release/src/router/snmp/agent/object_monitor.c

   1 /*
   2  * object_monitor.c
   3  *
   4  * $Id: object_monitor.c,v 1.1.2.1 2004/06/20 21:54:09 nikki Exp $
   5  *
   6  * functions and data structures for cooperating code to monitor objects.
   7  *
   8  * WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
   9  * WARNING!                                                       WARNING!
  10  * WARNING!                                                       WARNING!
  11  * WARNING!         This code is under active development         WARNING!
  12  * WARNING!         and is subject to change at any time.         WARNING!
  13  * WARNING!                                                       WARNING!
  14  * WARNING!                                                       WARNING!
  15  * WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
  16  */
  17
  18 #include <net-snmp/net-snmp-config.h>
  19 #include <net-snmp/net-snmp-includes.h>
  20 #include <net-snmp/agent/net-snmp-agent-includes.h>
  21 #include <net-snmp/library/container.h>
  22 #include <net-snmp/library/snmp_assert.h>
  23
  24 #include "net-snmp/agent/object_monitor.h"
  25
  26 #if ! defined TRUE
  27 #  define TRUE 1
  28 #elsif TRUE != 1
  29 error "TRUE != 1"
  30 #endif
  31 /**************************************************************************
  32  *
  33  * Private data structures
  34  *
  35  **************************************************************************/
  36     /*
  37      * individual callback info for an object
  38      */
  39     typedef struct monitor_info_s {
  40
  41    /** priority for this callback */
  42     int             priority;
  43
  44    /** handler that registred to watch this object */
  45     netsnmp_mib_handler *watcher;
  46
  47    /** events that the watcher cares about */
  48     unsigned int    events;
  49
  50    /** callback function */
  51     netsnmp_object_monitor_callback *cb;
  52
  53    /** pointer to data from the watcher */
  54     void           *watcher_data;
  55
  56     struct monitor_info_s *next;
  57
  58 } monitor_info;
  59
  60 /*
  61  * list of watchers for a given object
  62  */
  63 typedef struct watcher_list_s {
  64
  65    /** netsnmp_index must be first! */
  66     netsnmp_index  monitored_object;
  67
  68     monitor_info   *head;
  69
  70 } watcher_list;
  71
  72 /*
  73  * temp holder for ordered list of callbacks
  74  */
  75 typedef struct callback_placeholder_s {
  76
  77     monitor_info   *mi;
  78     netsnmp_monitor_callback_header *cbh;
  79
  80     struct callback_placeholder_s *next;
  81
  82 } callback_placeholder;
  83
  84
  85 /**************************************************************************
  86  *
  87  *
  88  *
  89  **************************************************************************/
  90
  91 /*
  92  * local statics
  93  */
  94 static char     need_init = 1;
  95 static netsnmp_container *monitored_objects = NULL;
  96 static netsnmp_monitor_callback_header *callback_pending_list;
  97 static callback_placeholder *callback_ready_list;
  98
  99 /*
 100  * local prototypes
 101  */
 102 static watcher_list *find_watchers(oid * object, size_t oid_len);
 103 static int      insert_watcher(oid *, size_t, monitor_info *);
 104 static int      check_registered(unsigned int event, oid * o, int o_l,
 105                                  watcher_list ** pWl, monitor_info ** pMi);
 106 static void     move_pending_to_ready(void);
 107
 108
 109 /**************************************************************************
 110  *
 111  * Public functions
 112  *
 113  **************************************************************************/
 114
 115 /*
 116  *
 117  */
 118 void
 119 netsnmp_monitor_init(void)
 120 {
 121     if (!need_init)
 122         return;
 123
 124     callback_pending_list = NULL;
 125     callback_ready_list = NULL;
 126
 127     monitored_objects = netsnmp_container_get("object_monitor:binary_array");
 128     if (NULL != monitored_objects)
 129         need_init = 0;
 130     monitored_objects->compare = netsnmp_compare_netsnmp_index;
 131     monitored_objects->ncompare = netsnmp_ncompare_netsnmp_index;
 132
 133     return;
 134 }
 135
 136
 137 /**************************************************************************
 138  *
 139  * Registration functions
 140  *
 141  **************************************************************************/
 142
 143 /**
 144  * Register a callback for the specified object.
