The large GULP->PJSIP renaming effort.

The general gist is to have a clear boundary between old SIP stuff
and new SIP stuff by having the word "SIP" for old stuff and "PJSIP"
for new stuff. Here's a brief rundown of the changes:

* The word "Gulp" in dialstrings, functions, and CLI commands is now
  "PJSIP"
* chan_gulp.c is now chan_pjsip.c
* Function names in chan_gulp.c that were "gulp_*" are now "chan_pjsip_*"
* All files that were "res_sip*" are now "res_pjsip*"
* The "res_sip" directory is now "res_pjsip"
* Files in the "res_pjsip" directory that began with "sip_*" are now "pjsip_*"
* The configuration file is now "pjsip.conf" instead of "res_sip.conf"
* The module info for all PJSIP-related files now uses "PJSIP" instead of "SIP"
* CLI and AMI commands created by Asterisk's PJSIP modules now have "pjsip" as
the starting word instead of "sip"



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@395764 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 867 insertions, 0 deletions

diff --git a/res/res_pjsip_refer.c b/res/res_pjsip_refer.c
new file mode 100644
index 000000000..d9c2aeceb
--- /dev/null
+++ b/res/res_pjsip_refer.c
@@ -0,0 +1,867 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2013, Digium, Inc.
+ *
+ * Joshua Colp <jcolp@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*** MODULEINFO
+	<depend>pjproject</depend>
+	<depend>res_pjsip</depend>
+	<depend>res_pjsip_session</depend>
+	<depend>res_pjsip_pubsub</depend>
+	<support_level>core</support_level>
+ ***/
+
+#include "asterisk.h"
+
+#include <pjsip.h>
+#include <pjsip_ua.h>
+
+#include "asterisk/res_pjsip.h"
+#include "asterisk/res_pjsip_session.h"
+#include "asterisk/module.h"
+#include "asterisk/pbx.h"
+#include "asterisk/taskprocessor.h"
+#include "asterisk/bridge.h"
+#include "asterisk/framehook.h"
+
+/*! \brief REFER Progress structure */
+struct refer_progress {
+	/*! \brief Subscription to provide updates on */
+	pjsip_evsub *sub;
+	/*! \brief Dialog for subscription */
+	pjsip_dialog *dlg;
+	/*! \brief Received packet, used to construct final response in case no subscription exists */
+	pjsip_rx_data *rdata;
+	/*! \brief Frame hook for monitoring REFER progress */
+	int framehook;
+	/*! \brief Last received subclass in frame hook */
+	int subclass;
+	/*! \brief Serializer for notifications */
+	struct ast_taskprocessor *serializer;
+};
+
+/*! \brief REFER Progress notification structure */
+struct refer_progress_notification {
+	/*! \brief Refer progress structure to send notification on */
+	struct refer_progress *progress;
+	/*! \brief SIP response code to send */
+	int response;
+	/*! \brief Subscription state */
+	pjsip_evsub_state state;
+};
+
+/*! \brief REFER Progress module, used to attach REFER progress structure to subscriptions */
+static pjsip_module refer_progress_module = {
+	.name = { "REFER Progress", 14 },
+	.id = -1,
+};
+
+/*! \brief Destructor for REFER Progress notification structure */
+static void refer_progress_notification_destroy(void *obj)
+{
+	struct refer_progress_notification *notification = obj;
+
+	ao2_cleanup(notification->progress);
+}
+
+/*! \brief Allocator for REFER Progress notification structure */
+static struct refer_progress_notification *refer_progress_notification_alloc(struct refer_progress *progress, int response,
+	pjsip_evsub_state state)
+{
+	struct refer_progress_notification *notification = ao2_alloc(sizeof(*notification), refer_progress_notification_destroy);
+
+	if (!notification) {
+		return NULL;
+	}
+
+	ao2_ref(progress, +1);
+	notification->progress = progress;
+	notification->response = response;
+	notification->state = state;
+
+	return notification;
+}
+
+/*! \brief Serialized callback for subscription notification */
+static int refer_progress_notify(void *data)
+{
+	RAII_VAR(struct refer_progress_notification *, notification, data, ao2_cleanup);
+	pjsip_evsub *sub;
+	pjsip_tx_data *tdata;
+
+	/* If the subscription has already been terminated we can't send a notification */
+	if (!(sub = notification->progress->sub)) {
