Mon May 14 04:42:58 2007

Asterisk developer's documentation


devicestate.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2006, Digium, Inc.
00005  *
00006  * Mark Spencer <markster@digium.com>
00007  *
00008  * See http://www.asterisk.org for more information about
00009  * the Asterisk project. Please do not directly contact
00010  * any of the maintainers of this project for assistance;
00011  * the project provides a web site, mailing lists and IRC
00012  * channels for your use.
00013  *
00014  * This program is free software, distributed under the terms of
00015  * the GNU General Public License Version 2. See the LICENSE file
00016  * at the top of the source tree.
00017  */
00018 
00019 /*! \file
00020  *
00021  * \brief Device state management
00022  *
00023  *
00024  * \author Mark Spencer <markster@digium.com> 
00025  *
00026  * \arg \ref AstExtState
00027  */
00028 /*! \page AstExtState Extension and device states in Asterisk
00029  *
00030  * Asterisk has an internal system that reports states
00031  * for an extension. By using the dialplan priority -1,
00032  * also called a \b hint, a connection can be made from an
00033  * extension to one or many devices. The state of the extension
00034  * now depends on the combined state of the devices.
00035  *
00036  * The device state is basically based on the current calls.
00037  * If the devicestate engine can find a call from or to the
00038  * device, it's in use.
00039  * 
00040  * Some channel drivers implement a callback function for 
00041  * a better level of reporting device states. The SIP channel
00042  * has a complicated system for this, which is improved 
00043  * by adding call limits to the configuration.
00044  * 
00045  * Functions that want to check the status of an extension
00046  * register themself as a \b watcher.
00047  * Watchers in this system can subscribe either to all extensions
00048  * or just a specific extensions.
00049  *
00050  * For non-device related states, there's an API called
00051  * devicestateproviders. This is an extendable system for
00052  * delivering state information from outside sources or
00053  * functions within Asterisk. Currently we have providers
00054  * for app_meetme.c - the conference bridge - and call
00055  * parking (metermaids).
00056  *
00057  * There are manly three subscribers to extension states 
00058  * within Asterisk:
00059  * - AMI, the manager interface
00060  * - app_queue.c - the Queue dialplan application
00061  * - SIP subscriptions, a.k.a. "blinking lamps" or 
00062  *   "buddy lists"
00063  *
00064  * The CLI command "show hints" show last known state
00065  *
00066  * \note None of these handle user states, like an IM presense
00067  * system. res_jabber.c can subscribe and watch such states
00068  * in jabber/xmpp based systems.
00069  *
00070  * \section AstDevStateArch Architecture for devicestates
00071  *
00072  * When a channel driver or asterisk app changes state for 
00073  * a watched object, it alerts the core. The core queues
00074  * a change. When the change is processed, there's a query
00075  * sent to the channel driver/provider if there's a function
00076  * to handle that, otherwise a channel walk is issued to find
00077  * a channel that involves the object.
00078  * 
00079  * The changes are queued and processed by a separate thread.
00080  * This thread calls the watchers subscribing to status 
00081  * changes for the object. For manager, this results 
00082  * in events. For SIP, NOTIFY requests.
00083  *
00084  * - Device states
00085  *    \arg \ref devicestate.c 
00086  *    \arg \ref devicestate.h 
00087  *
00088  * \section AstExtStateArch Architecture for extension states
00089  * 
00090  * Hints are connected to extension. If an extension changes state
00091  * it checks the hint devices. If there is a hint, the callbacks into
00092  * device states are checked. The aggregated state is set for the hint
00093  * and reported back.