 145  *
 146  * @param object  pointer to the OID of the object to monitor.
 147  * @param oid_len length of the OID pointed to by object.
 148  * @param priority the priority to associate with this callback. A
 149  *                 higher number indicates higher priority. This
 150  *                 allows multiple callbacks for the same object to
 151  *                 coordinate the order in which they are called. If
 152  *                 two callbacks register with the same priority, the
 153  *                 order is undefined.
 154  * @param events  the events which the callback is interested in.
 155  * @param watcher_data pointer to data that will be supplied to the
 156  *                     callback method when an event occurs.
 157  * @param cb pointer to the function to be called when an event occurs.
 158  *
 159  * NOTE: the combination of the object, priority and watcher_data must
 160  *       be unique, as they are the parameters for unregistering a
 161  *       callback.
 162  *
 163  * @return SNMPERR_NOERR registration was successful
 164  * @return SNMPERR_MALLOC memory allocation failed
 165  * @return SNMPERR_VALUE the combination of the object, priority and
 166  *                        watcher_data is not unique.
 167  */
 168 int
 169 netsnmp_monitor_register(oid * object, size_t oid_len, int priority,
 170                          unsigned int events, void *watcher_data,
 171                          netsnmp_object_monitor_callback * cb)
 172 {
 173     monitor_info   *mi;
 174     int             rc;
 175
 176     netsnmp_assert(need_init == 0);
 177
 178     mi = calloc(1, sizeof(monitor_info));
 179     if (NULL == mi)
 180         return SNMPERR_MALLOC;
 181
 182     mi->priority = priority;
 183     mi->events = events;
 184     mi->watcher_data = watcher_data;
 185     mi->cb = cb;
 186
 187     rc = insert_watcher(object, oid_len, mi);
 188     if (rc != SNMPERR_SUCCESS)
 189         free(mi);
 190
 191     return rc;
 192 }
 193
 194 /**
 195  * Unregister a callback for the specified object.
 196  *
 197  * @param object  pointer to the OID of the object to monitor.
 198  * @param oid_len length of the OID pointed to by object.
 199  * @param priority the priority to associate with this callback.
 200  * @param watcher_data pointer to data that was supplied when the
 201  *                     callback was registered.
 202  * @param cb pointer to the function to be called when an event occurs.
 203  */
 204 int
 205 netsnmp_monitor_unregister(oid * object, size_t oid_len, int priority,
 206                            void *wd, netsnmp_object_monitor_callback * cb)
 207 {
 208     monitor_info   *mi, *last;
 209
 210     watcher_list   *wl = find_watchers(object, oid_len);
 211     if (NULL == wl)
 212         return SNMPERR_GENERR;
 213
 214     last = NULL;
 215     mi = wl->head;
 216     while (mi) {
 217         if ((mi->cb == cb) && (mi->priority == priority) &&
 218             (mi->watcher_data == wd))
 219             break;
 220         last = mi;
 221         mi = mi->next;
 222     }
 223
 224     if (NULL == mi)
 225         return SNMPERR_GENERR;
 226
 227     if (NULL == last)
 228         wl->head = mi->next;
 229     else
 230         last->next = mi->next;
 231
 232     if (NULL == wl->head) {
 233         CONTAINER_REMOVE(monitored_objects, wl);
 234         free(wl->monitored_object.oids);
 235         free(wl);
 236     }
 237
 238     free(mi);
 239
 240     return SNMPERR_SUCCESS;
 241 }
 242
 243 /**************************************************************************
 244  *
 245  * object monitor functions
 246  *
 247  **************************************************************************/
 248
 249 /**
 250  * Notifies the object monitor of an event.
 251  *
 252  * The object monitor funtions will save the callback information
 253  * until all varbinds in the current PDU have been processed and
 254  * a response has been sent. At that time, the object monitor will
 255  * determine if there are any watchers monitoring for the event.