+		ast_debug(3, "Not sending NOTIFY of response '%d' and state '%d' on progress monitor '%p' as subscription has been terminated\n",
+			notification->response, notification->state, notification->progress);
+		return 0;
+	}
+
+	/* If the subscription is being terminated we want to actually remove the progress structure here to
+	 * stop a deadlock from occurring - basically terminated changes the state which queues a synchronous task
+	 * but we are already running a task... thus it would deadlock */
+	if (notification->state == PJSIP_EVSUB_STATE_TERMINATED) {
+		ast_debug(3, "Subscription '%p' is being terminated as a result of a NOTIFY, removing REFER progress structure early on progress monitor '%p'\n",
+			notification->progress->sub, notification->progress);
+		pjsip_dlg_inc_lock(notification->progress->dlg);
+		pjsip_evsub_set_mod_data(notification->progress->sub, refer_progress_module.id, NULL);
+		pjsip_dlg_dec_lock(notification->progress->dlg);
+
+		/* This is for dropping the reference on the subscription */
+		ao2_cleanup(notification->progress);
+
+		notification->progress->sub = NULL;
+	}
+
+	ast_debug(3, "Sending NOTIFY with response '%d' and state '%d' on subscription '%p' and progress monitor '%p'\n",
+		notification->response, notification->state, sub, notification->progress);
+
+	/* Actually send the notification */
+	if (pjsip_xfer_notify(sub, notification->state, notification->response, NULL, &tdata) == PJ_SUCCESS) {
+		pjsip_xfer_send_request(sub, tdata);
+	}
+
+	return 0;
+}
+
+/*! \brief Progress monitoring frame hook - examines frames to determine state of transfer */
+static struct ast_frame *refer_progress_framehook(struct ast_channel *chan, struct ast_frame *f, enum ast_framehook_event event, void *data)
+{
+	struct refer_progress *progress = data;
+	struct refer_progress_notification *notification = NULL;
+
+	/* We only care about frames *to* the channel */
+	if (!f || (event != AST_FRAMEHOOK_EVENT_WRITE)) {
+		return f;
+	}
+
+	/* Determine the state of the REFER based on the control frames (or voice frames) passing */
+	if (f->frametype == AST_FRAME_VOICE && !progress->subclass) {
+		/* Media is passing without progress, this means the call has been answered */
+		notification = refer_progress_notification_alloc(progress, 200, PJSIP_EVSUB_STATE_TERMINATED);
+	} else if (f->frametype == AST_FRAME_CONTROL) {
+		progress->subclass = f->subclass.integer;
+
+		/* Based on the control frame being written we can send a NOTIFY advising of the progress */
+		if ((f->subclass.integer == AST_CONTROL_RING) || (f->subclass.integer == AST_CONTROL_RINGING)) {
+			notification = refer_progress_notification_alloc(progress, 180, PJSIP_EVSUB_STATE_ACTIVE);
+		} else if (f->subclass.integer == AST_CONTROL_BUSY) {
+			notification = refer_progress_notification_alloc(progress, 486, PJSIP_EVSUB_STATE_TERMINATED);
+		} else if (f->subclass.integer == AST_CONTROL_CONGESTION) {
+			notification = refer_progress_notification_alloc(progress, 503, PJSIP_EVSUB_STATE_TERMINATED);
+		} else if (f->subclass.integer == AST_CONTROL_PROGRESS) {
+			notification = refer_progress_notification_alloc(progress, 183, PJSIP_EVSUB_STATE_ACTIVE);
+		} else if (f->subclass.integer == AST_CONTROL_PROCEEDING) {
+			notification = refer_progress_notification_alloc(progress, 100, PJSIP_EVSUB_STATE_ACTIVE);
+		} else if (f->subclass.integer == AST_CONTROL_ANSWER) {
+			notification = refer_progress_notification_alloc(progress, 200, PJSIP_EVSUB_STATE_TERMINATED);
+		}
+	}
+
+	/* If a notification is due to be sent push it to the thread pool */
+	if (notification) {
+		if (ast_sip_push_task(progress->serializer, refer_progress_notify, notification)) {
+			ao2_cleanup(notification);
+		}
+
+		/* If the subscription is being terminated we don't need the frame hook any longer */
+		if (notification->state == PJSIP_EVSUB_STATE_TERMINATED) {
+			ast_debug(3, "Detaching REFER progress monitoring hook from '%s' as subscription is being terminated\n",
+				ast_channel_name(chan));
