res_calendar_exchange.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008 - 2009, Digium, Inc.
 *
 * Terry Wilson <twilson@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.
 */

/*! \file
 * \brief Resource for handling MS Exchange calendars
 */

/*** MODULEINFO
   <depend>neon</depend>
   <depend>ical</depend>
   <depend>iksemel</depend>
   <support_level>core</support_level>
***/

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 413587 $")

#include <libical/ical.h>
#include <ne_session.h>
#include <ne_uri.h>
#include <ne_request.h>
#include <ne_auth.h>
#include <ne_redirect.h>
#include <iksemel.h>

#include "asterisk/module.h"
#include "asterisk/calendar.h"
#include "asterisk/lock.h"
#include "asterisk/config.h"
#include "asterisk/astobj2.h"

static void *exchangecal_load_calendar(void *data);
static void *unref_exchangecal(void *obj);
static int exchangecal_write_event(struct ast_calendar_event *event);

static struct ast_calendar_tech exchangecal_tech = {
   .type = "exchange",
   .description = "MS Exchange calendars",
   .module = AST_MODULE,
   .load_calendar = exchangecal_load_calendar,
   .unref_calendar = unref_exchangecal,
   .write_event = exchangecal_write_event,
};

struct exchangecal_pvt {
   AST_DECLARE_STRING_FIELDS(
      AST_STRING_FIELD(url);
      AST_STRING_FIELD(user);
      AST_STRING_FIELD(secret);
   );
   struct ast_calendar *owner;
   ne_uri uri;
   ne_session *session;
   struct ao2_container *events;
};

struct xmlstate {
   char tag[80];
   int in_response;
   int in_propstat;
   int in_prop;
   void *ptr;
   struct exchangecal_pvt *pvt;
};

static int parse_tag(void *data, char *name, char **atts, int type)
{
   struct xmlstate *state = data;
   char *tmp;

   if ((tmp = strchr(name, ':'))) {
      tmp++;
   } else {
      return IKS_HOOK;
   }

   ast_copy_string(state->tag, tmp, sizeof(state->tag));

   switch (type) {
   case IKS_OPEN:
      if (!strcasecmp(state->tag, "response")) {
         struct ast_calendar_event *event;

         state->in_response = 1;
         if (!(event = ast_calendar_event_alloc(state->pvt->owner))) {
            return IKS_NOMEM;
         }
         state->ptr = event;
      } else if (!strcasecmp(state->tag, "propstat")) {
         state->in_propstat = 1;
      } else if (!strcasecmp(state->tag, "prop")) {
         state->in_prop = 1;
      }
      break;

   case IKS_CLOSE:
      if (!strcasecmp(state->tag, "response")) {
         struct ao2_container *events = state->pvt->events;
         struct ast_calendar_event *event = state->ptr;

         state->in_response = 0;
         if (ast_strlen_zero(event->uid)) {
            ast_log(LOG_ERROR, "This event has no UID, something has gone wrong\n");
            event = ast_calendar_unref_event(event);
            return IKS_HOOK;
         }
         ao2_link(events, event);
         event = ast_calendar_unref_event(event);
      } else if (!strcasecmp(state->tag, "propstat")) {
         state->in_propstat = 0;
      } else if (!strcasecmp(state->tag, "prop")) {
         state->in_prop = 0;
      }
      break;

   default:
      return IKS_OK;
   }

   return IKS_OK;
}

static time_t mstime_to_time_t(char *mstime)
{
   char *read, *write;
   icaltimetype tt;
   for (read = write = mstime; *read; read++) {
      if (*read == '.') {
         *write++ = 'Z';
         *write = '\0';
         break;
      }
      if (*read == '-' || *read == ':')
         continue;
      *write = *read;
      write++;
   }

   tt = icaltime_from_string(mstime);
   return icaltime_as_timet(tt);
}

static enum ast_calendar_busy_state msbusy_to_bs(const char *msbusy)
{
   if (!strcasecmp(msbusy, "FREE")) {
      return AST_CALENDAR_BS_FREE;
   } else if (!strcasecmp(msbusy, "TENTATIVE")) {
      return AST_CALENDAR_BS_BUSY_TENTATIVE;
   } else {
      return AST_CALENDAR_BS_BUSY;
   }
}

static int parse_cdata(void *data, char *value, size_t len)
{
   char *str;
   struct xmlstate *state = data;
   struct ast_calendar_event *event = state->ptr;


