asterisk/res/res_pjsip_registrar.c

/*
 * 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_pjproject</depend>
	<depend>res_pjsip</depend>
	<support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <signal.h>
#include <pjsip.h>
#include <pjsip_ua.h>

#include "asterisk/res_pjsip.h"
#include "asterisk/module.h"
#include "asterisk/paths.h"
#include "asterisk/test.h"
#include "asterisk/taskprocessor.h"
#include "asterisk/manager.h"
#include "asterisk/named_locks.h"
#include "asterisk/res_pjproject.h"
#include "res_pjsip/include/res_pjsip_private.h"

/*** DOCUMENTATION
	<manager name="PJSIPShowRegistrationsInbound" language="en_US">
		<synopsis>
			Lists PJSIP inbound registrations.
		</synopsis>
		<syntax />
		<description>
			<para>
			In response, <literal>InboundRegistrationDetail</literal> events showing configuration
			and status information are raised for all contacts, static or dynamic.  Once all events
			are completed an <literal>InboundRegistrationDetailComplete</literal> is issued.
			</para>
			<warning><para>
				This command just dumps all coonfigured AORs with contacts, even if the contact
				is a permanent one.  To really get just inbound registrations, use
				<literal>PJSIPShowRegistrationInboundContactStatuses</literal>.
			</para>
			</warning>
		</description>
		<see-also>
			<ref type="manager" module="res_pjsip_registrar">PJSIPShowRegistrationInboundContactStatuses</ref>
		</see-also>
	</manager>
	<manager name="PJSIPShowRegistrationInboundContactStatuses" language="en_US">
		<synopsis>
			Lists ContactStatuses for PJSIP inbound registrations.
		</synopsis>
		<syntax />
		<description>
			<para>
			In response, <literal>ContactStatusDetail</literal> events showing status information
			are raised for each inbound registration (dynamic contact) object.  Once all events
			are completed a <literal>ContactStatusDetailComplete</literal> event is issued.
			</para>
		</description>
	</manager>
 ***/

static int pj_max_hostname = PJ_MAX_HOSTNAME;
static int pjsip_max_url_size = PJSIP_MAX_URL_SIZE;

/*! \brief Internal function which returns the expiration time for a contact */
static unsigned int registrar_get_expiration(const struct ast_sip_aor *aor, const pjsip_contact_hdr *contact, const pjsip_rx_data *rdata)
{
	pjsip_expires_hdr *expires;
	unsigned int expiration = aor->default_expiration;

	if (contact && contact->expires != PJSIP_EXPIRES_NOT_SPECIFIED) {
		/* Expiration was provided with the contact itself */
		expiration = contact->expires;
	} else if ((expires = pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_EXPIRES, NULL))) {
		/* Expiration was provided using the Expires header */
		expiration = expires->ivalue;
	}

	/* If the value has explicitly been set to 0, do not enforce */
	if (!expiration) {
		return expiration;
	}

	/* Enforce the range that we will allow for expiration */
	if (expiration < aor->minimum_expiration) {
		expiration = aor->minimum_expiration;
	} else if (expiration > aor->maximum_expiration) {
		expiration = aor->maximum_expiration;
	}

	return expiration;
}

/*! \brief Structure used for finding contact */
struct registrar_contact_details {
	/*! \brief Pool used for parsing URI */
	pj_pool_t *pool;
	/*! \brief URI being looked for */
	pjsip_sip_uri *uri;
};

/*! \brief Callback function for finding a contact */
static int registrar_find_contact(void *obj, void *arg, int flags)
{
	struct ast_sip_contact *contact = obj;
	const struct registrar_contact_details *details = arg;
	pjsip_uri *contact_uri;

	if (ast_tvzero(contact->expiration_time)) {
		return 0;
	}

	contact_uri = pjsip_parse_uri(details->pool, (char*)contact->uri, strlen(contact->uri), 0);
	if (!contact_uri) {
		ast_log(LOG_WARNING, "Unable to parse contact URI from '%s'.\n", contact->uri);
		return 0;
	}

	return (pjsip_uri_cmp(PJSIP_URI_IN_CONTACT_HDR, details->uri, contact_uri) == PJ_SUCCESS) ? CMP_MATCH : 0;
}

/*! \brief Internal function which validates provided Contact headers to confirm that they are acceptable, and returns number of contacts */
static int registrar_validate_contacts(const pjsip_rx_data *rdata, pj_pool_t *pool, struct ao2_container *contacts,
	struct ast_sip_aor *aor, int permanent, int *added, int *updated, int *deleted)
{
	pjsip_contact_hdr *previous = NULL;
	pjsip_contact_hdr *contact = (pjsip_contact_hdr *)&rdata->msg_info.msg->hdr;
	struct registrar_contact_details details = {
		.pool = pool,
	};

	for (; (contact = (pjsip_contact_hdr *) pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_CONTACT, contact->next)); pj_pool_reset(pool)) {
		unsigned int expiration = registrar_get_expiration(aor, contact, rdata);
		struct ast_sip_contact *existing;
		char contact_uri[pjsip_max_url_size];

		if (contact->star) {
			/* The expiration MUST be 0 when a '*' contact is used and there must be no other contact */
			if (expiration != 0 || previous) {
				return -1;
			}
			/* Count all contacts to delete */
			*deleted = ao2_container_count(contacts) - permanent;
			previous = contact;
			continue;
		} else if (previous && previous->star) {
			/* If there is a previous contact and it is a '*' this is a deal breaker */
			return -1;
		}
		previous = contact;

		if (!PJSIP_URI_SCHEME_IS_SIP(contact->uri) && !PJSIP_URI_SCHEME_IS_SIPS(contact->uri)) {
			continue;
		}

		details.uri = pjsip_uri_get_uri(contact->uri);

		/* pjsip_uri_print returns -1 if there's not enough room in the buffer */
		if (pjsip_uri_print(PJSIP_URI_IN_CONTACT_HDR, details.uri, contact_uri, sizeof(contact_uri)) < 0) {
			/* If the total length of the uri is greater than pjproject can handle, go no further */
			return -1;
		}

		if (details.uri->host.slen >= pj_max_hostname) {
			/* If the length of the hostname is greater than pjproject can handle, go no further */
			return -1;
		}

		/* Determine if this is an add, update, or delete for policy enforcement purposes */
		existing = ao2_callback(contacts, 0, registrar_find_contact, &details);
		ao2_cleanup(existing);
		if (!existing) {
			if (expiration) {
				++*added;
			}
		} else if (expiration) {
			++*updated;
		} else {
			++*deleted;
		}
	}

	return 0;
}

enum contact_delete_type {
	CONTACT_DELETE_ERROR,
	CONTACT_DELETE_EXISTING,
	CONTACT_DELETE_UNAVAILABLE,
	CONTACT_DELETE_EXPIRE,
	CONTACT_DELETE_REQUEST,
	CONTACT_DELETE_SHUTDOWN,
};

static int registrar_contact_delete(enum contact_delete_type type, pjsip_transport *transport,
	struct ast_sip_contact *contact, const char *aor_name);

