res_pjsip_mwi.c

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2013, Digium, Inc.
 *
 * Mark Michelson <mmichelson@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_pubsub</depend>
	<support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <pjsip.h>
#include <pjsip_simple.h>
#include <pjlib.h>

#include "asterisk/res_pjsip.h"
#include "asterisk/res_pjsip_pubsub.h"
#include "asterisk/res_pjsip_body_generator_types.h"
#include "asterisk/module.h"
#include "asterisk/logger.h"
#include "asterisk/astobj2.h"
#include "asterisk/sorcery.h"
#include "asterisk/stasis.h"
#include "asterisk/app.h"

struct mwi_subscription;
AO2_GLOBAL_OBJ_STATIC(unsolicited_mwi);

#define STASIS_BUCKETS 13
#define MWI_BUCKETS 53

#define MWI_TYPE "application"
#define MWI_SUBTYPE "simple-message-summary"

static void mwi_subscription_shutdown(struct ast_sip_subscription *sub);
static struct ast_sip_subscription *mwi_new_subscribe(struct ast_sip_endpoint *endpoint,
		pjsip_rx_data *rdata);
static void mwi_resubscribe(struct ast_sip_subscription *sub, pjsip_rx_data *rdata,
		struct ast_sip_subscription_response_data *response_data);
static void mwi_subscription_timeout(struct ast_sip_subscription *sub);
static void mwi_subscription_terminated(struct ast_sip_subscription *sub, pjsip_rx_data *rdata);
static void mwi_notify_response(struct ast_sip_subscription *sub, pjsip_rx_data *rdata);
static void mwi_notify_request(struct ast_sip_subscription *sub, pjsip_rx_data *rdata,
		struct ast_sip_subscription_response_data *response_data);
static int mwi_refresh_subscription(struct ast_sip_subscription *sub);
static void mwi_to_ami(struct ast_sip_subscription *sub, struct ast_str **buf);

static struct ast_sip_subscription_handler mwi_handler = {
	.event_name = "message-summary",
	.accept = { MWI_TYPE"/"MWI_SUBTYPE, },
	.default_accept =  MWI_TYPE"/"MWI_SUBTYPE,
	.subscription_shutdown = mwi_subscription_shutdown,
	.new_subscribe = mwi_new_subscribe,
	.resubscribe = mwi_resubscribe,
	.subscription_timeout = mwi_subscription_timeout,
	.subscription_terminated = mwi_subscription_terminated,
	.notify_response = mwi_notify_response,
	.notify_request = mwi_notify_request,
	.refresh_subscription = mwi_refresh_subscription,
	.to_ami = mwi_to_ami,
};

/*!
 * \brief Wrapper for stasis subscription
 *
 * An MWI subscription has a container of these. This
 * represents a stasis subscription for MWI state.
 */
struct mwi_stasis_subscription {
	/*! The MWI stasis subscription */
	struct stasis_subscription *stasis_sub;
	/*! The mailbox corresponding with the MWI subscription. Used as a hash key */
	char mailbox[1];
};

/*!
 * \brief A subscription for MWI
 *
 * This subscription is the basis for MWI for an endpoint. Each
 * endpoint that uses MWI will have a corresponding mwi_subscription.
 *
 * This structure acts as the owner for the underlying SIP subscription.
 * When the mwi_subscription is destroyed, the SIP subscription dies, too.
 * The mwi_subscription's lifetime is governed by its underlying stasis
 * subscriptions. When all stasis subscriptions are destroyed, the
 * mwi_subscription is destroyed as well.
 */
struct mwi_subscription {
	/*! Container of \ref mwi_stasis_subscription structures.
	 * A single MWI subscription may be fore multiple mailboxes, thus
	 * requiring multiple stasis subscriptions
	 */
	struct ao2_container *stasis_subs;
	/*! The SIP subscription. Unsolicited MWI does not use this */
	struct ast_sip_subscription *sip_sub;
	/*! Is the MWI solicited (i.e. Initiated with an external SUBSCRIBE) ? */
	unsigned int is_solicited;
	/*! Identifier for the subscription.
	 * The identifier is the same as the corresponding endpoint's stasis ID.
	 * Used as a hash key
	 */
	char id[1];
};