   str = ast_skip_blanks(value);

   if (str == value + len)
      return IKS_OK;

   if (!(str = ast_calloc(1, len + 1))) {
      return IKS_NOMEM;
   }
   memcpy(str, value, len);
   if (!(state->in_response && state->in_propstat && state->in_prop)) {
      ast_free(str);
      return IKS_OK;
   }
   /* We use ast_string_field_build here because libiksemel is parsing CDATA with &lt; as
    * new elements which is a bit odd and shouldn't happen */
   if (!strcasecmp(state->tag, "subject")) {
      ast_string_field_build(event, summary, "%s%s", event->summary, str);
   } else if (!strcasecmp(state->tag, "location")) {
      ast_string_field_build(event, location, "%s%s", event->location, str);
   } else if (!strcasecmp(state->tag, "uid")) {
      ast_string_field_build(event, uid, "%s%s", event->location, str);
   } else if (!strcasecmp(state->tag, "organizer")) {
      ast_string_field_build(event, organizer, "%s%s", event->organizer, str);
   } else if (!strcasecmp(state->tag, "textdescription")) {
      ast_string_field_build(event, description, "%s%s", event->description, str);
   } else if (!strcasecmp(state->tag, "dtstart")) {
      event->start = mstime_to_time_t(str);
   } else if (!strcasecmp(state->tag, "dtend")) {
      event->end = mstime_to_time_t(str);
   } else if (!strcasecmp(state->tag, "busystatus")) {
      event->busy_state = msbusy_to_bs(str);
   } else if (!strcasecmp(state->tag, "reminderoffset")) {
      /*XXX Currently we rely on event->start being set first which means we rely on the response order
       * which technically should be fine since the query returns in the order we ask for, but ... */
      event->alarm = event->start - atoi(str);
   }

   ast_free(str);
   return IKS_OK;
}

static void exchangecal_destructor(void *obj)
{
   struct exchangecal_pvt *pvt = obj;

   ast_debug(1, "Destroying pvt for Exchange calendar %s\n", pvt->owner->name);
   if (pvt->session) {
      ne_session_destroy(pvt->session);
   }
   ast_string_field_free_memory(pvt);

   ao2_callback(pvt->events, OBJ_UNLINK | OBJ_NODATA | OBJ_MULTIPLE, NULL, NULL);

   ao2_ref(pvt->events, -1);
}

static void *unref_exchangecal(void *obj)
{
   struct exchangecal_pvt *pvt = obj;

   ao2_ref(pvt, -1);
   return NULL;
}

/* It is very important to use the return value of this function as a realloc could occur */
static struct ast_str *generate_exchange_uuid(struct ast_str *uid)
{
   unsigned short val[8];
   int x;

   for (x = 0; x < 8; x++) {
      val[x] = ast_random();
   }
   ast_str_set(&uid, 0, "%04x%04x-%04x-%04x-%04x-%04x%04x%04x", (unsigned)val[0],
      (unsigned)val[1], (unsigned)val[2], (unsigned)val[3], (unsigned)val[4],
      (unsigned)val[5], (unsigned)val[6], (unsigned)val[7]);

   return uid;
}

static int is_valid_uuid(struct ast_str *uid)
{
   int i;

   if (ast_str_strlen(uid) != 36) {
      return 0;
   }

   for (i = 0; i < ast_str_strlen(uid); i++) {
      if (i == 8 || i == 13 || i == 18 || i == 23) {
         if (ast_str_buffer(uid)[i] != '-') {
            return 0;
         }
      } else if (!((ast_str_buffer(uid)[i] > 47 && ast_str_buffer(uid)[i] < 58) || (ast_str_buffer(uid)[i] > 96 && ast_str_buffer(uid)[i] < 103))) {
         return 0;
      }
   }

   return 1;
}

static struct ast_str *xml_encode_str(struct ast_str *dst, const char *src)
{
   const char *tmp;
   char buf[7];

   for (tmp = src; *tmp; tmp++) {
      switch (*tmp) {
      case '\"':
         strcpy(buf, "&quot;");
         break;

      case '\'':
         strcpy(buf, "&apos;");
         break;

      case '&':
         strcpy(buf, "&amp;");
         break;

      case '<':
         strcpy(buf, "&lt;");
         break;

      case '>':
         strcpy(buf, "&gt;");
         break;