/*! \brief Internal function used to delete a contact from an AOR */
static int registrar_delete_contact(void *obj, void *arg, int flags)
{
	return registrar_contact_delete(
		CONTACT_DELETE_REQUEST, NULL, obj, arg) ? 0 : CMP_MATCH;
}

/*! \brief Internal function which adds a contact to a response */
static int registrar_add_contact(void *obj, void *arg, int flags)
{
	struct ast_sip_contact *contact = obj;
	pjsip_tx_data *tdata = arg;
	pj_str_t uri;
	pjsip_uri *parsed;

	pj_strdup2_with_null(tdata->pool, &uri, contact->uri);
	parsed = pjsip_parse_uri(tdata->pool, uri.ptr, uri.slen, PJSIP_PARSE_URI_AS_NAMEADDR);

	if (parsed && (PJSIP_URI_SCHEME_IS_SIP(parsed) || PJSIP_URI_SCHEME_IS_SIPS(parsed))) {
		pjsip_contact_hdr *hdr = pjsip_contact_hdr_create(tdata->pool);
		hdr->uri = parsed;
		if (!ast_tvzero(contact->expiration_time)) {
			hdr->expires = ast_tvdiff_ms(contact->expiration_time, ast_tvnow()) / 1000;
		} else {
			hdr->expires = PJSIP_EXPIRES_NOT_SPECIFIED;
		}
		pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr *) hdr);
	} else {
		ast_log(LOG_WARNING, "Skipping invalid Contact URI \"%.*s\" for AOR %s\n",
			(int) uri.slen, uri.ptr, contact->aor);
	}

	return 0;
}

static const pj_str_t path_hdr_name = { "Path", 4 };

static int build_path_data(pjsip_rx_data *rdata, struct ast_str **path_str)
{
	pjsip_generic_string_hdr *path_hdr = pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &path_hdr_name, NULL);

	if (!path_hdr) {
		return 0;
	}

	*path_str = ast_str_create(64);
	if (!*path_str) {
		return -1;
	}

	ast_str_set(path_str, 0, "%.*s", (int)path_hdr->hvalue.slen, path_hdr->hvalue.ptr);

	while ((path_hdr = (pjsip_generic_string_hdr *) pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &path_hdr_name, path_hdr->next))) {
		ast_str_append(path_str, 0, ",%.*s", (int)path_hdr->hvalue.slen, path_hdr->hvalue.ptr);
	}

	return 0;
}

static int registrar_validate_path(pjsip_rx_data *rdata, struct ast_sip_aor *aor, struct ast_str **path_str)
{
	const pj_str_t path_supported_name = { "path", 4 };
	pjsip_supported_hdr *supported_hdr;
	int i;

	if (!aor->support_path) {
		return 0;
	}

	if (build_path_data(rdata, path_str)) {
		return -1;
	}

	if (!*path_str) {
		return 0;
	}

	supported_hdr = pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_SUPPORTED, NULL);
	if (!supported_hdr) {
		return -1;
	}

	/* Find advertised path support */
	for (i = 0; i < supported_hdr->count; i++) {
		if (!pj_stricmp(&supported_hdr->values[i], &path_supported_name)) {
			return 0;
		}
	}

	/* Path header present, but support not advertised */
	return -1;
}

/*! Transport monitor for incoming REGISTER contacts */
struct contact_transport_monitor {
	/*!
	 * \brief Sorcery contact name to remove on transport shutdown
	 * \note Stored after aor_name in space reserved when struct allocated.
	 */
	char *contact_name;
	/*! Indicates that the monitor is in the process of removing a contact */
	int removing;
	/*! AOR name the contact is associated */
	char aor_name[0];
};

static int contact_transport_monitor_matcher(void *a, void *b)
{
	struct contact_transport_monitor *ma = a;
	struct contact_transport_monitor *mb = b;

	return strcmp(ma->aor_name, mb->aor_name) == 0
		&& strcmp(ma->contact_name, mb->contact_name) == 0;
}

static int register_contact_transport_remove_cb(void *data)
{
	struct contact_transport_monitor *monitor = data;
	struct ast_sip_contact *contact;
	struct ast_sip_aor *aor;

	aor = ast_sip_location_retrieve_aor(monitor->aor_name);
	if (!aor) {
		ao2_lock(monitor);
		monitor->removing = 0;
		ao2_unlock(monitor);
		ao2_ref(monitor, -1);
		return 0;
	}

	ao2_lock(aor);

	contact = ast_sip_location_retrieve_contact(monitor->contact_name);
	if (contact) {
		registrar_contact_delete(CONTACT_DELETE_SHUTDOWN, NULL, contact, monitor->aor_name);
		ao2_ref(contact, -1);
	}
	ao2_unlock(aor);
	ao2_ref(aor, -1);

	ao2_ref(monitor, -1);
	return 0;
}

/*!
 * \internal
 * \brief The reliable transport we registered as a contact has shutdown.
 *
 * \param data What contact needs to be removed.
 *
 * \note Normally executed by the pjsip monitor thread.
 */
static void register_contact_transport_shutdown_cb(void *data)
{
	struct contact_transport_monitor *monitor = data;

	/*
	 * It's possible for this shutdown handler to get called multiple times for the
	 * same monitor from different threads. Only one of the calls needs to do the
	 * actual removing of the contact, so if one is currently removing then any
	 * subsequent calls can skip.
	 */
	ao2_lock(monitor);
	if (monitor->removing) {
		ao2_unlock(monitor);
		return;
	}

	monitor->removing = 1;

	/*
	 * Push off to a default serializer.  This is in case sorcery
	 * does database accesses for contacts.  Database accesses may
	 * not be on this machine.  We don't want to tie up the pjsip
	 * monitor thread with potentially long access times.
	 */
	ao2_ref(monitor, +1);
	if (ast_sip_push_task(NULL, register_contact_transport_remove_cb, monitor)) {
		monitor->removing = 0;
		ao2_ref(monitor, -1);
	}

	ao2_unlock(monitor);
}


static int registrar_contact_delete(enum contact_delete_type type, pjsip_transport *transport,
	struct ast_sip_contact *contact, const char *aor_name)
{
	int aor_size;