static void mwi_stasis_cb(void *userdata, struct stasis_subscription *sub,
		struct stasis_message *msg);

static struct mwi_stasis_subscription *mwi_stasis_subscription_alloc(const char *mailbox, struct mwi_subscription *mwi_sub)
{
	struct mwi_stasis_subscription *mwi_stasis_sub;
	struct stasis_topic *topic;

	if (!mwi_sub) {
		return NULL;
	}

	mwi_stasis_sub = ao2_alloc(sizeof(*mwi_stasis_sub) + strlen(mailbox), NULL);
	if (!mwi_stasis_sub) {
		return NULL;
	}

	topic = ast_mwi_topic(mailbox);

	/* Safe strcpy */
	strcpy(mwi_stasis_sub->mailbox, mailbox);
	ao2_ref(mwi_sub, +1);
	ast_debug(3, "Creating stasis MWI subscription to mailbox %s for endpoint %s\n", mailbox, mwi_sub->id);
	mwi_stasis_sub->stasis_sub = stasis_subscribe(topic, mwi_stasis_cb, mwi_sub);
	return mwi_stasis_sub;
}

static int stasis_sub_hash(const void *obj, int flags)
{
	const struct mwi_stasis_subscription *mwi_stasis = obj;

	return ast_str_hash(mwi_stasis->mailbox);
}

static int stasis_sub_cmp(void *obj, void *arg, int flags)
{
	struct mwi_stasis_subscription *mwi_stasis1 = obj;
	struct mwi_stasis_subscription *mwi_stasis2 = arg;

	return strcmp(mwi_stasis1->mailbox, mwi_stasis2->mailbox) ? 0 : CMP_MATCH;
}

static void mwi_subscription_destructor(void *obj)
{
	struct mwi_subscription *sub = obj;

	ast_debug(3, "Destroying MWI subscription for endpoint %s\n", sub->id);
	ao2_cleanup(sub->sip_sub);
	ao2_cleanup(sub->stasis_subs);
}

static struct mwi_subscription *mwi_subscription_alloc(struct ast_sip_endpoint *endpoint,
		enum ast_sip_subscription_role role, unsigned int is_solicited, pjsip_rx_data *rdata)
{
	struct mwi_subscription *sub;
	const char *endpoint_id = ast_sorcery_object_get_id(endpoint);

	sub = ao2_alloc(sizeof(*sub) + strlen(endpoint_id),
			mwi_subscription_destructor);

	if (!sub) {
		return NULL;
	}

	/* Safe strcpy */
	strcpy(sub->id, endpoint_id);
	/* Unsolicited MWI doesn't actually result in a SIP subscription being
	 * created. This is because a SIP subscription associates with a dialog.
	 * Most devices expect unsolicited MWI NOTIFYs to appear out of dialog. If
	 * they receive an in-dialog MWI NOTIFY (i.e. with a to-tag), then they
	 * will reject the NOTIFY with a 481, thus resulting in message-waiting
	 * state not being updated on the device
	 */
	if (is_solicited) {
		sub->sip_sub = ast_sip_create_subscription(&mwi_handler,
				role, endpoint, rdata);
		if (!sub->sip_sub) {
			ast_log(LOG_WARNING, "Unable to create MWI SIP subscription for endpoint %s\n", sub->id);
			ao2_cleanup(sub);
			return NULL;
		}
	}

	sub->stasis_subs = ao2_container_alloc(STASIS_BUCKETS, stasis_sub_hash, stasis_sub_cmp);
	if (!sub->stasis_subs) {
		ao2_cleanup(sub);
		return NULL;
	}
	sub->is_solicited = is_solicited;

