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List:       sr-dev
Subject:    [Serdev] sending a request within transaction
From:       Jiri Kuthan <jiri () iptel ! org>
Date:       2003-07-16 8:19:44
Message-ID: 5.2.0.9.0.20030716095358.0382f6c8 () localhost
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/* diverted to serdev -- we don't want to burden the user community with
   development, see "More help" at www.iptel.org/ser/ */

If you wish to cancel pending transactions, I suggest you to look at
the function 'cancel_uacs' -- it takes a bitmap if branches you would like
to cancel and does exactly that job.

As for the idea of doing so after receipt of  200/INVs, I suspect that has 
potential of transaction breaking. Sending a CANCEL after 200/INV is too late, many
UASs will certainly not like it, ignore it, think they are in a call and
keep resending 200s in a hope to get an ACK. 

To get around transaction/dialog state cleanly, you would need to dive in
dialog processing, and generate a proper BYE if you want to tear down an
existing call. That's actually a construct called "back-to-back UA".

-Jiri

At 07:11 PM 7/15/2003, Mario Kolberg wrote:
> Hi,
> 
> I'm trying to sent a CANCEL request within a transaction.
> 
> User A invites user B and the messaeges are sent via proxy P. In the scenario, A \
> sends an INVITE to B, and B replies with an 200OK. Depending on some conditions, \
> the proxy may decide that this 200OK should not be forwarded to A. And P will send \
> a CANCEL request to B (using request_within from the tm module). This causes two \
> problems: 
> 1) Sending this request fails !sometimes! and I have no idea why. According to the \
> log, it appears to be crashing within the request_within call. Is this because I \
> have not filled the dialog (dlg) data structure correctly? I have attached the \
> relevant code. Have I overlooked a data field? The log (compressed) can e obtained \
> from http://www.cs.stir.ac.uk/~mko/crash_log.gz (search for ' BUG' in the log). Can \
> you see anything obvious wrong? From the log it looks like the RR hooks in dlg may \
> be incomplete??? 
> 2) However, !sometimes! for some reason, the CANCEL actually is sent and reaches B. \
> B then answers with a 487 Request Cancelled message and also with a 200 OK for the \
> Cancel itself. But P when forwards the reply messages on to A, which is not aware \
> of the CANCEL at all! I see that B has put in an extra via header with A's address \
> into the replies. This via header is not in the CANCEL request. 
> Is request_within actually the best way of doing this?
> 
> Thanks very much for your help.
> 
> Regards,
> Mario
> -- 
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> 
> dlg_t* dlg;
> 
> dlg=pkg_malloc(sizeof(dlg_t));
> dlg->state = DLG_NEW;
> dlg->id.loc_tag.len=0;
> dlg->id.loc_tag.s=NULL;
> 
> if(tmb.dlg_response_uac(dlg, msg) < 0)
> LOG(L_ERR, "error in dlg_response_uac\n");
> else {
> LOG(L_ERR, "OCS reply dlg created\n");
> dlg->loc_uri.len=from_uri.len;
> dlg->loc_uri.s= from_uri.s;
> dlg->rem_uri.s= to_uri.s;
> dlg->rem_uri.len=to_uri.len;
> dlg->id.call_id.s=callid.s;
> dlg->id.call_id.len=callid.len;
> dlg->loc_seq.value = cseq_int;
> 
> cancelm.s="CANCEL";
> cancelm.len = 6;
> 
> LOG(L_ERR,"just before printing ...\n");
> tmb.print_dlg(stderr, dlg);
> 
> if(tmb.t_request_within(&cancelm, NULL, NULL, dlg, NULL, NULL) < 0)
> LOG(L_ERR, "ocs: sending of cancel request failed!\n");
> else {
> LOG(L_ERR, "OCS CANCEL sent\n");
> }
> 
> _______________________________________________
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> serusers@lists.iptel.org
> http://lists.iptel.org/mailman/listinfo/serusers

--
Jiri Kuthan            http://iptel.org/~jiri/ 


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