Wireshark-dev: Re: [Wireshark-dev] Request/Response tracking with multiple responses
From: "Martin Mathieson" <[email protected]>
Date: Fri, 20 Jun 2008 19:26:04 +0100


On Fri, Jun 20, 2008 at 6:26 PM, Guy Harris <[email protected]> wrote:
Thomas Boehne wrote:
> I followed the README.request_response_tracking to add
> request/response tracking to a UDP based protocol, but the protocol
> sometimes sends multiple responses to a single request. Does anybody
> know of a dissector that handles this case properly, so that I could
> take a look at the code?

I don't know of any.  I don't know of many protocols where multiple
responses are sent to a single request (other than responses sent to
retransmitted requests).

SIP is an example.  A single request may have one or more provisional responses e.g. progress, ringing, before the final response is received.
 
Responses currently track back to the request (and show a response time), but the request doesn't currently track forward to its response(s).

There I wasn't sure if I should have a different filter for the first resonse time (since this is the one that is probably of most interest), possibly also the last.  I also considered adding a generated field to responses to say that they are the nth response to the same request.  This would let someone isolate the first responses if they wanted to, e.g.

sip.response.nth == 1



> Or is it basically just a matter of extending the pana_transaction_t
> struct (see below) to handle a list of replies, and then iterate
> through it?
>
> typedef struct _pana_transaction_t {
>                 guint32 req_frame;
>                 guint32 rep_frame;
>                 nstime_t req_time;
>         } pana_transaction_t;

I.e., instead of a guint32 rep_frame, have a list of frames, or a GArray
of frame numbers, or something such as that?

That's pretty much what I had in mind to do for SIP.
 

That's probably the right answer.
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