	ast_debug(3, "Created %s MWI subscription for endpoint %s\n", is_solicited ? "solicited" : "unsolicited", sub->id);

	return sub;
}

static int mwi_sub_hash(const void *obj, int flags)
{
	const struct mwi_subscription *mwi_sub = obj;

	return ast_str_hash(mwi_sub->id);
}

static int mwi_sub_cmp(void *obj, void *arg, int flags)
{
	struct mwi_subscription *mwi_sub1 = obj;
	struct mwi_subscription *mwi_sub2 = arg;

	return strcmp(mwi_sub1->id, mwi_sub2->id) ? 0 : CMP_MATCH;
}

static int get_message_count(void *obj, void *arg, int flags)
{
	RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
	struct mwi_stasis_subscription *mwi_stasis = obj;
	struct ast_sip_message_accumulator *counter = arg;
	struct ast_mwi_state *mwi_state;

	msg = stasis_cache_get(ast_mwi_state_cache(), ast_mwi_state_type(), mwi_stasis->mailbox);
	if (!msg) {
		return 0;
	}

	mwi_state = stasis_message_data(msg);
	counter->old_msgs += mwi_state->old_msgs;
	counter->new_msgs += mwi_state->new_msgs;
	return 0;
}

struct unsolicited_mwi_data {
	struct mwi_subscription *sub;
	struct ast_sip_endpoint *endpoint;
	pjsip_evsub_state state;
	const char *reason;
	const struct ast_sip_body *body;
};

static int send_unsolicited_mwi_notify_to_contact(void *obj, void *arg, int flags)
{
	struct unsolicited_mwi_data *mwi_data = arg;
	struct mwi_subscription *sub = mwi_data->sub;
	struct ast_sip_endpoint *endpoint = mwi_data->endpoint;
	pjsip_evsub_state state = mwi_data->state;
	const char *reason = mwi_data->reason;
	const struct ast_sip_body *body = mwi_data->body;
	struct ast_sip_contact *contact = obj;
	const char *state_name;
	pjsip_tx_data *tdata;
	pjsip_sub_state_hdr *sub_state;
	pjsip_event_hdr *event;
	const pjsip_hdr *allow_events = pjsip_evsub_get_allow_events_hdr(NULL);

	if (ast_sip_create_request("NOTIFY", NULL, endpoint, NULL, contact, &tdata)) {
		ast_log(LOG_WARNING, "Unable to create unsolicited NOTIFY request to endpoint %s URI %s\n", sub->id, contact->uri);
		return 0;
	}

	if (!ast_strlen_zero(endpoint->subscription.mwi.fromuser)) {
		pjsip_fromto_hdr *from = pjsip_msg_find_hdr(tdata->msg, PJSIP_H_FROM, NULL);
		pjsip_name_addr *from_name_addr = (pjsip_name_addr *) from->uri;
		pjsip_sip_uri *from_uri = pjsip_uri_get_uri(from_name_addr->uri);

		pj_strdup2(tdata->pool, &from_uri->user, endpoint->subscription.mwi.fromuser);
	}

	switch (state) {
	case PJSIP_EVSUB_STATE_ACTIVE:
		state_name = "active";
		break;
	case PJSIP_EVSUB_STATE_TERMINATED:
	default:
		state_name = "terminated";
		break;
	}

	sub_state = pjsip_sub_state_hdr_create(tdata->pool);
	pj_cstr(&sub_state->sub_state, state_name);
	if (reason) {
		pj_cstr(&sub_state->reason_param, reason);
	}
	pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr *) sub_state);

	event = pjsip_event_hdr_create(tdata->pool);
	pj_cstr(&event->event_type, "message-summary");
	pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr *) event);

	pjsip_msg_add_hdr(tdata->msg, pjsip_hdr_shallow_clone(tdata->pool, allow_events));
	ast_sip_add_body(tdata, body);
	ast_sip_send_request(tdata, NULL, endpoint, NULL, NULL);