00094  *
00095  * - Extension states
00096  *    \arg \ref enum ast_extension_states
00097  *    \arg \ref pbx.c 
00098  *    \arg \ref pbx.h 
00099  * - Structures
00100  *    - \ref struct ast_state_cb  Callbacks for watchers
00101  *    - Callback ast_state_cb_type
00102  *    - \ref struct ast_hint
00103  *    - Functions
00104  *    - ast_extension_state_add()
00105  *    - ast_extension_state_del()
00106  *    - ast_get_hint()
00107  * 
00108  */
00109 
00110 #include "asterisk.h"
00111 
00112 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
00113 
00114 #include <sys/types.h>
00115 #include <unistd.h>
00116 #include <stdlib.h>
00117 #include <string.h>
00118 #include <stdio.h>
00119 
00120 #include "asterisk/channel.h"
00121 #include "asterisk/utils.h"
00122 #include "asterisk/lock.h"
00123 #include "asterisk/linkedlists.h"
00124 #include "asterisk/logger.h"
00125 #include "asterisk/devicestate.h"
00126 #include "asterisk/pbx.h"
00127 #include "asterisk/app.h"
00128 #include "asterisk/options.h"
00129 
00130 /*! \brief Device state strings for printing */
00131 static const char *devstatestring[] = {
00132    /* 0 AST_DEVICE_UNKNOWN */ "Unknown",  /*!< Valid, but unknown state */
00133    /* 1 AST_DEVICE_NOT_INUSE */  "Not in use",  /*!< Not used */
00134    /* 2 AST_DEVICE IN USE */  "In use",   /*!< In use */
00135    /* 3 AST_DEVICE_BUSY */    "Busy",     /*!< Busy */
00136    /* 4 AST_DEVICE_INVALID */ "Invalid",  /*!< Invalid - not known to Asterisk */
00137    /* 5 AST_DEVICE_UNAVAILABLE */   "Unavailable", /*!< Unavailable (not registred) */
00138    /* 6 AST_DEVICE_RINGING */ "Ringing",  /*!< Ring, ring, ring */
00139    /* 7 AST_DEVICE_RINGINUSE */  "Ring+Inuse",  /*!< Ring and in use */
00140    /* 8 AST_DEVICE_ONHOLD */  "On Hold"   /*!< On Hold */
00141 };
00142 
00143 /*! \brief  A device state provider (not a channel) */
00144 struct devstate_prov {
00145    char label[40];
00146    ast_devstate_prov_cb_type callback;
00147    AST_LIST_ENTRY(devstate_prov) list;
00148 };
00149 
00150 /*! \brief A list of providers */
00151 static AST_LIST_HEAD_STATIC(devstate_provs, devstate_prov);
00152 
00153 /*! \brief  A device state watcher (callback) */
00154 struct devstate_cb {
00155    void *data;
00156    ast_devstate_cb_type callback;   /*!< Where to report when state changes */
00157    AST_LIST_ENTRY(devstate_cb) list;
00158 };
00159 
00160 /*! \brief A device state watcher list */
00161 static AST_LIST_HEAD_STATIC(devstate_cbs, devstate_cb);
00162 
00163 struct state_change {
00164    AST_LIST_ENTRY(state_change) list;
00165    char device[1];
00166 };
00167 
00168 /*! \brief The state change queue. State changes are queued
00169    for processing by a separate thread */
00170 static AST_LIST_HEAD_STATIC(state_changes, state_change);
00171 
00172 /*! \brief The device state change notification thread */
00173 static pthread_t change_thread = AST_PTHREADT_NULL;
00174 
00175 /*! \brief Flag for the queue */
00176 static ast_cond_t change_pending;
00177 
00178 /* Forward declarations */
00179 static int getproviderstate(const char *provider, const char *address);
00180 
00181 /*! \brief Find devicestate as text message for output */
00182 const char *devstate2str(int devstate) 
00183 {
00184    return devstatestring[devstate];
00185 }
00186 
00187 /*! \brief Find out if device is active in a call or not 
00188    \note find channels with the device's name in it
00189    This function is only used for channels that does not implement 
00190    devicestate natively
00191 */
00192 int ast_parse_device_state(const char *device)
00193 {
00194    struct ast_channel *chan;
00195    char match[AST_CHANNEL_NAME];
00196    int res;
00197 
00198    ast_copy_string(match, device, sizeof(match)-1);
00199    strcat(match, "-");
00200    chan = ast_get_channel_by_name_prefix_locked(match, strlen(match));
00201 
00202    if (!chan)
00203       return AST_DEVICE_UNKNOWN;
00204 
00205    if (chan->_state == AST_STATE_RINGING)
00206       res = AST_DEVICE_RINGING;
00207    else
00208       res = AST_DEVICE_INUSE;
00209    
00210    ast_channel_unlock(chan);
00211 
00212    return res;
00213 }
00214 
00215 /*! \brief Check device state through channel specific function or generic function */
00216 int ast_device_state(const char *device)
00217 {
00218    char *buf;
00219    char *number;