 256  *
 257  * NOTE: the actual type of the callback structure may vary. The
 258  *       object monitor functions require only that the start of
 259  *       the structure match the netsnmp_monitor_callback_header
 260  *       structure. It is up to the watcher and monitored objects
 261  *       to agree on the format of other data.
 262  *
 263  * @param cbh pointer to a callback header.
 264  */
 265 void
 266 netsnmp_notify_monitor(netsnmp_monitor_callback_header * cbh)
 267 {
 268
 269     netsnmp_assert(need_init == 0);
 270
 271     /*
 272      * put processing of until response has been sent
 273      */
 274     cbh->private = callback_pending_list;
 275     callback_pending_list = cbh;
 276
 277     return;
 278 }
 279
 280 /**
 281  * check to see if a registration exists for an object/event combination
 282  *
 283  * @param event the event type to check for
 284  * @param o     the oid to check for
 285  * @param o_l   the length of the oid
 286  *
 287  * @returns TRUE(1) if a callback is registerd
 288  * @returns FALSE(0) if no callback is registered
 289  */
 290 int
 291 netsnmp_monitor_check_registered(int event, oid * o, int o_l)
 292 {
 293     return check_registered(event, o, o_l, NULL, NULL);
 294 }
 295
 296 /**
 297  * Process all pending callbacks
 298  *
 299  * NOTE: this method is not in the public header, as it should only be
 300  *       called in one place, in the agent.
 301  */
 302 void
 303 netsnmp_monitor_process_callbacks(void)
 304 {
 305     netsnmp_assert(need_init == 0);
 306     netsnmp_assert(NULL == callback_ready_list);
 307
 308     if (NULL == callback_pending_list) {
 309         DEBUGMSGT(("object_monitor", "No callbacks to process"));
 310         return;
 311     }
 312
 313     DEBUGMSG(("object_monitor", "Checking for registered " "callbacks."));
 314
 315     /*
 316      * move an pending notification which has a registered watcher to the
 317      * ready list. Free any other notifications.
 318      */
 319     move_pending_to_ready();
 320
 321     /*
 322      * call callbacks
 323      */
 324     while (callback_ready_list) {
 325
 326         /*
 327          * pop off the first item
 328          */
 329         callback_placeholder *current_cbr;
 330         current_cbr = callback_ready_list;
 331         callback_ready_list = current_cbr->next;
 332
 333         /*
 334          * setup, then call callback
 335          */
 336         current_cbr->cbh->watcher_data = current_cbr->mi->watcher_data;
 337         current_cbr->cbh->priority = current_cbr->mi->priority;
 338         (*current_cbr->mi->cb) (current_cbr->cbh);
 339
 340         /*
 341          * release memory (don't free current_cbr->mi)
 342          */
 343         if (--(current_cbr->cbh->refs) == 0) {
 344             free(current_cbr->cbh->monitored_object.oids);
 345             free(current_cbr->cbh);
 346         }
 347         free(current_cbr);
 348
 349         /*
 350          * check for any new pending notifications
 351          */
 352         move_pending_to_ready();
 353
 354     }
 355
 356     netsnmp_assert(callback_ready_list == NULL);
 357     netsnmp_assert(callback_pending_list = NULL);
 358
 359     return;
 360 }
 361
 362 /**************************************************************************
 363  *
 364  * COOPERATIVE helpers
 365  *
 366  **************************************************************************/
 367 /**
 368  * Notifies the object monitor of a cooperative event.
 369  *
 370  * This convenience function will build a
 371  * @link netsnmp_monitor_callback_header@endlink and call
 372  * @link netsnmp_notify_monitor@endlink.
 373  *
 374  * @param event the event type
 375  * @param object pointer to the oid of the object sending the event
 376  * @param len    the lenght of the oid
 377  * @param oid_steal set to true if the function may keep the pointer
 378  *                  to the memory (and free it later). set to false
 379  *                  to make the function allocate and copy the oid.
