Attended call transfer implementation. The changes involves:

- Added support for SIP Replaces extension (RFC 3891)
- Added pjsua_call_xfer_replaces() to perform attended call
  transfer.
- PJSUA checks and process Replaces header in incoming calls
- Added pjsip_ua_find_dialog() API.
- Added pjsip_endpt_has_capability() API.
- Added pjsip_endpt_send_response2() API.
- etc.



git-svn-id: http://svn.pjsip.org/repos/pjproject/trunk@797 74dad513-b988-da41-8d7b-12977e46ad98

2 files changed, 323 insertions, 8 deletions

diff --git a/pjsip/include/pjsip-ua/sip_replaces.h b/pjsip/include/pjsip-ua/sip_replaces.h
new file mode 100644
index 00000000..38c8aa99
--- /dev/null
+++ b/pjsip/include/pjsip-ua/sip_replaces.h
@@ -0,0 +1,300 @@
+/* $Id$ */
+/* 
+ * Copyright (C) 2003-2006 Benny Prijono <benny@prijono.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
+ */
+#ifndef __PJSIP_REPLACES_H__
+#define __PJSIP_REPLACES_H__
+
+
+/**
+ * @file sip_replaces.h
+ * @brief SIP Replaces support (RFC 3891 - SIP "Replaces" Header)
+ */
+#include <pjsip/sip_msg.h>
+
+/**
+ * @defgroup PJSIP_REPLACES SIP Replaces support (RFC 3891 - "Replaces" Header)
+ * @ingroup PJSIP_HIGH_UA
+ * @brief SIP Replaces support (RFC 3891 - "Replaces" Header)
+ * @{
+ *
+ * This module implements support for Replaces header in PJSIP. The Replaces
+ * specification is written in RFC 3891 - The Session Initiation Protocol (SIP) 
+ * "Replaces" Header, and can be used to enable a variety of features, 
+ * for example: "Attended Transfer" and "Call Pickup".
+ *
+ * 
+ *
+ * \section PJSIP_REPLACES_USING_SEC Using PJSIP Replaces Support
+ *
+ * \subsection PJSIP_REPLACES_INIT_SUBSEC Initialization
+ *
+ * Application needs to call #pjsip_replaces_init_module() during application
+ * initialization stage to register "replaces" support in PJSIP. 
+ *
+ *
+ * 
+ * \subsection PJSIP_REPLACES_UAC_SUBSEC UAC Behavior: Sending a Replaces Header
+ *
+ * A User Agent that wishes to replace a single existing early or
+ * confirmed dialog with a new dialog of its own, MAY send the target
+ * User Agent an INVITE request containing a Replaces header field.  The
+ * User Agent Client (UAC) places the Call-ID, to-tag, and from-tag
+ * information for the target dialog in a single Replaces header field
+ * and sends the new INVITE to the target.
+ *
+ * To initiate outgoing INVITE request with Replaces header, application
+ * would create the INVITE request with #pjsip_inv_invite(), then adds
+ * #pjsip_replaces_hdr instance into the request, filling up the Call-ID,
+ * To-tag, and From-tag properties of the header with the identification
+ * of the dialog to be replaced. Application may also optionally
+ * set the \a early_only property of the header to indicate that it only
+ * wants to replace early dialog.
+ *
+ * Note that when the outgoing INVITE request (with Replaces) is initiated
+ * from an incoming REFER request (as in Attended Call Transfer case),
+ * this process should be done rather more automatically by PJSIP. Upon 
+ * receiving incoming incoming REFER request, normally these processes
+ * will be performed:
+ *  - Application finds \a Refer-To header,
+ *  - Application creates outgoing dialog/invite session, specifying
+ *    the URI in the \a Refer-To header as the initial remote target,
+ *  - The URI in the \a Refer-To header may contain header parameters such
+ *    as \a Replaces and \a Require headers.
+ *  - The dialog keeps the header fields in the header parameters
+ *    of the URI, and the invite session would add these headers into
+ *    the outgoing INVITE request. Because of this, the outgoing 
+ *    INVITE request will contain the \a Replaces and \a Require headers.
+ *
+ *
+ * For more information, please see the implementation of 
+ * #pjsua_call_xfer_replaces() in \ref PJSUA_LIB source code.
+ *
+ *
+ * \subsection PJSIP_REPLACES_UAS_SUBSEC UAS Behavior: Receiving a Replaces Header
+ *
+ * The Replaces header contains information used to match an existing
+ * SIP dialog (call-id, to-tag, and from-tag).  Upon receiving an INVITE
+ * with a Replaces header, the User Agent (UA) attempts to match this
+ * information with a confirmed or early dialog.  
+ *
+ * In PJSIP, if application wants to process the Replaces header in the
+ * incoming INVITE request, it should call #pjsip_replaces_verify_request()
+ * before creating the INVITE session. The #pjsip_replaces_verify_request()
+ * function checks and verifies the request to see if Replaces request
+ * can be processed. To be more specific, it performs the following
+ * verification:
+ *  - checks that Replaces header is present. If not, the function will
+ *    return PJ_SUCCESS without doing anything.
+ *  - checks that no duplicate Replaces headers are present, or otherwise
+ *    it will return 400 "Bad Request" response.
+ *  - checks for matching dialog and verifies that the invite session has
+ *    the correct state, and may return 481 "Call/Transaction Does Not Exist",
+ *    603 "Declined", or 486 "Busy Here" according to the processing rules
+ *    specified in RFC 3891.
+ *  - if matching dialog with correct state is found, it will give PJ_SUCCESS
+ *    status and return the matching dialog back to the application.
+ *
+ * The following pseudocode illustrates how application can process the
+ * incoming INVITE if it wants to support Replaces extension:
+ *
+ \code
+  // Incoming INVITE request handler
+  pj_bool_t on_rx_invite(pjsip_rx_data *rdata)
+  {
+    pjsip_dialog *dlg, *replaced_dlg;