+			ast_framehook_detach(chan, progress->framehook);
+		}
+
+	}
+
+	return f;
+}
+
+/*! \brief Destroy callback for monitoring framehook */
+static void refer_progress_framehook_destroy(void *data)
+{
+	struct refer_progress *progress = data;
+	struct refer_progress_notification *notification = refer_progress_notification_alloc(progress, 503, PJSIP_EVSUB_STATE_TERMINATED);
+
+	if (notification && ast_sip_push_task(progress->serializer, refer_progress_notify, notification)) {
+		ao2_cleanup(notification);
+	}
+
+	ao2_cleanup(progress);
+}
+
+/*! \brief Serialized callback for subscription termination */
+static int refer_progress_terminate(void *data)
+{
+	struct refer_progress *progress = data;
+
+	/* The subscription is no longer valid */
+	progress->sub = NULL;
+
+	return 0;
+}
+
+/*! \brief Callback for REFER subscription state changes */
+static void refer_progress_on_evsub_state(pjsip_evsub *sub, pjsip_event *event)
+{
+	struct refer_progress *progress = pjsip_evsub_get_mod_data(sub, refer_progress_module.id);
+
+	/* If being destroyed queue it up to the serializer */
+	if (progress && (pjsip_evsub_get_state(sub) == PJSIP_EVSUB_STATE_TERMINATED)) {
+		/* To prevent a deadlock race condition we unlock the dialog so other serialized tasks can execute */
+		ast_debug(3, "Subscription '%p' has been remotely terminated, waiting for other tasks to complete on progress monitor '%p'\n",
+			sub, progress);
+
+		/* It's possible that a task is waiting to remove us already, so bump the refcount of progress so it doesn't get destroyed */
+		ao2_ref(progress, +1);
+		pjsip_dlg_dec_lock(progress->dlg);
+		ast_sip_push_task_synchronous(progress->serializer, refer_progress_terminate, progress);
+		pjsip_dlg_inc_lock(progress->dlg);
+		ao2_ref(progress, -1);
+
+		ast_debug(3, "Subscription '%p' removed from progress monitor '%p'\n", sub, progress);
+
+		/* Since it was unlocked it is possible for this to have been removed already, so check again */
+		if (pjsip_evsub_get_mod_data(sub, refer_progress_module.id)) {
+			pjsip_evsub_set_mod_data(sub, refer_progress_module.id, NULL);
+			ao2_cleanup(progress);
+		}
+	}
+}
+
+/*! \brief Callback structure for subscription */
+static pjsip_evsub_user refer_progress_evsub_cb = {
+	.on_evsub_state = refer_progress_on_evsub_state,
+};
+
+/*! \brief Destructor for REFER progress sutrcture */
+static void refer_progress_destroy(void *obj)
+{
+	struct refer_progress *progress = obj;
+
+	ast_taskprocessor_unreference(progress->serializer);
+}
+
+/*! \brief Internal helper function which sets up a refer progress structure if needed */
+static int refer_progress_alloc(struct ast_sip_session *session, pjsip_rx_data *rdata, struct refer_progress **progress)
+{
+	const pj_str_t str_refer_sub = { "Refer-Sub", 9 };
+	pjsip_generic_string_hdr *refer_sub = NULL;
+	const pj_str_t str_true = { "true", 4 };
+	pjsip_tx_data *tdata;
+	pjsip_hdr hdr_list;
+
+	*progress = NULL;
+
+	/* Grab the optional Refer-Sub header, it can be used to suppress the implicit subscription */
+	refer_sub = pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &str_refer_sub, NULL);
+	if ((refer_sub && pj_strnicmp(&refer_sub->hvalue, &str_true, 4))) {
+		return 0;
+	}
+
+	if (!(*progress = ao2_alloc(sizeof(struct refer_progress), refer_progress_destroy))) {
+		return -1;
+	}
+
+	ast_debug(3, "Created progress monitor '%p' for transfer occurring from channel '%s' and endpoint '%s'\n",
+		progress, ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+
+	(*progress)->framehook = -1;
+
+	/* To prevent a potential deadlock we need the dialog so we can lock/unlock */
+	(*progress)->dlg = session->inv_session->dlg;
+
+	if (!((*progress)->serializer = ast_sip_create_serializer())) {
+		goto error;
+	}
+
+	/* Create the implicit subscription for monitoring of this transfer */
+	if (pjsip_xfer_create_uas(session->inv_session->dlg, &refer_progress_evsub_cb, rdata, &(*progress)->sub) != PJ_SUCCESS) {
+		goto error;
+	}
+
+	/* Associate the REFER progress structure with the subscription */