      default:
         sprintf(buf, "%c", *tmp);
      }

      ast_str_append(&dst, 0, "%s", buf);
   }

   return dst;
}

static struct ast_str *epoch_to_exchange_time(struct ast_str *dst, time_t epoch)
{
   icaltimezone *utc = icaltimezone_get_utc_timezone();
   icaltimetype tt = icaltime_from_timet_with_zone(epoch, 0, utc);
   char tmp[30];
   int i;

   ast_copy_string(tmp, icaltime_as_ical_string(tt), sizeof(tmp));
   for (i = 0; tmp[i]; i++) {
      ast_str_append(&dst, 0, "%c", tmp[i]);
      if (i == 3 || i == 5)
         ast_str_append(&dst, 0, "%c", '-');
      if (i == 10 || i == 12)
         ast_str_append(&dst, 0, "%c", ':');
      if (i == 14)
         ast_str_append(&dst, 0, "%s", ".000");
   }

   return dst;
}

static struct ast_str *bs_to_exchange_bs(struct ast_str *dst, enum ast_calendar_busy_state bs)
{
   switch (bs) {
   case AST_CALENDAR_BS_BUSY:
      ast_str_set(&dst, 0, "%s", "BUSY");
      break;

   case AST_CALENDAR_BS_BUSY_TENTATIVE:
      ast_str_set(&dst, 0, "%s", "TENTATIVE");
      break;

   default:
      ast_str_set(&dst, 0, "%s", "FREE");
   }

   return dst;
}

static int fetch_response_reader(void *data, const char *block, size_t len)
{
   struct ast_str **response = data;
   unsigned char *tmp;

   if (!(tmp = ast_malloc(len + 1))) {
      return -1;
   }
   memcpy(tmp, block, len);
   tmp[len] = '\0';
   ast_str_append(response, 0, "%s", tmp);
   ast_free(tmp);

   return 0;
}

static int auth_credentials(void *userdata, const char *realm, int attempts, char *username, char *secret)
{
   struct exchangecal_pvt *pvt = userdata;

   if (attempts > 1) {
      ast_log(LOG_WARNING, "Invalid username or password for Exchange calendar '%s'\n", pvt->owner->name);
      return -1;
   }

   ne_strnzcpy(username, pvt->user, NE_ABUFSIZ);
   ne_strnzcpy(secret, pvt->secret, NE_ABUFSIZ);

   return 0;
}

static struct ast_str *exchangecal_request(struct exchangecal_pvt *pvt, const char *method, struct ast_str *req_body, struct ast_str *subdir)
{
   struct ast_str *response;
   ne_request *req;
   int ret;
   char buf[1000];

   if (!pvt) {
      ast_log(LOG_ERROR, "There is no private!\n");
      return NULL;
   }

   if (!(response = ast_str_create(512))) {
      ast_log(LOG_ERROR, "Could not allocate memory for response.\n");
      return NULL;
   }

   snprintf(buf, sizeof(buf), "%s%s", pvt->uri.path, subdir ? ast_str_buffer(subdir) : "");

   req = ne_request_create(pvt->session, method, buf);
   ne_add_response_body_reader(req, ne_accept_2xx, fetch_response_reader, &response);
   ne_set_request_body_buffer(req, ast_str_buffer(req_body), ast_str_strlen(req_body));
   ne_add_request_header(req, "Content-type", "text/xml");

   ret = ne_request_dispatch(req);
   ne_request_destroy(req);

   if (ret != NE_OK || !ast_str_strlen(response)) {
      ast_log(LOG_WARNING, "Unknown response to CalDAV calendar %s, request %s to %s: %s\n", pvt->owner->name, method, pvt->url, ne_get_error(pvt->session));
      ast_free(response);
      return NULL;
   }

   return response;
}

static int exchangecal_write_event(struct ast_calendar_event *event)
{
   struct ast_str *body = NULL, *response = NULL, *subdir = NULL;
   struct ast_str *uid = NULL, *summary = NULL, *description = NULL, *organizer = NULL,
                  *location = NULL, *start = NULL, *end = NULL, *busystate = NULL;
   int ret = -1;

   if (!event) {
      ast_log(LOG_WARNING, "No event passed!\n");
      return -1;
   }