	/* Permanent contacts can't be deleted */
	if (ast_tvzero(contact->expiration_time)) {
		return -1;
	}

	aor_size = aor_name ? strlen(aor_name) : 0;
	if (contact->prune_on_boot && type != CONTACT_DELETE_SHUTDOWN && aor_size) {
		const char *contact_name = ast_sorcery_object_get_id(contact);
		size_t contact_name_len = strlen(contact_name) + 1;
		struct contact_transport_monitor *monitor = ast_alloca(
			sizeof(*monitor) + 1 + aor_size + contact_name_len);

		strcpy(monitor->aor_name, aor_name); /* Safe */
		monitor->contact_name = monitor->aor_name + aor_size + 1;
		ast_copy_string(monitor->contact_name, contact_name, contact_name_len); /* Safe */

		if (transport) {
			ast_sip_transport_monitor_unregister(transport,
				register_contact_transport_shutdown_cb,	monitor,
				contact_transport_monitor_matcher);
		} else {
			/*
			 * If a specific transport is not supplied then unregister the matching
			 * monitor from all reliable transports.
			 */
			ast_sip_transport_monitor_unregister_all(register_contact_transport_shutdown_cb,
				monitor, contact_transport_monitor_matcher);
		}
	}

	ast_sip_location_delete_contact(contact);

	if (aor_size) {
		if (VERBOSITY_ATLEAST(3)) {
			const char *reason = "none";

			switch (type) {
			case CONTACT_DELETE_ERROR:
				reason = "registration failure";
				break;
			case CONTACT_DELETE_EXISTING:
				reason = "remove existing";
				break;
			case CONTACT_DELETE_UNAVAILABLE:
				reason = "remove unavailable";
				break;
			case CONTACT_DELETE_EXPIRE:
				reason = "expiration";
				break;
			case CONTACT_DELETE_REQUEST:
				reason = "request";
				break;
			case CONTACT_DELETE_SHUTDOWN:
				reason = "shutdown";
				break;
			}

			ast_verb(3, "Removed contact '%s' from AOR '%s' due to %s\n",
					 contact->uri, aor_name, reason);
		}

		ast_test_suite_event_notify("AOR_CONTACT_REMOVED",
				"Contact: %s\r\n"
				"AOR: %s\r\n"
				"UserAgent: %s",
				contact->uri,
				aor_name,
				contact->user_agent);
	}

	return 0;
}

AST_VECTOR(excess_contact_vector, struct ast_sip_contact *);

static int vec_contact_cmp(struct ast_sip_contact *left, struct ast_sip_contact *right)
{
	struct ast_sip_contact *left_contact = left;
	struct ast_sip_contact *right_contact = right;

	/* Sort from soonest to expire to last to expire */
	int time_sorted = ast_tvcmp(left_contact->expiration_time, right_contact->expiration_time);

	struct ast_sip_aor *aor = ast_sip_location_retrieve_aor(left_contact->aor);
	struct ast_sip_contact_status *left_status;
	struct ast_sip_contact_status *right_status;
	int remove_unavailable = 0;
	int left_unreachable;
	int right_unreachable;

	if (aor) {
		remove_unavailable = aor->remove_unavailable;
		ao2_ref(aor, -1);
	}

	if (!remove_unavailable) {
		return time_sorted;
	}

	/* Get contact status if available */
	left_status = ast_sip_get_contact_status(left_contact);
	if (!left_status) {
		return time_sorted;
	}

	right_status = ast_sip_get_contact_status(right_contact);
	if (!right_status) {
		ao2_ref(left_status, -1);
		return time_sorted;
	}

	left_unreachable = (left_status->status == UNAVAILABLE);
	right_unreachable = (right_status->status == UNAVAILABLE);
	ao2_ref(left_status, -1);
	ao2_ref(right_status, -1);
	if (left_unreachable != right_unreachable) {
		/* Set unavailable contact to top of vector */
		if (left_unreachable) return -1;
		if (right_unreachable) return 1;
	}

	/* Either both available or both unavailable */
	return time_sorted;
}

static int vec_contact_add(void *obj, void *arg, int flags)
{
	struct ast_sip_contact *contact = obj;
	struct excess_contact_vector *contact_vec = arg;

	/*
	 * Performance wise, an insertion sort is fine because we
	 * shouldn't need to remove more than a handful of contacts.
	 * I expect we'll typically be removing only one contact.
	 */
	AST_VECTOR_ADD_SORTED(contact_vec, contact, vec_contact_cmp);
	if (AST_VECTOR_SIZE(contact_vec) == AST_VECTOR_MAX_SIZE(contact_vec)) {
		/*
		 * We added a contact over the number we need to remove.
		 * Remove the longest to expire contact from the vector
		 * which is the last element in the vector.  It may be
		 * the one we just added or the one we just added pushed
		 * out an earlier contact from removal consideration.
		 */
		--AST_VECTOR_SIZE(contact_vec);
	}
	return 0;
}

/*!
 * \internal
 * \brief Remove excess existing contacts that are unavailable or expire soonest.
 * \since 13.18.0
 *
 * \param contacts Container of unmodified contacts that could remove.
 * \param to_remove Maximum number of contacts to remove.
 * \param response_contacts, remove_existing
 */
static void remove_excess_contacts(struct ao2_container *contacts, struct ao2_container *response_contacts,
	unsigned int to_remove, unsigned int remove_existing)
{
	struct excess_contact_vector contact_vec;

	/*
	 * Create a sorted vector to hold the to_remove soonest to
	 * expire contacts.  The vector has an extra space to
	 * temporarily hold the longest to expire contact that we
	 * won't remove.
	 */
	if (AST_VECTOR_INIT(&contact_vec, to_remove + 1)) {
		return;
	}
	ao2_callback(contacts, OBJ_NODATA | OBJ_MULTIPLE, vec_contact_add, &contact_vec);

	/*
	 * The vector should always be populated with the number
	 * of contacts we need to remove.  Just in case, we will
	 * remove all contacts in the vector even if the contacts
	 * container had fewer contacts than there should be.
	 */
	ast_assert(AST_VECTOR_SIZE(&contact_vec) == to_remove);
	to_remove = AST_VECTOR_SIZE(&contact_vec);