+	ao2_ref(*progress, +1);
+	pjsip_evsub_set_mod_data((*progress)->sub, refer_progress_module.id, *progress);
+
+	pj_list_init(&hdr_list);
+	if (refer_sub) {
+		pjsip_hdr *hdr = (pjsip_hdr*)pjsip_generic_string_hdr_create(session->inv_session->dlg->pool, &str_refer_sub, &str_true);
+
+		pj_list_push_back(&hdr_list, hdr);
+	}
+
+	/* Accept the REFER request */
+	ast_debug(3, "Accepting REFER request for progress monitor '%p'\n", *progress);
+	pjsip_xfer_accept((*progress)->sub, rdata, 202, &hdr_list);
+
+	/* Send initial NOTIFY Request */
+	ast_debug(3, "Sending initial 100 Trying NOTIFY for progress monitor '%p'\n", *progress);
+	if (pjsip_xfer_notify((*progress)->sub, PJSIP_EVSUB_STATE_ACTIVE, 100, NULL, &tdata) == PJ_SUCCESS) {
+		pjsip_xfer_send_request((*progress)->sub, tdata);
+	}
+
+	return 0;
+
+error:
+	ao2_cleanup(*progress);
+	*progress = NULL;
+	return -1;
+}
+
+/*! \brief Structure for attended transfer task */
+struct refer_attended {
+	/*! \brief Transferer session */
+	struct ast_sip_session *transferer;
+	/*! \brief Transferer channel */
+	struct ast_channel *transferer_chan;
+	/*! \brief Second transferer session */
+	struct ast_sip_session *transferer_second	;
+	/*! \brief Optional refer progress structure */
+	struct refer_progress *progress;
+};
+
+/*! \brief Destructor for attended transfer task */
+static void refer_attended_destroy(void *obj)
+{
+	struct refer_attended *attended = obj;
+
+	ao2_cleanup(attended->transferer);
+	ast_channel_unref(attended->transferer_chan);
+	ao2_cleanup(attended->transferer_second);
+}
+
+/*! \brief Allocator for attended transfer task */
+static struct refer_attended *refer_attended_alloc(struct ast_sip_session *transferer, struct ast_sip_session *transferer_second,
+	struct refer_progress *progress)
+{
+	struct refer_attended *attended = ao2_alloc(sizeof(*attended), refer_attended_destroy);
+
+	if (!attended) {
+		return NULL;
+	}
+
+	ao2_ref(transferer, +1);
+	attended->transferer = transferer;
+	ast_channel_ref(transferer->channel);
+	attended->transferer_chan = transferer->channel;
+	ao2_ref(transferer_second, +1);
+	attended->transferer_second = transferer_second;
+
+	if (progress) {
+		ao2_ref(progress, +1);
+		attended->progress = progress;
+	}
+
+	return attended;
+}
+
+/*! \brief Task for attended transfer */
+static int refer_attended(void *data)
+{
+	RAII_VAR(struct refer_attended *, attended, data, ao2_cleanup);
+	int response = 0;
+
+	ast_debug(3, "Performing a REFER attended transfer - Transferer #1: %s Transferer #2: %s\n",
+		ast_channel_name(attended->transferer_chan), ast_channel_name(attended->transferer_second->channel));
+
+	switch (ast_bridge_transfer_attended(attended->transferer_chan, attended->transferer_second->channel)) {
+	case AST_BRIDGE_TRANSFER_INVALID:
+		response = 400;
+		break;
+	case AST_BRIDGE_TRANSFER_NOT_PERMITTED:
+		response = 403;
+		break;
+	case AST_BRIDGE_TRANSFER_FAIL:
+		response = 500;
+		break;
+	case AST_BRIDGE_TRANSFER_SUCCESS:
+		response = 200;
+		ast_sip_session_defer_termination(attended->transferer);
+		break;
+	}
+
+	ast_debug(3, "Final response for REFER attended transfer - Transferer #1: %s Transferer #2: %s is '%d'\n",
+		ast_channel_name(attended->transferer_chan), ast_channel_name(attended->transferer_second->channel), response);
+
+	if (attended->progress && response) {
+		struct refer_progress_notification *notification = refer_progress_notification_alloc(attended->progress, response, PJSIP_EVSUB_STATE_TERMINATED);
+
+		if (notification) {
+			refer_progress_notify(notification);
+		}
+	}
+
+	return 0;
+}
+
+/*! \brief Structure for blind transfer callback details */
+struct refer_blind {
+	/*! \brief Context being used for transfer */
+	const char *context;
+	/*! \brief Optional progress structure */
+	struct refer_progress *progress;
+	/*! \brief REFER message */
+	pjsip_rx_data *rdata;
+	/*! \brief Optional Replaces header */
+	pjsip_replaces_hdr *replaces;
+	/*! \brief Optional Refer-To header */
+	pjsip_sip_uri *refer_to;