00220    const struct ast_channel_tech *chan_tech;
00221    int res = 0;
00222    /*! \brief Channel driver that provides device state */
00223    char *tech;
00224    /*! \brief Another provider of device state */
00225    char *provider = NULL;
00226    
00227    buf = ast_strdupa(device);
00228    tech = strsep(&buf, "/");
00229    number = buf;
00230    if (!number) {
00231       provider = strsep(&tech, ":");
00232       if (!provider)
00233          return AST_DEVICE_INVALID;
00234       /* We have a provider */
00235       number = tech;
00236       tech = NULL;
00237    }
00238 
00239    if (provider)  {
00240       if(option_debug > 2)
00241          ast_log(LOG_DEBUG, "Checking if I can find provider for \"%s\" - number: %s\n", provider, number);
00242       return getproviderstate(provider, number);
00243    }
00244    if (option_debug > 3)
00245       ast_log(LOG_DEBUG, "No provider found, checking channel drivers for %s - %s\n", tech, number);
00246 
00247    chan_tech = ast_get_channel_tech(tech);
00248    if (!chan_tech)
00249       return AST_DEVICE_INVALID;
00250 
00251    if (!chan_tech->devicestate)  /* Does the channel driver support device state notification? */
00252       return ast_parse_device_state(device); /* No, try the generic function */
00253    else {
00254       res = chan_tech->devicestate(number);  /* Ask the channel driver for device state */
00255       if (res == AST_DEVICE_UNKNOWN) {
00256          res = ast_parse_device_state(device);
00257          /* at this point we know the device exists, but the channel driver
00258             could not give us a state; if there is no channel state available,
00259             it must be 'not in use'
00260          */
00261          if (res == AST_DEVICE_UNKNOWN)
00262             res = AST_DEVICE_NOT_INUSE;
00263          return res;
00264       } else
00265          return res;
00266    }
00267 }
00268 
00269 /*! \brief Add device state provider */
00270 int ast_devstate_prov_add(const char *label, ast_devstate_prov_cb_type callback)
00271 {
00272    struct devstate_prov *devprov;
00273 
00274    if (!callback || !(devprov = ast_calloc(1, sizeof(*devprov))))
00275       return -1;
00276 
00277    devprov->callback = callback;
00278    ast_copy_string(devprov->label, label, sizeof(devprov->label));
00279 
00280    AST_LIST_LOCK(&devstate_provs);
00281    AST_LIST_INSERT_HEAD(&devstate_provs, devprov, list);
00282    AST_LIST_UNLOCK(&devstate_provs);
00283 
00284    return 0;
00285 }
00286 
00287 /*! \brief Remove device state provider */
00288 void ast_devstate_prov_del(const char *label)
00289 {
00290    struct devstate_prov *devcb;
00291 
00292    AST_LIST_LOCK(&devstate_provs);
00293    AST_LIST_TRAVERSE_SAFE_BEGIN(&devstate_provs, devcb, list) {
00294       if (!strcasecmp(devcb->label, label)) {
00295          AST_LIST_REMOVE_CURRENT(&devstate_provs, list);
00296          free(devcb);
00297          break;
00298       }
00299    }
00300    AST_LIST_TRAVERSE_SAFE_END;
00301    AST_LIST_UNLOCK(&devstate_provs);
00302 }
00303 
00304 /*! \brief Get provider device state */
00305 static int getproviderstate(const char *provider, const char *address)
00306 {
00307    struct devstate_prov *devprov;
00308    int res = AST_DEVICE_INVALID;
00309 
00310 
00311    AST_LIST_LOCK(&devstate_provs);
00312    AST_LIST_TRAVERSE_SAFE_BEGIN(&devstate_provs, devprov, list) {
00313       if(option_debug > 4)
00314          ast_log(LOG_DEBUG, "Checking provider %s with %s\n", devprov->label, provider);
00315 
00316       if (!strcasecmp(devprov->label, provider)) {
00317          res = devprov->callback(address);
00318          break;
00319       }
00320    }
00321    AST_LIST_TRAVERSE_SAFE_END;
00322    AST_LIST_UNLOCK(&devstate_provs);
00323    return res;
00324 }
00325 
00326 /*! \brief Add device state watcher */
00327 int ast_devstate_add(ast_devstate_cb_type callback, void *data)
00328 {
00329    struct devstate_cb *devcb;
00330 
00331    if (!callback || !(devcb = ast_calloc(1, sizeof(*devcb))))
00332       return -1;
00333 
00334    devcb->data = data;
00335    devcb->callback = callback;
00336 
00337    AST_LIST_LOCK(&devstate_cbs);
00338    AST_LIST_INSERT_HEAD(&devstate_cbs, devcb, list);
00339    AST_LIST_UNLOCK(&devstate_cbs);
00340 
00341    return 0;
00342 }
00343 
00344 /*! \brief Remove device state watcher */
00345 void ast_devstate_del(ast_devstate_cb_type callback, void *data)