	/* Remove the excess contacts that are unavailable or expire the soonest */
	while (to_remove--) {
		struct ast_sip_contact *contact;

		contact = AST_VECTOR_GET(&contact_vec, to_remove);

		if (!remove_existing) {
			registrar_contact_delete(CONTACT_DELETE_UNAVAILABLE, NULL, contact, contact->aor);
		} else {
			registrar_contact_delete(CONTACT_DELETE_EXISTING, NULL, contact, contact->aor);
		}

		ao2_unlink(response_contacts, contact);
	}

	AST_VECTOR_FREE(&contact_vec);
}

/*! \brief Callback function which adds non-permanent contacts to a container */
static int registrar_add_non_permanent(void *obj, void *arg, int flags)
{
	struct ast_sip_contact *contact = obj;
	struct ao2_container *container = arg;

	if (ast_tvzero(contact->expiration_time)) {
		return 0;
	}

	ao2_link(container, contact);

	return 0;
}

/*! \brief Internal callback function which adds any contact which is unreachable */
static int registrar_add_unreachable(void *obj, void *arg, int flags)
{
	struct ast_sip_contact *contact = obj;
	struct ao2_container *container = arg;
	struct ast_sip_contact_status *status;
	int unreachable;

	status = ast_sip_get_contact_status(contact);
	if (!status) {
		return 0;
	}

	unreachable = (status->status == UNAVAILABLE);
	ao2_ref(status, -1);

	if (unreachable) {
		ao2_link(container, contact);
	}

	return 0;
}

struct aor_core_response {
	/*! Tx data to use for statefull response.  NULL for stateless response. */
	pjsip_tx_data *tdata;
	/*! SIP response code to send in stateless response */
	int code;
};

static void register_aor_core(pjsip_rx_data *rdata,
	struct ast_sip_endpoint *endpoint,
	struct ast_sip_aor *aor,
	const char *aor_name,
	struct ao2_container *contacts,
	struct aor_core_response *response)
{
	static const pj_str_t USER_AGENT = { "User-Agent", 10 };

	int added = 0;
	int updated = 0;
	int deleted = 0;
	int permanent = 0;
	int contact_count;
	struct ao2_container *existing_contacts = NULL;
	struct ao2_container *unavail_contacts = NULL;
	pjsip_contact_hdr *contact_hdr = (pjsip_contact_hdr *)&rdata->msg_info.msg->hdr;
	struct registrar_contact_details details = { 0, };
	pjsip_tx_data *tdata;
	RAII_VAR(struct ast_str *, path_str, NULL, ast_free);
	struct ast_sip_contact *response_contact;
	char *user_agent = NULL;
	pjsip_user_agent_hdr *user_agent_hdr;
	pjsip_expires_hdr *expires_hdr;
	pjsip_via_hdr *via_hdr;
	pjsip_via_hdr *via_hdr_last;
	char *via_addr = NULL;
	int via_port = 0;
	pjsip_cid_hdr *call_id_hdr;
	char *call_id = NULL;
	size_t alloc_size;

	/* We create a single pool and use it throughout this function where we need one */
	details.pool = pjsip_endpt_create_pool(ast_sip_get_pjsip_endpoint(),
		"Contact Comparison", 1024, 256);
	if (!details.pool) {
		response->code = 500;
		return;
	}

	/* If there are any permanent contacts configured on the AOR we need to take them
	 * into account when counting contacts.
	 */
	if (aor->permanent_contacts) {
		permanent = ao2_container_count(aor->permanent_contacts);
	}

	if (registrar_validate_contacts(rdata, details.pool, contacts, aor, permanent, &added, &updated, &deleted)) {
		/* The provided Contact headers do not conform to the specification */
		ast_sip_report_failed_acl(endpoint, rdata, "registrar_invalid_contacts_provided");
		ast_log(LOG_WARNING, "Failed to validate contacts in REGISTER request from '%s'\n",
				ast_sorcery_object_get_id(endpoint));
		response->code = 400;
		pjsip_endpt_release_pool(ast_sip_get_pjsip_endpoint(), details.pool);
		return;
	}

	if (registrar_validate_path(rdata, aor, &path_str)) {
		/* Ensure that intervening proxies did not make invalid modifications to the request */
		ast_log(LOG_WARNING, "Invalid modifications made to REGISTER request from '%s' by intervening proxy\n",
				ast_sorcery_object_get_id(endpoint));
		response->code = 420;
		pjsip_endpt_release_pool(ast_sip_get_pjsip_endpoint(), details.pool);
		return;
	}

	if (aor->remove_existing) {
		/* Cumulative number of contacts affected by this registration */
		contact_count = MAX(updated + added - deleted,  0);

		/* We need to keep track of only existing contacts so we can later
		 * remove them if need be.
		 */
		existing_contacts = ao2_container_alloc_list(AO2_ALLOC_OPT_LOCK_NOLOCK, 0,
			NULL, ast_sorcery_object_id_compare);
		if (!existing_contacts) {
			response->code = 500;
			pjsip_endpt_release_pool(ast_sip_get_pjsip_endpoint(), details.pool);
			return;
		}

		ao2_callback(contacts, OBJ_NODATA, registrar_add_non_permanent, existing_contacts);
	} else {
		/* Total contacts after this registration */
		contact_count = ao2_container_count(contacts) - permanent + added - deleted;
	}

	if (contact_count > aor->max_contacts && aor->remove_unavailable) {
		/* Get unavailable contact total */
		int unavail_count = 0;

		unavail_contacts = ao2_container_alloc_list(AO2_ALLOC_OPT_LOCK_NOLOCK, 0,
			NULL, ast_sorcery_object_id_compare);
		if (!unavail_contacts) {
			response->code = 500;
			pjsip_endpt_release_pool(ast_sip_get_pjsip_endpoint(), details.pool);
			return;
		}
		ao2_callback(contacts, OBJ_NODATA, registrar_add_unreachable, unavail_contacts);
		if (unavail_contacts) {
			unavail_count = ao2_container_count(unavail_contacts);
		}

		/* Check to see if removing unavailable contacts will help */
		if (contact_count - unavail_count <= aor->max_contacts) {
			/* Remove any unavailable contacts */
			remove_excess_contacts(unavail_contacts, contacts, contact_count - aor->max_contacts, aor->remove_existing);
			ao2_cleanup(unavail_contacts);
			/* We're only here if !aor->remove_existing so this count is correct */
			contact_count = ao2_container_count(contacts) - permanent + added - deleted;
		}
	}

	if (contact_count > aor->max_contacts) {
		/* Enforce the maximum number of contacts */
		ast_sip_report_failed_acl(endpoint, rdata, "registrar_attempt_exceeds_maximum_configured_contacts");
		ast_log(LOG_WARNING, "Registration attempt from endpoint '%s' (%s:%d) to AOR '%s' will exceed max contacts of %u\n",
				ast_sorcery_object_get_id(endpoint), rdata->pkt_info.src_name, rdata->pkt_info.src_port,
				aor_name, aor->max_contacts);
		response->code = 403;
		pjsip_endpt_release_pool(ast_sip_get_pjsip_endpoint(), details.pool);
		ao2_cleanup(existing_contacts);
		return;
	}

	user_agent_hdr = pjsip_msg_find_hdr_by_name(rdata->msg_info.msg, &USER_AGENT, NULL);
	if (user_agent_hdr) {
		alloc_size = pj_strlen(&user_agent_hdr->hvalue) + 1;
		user_agent = ast_alloca(alloc_size);
		ast_copy_pj_str(user_agent, &user_agent_hdr->hvalue, alloc_size);
	}