   if (!(event->start && event->end)) {
      ast_log(LOG_WARNING, "The event must contain a start and an end\n");
      return -1;
   }
   if (!(body = ast_str_create(512)) ||
      !(subdir = ast_str_create(32))) {
      ast_log(LOG_ERROR, "Could not allocate memory for request!\n");
      goto write_cleanup;
   }

   if (!(uid = ast_str_create(32)) ||
      !(summary = ast_str_create(32)) ||
      !(description = ast_str_create(32)) ||
      !(organizer = ast_str_create(32)) ||
      !(location = ast_str_create(32)) ||
      !(start = ast_str_create(32)) ||
      !(end = ast_str_create(32)) ||
      !(busystate = ast_str_create(32))) {
      ast_log(LOG_ERROR, "Unable to allocate memory for request values\n");
      goto write_cleanup;
   }

   if (ast_strlen_zero(event->uid)) {
      uid = generate_exchange_uuid(uid);
   } else {
      ast_str_set(&uid, 36, "%s", event->uid);
   }

   if (!is_valid_uuid(uid)) {
      ast_log(LOG_WARNING, "An invalid uid was provided, you may leave this field blank to have one generated for you\n");
      goto write_cleanup;
   }

   summary = xml_encode_str(summary, event->summary);
   description = xml_encode_str(description, event->description);
   organizer = xml_encode_str(organizer, event->organizer);
   location = xml_encode_str(location, event->location);
   start = epoch_to_exchange_time(start, event->start);
   end = epoch_to_exchange_time(end, event->end);
   busystate = bs_to_exchange_bs(busystate, event->busy_state);

   ast_str_append(&body, 0,
      "<?xml version=\"1.0\"?>\n"
      "<a:propertyupdate\n"
      "  xmlns:a=\"DAV:\"\n"
      "  xmlns:e=\"http://schemas.microsoft.com/exchange/\"\n"
      "  xmlns:mapi=\"http://schemas.microsoft.com/mapi/\"\n"
      "  xmlns:mapit=\"http://schemas.microsoft.com/mapi/proptag/\"\n"
      "  xmlns:x=\"xml:\" xmlns:cal=\"urn:schemas:calendar:\"\n"
      "  xmlns:dt=\"uuid:%s/\"\n" /* uid */
      "  xmlns:header=\"urn:schemas:mailheader:\"\n"
      "  xmlns:mail=\"urn:schemas:httpmail:\"\n"
      ">\n"
      "    <a:set>\n"
      "      <a:prop>\n"
      "        <a:contentclass>urn:content-classes:appointment</a:contentclass>\n"
      "        <e:outlookmessageclass>IPM.Appointment</e:outlookmessageclass>\n"
      "        <mail:subject>%s</mail:subject>\n" /* summary */
      "        <mail:description>%s</mail:description>\n" /* description */
      "        <header:to>%s</header:to>\n" /* organizer */
      "        <cal:location>%s</cal:location>\n" /* location */
      "        <cal:dtstart dt:dt=\"dateTime.tz\">%s</cal:dtstart>\n" /* start */
      "        <cal:dtend dt:dt=\"dateTime.tz\">%s</cal:dtend>\n" /* end */
      "        <cal:instancetype dt:dt=\"int\">0</cal:instancetype>\n"
      "        <cal:busystatus>%s</cal:busystatus>\n" /* busy_state (BUSY, FREE, BUSY_TENTATIVE) */
      "        <cal:meetingstatus>CONFIRMED</cal:meetingstatus>\n"
      "        <cal:alldayevent dt:dt=\"boolean\">0</cal:alldayevent>\n" /* XXX need to add event support for all day events */
      "        <cal:responserequested dt:dt=\"boolean\">0</cal:responserequested>\n"
      "        <mapi:finvited dt:dt=\"boolean\">1</mapi:finvited>\n"
      "      </a:prop>\n"
      "    </a:set>\n"
      "</a:propertyupdate>\n",
      ast_str_buffer(uid), ast_str_buffer(summary), ast_str_buffer(description), ast_str_buffer(organizer), ast_str_buffer(location), ast_str_buffer(start), ast_str_buffer(end), ast_str_buffer(busystate));
   ast_verb(0, "\n\n%s\n\n", ast_str_buffer(body));
   ast_str_set(&subdir, 0, "/Calendar/%s.eml", ast_str_buffer(uid));

   if ((response = exchangecal_request(event->owner->tech_pvt, "PROPPATCH", body, subdir))) {
      ret = 0;
   }

