Re: Adding offset to 'Address

[Björn <ssh9614@hotmail.com>]

On 12 Sep, 10:35, Kim Rostgaard Christensen <k...@greenpc.dk> wrote:
> Hi
>
> How does one go about setting a 'Address + (size of other record) to a
> record at runtime ?
>
> In brief, I am switching over "Frametype" in a Ethernet frame record, to
> dynamically assign the next record by type (IPv4,IPv6,ARP, etc.)
> My "datablob" is a *u_char from a imported C function.
>
> So I have:
>
>   Raw_Bytes : access Unsigned_Char
>   for Ethernet_Header'Address use Raw_Bytes.all'Address;
>
> and additionally need something like:
>   for IP_Packet'Address use Raw_Bytes.all'Address + Ethernet_Header'Size;
>
> Also, I am not confident that this _the_ solution, so other approaches
> are very welcome. For those curious about what it is all about, I ran a
> gnathtml on the source and made it available athttp://krc.greenpc.dk/hovedopgave/html/index.htm
>
> Regards
> Kim Rostgaard Christensen

I was also playing around with PCAP earlier this year. I have not yet
finished what I intended to do but I got basic IP reassembly and TCP
session reconstruction to work. I uploaded the files to
http://www.mediafire.com/?1neezbx5bb1 if you want to have a peek.
However, note that this is work in progress. The application is not
finished and the quality of the code will need improvement. There are
also a lot more special cases in TCP handling that will need to be
handled.

Regards
Björn