Wireshark-dev: Re: [Wireshark-dev] ATM over Ethernet

From: Alex Bennée <kernel-hacker@xxxxxxxxxx>
Date: Tue, 6 Nov 2012 10:13:52 +0000
On 5 November 2012 18:53, Guy Harris <guy@xxxxxxxxxxxx> wrote:
> On Nov 5, 2012, at 4:14 AM, Alex Bennee <kernel-hacker@xxxxxxxxxx> wrote:
>
>> Currently I can't see a way to specify treating the rest of the frame
>> as multiple frames. Do I need to extend the ATM dissector to call
>> itself if the remaining frame is larger than 53 bytes?
>
> No, you need to implement a dissector for your ATM-over-Ethernet encapsulation that repeatedly calls the ATM dissector for each cell.  Multiple cells encapsulated in an Ethernet packet is a characteristic of your encapsulation, not of ATM, so the code to handle that should be part of the dissector for your encapsulation, not the dissector for ATM.

Is there another example encapsulation that does that sort of thing I
can look at?

I'm a little unclear on the two prototypes for the dissector. The
second one returns the number of bytes processes which I assume will
always be zero in my case.

>> Also how is the AAL encoding determined? Should I just register the
>> handlers for the multiple AAL types and let the user decide?
>
> Yes.  The AAL encoding is determined by whatever AAL information is in the capture file, and I suspect that is often put there by a user explicitly configuring the capturing machine.

It looks like I'll have to set a preference for that then as it's only
really specified by the application specific VC.

-- 
Alex, homepage: http://www.bennee.com/~alex/
http://www.half-llama.co.uk