	return 0;
}

static void send_unsolicited_mwi_notify(struct mwi_subscription *sub, pjsip_evsub_state state, const char *reason,
		struct ast_sip_body *body)
{
	RAII_VAR(struct ast_sip_endpoint *, endpoint, ast_sorcery_retrieve_by_id(ast_sip_get_sorcery(),
				"endpoint", sub->id), ao2_cleanup);
	char *endpoint_aors;
	char *aor_name;

	if (!endpoint) {
		ast_log(LOG_WARNING, "Unable to send unsolicited MWI to %s because endpoint does not exist\n",
				sub->id);
		return;
	}
	if (ast_strlen_zero(endpoint->aors)) {
		ast_log(LOG_WARNING, "Unable to send unsolicited MWI to %s because the endpoint has no"
				" configured AORs\n", sub->id);
		return;
	}

	endpoint_aors = ast_strdupa(endpoint->aors);

	while ((aor_name = strsep(&endpoint_aors, ","))) {
		RAII_VAR(struct ast_sip_aor *, aor, ast_sip_location_retrieve_aor(aor_name), ao2_cleanup);
		RAII_VAR(struct ao2_container *, contacts, NULL, ao2_cleanup);
		struct unsolicited_mwi_data mwi_data = {
			.sub = sub,
			.endpoint = endpoint,
			.state = state,
			.reason = reason,
			.body = body,
		};

		if (!aor) {
			ast_log(LOG_WARNING, "Unable to locate AOR %s for unsolicited MWI\n", aor_name);
			continue;
		}

		contacts = ast_sip_location_retrieve_aor_contacts(aor);
		if (!contacts || (ao2_container_count(contacts) == 0)) {
			ast_log(LOG_WARNING, "No contacts bound to AOR %s. Cannot send unsolicited MWI.\n", aor_name);
			continue;
		}

		ao2_callback(contacts, OBJ_NODATA, send_unsolicited_mwi_notify_to_contact, &mwi_data);
	}
}

static void send_mwi_notify(struct mwi_subscription *sub, pjsip_evsub_state state, const char *reason)
{
	const pj_str_t *reason_str_ptr = NULL;
	struct ast_sip_message_accumulator counter = {
		.old_msgs = 0,
		.new_msgs = 0,
	};
	RAII_VAR(struct ast_str *, body_text, ast_str_create(64), ast_free_ptr);
	pjsip_tx_data *tdata;
	pj_str_t reason_str;
	struct ast_sip_body body;

	body.type = sub->is_solicited ?
		ast_sip_subscription_get_body_type(sub->sip_sub) :
		MWI_TYPE;

	body.subtype = sub->is_solicited ?
		ast_sip_subscription_get_body_subtype(sub->sip_sub) :
		MWI_SUBTYPE;

	ao2_callback(sub->stasis_subs, OBJ_NODATA, get_message_count, &counter);

	if (reason) {
		pj_cstr(&reason_str, reason);
		reason_str_ptr = &reason_str;
	}

	if (ast_sip_pubsub_generate_body_content(body.type, body.subtype, &counter, &body_text)) {
		ast_log(LOG_WARNING, "Unable to generate SIP MWI NOTIFY body.\n");
		return;
	}

	body.body_text = ast_str_buffer(body_text);

	ast_debug(5, "Sending %s MWI NOTIFY to endpoint %s, new messages: %d, old messages: %d\n",
			sub->is_solicited ? "solicited" : "unsolicited", sub->id, counter.new_msgs,
			counter.old_msgs);

	if (sub->is_solicited) {
		if (pjsip_evsub_notify(ast_sip_subscription_get_evsub(sub->sip_sub),
					state, NULL, reason_str_ptr, &tdata) != PJ_SUCCESS) {
			ast_log(LOG_WARNING, "Unable to create MWI NOTIFY request to %s.\n", sub->id);
			return;
		}
		if (ast_sip_add_body(tdata, &body)) {
			ast_log(LOG_WARNING, "Unable to add body to MWI NOTIFY request\n");
			return;
		}
		if (ast_sip_subscription_send_request(sub->sip_sub, tdata) != PJ_SUCCESS) {
			ast_log(LOG_WARNING, "Unable to send MWI NOTIFY request to %s\n", sub->id);
			return;
		}
	} else {
		send_unsolicited_mwi_notify(sub, state, reason, &body);
	}
}