	/* Find the first Via header */
	via_hdr = via_hdr_last = (pjsip_via_hdr*) pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_VIA, NULL);
	if (via_hdr) {
		/* Find the last Via header */
		while ( (via_hdr = (pjsip_via_hdr*) pjsip_msg_find_hdr(rdata->msg_info.msg,
				PJSIP_H_VIA, via_hdr->next)) != NULL) {
			via_hdr_last = via_hdr;
		}
		alloc_size = pj_strlen(&via_hdr_last->sent_by.host) + 1;
		via_addr = ast_alloca(alloc_size);
		ast_copy_pj_str(via_addr, &via_hdr_last->sent_by.host, alloc_size);
		via_port=via_hdr_last->sent_by.port;
	}

	call_id_hdr = (pjsip_cid_hdr*) pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_CALL_ID, NULL);
	if (call_id_hdr) {
		alloc_size = pj_strlen(&call_id_hdr->id) + 1;
		call_id = ast_alloca(alloc_size);
		ast_copy_pj_str(call_id, &call_id_hdr->id, alloc_size);
	}

	/* Iterate each provided Contact header and add, update, or delete */
	for (; (contact_hdr = (pjsip_contact_hdr *) pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_CONTACT, contact_hdr->next)); pj_pool_reset(details.pool)) {
		int expiration;
		char contact_uri[pjsip_max_url_size];
		RAII_VAR(struct ast_sip_contact *, contact, NULL, ao2_cleanup);

		if (contact_hdr->star) {
			/* A star means to unregister everything, so do so for the possible contacts */
			ao2_callback(contacts, OBJ_NODATA | OBJ_UNLINK | OBJ_MULTIPLE,
				registrar_delete_contact, (void *)aor_name);
			/* If we are keeping track of existing contacts for removal then, well, there is
			 * absolutely nothing left so no need to try to remove any.
			 */
			if (existing_contacts) {
				ao2_ref(existing_contacts, -1);
				existing_contacts = NULL;
			}
			break;
		}

		if (!PJSIP_URI_SCHEME_IS_SIP(contact_hdr->uri) && !PJSIP_URI_SCHEME_IS_SIPS(contact_hdr->uri)) {
			/* This registrar only currently supports sip: and sips: URI schemes */
			continue;
		}

		expiration = registrar_get_expiration(aor, contact_hdr, rdata);
		details.uri = pjsip_uri_get_uri(contact_hdr->uri);
		pjsip_uri_print(PJSIP_URI_IN_CONTACT_HDR, details.uri, contact_uri, sizeof(contact_uri));

		contact = ao2_callback(contacts, OBJ_UNLINK, registrar_find_contact, &details);

		/* If a contact was returned and we need to keep track of existing contacts then it
		 * should be removed.
		 */
		if (contact && existing_contacts) {
			ao2_unlink(existing_contacts, contact);
		}

		if (!contact) {
			int prune_on_boot;

			/* If they are actually trying to delete a contact that does not exist... be forgiving */
			if (!expiration) {
				ast_verb(3, "Attempted to remove non-existent contact '%s' from AOR '%s' by request\n",
					contact_uri, aor_name);
				continue;
			}

			prune_on_boot = !ast_sip_will_uri_survive_restart(details.uri, endpoint, rdata);

			contact = ast_sip_location_create_contact(aor, contact_uri,
				ast_tvadd(ast_tvnow(), ast_samp2tv(expiration, 1)),
				path_str ? ast_str_buffer(path_str) : NULL,
				user_agent, via_addr, via_port, call_id, prune_on_boot, endpoint);
			if (!contact) {
				ast_log(LOG_ERROR, "Unable to bind contact '%s' to AOR '%s'\n",
					contact_uri, aor_name);
				continue;
			}

			if (prune_on_boot) {
				size_t contact_name_len;
				const char *contact_name;
				struct contact_transport_monitor *monitor;

				/*
				 * Monitor the transport in case it gets disconnected because
				 * the contact won't be valid anymore if that happens.
				 */
				contact_name = ast_sorcery_object_get_id(contact);
				contact_name_len = strlen(contact_name) + 1;
				monitor = ao2_alloc(sizeof(*monitor) + 1 + strlen(aor_name)
					+ contact_name_len, NULL);
				if (monitor) {
					strcpy(monitor->aor_name, aor_name);/* Safe */
					monitor->contact_name = monitor->aor_name + strlen(aor_name) + 1;
					ast_copy_string(monitor->contact_name, contact_name, contact_name_len);/* Safe */

					ast_sip_transport_monitor_register_replace(rdata->tp_info.transport,
						register_contact_transport_shutdown_cb, monitor, contact_transport_monitor_matcher);
					ao2_ref(monitor, -1);
				}
			}

			ast_verb(3, "Added contact '%s' to AOR '%s' with expiration of %d seconds\n",
				contact_uri, aor_name, expiration);
			ast_test_suite_event_notify("AOR_CONTACT_ADDED",
					"Contact: %s\r\n"
					"AOR: %s\r\n"
					"Expiration: %d\r\n"
					"UserAgent: %s",
					contact_uri,
					aor_name,
					expiration,
					user_agent);

			ao2_link(contacts, contact);
		} else if (expiration) {
			struct ast_sip_contact *contact_update;

			contact_update = ast_sorcery_copy(ast_sip_get_sorcery(), contact);
			if (!contact_update) {
				ast_log(LOG_ERROR, "Failed to update contact '%s' expiration time to %d seconds.\n",
					contact->uri, expiration);
				continue;
			}

			contact_update->expiration_time = ast_tvadd(ast_tvnow(), ast_samp2tv(expiration, 1));
			contact_update->qualify_frequency = aor->qualify_frequency;
			contact_update->authenticate_qualify = aor->authenticate_qualify;
			if (path_str) {
				ast_string_field_set(contact_update, path, ast_str_buffer(path_str));
			}
			if (user_agent) {
				ast_string_field_set(contact_update, user_agent, user_agent);
			}
			if (!ast_strlen_zero(ast_config_AST_SYSTEM_NAME)) {
				ast_string_field_set(contact_update, reg_server, ast_config_AST_SYSTEM_NAME);
			}

			if (ast_sip_location_update_contact(contact_update)) {
				ast_log(LOG_ERROR, "Failed to update contact '%s' expiration time to %d seconds.\n",
					contact->uri, expiration);
				registrar_contact_delete(CONTACT_DELETE_ERROR, rdata->tp_info.transport,
					contact, aor_name);
				continue;
			}
			ast_debug(3, "Refreshed contact '%s' on AOR '%s' with new expiration of %d seconds\n",
				contact_uri, aor_name, expiration);
			ast_test_suite_event_notify("AOR_CONTACT_REFRESHED",
					"Contact: %s\r\n"
					"AOR: %s\r\n"
					"Expiration: %d\r\n"
					"UserAgent: %s",
					contact_uri,
					aor_name,
					expiration,
					contact_update->user_agent);
			ao2_link(contacts, contact_update);
			ao2_cleanup(contact_update);
		} else {
			registrar_contact_delete(CONTACT_DELETE_REQUEST, rdata->tp_info.transport,
					contact, aor_name);
		}
	}

	pjsip_endpt_release_pool(ast_sip_get_pjsip_endpoint(), details.pool);