write_cleanup:
   if (uid) {
      ast_free(uid);
   }
   if (summary) {
      ast_free(summary);
   }
   if (description) {
      ast_free(description);
   }
   if (organizer) {
      ast_free(organizer);
   }
   if (location) {
      ast_free(location);
   }
   if (start) {
      ast_free(start);
   }
   if (end) {
      ast_free(end);
   }
   if (busystate) {
      ast_free(busystate);
   }
   if (body) {
      ast_free(body);
   }
   if (response) {
      ast_free(response);
   }
   if (subdir) {
      ast_free(subdir);
   }

   return ret;
}


static struct ast_str *exchangecal_get_events_between(struct exchangecal_pvt *pvt, time_t start_time, time_t end_time)
{
   struct ast_str *body, *response;
   char start[80], end[80];
   struct timeval tv = {0,};
   struct ast_tm tm;

   tv.tv_sec = start_time;
   ast_localtime(&tv, &tm, "UTC");
   ast_strftime(start, sizeof(start), "%Y/%m/%d %T", &tm);

   tv.tv_sec = end_time;
   ast_localtime(&tv, &tm, "UTC");
   ast_strftime(end, sizeof(end), "%Y/%m/%d %T", &tm);

   if (!(body = ast_str_create(512))) {
      ast_log(LOG_ERROR, "Could not allocate memory for body of request!\n");
      return NULL;
   }

   ast_str_append(&body, 0,
      "<?xml version=\"1.0\"?>\n"
      "<g:searchrequest xmlns:g=\"DAV:\">\n"
      "        <g:sql> SELECT \"urn:schemas:calendar:location\", \"urn:schemas:httpmail:subject\",\n"
      "                \"urn:schemas:calendar:dtstart\", \"urn:schemas:calendar:dtend\",\n"
      "                \"urn:schemas:calendar:busystatus\", \"urn:schemas:calendar:instancetype\",\n"
      "                \"urn:schemas:calendar:uid\", \"urn:schemas:httpmail:textdescription\",\n"
      "                \"urn:schemas:calendar:organizer\", \"urn:schemas:calendar:reminderoffset\"\n"
      "                FROM Scope('SHALLOW TRAVERSAL OF \"%s/Calendar\"')\n"
      "                WHERE NOT \"urn:schemas:calendar:instancetype\" = 1\n"
      "                AND \"DAV:contentclass\" = 'urn:content-classes:appointment'\n"
      "                AND NOT (\"urn:schemas:calendar:dtend\" &lt; '%s'\n"
      "                OR \"urn:schemas:calendar:dtstart\" &gt; '%s')\n"
      "                ORDER BY \"urn:schemas:calendar:dtstart\" ASC\n"
      "         </g:sql>\n"
      "</g:searchrequest>\n", pvt->url, start, end);

   ast_debug(5, "Request:\n%s\n", ast_str_buffer(body));
   response = exchangecal_request(pvt, "SEARCH", body, NULL);
   ast_debug(5, "Response:\n%s\n", ast_str_buffer(response));
   ast_free(body);

   return response;
}

static int update_exchangecal(struct exchangecal_pvt *pvt)
{
   struct xmlstate state;
   struct timeval now = ast_tvnow();
   time_t start, end;
   struct ast_str *response;
   iksparser *p;

   state.pvt = pvt;
   start = now.tv_sec;
   end = now.tv_sec + 60 * pvt->owner->timeframe;
   if (!(response = exchangecal_get_events_between(pvt, start, end))) {
      return -1;
   }

   p = iks_sax_new(&state, parse_tag, parse_cdata);
   iks_parse(p, ast_str_buffer(response), ast_str_strlen(response), 1);
   ast_calendar_merge_events(pvt->owner, pvt->events);
   ast_free(response);

   return 0;
}

static void *exchangecal_load_calendar(void *void_data)
{
   struct exchangecal_pvt *pvt;
   const struct ast_config *cfg;
   struct ast_variable *v;
   struct ast_calendar *cal = void_data;
   ast_mutex_t refreshlock;

   if (!(cal && (cfg = ast_calendar_config_acquire()))) {
      ast_log(LOG_ERROR, "You must enable calendar support for res_exchangecal to load\n");
      return NULL;
   }

