> struct tcphdr *tcp;
>
> eth=(struct ethhdr *)packet;
> ip=(struct iphdr *)(eth+1);
> tcp=(struct tcphdr *)((u_char *)ip+(ip->ihl<<2));
>
> and you can see linux/tcp.h for details
>
> rootclown
>
>
>
> ======= 2005-07-09 01:58:38 您在来信中写道：=======
>
> >Hello,
> >I am new to the mailing list and also new to pcap, tcpdump, and tcp, in
> >general.
> >I am trying to capture tcp packets and extract/print all its fields in
> >readable format. The sniffer works and I was able to print out the
> >whole packet (in hex) and confirmed it with Ethereal. The struct I
> >have for the tcp header is below:
> >
> >typedef struct tcp_header
> >{
> > u_short sport; // Source port
> > u_short dport; // Destination port
> > u_int seqnum; // Sequence Number
> > u_int acknum; // Acknowledgement number
> > u_char hlen; // Header length
> > u_char flags; // packet flags
> > u_short win; // Window size
> > u_short crc; // Header Checksum
> > u_short urgptr; // Urgent pointer
> >
> > // options field of tcp_header
> > typedef struct option
> > {
> > byte kind;
> > byte length;
> > unsigned long tsval;
> > unsigned long tserc;
> > }option;
> >
> > struct option op;
> >} tcp_header;
> >
> >When call the acknum and each field of options (and everything else,
> >but for now I am concentrating on these two fields), it is not
> >displaying the correct data for some packets because the sizes of
> >ethernet header and ip header varies:
> >
> >tcp_header* tcp = (tcp_header*) (pkt_data + sizeof(struct
> >ethernet_header) + sizeof(struct ip_header));
> >
> >Do I have to define every part of the tcp header such as flags,
> >padding, etc in the struct? Any input on this will greatly be
> >appreciated, and I apologize if this is a newbie question.
> >
> >-Thinh
> >-
> >This is the tcpdump-workers list.
> >Visit https://lists.sandelman.ca/ to unsubscribe.
> >
>
> = = = = = = = = = = = = = = = = = = = =
>
>
> 致
> 礼！
>
>
> rootclown
> [EMAIL PROTECTED]
> 2005-07-09
>
> -
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> Visit https://lists.sandelman.ca/ to unsubscribe.
>
--
Thinh Ho
University of Virginia
Engineering School
C: 571-594-1473
-
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