+};
+
+/*! \brief Blind transfer callback function */
+static void refer_blind_callback(struct ast_channel *chan, void *user_data, enum ast_transfer_type transfer_type)
+{
+	struct refer_blind *refer = user_data;
+	const pj_str_t str_referred_by = { "Referred-By", 11 };
+	pjsip_generic_string_hdr *referred_by = pjsip_msg_find_hdr_by_name(refer->rdata->msg_info.msg, &str_referred_by, NULL);
+
+	pbx_builtin_setvar_helper(chan, "SIPTRANSFER", "yes");
+
+	/* If progress monitoring is being done attach a frame hook so we can monitor it */
+	if (refer->progress) {
+		struct ast_framehook_interface hook = {
+			.version = AST_FRAMEHOOK_INTERFACE_VERSION,
+			.event_cb = refer_progress_framehook,
+			.destroy_cb = refer_progress_framehook_destroy,
+			.data = refer->progress,
+		};
+
+		/* We need to bump the reference count up on the progress structure since it is in the frame hook now */
+		ao2_ref(refer->progress, +1);
+
+		/* If we can't attach a frame hook for whatever reason send a notification of success immediately */
+		if ((refer->progress->framehook = ast_framehook_attach(chan, &hook)) < 0) {
+			struct refer_progress_notification *notification = refer_progress_notification_alloc(refer->progress, 200,
+				PJSIP_EVSUB_STATE_TERMINATED);
+
+			ast_log(LOG_WARNING, "Could not attach REFER transfer progress monitoring hook to channel '%s' - assuming success\n",
+				ast_channel_name(chan));
+
+			if (notification) {
+				refer_progress_notify(notification);
+			}
+
+			ao2_cleanup(refer->progress);
+		}
+	}
+
+	if (!ast_strlen_zero(refer->context)) {
+		pbx_builtin_setvar_helper(chan, "SIPREFERRINGCONTEXT", refer->context);
+	}
+
+	if (referred_by) {
+		char *uri = referred_by->hvalue.ptr;
+
+		uri[referred_by->hvalue.slen] = '\0';
+		pbx_builtin_setvar_helper(chan, "SIPREFERREDBYHDR", uri);
+	}
+
+	if (refer->replaces) {
+		char replaces[512];
+
+		pjsip_hdr_print_on(refer->replaces, replaces, sizeof(replaces));
+		pbx_builtin_setvar_helper(chan, "SIPREPLACESHDR", replaces);
+	}
+
+	if (refer->refer_to) {
+		char refer_to[PJSIP_MAX_URL_SIZE];
+
+		pjsip_uri_print(PJSIP_URI_IN_REQ_URI, refer->refer_to, refer_to, sizeof(refer_to));
+		pbx_builtin_setvar_helper(chan, "SIPREFERTOHDR", refer_to);
+	}
+}
+
+static int refer_incoming_attended_request(struct ast_sip_session *session, pjsip_rx_data *rdata, pjsip_sip_uri *target_uri,
+	pjsip_param *replaces_param, struct refer_progress *progress)
+{
+	const pj_str_t str_replaces = { "Replaces", 8 };
+	pj_str_t replaces_content;
+	pjsip_replaces_hdr *replaces;
+	int parsed_len;
+	pjsip_dialog *dlg;
+
+	pj_strdup_with_null(rdata->tp_info.pool, &replaces_content, &replaces_param->value);
+
+	/* Parsing the parameter as a Replaces header easily grabs the needed information */
+	if (!(replaces = pjsip_parse_hdr(rdata->tp_info.pool, &str_replaces, replaces_content.ptr,
+		pj_strlen(&replaces_content), &parsed_len))) {
+		ast_log(LOG_ERROR, "Received REFER request on channel '%s' from endpoint '%s' with invalid Replaces header, rejecting\n",
+			ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+		return 400;
+	}
+
+	/* See if the dialog is local, or remote */
+	if ((dlg = pjsip_ua_find_dialog(&replaces->call_id, &replaces->to_tag, &replaces->from_tag, PJ_TRUE))) {
+		RAII_VAR(struct ast_sip_session *, other_session, ast_sip_dialog_get_session(dlg), ao2_cleanup);
+		struct refer_attended *attended;
+
+		pjsip_dlg_dec_lock(dlg);
+
+		if (!other_session) {
+			ast_debug(3, "Received REFER request on channel '%s' from endpoint '%s' for local dialog but no session exists on it\n",
+				ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+			return 603;
+		}
+
+		/* We defer actually doing the attended transfer to the other session so no deadlock can occur */
+		if (!(attended = refer_attended_alloc(session, other_session, progress))) {
+			ast_log(LOG_ERROR, "Received REFER request on channel '%s' from endpoint '%s' for local dialog but could not allocate structure to complete, rejecting\n",