 380  * @param object_info pointer to data supplied by the object for
 381  *                    the callback. This pointer must remain valid,
 382  *                    will be provided to each callback registered
 383  *                    for the object (i.e. it will not be copied or
 384  *                    freed).
 385  */
 386 void
 387 netsnmp_notify_cooperative(int event, oid * o, size_t o_len, char o_steal,
 388                            void *object_info)
 389 {
 390     netsnmp_monitor_callback_cooperative *cbh;
 391
 392     netsnmp_assert(need_init == 0);
 393
 394     cbh = SNMP_MALLOC_TYPEDEF(netsnmp_monitor_callback_cooperative);
 395     if (NULL == cbh) {
 396         snmp_log(LOG_ERR, "could not allocate memory for "
 397                  "cooperative callback");
 398         return;
 399     }
 400
 401     cbh->hdr.event = event;
 402     cbh->hdr.object_info = object_info;
 403     cbh->hdr.monitored_object.len = o_len;
 404
 405     if (o_steal) {
 406         cbh->hdr.monitored_object.oids = o;
 407     } else {
 408         cbh->hdr.monitored_object.oids = snmp_duplicate_objid(o, o_len);
 409     }
 410
 411     netsnmp_notify_monitor((netsnmp_monitor_callback_header *) cbh);
 412 }
 413
 414 #ifndef DOXYGEN_SHOULD_IGNORE_THIS
 415 /*************************************************************************
 416  *************************************************************************
 417  *************************************************************************
 418  * WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
 419  * WARNING!                                                       WARNING!
 420  * WARNING!                                                       WARNING!
 421  * WARNING!         This code is under active development         WARNING!
 422  * WARNING!         and is subject to change at any time.         WARNING!
 423  * WARNING!                                                       WARNING!
 424  * WARNING!                                                       WARNING!
 425  * WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
 426  *************************************************************************
 427  *************************************************************************
 428  *************************************************************************
 429  */
 430 static watcher_list *
 431 find_watchers(oid * object, size_t oid_len)
 432 {
 433     netsnmp_index oah;
 434
 435     oah.oids = object;
 436     oah.len = oid_len;
 437
 438     return (watcher_list *)CONTAINER_FIND(monitored_objects, &oah);
 439 }
 440
 441 static int
 442 insert_watcher(oid * object, size_t oid_len, monitor_info * mi)
 443 {
 444     watcher_list   *wl = find_watchers(object, oid_len);
 445     int             rc = SNMPERR_SUCCESS;
 446
 447     if (NULL != wl) {
 448
 449         monitor_info   *last, *current;
 450
 451         netsnmp_assert(wl->head != NULL);
 452
 453         last = NULL;
 454         current = wl->head;
 455         while (current) {
 456             if (mi->priority == current->priority) {
 457                 /*
 458                  * check for duplicate
 459                  */
 460                 if (mi->watcher_data == current->watcher_data)
 461                     return SNMPERR_VALUE; /** duplicate! */
 462             } else if (mi->priority > current->priority) {
 463                 break;
 464             }
 465             last = current;
 466             current = current->next;
 467         }
 468         if (NULL == last) {
 469             mi->next = wl->head;
 470             wl->head = mi;
 471         } else {
 472             mi->next = last->next;
 473             last->next = mi;
 474         }
 475     } else {
 476
 477         /*
 478          * first watcher for this oid; set up list
 479          */
 480         wl = SNMP_MALLOC_TYPEDEF(watcher_list);
 481         if (NULL == wl)
 482             return SNMPERR_MALLOC;
 483
 484         /*
 485          * copy index oid
 486          */
 487         wl->monitored_object.len = oid_len;
 488         wl->monitored_object.oids = malloc(sizeof(oid) * oid_len);
 489         if (NULL == wl->monitored_object.oids) {
 490             free(wl);
 491             return SNMPERR_MALLOC;
 492         }
 493         memcpy(wl->monitored_object.oids, object, sizeof(oid) * oid_len);
 494
 495         /*
 496          * add watcher, and insert into array
 497          */
 498         wl->head = mi;
 499         mi->next = NULL;
 500         rc = CONTAINER_INSERT(monitored_objects, wl);
 501         if (rc) {
 502             free(wl->monitored_object.oids);
 503             free(wl);
 504             return rc;
 505         }
 506     }
 507     return rc;
 508 }
 509
 510 /**
 511  * @internal
 512  * check to see if a registration exists for an object/event combination
 513  *
 514  * @param event the event type to check for
 515  * @param o     the oid to check for
 516  * @param o_l   the length of the oid
 517  * @param pWl   if a pointer to a watcher_list pointer is supplied,
 518  *              upon return the watcher list pointer will be set to
 519  *              the watcher list for the object, or NULL if there are
 520  *              no watchers for the object.