	/*
	 * If the AOR is configured to remove any contacts over max_contacts
	 * that have not been updated/added/deleted as a result of this
	 * REGISTER do so.
	 *
	 * The existing contacts container holds all contacts that were not
	 * involved in this REGISTER.
	 * The contacts container holds the current contacts of the AOR.
	 */
	if (aor->remove_existing && existing_contacts) {
		/* Total contacts after this registration */
		contact_count = ao2_container_count(existing_contacts) + updated + added;
		if (contact_count > aor->max_contacts) {
			/* Remove excess existing contacts that are unavailable or expire soonest */
			remove_excess_contacts(existing_contacts, contacts, contact_count - aor->max_contacts,
				aor->remove_existing);
		}
		ao2_ref(existing_contacts, -1);
	}

	response_contact = ao2_callback(contacts, 0, NULL, NULL);

	/* Send a response containing all of the contacts (including static) that are present on this AOR */
	if (ast_sip_create_response(rdata, 200, response_contact, &tdata) != PJ_SUCCESS) {
		ao2_cleanup(response_contact);
		ao2_cleanup(contacts);
		response->code = 500;
		return;
	}
	ao2_cleanup(response_contact);

	/* Add the date header to the response, some UAs use this to set their date and time */
	ast_sip_add_date_header(tdata);

	ao2_callback(contacts, 0, registrar_add_contact, tdata);

	if ((expires_hdr = pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_EXPIRES, NULL))) {
		expires_hdr = pjsip_expires_hdr_create(tdata->pool, registrar_get_expiration(aor, NULL, rdata));
		pjsip_msg_add_hdr(tdata->msg, (pjsip_hdr*)expires_hdr);
	}

	response->tdata = tdata;
}

static int register_aor(pjsip_rx_data *rdata,
	struct ast_sip_endpoint *endpoint,
	struct ast_sip_aor *aor,
	const char *aor_name)
{
	struct aor_core_response response = {
		.code = 500,
	};
	struct ao2_container *contacts = NULL;

	ao2_lock(aor);
	contacts = ast_sip_location_retrieve_aor_contacts_nolock(aor);
	if (!contacts) {
		ao2_unlock(aor);
		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(),
			rdata, response.code, NULL, NULL, NULL);
		return PJ_TRUE;
	}

	register_aor_core(rdata, endpoint, aor, aor_name, contacts, &response);
	ao2_cleanup(contacts);
	ao2_unlock(aor);

	/* Now send the REGISTER response to the peer */
	if (response.tdata) {
		ast_sip_send_stateful_response(rdata, response.tdata, endpoint);
	} else {
		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(),
			rdata, response.code, NULL, NULL, NULL);
	}
	return PJ_TRUE;
}

static int match_aor(const char *aor_name, const char *id)
{
	if (ast_strlen_zero(aor_name)) {
		return 0;
	}

	if (!strcmp(aor_name, id)) {
		ast_debug(3, "Matched id '%s' to aor '%s'\n", id, aor_name);
		return 1;
	}

	return 0;
}

static char *find_aor_name(const pj_str_t *pj_username, const pj_str_t *pj_domain, const char *aors)
{
	char *configured_aors;
	char *aors_buf;
	char *aor_name;
	char *id_domain;
	char *username, *domain;
	struct ast_sip_domain_alias *alias;

	/* Turn these into C style strings for convenience */
	username = ast_alloca(pj_strlen(pj_username) + 1);
	ast_copy_pj_str(username, pj_username, pj_strlen(pj_username) + 1);
	domain = ast_alloca(pj_strlen(pj_domain) + 1);
	ast_copy_pj_str(domain, pj_domain, pj_strlen(pj_domain) + 1);

	id_domain = ast_alloca(strlen(username) + strlen(domain) + 2);
	sprintf(id_domain, "%s@%s", username, domain);

	aors_buf = ast_strdupa(aors);

	/* Look for exact match on username@domain */
	configured_aors = aors_buf;
	while ((aor_name = ast_strip(strsep(&configured_aors, ",")))) {
		if (match_aor(aor_name, id_domain)) {
			return ast_strdup(aor_name);
		}
	}

	/* If there's a domain alias, look for exact match on username@domain_alias */
	alias = ast_sorcery_retrieve_by_id(ast_sip_get_sorcery(), "domain_alias", domain);
	if (alias) {
		char *id_domain_alias = ast_alloca(strlen(username) + strlen(alias->domain) + 2);

		sprintf(id_domain_alias, "%s@%s", username, alias->domain);
		ao2_cleanup(alias);

		configured_aors = strcpy(aors_buf, aors);/* Safe */
		while ((aor_name = ast_strip(strsep(&configured_aors, ",")))) {
			if (match_aor(aor_name, id_domain_alias)) {
				return ast_strdup(aor_name);
			}
		}
	}

	if (ast_strlen_zero(username)) {
		/* No username, no match */
		return NULL;
	}

	/* Look for exact match on username only */
	configured_aors = strcpy(aors_buf, aors);/* Safe */
	while ((aor_name = ast_strip(strsep(&configured_aors, ",")))) {
		if (match_aor(aor_name, username)) {
			return ast_strdup(aor_name);
		}
	}

	return NULL;
}

static struct ast_sip_aor *find_registrar_aor(struct pjsip_rx_data *rdata, struct ast_sip_endpoint *endpoint)
{
	struct ast_sip_aor *aor = NULL;
	char *aor_name = NULL;
	int i;

	for (i = 0; i < AST_VECTOR_SIZE(&endpoint->ident_method_order); ++i) {
		pj_str_t username;
		pjsip_sip_uri *uri;
		pjsip_authorization_hdr *header = NULL;

		switch (AST_VECTOR_GET(&endpoint->ident_method_order, i)) {
		case AST_SIP_ENDPOINT_IDENTIFY_BY_USERNAME:
			uri = pjsip_uri_get_uri(rdata->msg_info.to->uri);

			pj_strassign(&username, &uri->user);