+				ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+			return 500;
+		}
+
+		/* Push it to the other session, which will have both channels with minimal locking */
+		if (ast_sip_push_task(other_session->serializer, refer_attended, attended)) {
+			ao2_cleanup(attended);
+			return 500;
+		}
+
+		ast_debug(3, "Attended transfer from '%s' pushed to second channel serializer\n",
+			ast_channel_name(session->channel));
+
+		return 200;
+	} else {
+		const char *context = (session->channel ? pbx_builtin_getvar_helper(session->channel, "TRANSFER_CONTEXT") : "");
+		struct refer_blind refer = { 0, };
+
+		if (ast_strlen_zero(context)) {
+			context = session->endpoint->context;
+		}
+
+		if (!ast_exists_extension(NULL, context, "external_replaces", 1, NULL)) {
+			ast_log(LOG_ERROR, "Received REFER for remote session on channel '%s' from endpoint '%s' but 'external_replaces' context does not exist for handling\n",
+				ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+			return 404;
+		}
+
+		refer.context = context;
+		refer.progress = progress;
+		refer.rdata = rdata;
+		refer.replaces = replaces;
+		refer.refer_to = target_uri;
+
+		switch (ast_bridge_transfer_blind(1, session->channel, "external_replaces", context, refer_blind_callback, &refer)) {
+		case AST_BRIDGE_TRANSFER_INVALID:
+			return 400;
+		case AST_BRIDGE_TRANSFER_NOT_PERMITTED:
+			return 403;
+		case AST_BRIDGE_TRANSFER_FAIL:
+			return 500;
+		case AST_BRIDGE_TRANSFER_SUCCESS:
+			ast_sip_session_defer_termination(session);
+			return 200;
+		}
+
+		return 503;
+	}
+
+	return 0;
+}
+
+static int refer_incoming_blind_request(struct ast_sip_session *session, pjsip_rx_data *rdata, pjsip_sip_uri *target,
+	struct refer_progress *progress)
+{
+	const char *context = (session->channel ? pbx_builtin_getvar_helper(session->channel, "TRANSFER_CONTEXT") : "");
+	char exten[AST_MAX_EXTENSION];
+	struct refer_blind refer = { 0, };
+
+	/* If no explicit transfer context has been provided use their configured context */
+	if (ast_strlen_zero(context)) {
+		context = session->endpoint->context;
+	}
+
+	/* Using the user portion of the target URI see if it exists as a valid extension in their context */
+	ast_copy_pj_str(exten, &target->user, sizeof(exten));
+	if (!ast_exists_extension(NULL, context, exten, 1, NULL)) {
+		ast_log(LOG_ERROR, "Channel '%s' from endpoint '%s' attempted blind transfer to '%s@%s' but target does not exist\n",
+			ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint), exten, context);
+		return 404;
+	}
+
+	refer.context = context;
+	refer.progress = progress;
+	refer.rdata = rdata;
+
+	switch (ast_bridge_transfer_blind(1, session->channel, exten, context, refer_blind_callback, &refer)) {
+	case AST_BRIDGE_TRANSFER_INVALID:
+		return 400;
+	case AST_BRIDGE_TRANSFER_NOT_PERMITTED:
+		return 403;
+	case AST_BRIDGE_TRANSFER_FAIL:
+		return 500;
+	case AST_BRIDGE_TRANSFER_SUCCESS:
+		ast_sip_session_defer_termination(session);
+		return 200;
+	}
+
+	return 503;
+}
+
+/*! \brief Structure used to retrieve channel from another session */
+struct invite_replaces {
+	/*! \brief Session we want the channel from */
+	struct ast_sip_session *session;
+	/*! \brief Channel from the session (with reference) */
+	struct ast_channel *channel;
+	/*! \brief Bridge the channel is in */
+	struct ast_bridge *bridge;
+};
+
+/*! \brief Task for invite replaces */
+static int invite_replaces(void *data)
+{
+	struct invite_replaces *invite = data;
+
+	if (!invite->session->channel) {
+		return -1;
+	}
+
+	ast_channel_ref(invite->session->channel);
+	invite->channel = invite->session->channel;
+
+	ast_channel_lock(invite->channel);
+	invite->bridge = ast_channel_get_bridge(invite->channel);
+	ast_channel_unlock(invite->channel);
+
+	return 0;
+}
+
+static int refer_incoming_invite_request(struct ast_sip_session *session, struct pjsip_rx_data *rdata)
+{
+	pjsip_dialog *other_dlg = NULL;
+	pjsip_tx_data *packet;
+	int response = 0;
+	RAII_VAR(struct ast_sip_session *, other_session, NULL, ao2_cleanup);
+	struct invite_replaces invite;