00346 {
00347    struct devstate_cb *devcb;
00348 
00349    AST_LIST_LOCK(&devstate_cbs);
00350    AST_LIST_TRAVERSE_SAFE_BEGIN(&devstate_cbs, devcb, list) {
00351       if ((devcb->callback == callback) && (devcb->data == data)) {
00352          AST_LIST_REMOVE_CURRENT(&devstate_cbs, list);
00353          free(devcb);
00354          break;
00355       }
00356    }
00357    AST_LIST_TRAVERSE_SAFE_END;
00358    AST_LIST_UNLOCK(&devstate_cbs);
00359 }
00360 
00361 /*! \brief Notify callback watchers of change, and notify PBX core for hint updates
00362    Normally executed within a separate thread
00363 */
00364 static void do_state_change(const char *device)
00365 {
00366    int state;
00367    struct devstate_cb *devcb;
00368 
00369    state = ast_device_state(device);
00370    if (option_debug > 2)
00371       ast_log(LOG_DEBUG, "Changing state for %s - state %d (%s)\n", device, state, devstate2str(state));
00372 
00373    AST_LIST_LOCK(&devstate_cbs);
00374    AST_LIST_TRAVERSE(&devstate_cbs, devcb, list)
00375       devcb->callback(device, state, devcb->data);
00376    AST_LIST_UNLOCK(&devstate_cbs);
00377 
00378    ast_hint_state_changed(device);
00379 }
00380 
00381 static int __ast_device_state_changed_literal(char *buf)
00382 {
00383    char *device, *tmp;
00384    struct state_change *change;
00385 
00386    if (option_debug > 2)
00387       ast_log(LOG_DEBUG, "Notification of state change to be queued on device/channel %s\n", buf);
00388 
00389    device = buf;
00390    if ((tmp = strrchr(device, '-')))
00391       *tmp = '\0';
00392 
00393    
00394 
00395    if (change_thread == AST_PTHREADT_NULL || !(change = ast_calloc(1, sizeof(*change) + strlen(device)))) {
00396       /* we could not allocate a change struct, or */
00397       /* there is no background thread, so process the change now */
00398       do_state_change(device);
00399    } else {
00400       /* queue the change */
00401       strcpy(change->device, device);
00402       AST_LIST_LOCK(&state_changes);
00403       AST_LIST_INSERT_TAIL(&state_changes, change, list);
00404       if (AST_LIST_FIRST(&state_changes) == change)
00405          /* the list was empty, signal the thread */
00406          ast_cond_signal(&change_pending);
00407       AST_LIST_UNLOCK(&state_changes);
00408    }
00409 
00410    return 1;
00411 }
00412 
00413 int ast_device_state_changed_literal(const char *dev)
00414 {
00415    char *buf;
00416    buf = ast_strdupa(dev);
00417    return __ast_device_state_changed_literal(buf);
00418 }
00419 
00420 /*! \brief Accept change notification, add it to change queue */
00421 int ast_device_state_changed(const char *fmt, ...) 
00422 {
00423    char buf[AST_MAX_EXTENSION];
00424    va_list ap;
00425 
00426    va_start(ap, fmt);
00427    vsnprintf(buf, sizeof(buf), fmt, ap);
00428    va_end(ap);
00429    return __ast_device_state_changed_literal(buf);
00430 }
00431 
00432 /*! \brief Go through the dev state change queue and update changes in the dev state thread */
00433 static void *do_devstate_changes(void *data)
00434 {
00435    struct state_change *cur;
00436 
00437    AST_LIST_LOCK(&state_changes);
00438    for(;;) {
00439       /* the list lock will _always_ be held at this point in the loop */
00440       cur = AST_LIST_REMOVE_HEAD(&state_changes, list);
00441       if (cur) {
00442          /* we got an entry, so unlock the list while we process it */
00443          AST_LIST_UNLOCK(&state_changes);
00444          do_state_change(cur->device);
00445          free(cur);
00446          AST_LIST_LOCK(&state_changes);
00447       } else {
00448          /* there was no entry, so atomically unlock the list and wait for
00449             the condition to be signalled (returns with the lock held) */
00450          ast_cond_wait(&change_pending, &state_changes.lock);
00451       }
00452    }
00453 
00454    return NULL;
00455 }
00456 
00457 /*! \brief Initialize the device state engine in separate thread */
00458 int ast_device_state_engine_init(void)
00459 {
00460    ast_cond_init(&change_pending, NULL);
00461    if (ast_pthread_create_background(&change_thread, NULL, do_devstate_changes, NULL) < 0) {
00462       ast_log(LOG_ERROR, "Unable to start device state change thread.\n");
00463       return -1;
00464    }
00465 
00466    return 0;
00467 }

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