 521  * @param pMi   if a pointer to a monitor_info pointer is supplied,
 522  *              upon return the pointer will be set to the first
 523  *              monitor_info object for the specified event.
 524  *
 525  * @returns TRUE(1) if a callback is registerd
 526  * @returns FALSE(0) if no callback is registered
 527  */
 528 static int
 529 check_registered(unsigned int event, oid * o, int o_l,
 530                  watcher_list ** pWl, monitor_info ** pMi)
 531 {
 532     watcher_list   *wl;
 533     monitor_info   *mi;
 534
 535     netsnmp_assert(need_init == 0);
 536
 537     /*
 538      * check to see if anyone has registered for callbacks
 539      * for the object.
 540      */
 541     wl = find_watchers(o, o_l);
 542     if (pWl)
 543         *pWl = wl;
 544     if (NULL == wl)
 545         return 0;
 546
 547     /*
 548      * check if any watchers are watching for this specific event
 549      */
 550     for (mi = wl->head; mi; mi = mi->next) {
 551
 552         if (mi->events & event) {
 553             if (pMi)
 554                 *pMi = mi;
 555             return TRUE;
 556         }
 557     }
 558
 559     return 0;
 560 }
 561
 562 /**
 563  *@internal
 564  */
 565 NETSNMP_INLINE void
 566 insert_ready(callback_placeholder * new_cbr)
 567 {
 568     callback_placeholder *current_cbr, *last_cbr;
 569
 570     /*
 571      * insert in callback ready list
 572      */
 573     last_cbr = NULL;
 574     current_cbr = callback_ready_list;
 575     while (current_cbr) {
 576
 577         if (new_cbr->mi->priority > current_cbr->mi->priority)
 578             break;
 579
 580         last_cbr = current_cbr;
 581         current_cbr = current_cbr->next;
 582     }
 583     if (NULL == last_cbr) {
 584         new_cbr->next = callback_ready_list;
 585         callback_ready_list = new_cbr;
 586     } else {
 587         new_cbr->next = last_cbr->next;
 588         last_cbr->next = new_cbr;
 589     }
 590 }
 591
 592 /**
 593  *@internal
 594  *
 595  * move an pending notification which has a registered watcher to the
 596  * ready list. Free any other notifications.
 597  */
 598 static void
 599 move_pending_to_ready(void)
 600 {
 601     /*
 602      * check to see if anyone has registered for callbacks
 603      * for each object.
 604      */
 605     while (callback_pending_list) {
 606
 607         watcher_list   *wl;
 608         monitor_info   *mi;
 609         netsnmp_monitor_callback_header *cbp;
 610
 611         /*
 612          * pop off first item
 613          */
 614         cbp = callback_pending_list;
 615         callback_pending_list = cbp->private; /** next */
 616
 617         if (0 == check_registered(cbp->event, cbp->monitored_object.oids,
 618                                   cbp->monitored_object.len, &wl,
 619                                   &mi)) {
 620
 621             /*
 622              * nobody watching, free memory
 623              */
 624             free(cbp);
 625             continue;
 626         }
 627
 628         /*
 629          * Found at least one; check the rest of the list and
 630          * save callback for processing
 631          */
 632         for (; mi; mi = mi->next) {
 633
 634             callback_placeholder *new_cbr;
 635
 636             if (0 == (mi->events & cbp->event))
 637                 continue;
 638
 639             /*
 640              * create temprory placeholder.
