Attended transfer missing to and from tags #3367

gordongrech · 2025-04-25T14:29:44Z

Hello,

I've have been working on attended transfers using the call_replace_transfer. While the Replaces portion of the header is added with the correct call id, the to-tag and from tag are not being included. This seems to be incompatible with RFC 3891, also on phone systems such as Asterisk, the transfer request is detected as non-local and fails as the respective dialogs are not found.

I've managed to address this by exposing rtag and ltag in re/src/sip/dialog.c and adding these to the Replaces portion of the header.

const char *sip_dialog_ltag(const struct sip_dialog *dlg)
{
	return dlg ? dlg->ltag : NULL;
}

const char *sip_dialog_rtag(const struct sip_dialog *dlg)
{
	return dlg ? dlg->rtag : NULL;
}

and

int call_replace_transfer(struct call *call, struct call *source_call)
{
	int err;

	call->sub = mem_deref(call->sub);

	err = sipevent_drefer(&call->sub, uag_sipevent_sock(),
			      sipsess_dialog(call->sess), ua_cuser(call->ua),
			      auth_handler, call->acc, true,
			      sipsub_notify_handler, sipsub_close_handler,
                              call,
	                      "Refer-To: <%s?Replaces=%s%%3Bto-tag%%3D%s%%3Bfrom-tag%%3D%s>\r\n"
	                      "Referred-By: %s\r\n",
	                      source_call->peer_uri,
	                      source_call->id,
	                      sip_dialog_rtag(sipsess_dialog(source_call->sess)),
                              sip_dialog_ltag(sipsess_dialog(source_call->sess)),
	                      account_aor(ua_account(call->ua)));

	if (err) {
		warning("call: sipevent_drefer: %m\n", err);
	}

	return err;
}

If you believe that the above approach is correct I will happily create a pull request.

Thanks,
Gordon

cspiel1 · 2025-04-28T05:49:08Z

Related commit: e02d727
We will have a look on this.

alfredh · 2025-05-10T15:35:32Z

Could you please also include the relevant SIP traffic, enable with baresip -s

cspiel1 added this to the v3.23.0 milestone Apr 30, 2025

alfredh removed this from the v3.23.0 milestone May 8, 2025

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Attended transfer missing to and from tags #3367

Attended transfer missing to and from tags #3367

Attended transfer missing to and from tags #3367

Attended transfer missing to and from tags #3367

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