+    pjsip_inv_session *inv;
+    pjsip_tx_data *response;
+    pj_status_t status;
+
+    // Check whether Replaces header is present in the request and process accordingly.
+    //
+    status = pjsip_replaces_verify_request(rdata, &replaced_dlg, PJ_FALSE, &response);
+    if (status != PJ_SUCCESS) {
+	// Something wrong with Replaces request.
+	//
+	if (response) {
+	    pjsip_endpt_send_response(endpt, rdata, response, NULL, NULL);
+	} else {
+	    // Respond with 500 (Internal Server Error)
+	    pjsip_endpt_respond_stateless(endpt, rdata, 500, NULL, NULL, NULL);
+	}
+    }
+
+    // Create UAS Invite session as usual.
+    //
+    status = pjsip_dlg_create_uas(.., rdata, .., &dlg);
+    ..
+    status = pjsip_inv_create_uas(dlg, .., &inv);
+
+    // Send initial 100 "Trying" to the INVITE request
+    //
+    status = pjsip_inv_initial_answer(inv, rdata, 100, ..., &response);
+    if (status == PJ_SUCCESS)
+	pjsip_inv_send_msg(inv, response);
+
+
+    // This is where processing is different between normal call
+    // (without Replaces) and call with Replaces.
+    //
+    if (replaced_dlg) {
+	pjsip_inv_session *replaced_inv;
+
+	// Always answer the new INVITE with 200, regardless whether
+	// the replaced call is in early or confirmed state.
+	//
+	status = pjsip_inv_answer(inv, 200, NULL, NULL, &response);
+	if (status == PJ_SUCCESS)
+	    pjsip_inv_send_msg(inv, response);
+
+
+	// Get the INVITE session associated with the replaced dialog.
+	//
+	replaced_inv = pjsip_dlg_get_inv_session(replaced_dlg);
+
+
+	// Disconnect the "replaced" INVITE session.
+	//
+	status = pjsip_inv_end_session(replaced_inv, PJSIP_SC_GONE, NULL, &tdata);
+	if (status == PJ_SUCCESS && tdata)
+	    status = pjsip_inv_send_msg(replaced_inv, tdata);
+
+
+	// It's up to application to associate the new INVITE session
+	// with the old (now terminated) session. For example, application
+	// may assign the same User Interface object for the new INVITE
+	// session.
+
+    } else {
+	// Process normal INVITE without Replaces.
+	...
+    }
+  }
+
+ \endcode
+ *
+ *
+ * For a complete sample implementation, please see \a pjsua_call_on_incoming()
+ * function of \ref PJSUA_LIB in \a pjsua_call.c file.
+ *
+ *
+ * \section PJSIP_REPLACES_REFERENCE References
+ *
+ * References:
+ *  - <A HREF="http://www.ietf.org/rfc/rfc3891.txt">RFC 3891: The Session 
+ *    Initiation Protocol (SIP) "Replaces" Header</A>
+ *  - \ref PJSUA_XFER
+ */
+
+PJ_BEGIN_DECL
+
+
+/**
+ * Declaration of SIP Replaces header (RFC 3891).
+ */
+typedef struct pjsip_replaces_hdr
+{
+    /** Standard header field. */
+    PJSIP_DECL_HDR_MEMBER(struct pjsip_replaces_hdr);
+
+    /** Call-Id */
+    pj_str_t	call_id;
+
+    /** to-tag */
+    pj_str_t	to_tag;
+
+    /** from-tag */
+    pj_str_t	from_tag;
+
+    /** early-only? */
+    pj_bool_t	early_only;
+
+    /** Other parameters */
+    pjsip_param	other_param;
+
+} pjsip_replaces_hdr;
+
+
+
+/**
+ * Initialize Replaces support in PJSIP. This would, among other things, 
+ * register the header parser for Replaces header.
+ *
+ * @param endpt	    The endpoint instance.
+ *
+ * @return	    PJ_SUCCESS on success.
+ */
+PJ_DECL(pj_status_t) pjsip_replaces_init_module(pjsip_endpoint *endpt);
+
+
+/**
+ * Create Replaces header.
+ *
+ * @param pool	    Pool to allocate the header instance from.
+ *
+ * @return	    An empty Replaces header instance.
+ */
+PJ_DECL(pjsip_replaces_hdr*) pjsip_replaces_hdr_create(pj_pool_t *pool);
+
+
+/**
+ * Verify that incoming request with Replaces header can be processed.
+ * This function will perform all necessary checks according to RFC 3891
+ * Section 3 "User Agent Server Behavior: Receiving a Replaces Header".
+ *
+ * @param rdata	    The incoming request to be verified.
+ * @param p_dlg	    On return, it will be filled with the matching 
+ *		    dialog.
+ * @param lock_dlg  Specifies whether this function should acquire lock
+ *		    to the matching dialog. If yes (and should be yes!),
+ *		    then application will need to release the dialog's
+ *		    lock with #pjsip_dlg_dec_lock() when the function
+ *		    returns PJ_SUCCESS and the \a p_dlg parameter is filled
+ *		    with the dialog instance.
+ * @param p_tdata   Upon error, it will be filled with the final response
+ *		    to be sent to the request sender.
+ *
+ * @return	    The function returns the following:
+ *		    - If the request doesn't contain Replaces header, the
+ *		      function returns PJ_SUCCESS and \a p_dlg parameter
+ *		      will be set to NULL.
+ *		    - If the request contains Replaces header and a valid,
+ *		      matching dialog is found, the function returns 
+ *		      PJ_SUCCESS and \a p_dlg parameter will be set to the
+ *		      matching dialog instance.
+ *		    - Upon error condition (as described by RFC 3891), the
+ *		      function returns non-PJ_SUCCESS, and \a p_tdata 
+ *		      parameter SHOULD be set with a final response message
+ *		      to be sent to the sender of the request.
+ */
+PJ_DECL(pj_status_t) pjsip_replaces_verify_request(pjsip_rx_data *rdata,
+						   pjsip_dialog **p_dlg,
+						   pj_bool_t lock_dlg,
+						   pjsip_tx_data **p_tdata);
+
+
+
+PJ_END_DECL
+
+
+/**
+ * @}
+ */
+
+
+#endif	/* __PJSIP_REPLACES_H__ */
+
diff --git a/pjsip/include/pjsip-ua/sip_xfer.h b/pjsip/include/pjsip-ua/sip_xfer.h
index 56809141..53d98e90 100644
--- a/pjsip/include/pjsip-ua/sip_xfer.h
+++ b/pjsip/include/pjsip-ua/sip_xfer.h
@@ -29,17 +29,32 @@
 #include <pjsip/sip_msg.h>
 