static int unsubscribe_stasis(void *obj, void *arg, int flags)
{
	struct mwi_stasis_subscription *mwi_stasis = obj;
	if (mwi_stasis->stasis_sub) {
		ast_debug(3, "Removing stasis subscription to mailbox %s\n", mwi_stasis->mailbox);
		mwi_stasis->stasis_sub = stasis_unsubscribe(mwi_stasis->stasis_sub);
	}
	return CMP_MATCH;
}

static void mwi_subscription_shutdown(struct ast_sip_subscription *sub)
{
	struct mwi_subscription *mwi_sub;
	RAII_VAR(struct ast_datastore *, mwi_datastore,
			ast_sip_subscription_get_datastore(sub, "MWI datastore"), ao2_cleanup);

	if (!mwi_datastore) {
		return;
	}

	mwi_sub = mwi_datastore->data;
	ao2_callback(mwi_sub->stasis_subs, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, unsubscribe_stasis, NULL);
}

static struct ast_datastore_info mwi_ds_info = { };

static int add_mwi_datastore(struct mwi_subscription *sub)
{
	RAII_VAR(struct ast_datastore *, mwi_datastore, NULL, ao2_cleanup);

	mwi_datastore = ast_sip_subscription_alloc_datastore(&mwi_ds_info, "MWI datastore");
	if (!mwi_datastore) {
		return -1;
	}
	mwi_datastore->data = sub;

	ast_sip_subscription_add_datastore(sub->sip_sub, mwi_datastore);
	return 0;
}

static int mwi_on_aor(void *obj, void *arg, int flags)
{
	struct ast_sip_aor *aor = obj;
	struct mwi_subscription *sub = arg;
	char *mailboxes;
	char *mailbox;

	if (ast_strlen_zero(aor->mailboxes)) {
		return 0;
	}

	mailboxes = ast_strdupa(aor->mailboxes);
	while ((mailbox = strsep(&mailboxes, ","))) {
		RAII_VAR(struct mwi_stasis_subscription *, mwi_stasis_sub,
				mwi_stasis_subscription_alloc(mailbox, sub), ao2_cleanup);
		if (mwi_stasis_sub) {
			ao2_link(sub->stasis_subs, mwi_stasis_sub);
		}
	}

	return 0;
}

static struct mwi_subscription *mwi_create_subscription(
	struct ast_sip_endpoint *endpoint, pjsip_rx_data *rdata)
{
	struct mwi_subscription *sub = mwi_subscription_alloc(
		endpoint, AST_SIP_NOTIFIER, 1, rdata);

	if (!sub) {
		return NULL;
	}

	if (add_mwi_datastore(sub)) {
		ast_log(LOG_WARNING, "Unable to allocate datastore on MWI "
			"subscription from %s\n", sub->id);
		ao2_ref(sub, -1);
		return NULL;
	}

	return sub;
}

static struct mwi_subscription *mwi_subscribe_single(
	struct ast_sip_endpoint *endpoint, pjsip_rx_data *rdata, const char *name)
{
	RAII_VAR(struct ast_sip_aor *, aor,
		 ast_sip_location_retrieve_aor(name), ao2_cleanup);
	struct mwi_subscription *sub;

	if (!aor) {
		ast_log(LOG_WARNING, "Unable to locate aor %s. MWI "
			"subscription failed.\n", name);
		return NULL;
	}

	if (ast_strlen_zero(aor->mailboxes)) {
		ast_log(LOG_WARNING, "AOR %s has no configured mailboxes. "
			"MWI subscription failed\n", name);
		return NULL;
	}