+	RAII_VAR(struct ast_bridge *, bridge, NULL, ao2_cleanup);
+
+	/* If a Replaces header is present make sure it is valid */
+	if (pjsip_replaces_verify_request(rdata, &other_dlg, PJ_TRUE, &packet) != PJ_SUCCESS) {
+		response = packet->msg->line.status.code;
+		pjsip_tx_data_dec_ref(packet);
+		goto end;
+	}
+
+	/* If no other dialog exists then this INVITE request does not have a Replaces header */
+	if (!other_dlg) {
+		return 0;
+	}
+
+	other_session = ast_sip_dialog_get_session(other_dlg);
+	pjsip_dlg_dec_lock(other_dlg);
+
+	if (!other_session) {
+		response = 481;
+		ast_debug(3, "INVITE with Replaces received on channel '%s' from endpoint '%s', but requested session does not exist\n",
+			ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+		goto end;
+	}
+
+	invite.session = other_session;
+
+	if (ast_sip_push_task_synchronous(other_session->serializer, invite_replaces, &invite)) {
+		response = 481;
+		goto end;
+	}
+
+	ast_setstate(session->channel, AST_STATE_RING);
+	ast_raw_answer(session->channel);
+
+	if (!invite.bridge) {
+		struct ast_channel *chan = session->channel;
+
+		/* This will use a synchronous task but we aren't operating in the serializer at this point in time, so it
+		 * won't deadlock */
+		if (!ast_channel_move(invite.channel, session->channel)) {
+			ast_hangup(chan);
+		} else {
+			response = 500;
+		}
+	} else {
+		if (ast_bridge_impart(invite.bridge, session->channel, invite.channel, NULL, 1)) {
+			response = 500;
+		}
+	}
+
+	if (!response) {
+		ast_debug(3, "INVITE with Replaces successfully completed on channels '%s' and '%s'\n",
+			ast_channel_name(session->channel), ast_channel_name(invite.channel));
+	}
+
+	ast_channel_unref(invite.channel);
+	ao2_cleanup(invite.bridge);
+
+end:
+	if (response) {
+		ast_debug(3, "INVITE with Replaces failed on channel '%s', sending response of '%d'\n",
+			ast_channel_name(session->channel), response);
+		session->defer_terminate = 1;
+		ast_hangup(session->channel);
+		session->channel = NULL;
+
+		if (pjsip_inv_end_session(session->inv_session, response, NULL, &packet) == PJ_SUCCESS) {
+			ast_sip_session_send_response(session, packet);
+		}
+	}
+
+	return 1;
+}
+
+static int refer_incoming_refer_request(struct ast_sip_session *session, struct pjsip_rx_data *rdata)
+{
+	const pj_str_t str_refer_to = { "Refer-To", 8 };
+	pjsip_generic_string_hdr *refer_to;
+	char *uri;
+	const pj_str_t str_to = { "To", 2 };
+	pjsip_fromto_hdr *target;
+	pjsip_sip_uri *target_uri;
+	RAII_VAR(struct refer_progress *, progress, NULL, ao2_cleanup);
+	const pj_str_t str_replaces = { "Replaces", 8 };
+	pjsip_param *replaces;
+	int response;
+
+	if (!session->endpoint->allowtransfer) {
+		pjsip_dlg_respond(session->inv_session->dlg, rdata, 603, NULL, NULL, NULL);
+		ast_log(LOG_WARNING, "Endpoint %s transfer attempt blocked due to configuration\n",
+				ast_sorcery_object_get_id(session->endpoint));
+		return 0;
+	}
+
+	/* A Refer-To header is required */
+	if (!(refer_to = pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &str_refer_to, NULL))) {
+		pjsip_dlg_respond(session->inv_session->dlg, rdata, 400, NULL, NULL, NULL);
+		ast_debug(3, "Received a REFER without Refer-To on channel '%s' from endpoint '%s'\n",
+			ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+		return 0;
+	}
+	uri = refer_to->hvalue.ptr;
+	uri[refer_to->hvalue.slen] = '\0';
+
+	/* Parse the provided URI string as a To header so we can get the target */
+	if (!(target = pjsip_parse_hdr(rdata->tp_info.pool, &str_to, refer_to->hvalue.ptr, refer_to->hvalue.slen, NULL)) ||
+		(!PJSIP_URI_SCHEME_IS_SIP(target->uri) && !PJSIP_URI_SCHEME_IS_SIPS(target->uri))) {
+		pjsip_dlg_respond(session->inv_session->dlg, rdata, 400, NULL, NULL, NULL);
+		ast_debug(3, "Received a REFER without a parseable Refer-To ('%s') on channel '%s' from endpoint '%s'\n",
+			uri, ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+		return 0;
+	}
+	target_uri = pjsip_uri_get_uri(target->uri);
+
+	/* Set up REFER progress subscription if requested/possible */