			/*
			 * We may want to match without any user options getting
			 * in the way.
			 *
			 * Logic adapted from AST_SIP_USER_OPTIONS_TRUNCATE_CHECK for pj_str_t.
			 */
			if (ast_sip_get_ignore_uri_user_options()) {
				pj_ssize_t semi = pj_strcspn2(&username, ";");
				if (semi < pj_strlen(&username)) {
					username.slen = semi;
				}
			}

			aor_name = find_aor_name(&username, &uri->host, endpoint->aors);
			if (aor_name) {
				ast_debug(3, "Matched aor '%s' by To username\n", aor_name);
			}
			break;
		case AST_SIP_ENDPOINT_IDENTIFY_BY_AUTH_USERNAME:
			while ((header = pjsip_msg_find_hdr(rdata->msg_info.msg, PJSIP_H_AUTHORIZATION,
				header ? header->next : NULL))) {
				if (header && !pj_stricmp2(&header->scheme, "digest")) {
					aor_name = find_aor_name(&header->credential.digest.username,
						&header->credential.digest.realm, endpoint->aors);
					if (aor_name) {
						ast_debug(3, "Matched aor '%s' by Authentication username\n", aor_name);
						break;
					}
				}
			}
			break;
		default:
			continue;
		}

		if (aor_name) {
			break;
		}
	}

	if (ast_strlen_zero(aor_name) || !(aor = ast_sip_location_retrieve_aor(aor_name))) {
		/* The provided AOR name was not found (be it within the configuration or sorcery itself) */
		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 404, NULL, NULL, NULL);
		ast_sip_report_req_no_support(endpoint, rdata, "registrar_requested_aor_not_found");
		ast_log(LOG_WARNING, "AOR '%s' not found for endpoint '%s' (%s:%d)\n",
			aor_name ?: "", ast_sorcery_object_get_id(endpoint),
			rdata->pkt_info.src_name, rdata->pkt_info.src_port);
	}
	ast_free(aor_name);
	return aor;
}

static pj_bool_t registrar_on_rx_request(struct pjsip_rx_data *rdata)
{
	RAII_VAR(struct ast_sip_endpoint *, endpoint,
		 ast_pjsip_rdata_get_endpoint(rdata), ao2_cleanup);
	struct ast_sip_aor *aor;
	const char *aor_name;

	if (pjsip_method_cmp(&rdata->msg_info.msg->line.req.method, &pjsip_register_method) || !endpoint) {
		return PJ_FALSE;
	}

	if (ast_strlen_zero(endpoint->aors)) {
		/* Short circuit early if the endpoint has no AORs configured on it, which means no registration possible */
		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 403, NULL, NULL, NULL);
		ast_sip_report_failed_acl(endpoint, rdata, "registrar_attempt_without_configured_aors");
		ast_log(LOG_WARNING, "Endpoint '%s' (%s:%d) has no configured AORs\n", ast_sorcery_object_get_id(endpoint),
			rdata->pkt_info.src_name, rdata->pkt_info.src_port);
		return PJ_TRUE;
	}

	if (!PJSIP_URI_SCHEME_IS_SIP(rdata->msg_info.to->uri) && !PJSIP_URI_SCHEME_IS_SIPS(rdata->msg_info.to->uri)) {
		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 416, NULL, NULL, NULL);
		ast_sip_report_failed_acl(endpoint, rdata, "registrar_invalid_uri_in_to_received");
		ast_log(LOG_WARNING, "Endpoint '%s' (%s:%d) attempted to register to an AOR with a non-SIP URI\n", ast_sorcery_object_get_id(endpoint),
			rdata->pkt_info.src_name, rdata->pkt_info.src_port);
		return PJ_TRUE;
	}

	aor = find_registrar_aor(rdata, endpoint);
	if (!aor) {
		/* We've already responded about not finding an AOR. */
		return PJ_TRUE;
	}

	aor_name = ast_sorcery_object_get_id(aor);

	if (!aor->max_contacts) {
		/* Registration is not permitted for this AOR */
		pjsip_endpt_respond_stateless(ast_sip_get_pjsip_endpoint(), rdata, 403, NULL, NULL, NULL);
		ast_sip_report_req_no_support(endpoint, rdata, "registrar_attempt_without_registration_permitted");
		ast_log(LOG_WARNING, "AOR '%s' has no configured max_contacts. Endpoint '%s' (%s:%d) unable to register\n",
			aor_name, ast_sorcery_object_get_id(endpoint),
			rdata->pkt_info.src_name, rdata->pkt_info.src_port);
	} else {
		register_aor(rdata, endpoint, aor, aor_name);
	}
	ao2_ref(aor, -1);
	return PJ_TRUE;
}

/* function pointer to callback needs to be within the module
   in order to avoid problems with an undefined symbol */
static int sip_contact_to_str(void *acp, void *arg, int flags)
{
	return ast_sip_contact_to_str(acp, arg, flags);
}

static int ami_registrations_aor(void *obj, void *arg, int flags)
{
	struct ast_sip_aor *aor = obj;
	struct ast_sip_ami *ami = arg;
	int *count = ami->arg;
	RAII_VAR(struct ast_str *, buf,
		 ast_sip_create_ami_event("InboundRegistrationDetail", ami), ast_free);

	if (!buf) {
		return -1;
	}

	ast_sip_sorcery_object_to_ami(aor, &buf);
	ast_str_append(&buf, 0, "Contacts: ");
	ast_sip_for_each_contact(aor, sip_contact_to_str, &buf);
	ast_str_append(&buf, 0, "\r\n");

	astman_append(ami->s, "%s\r\n", ast_str_buffer(buf));
	(*count)++;
	return 0;
}

static int ami_registrations_endpoint(void *obj, void *arg, int flags)
{
	struct ast_sip_endpoint *endpoint = obj;
	return ast_sip_for_each_aor(
		endpoint->aors, ami_registrations_aor, arg);
}

static int ami_registrations_endpoints(void *arg)
{
	RAII_VAR(struct ao2_container *, endpoints,
		 ast_sip_get_endpoints(), ao2_cleanup);

	if (!endpoints) {
		return 0;
	}

	ao2_callback(endpoints, OBJ_NODATA, ami_registrations_endpoint, arg);
	return 0;
}

static int ami_show_registrations(struct mansession *s, const struct message *m)
{
	int count = 0;
	struct ast_sip_ami ami = { .s = s, .m = m, .arg = &count, .action_id = astman_get_header(m, "ActionID"), };

	astman_send_listack(s, m, "Following are Events for each Inbound registration",
		"start");

	ami_registrations_endpoints(&ami);

	astman_send_list_complete_start(s, m, "InboundRegistrationDetailComplete", count);
	astman_send_list_complete_end(s);
	return 0;
}

static int ami_show_registration_contact_statuses(struct mansession *s, const struct message *m)
{
	int count = 0;
	struct ast_sip_ami ami = { .s = s, .m = m, .arg = NULL, .action_id = astman_get_header(m, "ActionID"), };
	struct ao2_container *contacts = ast_sorcery_retrieve_by_fields(
		ast_sip_get_sorcery(), "contact", AST_RETRIEVE_FLAG_MULTIPLE | AST_RETRIEVE_FLAG_ALL, NULL);
	struct ao2_iterator i;
	struct ast_sip_contact *contact;

	astman_send_listack(s, m, "Following are ContactStatusEvents for each Inbound "
			    "registration", "start");

	if (contacts) {
		i = ao2_iterator_init(contacts, 0);
		while ((contact = ao2_iterator_next(&i))) {
			struct ast_sip_contact_wrapper wrapper;

			wrapper.aor_id = (char *)contact->aor;
			wrapper.contact = contact;
			wrapper.contact_id = (char *)ast_sorcery_object_get_id(contact);

			ast_sip_format_contact_ami(&wrapper, &ami, 0);
			count++;

			ao2_ref(contact, -1);
		}
		ao2_iterator_destroy(&i);
		ao2_ref(contacts, -1);
	}

	astman_send_list_complete_start(s, m, "ContactStatusDetailComplete", count);
	astman_send_list_complete_end(s);
	return 0;
}