   if (ao2_trylock(cal)) {
      if (cal->unloading) {
         ast_log(LOG_WARNING, "Unloading module, load_calendar cancelled.\n");
      } else {
         ast_log(LOG_WARNING, "Could not lock calendar, aborting!\n");
      }
      ast_calendar_config_release();
      return NULL;
   }

   if (!(pvt = ao2_alloc(sizeof(*pvt), exchangecal_destructor))) {
      ast_log(LOG_ERROR, "Could not allocate exchangecal_pvt structure for calendar: %s\n", cal->name);
      ast_calendar_config_release();
      return NULL;
   }

   pvt->owner = cal;

   if (!(pvt->events = ast_calendar_event_container_alloc())) {
      ast_log(LOG_ERROR, "Could not allocate space for fetching events for calendar: %s\n", cal->name);
      pvt = unref_exchangecal(pvt);
      ao2_unlock(cal);
      ast_calendar_config_release();
      return NULL;
   }

   if (ast_string_field_init(pvt, 32)) {
      ast_log(LOG_ERROR, "Couldn't allocate string field space for calendar: %s\n", cal->name);
      pvt = unref_exchangecal(pvt);
      ao2_unlock(cal);
      ast_calendar_config_release();
      return NULL;
   }

   for (v = ast_variable_browse(cfg, cal->name); v; v = v->next) {
      if (!strcasecmp(v->name, "url")) {
         ast_string_field_set(pvt, url, v->value);
      } else if (!strcasecmp(v->name, "user")) {
         ast_string_field_set(pvt, user, v->value);
      } else if (!strcasecmp(v->name, "secret")) {
         ast_string_field_set(pvt, secret, v->value);
      }
   }

   ast_calendar_config_release();

   if (ast_strlen_zero(pvt->url)) {
      ast_log(LOG_WARNING, "No URL was specified for Exchange calendar '%s' - skipping.\n", cal->name);
      pvt = unref_exchangecal(pvt);
      ao2_unlock(cal);
      return NULL;
   }

   if (ne_uri_parse(pvt->url, &pvt->uri) || pvt->uri.host == NULL || pvt->uri.path == NULL) {
      ast_log(LOG_WARNING, "Could not parse url '%s' for Exchange calendar '%s' - skipping.\n", pvt->url, cal->name);
      pvt = unref_exchangecal(pvt);
      ao2_unlock(cal);
      return NULL;
   }

   if (pvt->uri.scheme == NULL) {
      pvt->uri.scheme = "http";
   }

   if (pvt->uri.port == 0) {
      pvt->uri.port = ne_uri_defaultport(pvt->uri.scheme);
   }

   pvt->session = ne_session_create(pvt->uri.scheme, pvt->uri.host, pvt->uri.port);
   ne_redirect_register(pvt->session);
   ne_set_server_auth(pvt->session, auth_credentials, pvt);
   if (!strcasecmp(pvt->uri.scheme, "https")) {
      ne_ssl_trust_default_ca(pvt->session);
   }

   cal->tech_pvt = pvt;

   ast_mutex_init(&refreshlock);

   /* Load it the first time */
   update_exchangecal(pvt);

   ao2_unlock(cal);

   /* The only writing from another thread will be if unload is true */
   for (;;) {
      struct timeval tv = ast_tvnow();
      struct timespec ts = {0,};

      ts.tv_sec = tv.tv_sec + (60 * pvt->owner->refresh);

      ast_mutex_lock(&refreshlock);
      while (!pvt->owner->unloading) {
         if (ast_cond_timedwait(&pvt->owner->unload, &refreshlock, &ts) == ETIMEDOUT) {
            break;
         }
      }
      ast_mutex_unlock(&refreshlock);

      if (pvt->owner->unloading) {
         ast_debug(10, "Skipping refresh since we got a shutdown signal\n");
         return NULL;
      }

      ast_debug(10, "Refreshing after %d minute timeout\n", pvt->owner->refresh);

      update_exchangecal(pvt);
   }

   return NULL;
}

static int load_module(void)
{
   ne_sock_init();
   if (ast_calendar_register(&exchangecal_tech)) {
      ne_sock_exit();
      return AST_MODULE_LOAD_DECLINE;
   }

   return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   ast_calendar_unregister(&exchangecal_tech);
   ne_sock_exit();
   return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Asterisk MS Exchange Calendar Integration",
      .load = load_module,
      .unload = unload_module,
      .load_pri = AST_MODPRI_DEVSTATE_PLUGIN,
   );