 641              *
 642              * I hate to allocate memory here, as I'd like this code to
 643              * be fast and lean. But I don't have time to think of another
 644              * solution os this will have to do for now.
 645              *
 646              * I need a list of monitor_info (mi) objects for each
 647              * callback which has registered for the event, and want
 648              * that list sorted by the priority required by the watcher.
 649              */
 650             new_cbr = SNMP_MALLOC_TYPEDEF(callback_placeholder);
 651             if (NULL == new_cbr) {
 652                 snmp_log(LOG_ERR, "malloc failed, callback dropped.");
 653                 continue;
 654             }
 655             new_cbr->cbh = cbp;
 656             new_cbr->mi = mi;
 657             ++cbp->refs;
 658
 659             /*
 660              * insert in callback ready list
 661              */
 662             insert_ready(new_cbr);
 663
 664         } /** end mi loop */
 665     } /** end cbp loop */
 666
 667     netsnmp_assert(callback_pending_list == NULL);
 668 }
 669
 670
 671 #if defined TESTING_OBJECT_MONITOR
 672 /**************************************************************************
 673  *
 674  * (untested) TEST CODE
 675  *
 676  */
 677 void
 678 dummy_callback(netsnmp_monitor_callback_header * cbh)
 679 {
 680     printf("Callback received.\n");
 681 }
 682
 683 void
 684 dump_watchers(netsnmp_index *oah, void *)
 685 {
 686     watcher_list   *wl = (watcher_list *) oah;
 687     netsnmp_monitor_callback_header *cbh = wl->head;
 688
 689     printf("Watcher List for OID ");
 690     print_objid(wl->hdr->oids, wl->hdr->len);
 691     printf("\n");
 692
 693     while (cbh) {
 694
 695         printf("Priority = %d;, Events = %d; Watcher Data = 0x%x\n",
 696                cbh->priority, cbh->events, cbh->watcher_data);
 697
 698         cbh = cbh->private;
 699     }
 700 }
 701
 702 void
 703 main(int argc, char **argv)
 704 {
 705
 706     oid             object[3] = { 1, 3, 6 };
 707     int             object_len = 3;
 708     int             rc;
 709
 710     /*
 711      * init
 712      */
 713     netsnmp_monitor_init();
 714
 715     /*
 716      * insert an object
 717      */
 718     rc = netsnmp_monitor_register(object, object_len, 0,
 719                                   EVENT_ROW_ADD, (void *) 0xdeadbeef,
 720                                   dummy_callback);
 721     printf("insert an object: %d\n", rc);
 722
 723     /*
 724      * insert same object, new priority
 725      */
 726     netsnmp_monitor_register(object, object_len, 10,
 727                              EVENT_ROW_ADD, (void *) 0xdeadbeef,
 728                              dummy_callback);
 729     printf("insert same object, new priority: %d\n", rc);
 730
 731     /*
 732      * insert same object, same priority, new data
 733      */
 734     netsnmp_monitor_register(object, object_len, 10,
 735                              EVENT_ROW_ADD, (void *) 0xbeefdead,
 736                              dummy_callback);
 737     printf("insert same object, same priority, new data: %d\n", rc);
 738
 739     /*
 740      * insert same object, same priority, same data
 741      */
 742     netsnmp_monitor_register(object, object_len, 10,
 743                              EVENT_ROW_ADD, (void *) 0xbeefdead,
 744                              dummy_callback);
 745     printf("insert same object, same priority, new data: %d\n", rc);
 746
 747
 748     /*
 749      * dump table
 750      */
 751     CONTAINER_FOR_EACH(monitored_objects, dump_watchers, NULL);
 752 }
 753 #endif /** defined TESTING_OBJECT_MONITOR */
 754
 755 #endif /** DOXYGEN_SHOULD_IGNORE_THIS */