	if (!(sub = mwi_create_subscription(endpoint, rdata))) {
		return NULL;
	}

	mwi_on_aor(aor, sub, 0);
	return sub;
}

static struct mwi_subscription *mwi_subscribe_all(
	struct ast_sip_endpoint *endpoint, pjsip_rx_data *rdata)
{
	struct mwi_subscription *sub = mwi_create_subscription(endpoint, rdata);

	if (!sub) {
		return NULL;
	}

	ast_sip_for_each_aor(endpoint->aors, mwi_on_aor, sub);
	return sub;
}

static struct ast_sip_subscription *mwi_new_subscribe(struct ast_sip_endpoint *endpoint,
		pjsip_rx_data *rdata)
{
	/* It's not obvious here, but the reference(s) to this subscription,
	 * once this function exits, is held by the stasis subscription(s)
	 * created in mwi_stasis_subscription_alloc()
	 */
	RAII_VAR(struct mwi_subscription *, sub, NULL, ao2_cleanup);
	pjsip_uri *ruri = rdata->msg_info.msg->line.req.uri;
	pjsip_sip_uri *sip_ruri;
	pjsip_evsub *evsub;
	char aor_name[80];

	if (!PJSIP_URI_SCHEME_IS_SIP(ruri) && !PJSIP_URI_SCHEME_IS_SIPS(ruri)) {
		ast_log(LOG_WARNING, "Attempt to SUBSCRIBE to a non-SIP URI\n");
		return NULL;
	}
	sip_ruri = pjsip_uri_get_uri(ruri);
	ast_copy_pj_str(aor_name, &sip_ruri->user, sizeof(aor_name));

	/* no aor in uri? subscribe to all on endpoint */
	if (!(sub = ast_strlen_zero(aor_name) ? mwi_subscribe_all(endpoint, rdata) :
	      mwi_subscribe_single(endpoint, rdata, aor_name))) {
		return NULL;
	}

	evsub = ast_sip_subscription_get_evsub(sub->sip_sub);
	pjsip_evsub_accept(evsub, rdata, 200, NULL);
	send_mwi_notify(sub, PJSIP_EVSUB_STATE_ACTIVE, NULL);

	return sub->sip_sub;
}

static void mwi_resubscribe(struct ast_sip_subscription *sub,
		pjsip_rx_data *rdata, struct ast_sip_subscription_response_data *response_data)
{
	struct mwi_subscription *mwi_sub;
	pjsip_evsub_state state;
	pjsip_evsub *evsub;
	RAII_VAR(struct ast_datastore *, mwi_datastore,
			ast_sip_subscription_get_datastore(sub, "MWI datastore"), ao2_cleanup);

	if (!mwi_datastore) {
		return;
	}

	mwi_sub = mwi_datastore->data;
	evsub = ast_sip_subscription_get_evsub(sub);
	state = pjsip_evsub_get_state(evsub);

	send_mwi_notify(mwi_sub, state, NULL);
}

static void mwi_subscription_timeout(struct ast_sip_subscription *sub)
{
	struct mwi_subscription *mwi_sub;
	RAII_VAR(struct ast_datastore *, mwi_datastore,
			ast_sip_subscription_get_datastore(sub, "MWI datastore"), ao2_cleanup);

	if (!mwi_datastore) {
		return;
	}


	mwi_sub = mwi_datastore->data;

	ast_log(LOG_NOTICE, "MWI subscription for %s has timed out.\n", mwi_sub->id);

	send_mwi_notify(mwi_sub, PJSIP_EVSUB_STATE_TERMINATED, "timeout");
}

static void mwi_subscription_terminated(struct ast_sip_subscription *sub, pjsip_rx_data *rdata)
{
	struct mwi_subscription *mwi_sub;
	RAII_VAR(struct ast_datastore *, mwi_datastore,
			ast_sip_subscription_get_datastore(sub, "MWI datastore"), ao2_cleanup);

	if (!mwi_datastore) {
		return;
	}

	mwi_sub = mwi_datastore->data;

