/* * Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com) * Copyright (C) 2003-2008 Benny Prijono * * 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 /** * @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. // pj_status_t status; if (response) { status = pjsip_endpt_send_response(endpt, rdata, response, NULL, NULL); if (status != PJ_SUCCESS) pjsip_tx_data_dec_ref(tdata); } else { // Respond with 500 (Internal Server Error) status = pjsip_endpt_respond_stateless(endpt, rdata, 500, NULL, NULL, NULL); if (status != PJ_SUCCESS) pjsip_tx_data_dec_ref(tdata); } } // Create UAS Invite session as usual. // status = pjsip_dlg_create_uas_and_inc_lock(.., 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: * - RFC 3891: The Session * Initiation Protocol (SIP) "Replaces" Header * - \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__ */