#define AMI_SHOW_REGISTRATION_CONTACT_STATUSES "PJSIPShowRegistrationInboundContactStatuses"
#define AMI_SHOW_REGISTRATIONS "PJSIPShowRegistrationsInbound"

static pjsip_module registrar_module = {
	.name = { "Registrar", 9 },
	.id = -1,
	.priority = PJSIP_MOD_PRIORITY_APPLICATION,
	.on_rx_request = registrar_on_rx_request,
};

/*! \brief Thread keeping things alive */
static pthread_t check_thread = AST_PTHREADT_NULL;

/*! \brief The global interval at which to check for contact expiration */
static unsigned int check_interval;

/*! \brief Callback function which deletes a contact */
static int expire_contact(void *obj, void *arg, int flags)
{
	struct ast_sip_contact *contact = obj;
	struct ast_named_lock *lock;

	lock = ast_named_lock_get(AST_NAMED_LOCK_TYPE_MUTEX, "aor", contact->aor);
	if (!lock) {
		return 0;
	}

	/*
	 * We need to check the expiration again with the aor lock held
	 * in case another thread is attempting to renew the contact.
	 */
	ao2_lock(lock);
	if (ast_tvdiff_ms(ast_tvnow(), contact->expiration_time) > 0) {
		registrar_contact_delete(CONTACT_DELETE_EXPIRE, NULL, contact, contact->aor);
	}
	ao2_unlock(lock);
	ast_named_lock_put(lock);

	return 0;
}

static void *check_expiration_thread(void *data)
{
	struct ao2_container *contacts;
	struct ast_variable *var;
	char time[AST_TIME_T_LEN];

	while (check_interval) {
		sleep(check_interval);

		ast_time_t_to_string(ast_tvnow().tv_sec, time, sizeof(time));

		var = ast_variable_new("expiration_time <=", time, "");

		ast_debug(4, "Woke up at %s  Interval: %d\n", time, check_interval);

		contacts = ast_sorcery_retrieve_by_fields(ast_sip_get_sorcery(), "contact",
			AST_RETRIEVE_FLAG_MULTIPLE, var);

		ast_variables_destroy(var);
		if (contacts) {
			ast_debug(3, "Expiring %d contacts\n", ao2_container_count(contacts));
			ao2_callback(contacts, OBJ_NODATA, expire_contact, NULL);
			ao2_ref(contacts, -1);
		}
	}

	return NULL;
}

static void expiration_global_loaded(const char *object_type)
{
	check_interval = ast_sip_get_contact_expiration_check_interval();

	/* Observer calls are serialized so this is safe without it's own lock */
	if (check_interval) {
		if (check_thread == AST_PTHREADT_NULL) {
			if (ast_pthread_create_background(&check_thread, NULL, check_expiration_thread, NULL)) {
				ast_log(LOG_ERROR, "Could not create thread for checking contact expiration.\n");
				return;
			}
			ast_debug(3, "Interval = %d, starting thread\n", check_interval);
		}
	} else {
		if (check_thread != AST_PTHREADT_NULL) {
			pthread_kill(check_thread, SIGURG);
			pthread_join(check_thread, NULL);
			check_thread = AST_PTHREADT_NULL;
			ast_debug(3, "Interval = 0, shutting thread down\n");
		}
	}
}

/*! \brief Observer which is used to update our interval when the global setting changes */
static struct ast_sorcery_observer expiration_global_observer = {
	.loaded = expiration_global_loaded,
};

static int load_module(void)
{
	const pj_str_t STR_REGISTER = { "REGISTER", 8 };

	ast_pjproject_get_buildopt("PJ_MAX_HOSTNAME", "%d", &pj_max_hostname);
	/* As of pjproject 2.4.5, PJSIP_MAX_URL_SIZE isn't exposed yet but we try anyway. */
	ast_pjproject_get_buildopt("PJSIP_MAX_URL_SIZE", "%d", &pjsip_max_url_size);

	if (ast_sip_register_service(&registrar_module)) {
		return AST_MODULE_LOAD_DECLINE;
	}

	if (pjsip_endpt_add_capability(ast_sip_get_pjsip_endpoint(), NULL, PJSIP_H_ALLOW, NULL, 1, &STR_REGISTER) != PJ_SUCCESS) {
		ast_sip_unregister_service(&registrar_module);
		return AST_MODULE_LOAD_DECLINE;
	}

	ast_manager_register_xml(AMI_SHOW_REGISTRATIONS, EVENT_FLAG_SYSTEM,
				 ami_show_registrations);
	ast_manager_register_xml(AMI_SHOW_REGISTRATION_CONTACT_STATUSES, EVENT_FLAG_SYSTEM,
				 ami_show_registration_contact_statuses);

	ast_sorcery_observer_add(ast_sip_get_sorcery(), "global", &expiration_global_observer);
	ast_sorcery_reload_object(ast_sip_get_sorcery(), "global");

	return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
	if (check_thread != AST_PTHREADT_NULL) {
		check_interval = 0;
		pthread_kill(check_thread, SIGURG);
		pthread_join(check_thread, NULL);

		check_thread = AST_PTHREADT_NULL;
	}

	ast_sorcery_observer_remove(ast_sip_get_sorcery(), "global", &expiration_global_observer);

	ast_manager_unregister(AMI_SHOW_REGISTRATIONS);
	ast_manager_unregister(AMI_SHOW_REGISTRATION_CONTACT_STATUSES);
	ast_sip_unregister_service(&registrar_module);
	ast_sip_transport_monitor_unregister_all(register_contact_transport_shutdown_cb, NULL, NULL);
	return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP Registrar Support",
	.support_level = AST_MODULE_SUPPORT_CORE,
	.load = load_module,
	.unload = unload_module,
	.load_pri = AST_MODPRI_CHANNEL_DEPEND - 3,
	.requires = "res_pjproject,res_pjsip",
);