	ast_log(LOG_NOTICE, "MWI subscription for %s has been terminated\n", mwi_sub->id);

	send_mwi_notify(mwi_sub, PJSIP_EVSUB_STATE_TERMINATED, NULL);
}

static void mwi_notify_response(struct ast_sip_subscription *sub, pjsip_rx_data *rdata)
{
	/* We don't really care about NOTIFY responses for the moment */
}

static void mwi_notify_request(struct ast_sip_subscription *sub, pjsip_rx_data *rdata,
		struct ast_sip_subscription_response_data *response_data)
{
	ast_log(LOG_WARNING, "Received an MWI NOTIFY request? This should not happen\n");
}

static int mwi_refresh_subscription(struct ast_sip_subscription *sub)
{
	ast_log(LOG_WARNING, "Being told to refresh an MWI subscription? This should not happen\n");
	return 0;
}

static void mwi_subscription_mailboxes_str(struct ao2_container *stasis_subs,
					   struct ast_str **str)
{
	int num = ao2_container_count(stasis_subs);

	struct mwi_stasis_subscription *node;
	struct ao2_iterator i = ao2_iterator_init(stasis_subs, 0);

	while ((node = ao2_iterator_next(&i))) {
		if (--num) {
			ast_str_append(str, 0, "%s,", node->mailbox);
		} else {
			ast_str_append(str, 0, "%s", node->mailbox);
		}
		ao2_ref(node, -1);
	}
	ao2_iterator_destroy(&i);
}

static void mwi_to_ami(struct ast_sip_subscription *sub,
		       struct ast_str **buf)
{
	struct mwi_subscription *mwi_sub;
	RAII_VAR(struct ast_datastore *, mwi_datastore,
			ast_sip_subscription_get_datastore(sub, "MWI datastore"), ao2_cleanup);

	if (!mwi_datastore) {
		return;
	}

	mwi_sub = mwi_datastore->data;

	ast_str_append(buf, 0, "SubscriptionType: mwi\r\n");
	ast_str_append(buf, 0, "Mailboxes: ");
	mwi_subscription_mailboxes_str(mwi_sub->stasis_subs, buf);
	ast_str_append(buf, 0, "\r\n");
}

static int serialized_notify(void *userdata)
{
	struct mwi_subscription *mwi_sub = userdata;

	send_mwi_notify(mwi_sub, PJSIP_EVSUB_STATE_ACTIVE, NULL);
	ao2_ref(mwi_sub, -1);
	return 0;
}

static int serialized_cleanup(void *userdata)
{
	struct mwi_subscription *mwi_sub = userdata;

	/* This is getting rid of the reference that was added
	 * just before this serialized task was pushed.
	 */
	ao2_cleanup(mwi_sub);
	/* This is getting rid of the reference held by the
	 * stasis subscription
	 */
	ao2_cleanup(mwi_sub);
	return 0;
}

static void mwi_stasis_cb(void *userdata, struct stasis_subscription *sub,
		struct stasis_message *msg)
{
	struct mwi_subscription *mwi_sub = userdata;

	if (stasis_subscription_final_message(sub, msg)) {
		ao2_ref(mwi_sub, +1);
		ast_sip_push_task(NULL, serialized_cleanup, mwi_sub);
		return;
	}

	if (ast_mwi_state_type() == stasis_message_type(msg)) {
		struct ast_taskprocessor *serializer = mwi_sub->is_solicited ? ast_sip_subscription_get_serializer(mwi_sub->sip_sub) : NULL;
		ao2_ref(mwi_sub, +1);
		ast_sip_push_task(serializer, serialized_notify, mwi_sub);
	}
}

static int create_mwi_subscriptions_for_endpoint(void *obj, void *arg, int flags)
{
	RAII_VAR(struct mwi_subscription *, aggregate_sub, NULL, ao2_cleanup);
	struct ast_sip_endpoint *endpoint = obj;
	struct ao2_container *mwi_subscriptions = arg;
	char *mailboxes;
	char *mailbox;