 /**
- * @defgroup PJSUA_XFER Call Transfer
+ * @defgroup PJSUA_XFER SIP REFER (RFC 3515) for Call Transfer etc.
  * @ingroup PJSIP_HIGH_UA
- * @brief Provides call transfer functionality.
+ * @brief SIP REFER dialog usage (call transfer, etc.)
  * @{
  *
- * This implements call transfer functionality to INVITE sessions. The call
- * transfer functionality uses SIP Event Subscription framework for
- * managing call transfer status.
- *
- * Application must link with <b>pjsip-ua</b> AND <b>pjsip-simple</b> static
- * libraries to use call transfer functionality.
+ * This describes a generic handling of SIP REFER request. The SIP REFER
+ * request is described in RFC 3515, and commonly used to perform call
+ * transfer functionality. Other types of SIP REFER usages are described
+ * in draft-worley-sip-many-refers-00 draft, for example:
+ *  - Remote Dial: where UAC sends REFER to instruct REFER recipient to
+ *    initiate an INVITE session to some target.
+ * 
+ * A REFER request can be sent inside or outside existing dialog context,
+ * although for call transfer case, it is more common to send REFER inside
+ * existing INVITE session context. PJSIP supports both sending REFER request
+ * inside or outside dialog context.
+ *
+ * The REFER framework uses @ref PJSIP_EVENT_NOT to manage the event
+ * subscription created by the REFER request. Because of this, application 
+ * must link with <b>pjsip-ua</b> AND <b>pjsip-simple</b> static libraries 
+ * to use REFER functionality.
+ *
+ * Reference:
+ *  - <A HREF="http://www.ietf.org/rfc/rfc3515.txt">RFC 3515: The Session 
+ *    Initiation Protocol (SIP) Refer Method</A>
+ *  - @ref PJSIP_EVENT_NOT
  */