+	if (refer_progress_alloc(session, rdata, &progress)) {
+		pjsip_dlg_respond(session->inv_session->dlg, rdata, 500, NULL, NULL, NULL);
+		ast_debug(3, "Could not set up subscription for REFER on channel '%s' from endpoint '%s'\n",
+			ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint));
+		return 0;
+	}
+
+	/* Determine if this is an attended or blind transfer */
+	if ((replaces = pjsip_param_find(&target_uri->header_param, &str_replaces)) ||
+		(replaces = pjsip_param_find(&target_uri->other_param, &str_replaces))) {
+		response = refer_incoming_attended_request(session, rdata, target_uri, replaces, progress);
+	} else {
+		response = refer_incoming_blind_request(session, rdata, target_uri, progress);
+	}
+
+	if (!progress) {
+		/* The transferer has requested no subscription, so send a final response immediately */
+		pjsip_tx_data *tdata;
+		const pj_str_t str_refer_sub = { "Refer-Sub", 9 };
+		const pj_str_t str_false = { "false", 5 };
+		pjsip_hdr *hdr;
+
+		ast_debug(3, "Progress monitoring not requested for REFER on channel '%s' from endpoint '%s', sending immediate response of '%d'\n",
+			ast_channel_name(session->channel), ast_sorcery_object_get_id(session->endpoint), response);
+
+		if (pjsip_dlg_create_response(session->inv_session->dlg, rdata, response, NULL, &tdata) != PJ_SUCCESS) {
+			pjsip_dlg_respond(session->inv_session->dlg, rdata, response, NULL, NULL, NULL);
+			return 0;
+		}
+
+		hdr = (pjsip_hdr*)pjsip_generic_string_hdr_create(tdata->pool, &str_refer_sub, &str_false);
+		pjsip_msg_add_hdr(tdata->msg, hdr);
+
+		pjsip_dlg_send_response(session->inv_session->dlg, pjsip_rdata_get_tsx(rdata), tdata);
+	} else if (response != 200) {
+		/* Since this failed we can send a final NOTIFY now and terminate the subscription */
+		struct refer_progress_notification *notification = refer_progress_notification_alloc(progress, response, PJSIP_EVSUB_STATE_TERMINATED);
+
+		if (notification) {
+			/* The refer_progress_notify function will call ao2_cleanup on this for us */
+			refer_progress_notify(notification);
+		}
+	}
+
+	return 0;
+}
+
+static int refer_incoming_request(struct ast_sip_session *session, pjsip_rx_data *rdata)
+{
+	if (!pjsip_method_cmp(&rdata->msg_info.msg->line.req.method, pjsip_get_refer_method())) {
+		return refer_incoming_refer_request(session, rdata);
+	} else if (!pjsip_method_cmp(&rdata->msg_info.msg->line.req.method, &pjsip_invite_method)) {
+		return refer_incoming_invite_request(session, rdata);
+	} else {
+		return 0;
+	}
+}
+
+static void refer_outgoing_request(struct ast_sip_session *session, struct pjsip_tx_data *tdata)
+{
+	const char *replaces;
+
+	if (pjsip_method_cmp(&tdata->msg->line.req.method, &pjsip_invite_method) ||
+		!session->channel ||
+		(session->inv_session->state != PJSIP_INV_STATE_CALLING) ||
+		!(replaces = pbx_builtin_getvar_helper(session->channel, "SIPREPLACESHDR"))) {
+		return;
+	}
+
+	ast_sip_add_header(tdata, "Replaces", replaces);
+}
+
+static struct ast_sip_session_supplement refer_supplement = {
+	.priority = AST_SIP_SESSION_SUPPLEMENT_PRIORITY_CHANNEL + 1,
+	.incoming_request = refer_incoming_request,
+	.outgoing_request = refer_outgoing_request,
+};
+
+static int load_module(void)
+{
+	const pj_str_t str_norefersub = { "norefersub", 10 };
+
+	pjsip_replaces_init_module(ast_sip_get_pjsip_endpoint());
+	pjsip_xfer_init_module(ast_sip_get_pjsip_endpoint());
+	pjsip_endpt_add_capability(ast_sip_get_pjsip_endpoint(), NULL, PJSIP_H_SUPPORTED, NULL, 1, &str_norefersub);
+
+	ast_sip_register_service(&refer_progress_module);
+	ast_sip_session_register_supplement(&refer_supplement);
+
+	return AST_MODULE_LOAD_SUCCESS;
+}
+
+static int unload_module(void)
+{
+	ast_sip_session_unregister_supplement(&refer_supplement);
+	ast_sip_unregister_service(&refer_progress_module);
+
+	return 0;
+}
+
+AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP Blind and Attended Transfer Support",
+		.load = load_module,
+		.unload = unload_module,
+		.load_pri = AST_MODPRI_APP_DEPEND,
+		   );