	if (ast_strlen_zero(endpoint->subscription.mwi.mailboxes)) {
		return 0;
	}

	if (endpoint->subscription.mwi.aggregate) {
		aggregate_sub = mwi_subscription_alloc(endpoint, AST_SIP_NOTIFIER, 0, NULL);
		if (!aggregate_sub) {
			return 0;
		}
	}

	mailboxes = ast_strdupa(endpoint->subscription.mwi.mailboxes);
	while ((mailbox = strsep(&mailboxes, ","))) {
		struct mwi_subscription *sub = aggregate_sub ?:
			mwi_subscription_alloc(endpoint, AST_SIP_SUBSCRIBER, 0, NULL);
		RAII_VAR(struct mwi_stasis_subscription *, mwi_stasis_sub,
				mwi_stasis_subscription_alloc(mailbox, sub), ao2_cleanup);
		if (mwi_stasis_sub) {
			ao2_link(sub->stasis_subs, mwi_stasis_sub);
		}
		if (!aggregate_sub) {
			ao2_link(mwi_subscriptions, sub);
			ao2_cleanup(sub);
		}
	}
	if (aggregate_sub) {
		ao2_link(mwi_subscriptions, aggregate_sub);
	}
	return 0;
}

static int unsubscribe(void *obj, void *arg, int flags)
{
	struct mwi_subscription *mwi_sub = obj;

	ao2_callback(mwi_sub->stasis_subs, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, unsubscribe_stasis, NULL);
	return CMP_MATCH;
}

static void create_mwi_subscriptions(void)
{
	struct ao2_container *mwi_subscriptions = ao2_container_alloc(MWI_BUCKETS, mwi_sub_hash, mwi_sub_cmp);
	RAII_VAR(struct ao2_container *, old_mwi_subscriptions, ao2_global_obj_ref(unsolicited_mwi), ao2_cleanup);
	RAII_VAR(struct ao2_container *, endpoints, ast_sorcery_retrieve_by_fields(
				ast_sip_get_sorcery(), "endpoint", AST_RETRIEVE_FLAG_MULTIPLE | AST_RETRIEVE_FLAG_ALL, NULL),
			ao2_cleanup);

	if (!mwi_subscriptions) {
		return;
	}

	/* We remove all the old stasis subscriptions first before applying the new configuration. This
	 * prevents a situation where there might be multiple overlapping stasis subscriptions for an
	 * endpoint for mailboxes. Though there may be mailbox changes during the gap between unsubscribing
	 * and resubscribing, up-to-date mailbox state will be sent out to the endpoint when the
	 * new stasis subscription is established
	 */
	if (old_mwi_subscriptions) {
		ao2_callback(old_mwi_subscriptions, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, unsubscribe, NULL);
	}
	ao2_callback(endpoints, OBJ_NODATA, create_mwi_subscriptions_for_endpoint, mwi_subscriptions);
	ao2_global_obj_replace_unref(unsolicited_mwi, mwi_subscriptions);
	ao2_ref(mwi_subscriptions, -1);
}

static int reload(void)
{
	create_mwi_subscriptions();
	return 0;
}

static int load_module(void)
{
	if (ast_sip_register_subscription_handler(&mwi_handler)) {
		return AST_MODULE_LOAD_DECLINE;
	}
	create_mwi_subscriptions();
	return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
	RAII_VAR(struct ao2_container *, mwi_subscriptions, ao2_global_obj_ref(unsolicited_mwi), ao2_cleanup);
	if (mwi_subscriptions) {
		ao2_callback(mwi_subscriptions, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, unsubscribe, NULL);
		ao2_global_obj_release(unsolicited_mwi);
	}
	ast_sip_unregister_subscription_handler(&mwi_handler);
	return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP MWI resource",
		.load = load_module,
		.unload = unload_module,
		.reload = reload,
		.load_pri = AST_MODPRI_CHANNEL_DEPEND,
);