lib/tevent/tevent_wrapper.c

   1 /*
   2    Infrastructure for event context wrappers
   3
   4    Copyright (C) Stefan Metzmacher 2014
   5
   6      ** NOTE! The following LGPL license applies to the tevent
   7      ** library. This does NOT imply that all of Samba is released
   8      ** under the LGPL
   9
  10    This library is free software; you can redistribute it and/or
  11    modify it under the terms of the GNU Lesser General Public
  12    License as published by the Free Software Foundation; either
  13    version 3 of the License, or (at your option) any later version.
  14
  15    This library is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18    Lesser General Public License for more details.
  19
  20    You should have received a copy of the GNU Lesser General Public
  21    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  22 */
  23
  24 #include "replace.h"
  25 #ifdef HAVE_PTHREAD
  26 #include "system/threads.h"
  27 #endif
  28 #include "tevent.h"
  29 #include "tevent_internal.h"
  30 #include "tevent_util.h"
  31
  32 static int tevent_wrapper_glue_context_init(struct tevent_context *ev)
  33 {
  34         tevent_abort(ev, "tevent_wrapper_glue_context_init() called");
  35         errno = ENOSYS;
  36         return -1;
  37 }
  38
  39 static struct tevent_fd *tevent_wrapper_glue_add_fd(struct tevent_context *ev,
  40                                                     TALLOC_CTX *mem_ctx,
  41                                                     int fd, uint16_t flags,
  42                                                     tevent_fd_handler_t handler,
  43                                                     void *private_data,
  44                                                     const char *handler_name,
  45                                                     const char *location)
  46 {
  47         struct tevent_wrapper_glue *glue = ev->wrapper.glue;
  48         struct tevent_fd *fde = NULL;
  49
  50         if (glue->destroyed) {
  51                 tevent_abort(ev, "add_fd wrapper use after free");
  52                 return NULL;
  53         }
  54
  55         if (glue->main_ev == NULL) {
  56                 errno = EINVAL;
  57                 return NULL;
  58         }
  59
  60         fde = _tevent_add_fd(glue->main_ev, mem_ctx, fd, flags,
  61                              handler, private_data,
  62                              handler_name, location);
  63         if (fde == NULL) {
  64                 return NULL;
  65         }
  66
  67         fde->wrapper = glue;
  68
  69         return fde;
  70 }
  71
  72 static struct tevent_timer *tevent_wrapper_glue_add_timer(struct tevent_context *ev,
  73                                                           TALLOC_CTX *mem_ctx,
  74                                                           struct timeval next_event,
  75                                                           tevent_timer_handler_t handler,
  76                                                           void *private_data,
  77                                                           const char *handler_name,
  78                                                           const char *location)
  79 {
  80         struct tevent_wrapper_glue *glue = ev->wrapper.glue;
  81         struct tevent_timer *te = NULL;
  82
  83         if (glue->destroyed) {
  84                 tevent_abort(ev, "add_timer wrapper use after free");
  85                 return NULL;
  86         }
  87
  88         if (glue->main_ev == NULL) {
  89                 errno = EINVAL;
  90                 return NULL;
  91         }
  92
  93         te = _tevent_add_timer(glue->main_ev, mem_ctx, next_event,
  94                                handler, private_data,
  95                                handler_name, location);
  96         if (te == NULL) {
  97                 return NULL;
  98         }
  99
 100         te->wrapper = glue;
 101
 102         return te;
 103 }
 104
 105 static void tevent_wrapper_glue_schedule_immediate(struct tevent_immediate *im,
 106                                                    struct tevent_context *ev,
 107                                                    tevent_immediate_handler_t handler,
 108                                                    void *private_data,
 109                                                    const char *handler_name,
 110                                                    const char *location)
 111 {
 112         struct tevent_wrapper_glue *glue = ev->wrapper.glue;
 113
 114         if (glue->destroyed) {
 115                 tevent_abort(ev, "scheduke_immediate wrapper use after free");
 116                 return;
 117         }
 118
 119         if (glue->main_ev == NULL) {
 120                 tevent_abort(ev, location);
 121                 errno = EINVAL;
 122                 return;
 123         }
 124
 125         _tevent_schedule_immediate(im, glue->main_ev,
 126                                    handler, private_data,
 127                                    handler_name, location);
 128
 129         im->wrapper = glue;
 130
 131         return;
 132 }
 133
 134 static struct tevent_signal *tevent_wrapper_glue_add_signal(struct tevent_context *ev,
 135                                                             TALLOC_CTX *mem_ctx,
 136                                                             int signum, int sa_flags,
 137                                                             tevent_signal_handler_t handler,
 138                                                             void *private_data,
 139                                                             const char *handler_name,
 140                                                             const char *location)
 141 {
 142         struct tevent_wrapper_glue *glue = ev->wrapper.glue;
 143         struct tevent_signal *se = NULL;
 144
 145         if (glue->destroyed) {
 146                 tevent_abort(ev, "add_signal wrapper use after free");
 147                 return NULL;
 148         }
 149
 150         if (glue->main_ev == NULL) {
 151                 errno = EINVAL;
 152                 return NULL;
 153         }
 154
 155         se = _tevent_add_signal(glue->main_ev, mem_ctx,
 156                                 signum, sa_flags,
 157                                 handler, private_data,
 158                                 handler_name, location);
 159         if (se == NULL) {
 160                 return NULL;
 161         }
 162
 163         se->wrapper = glue;
 164
 165         return se;
 166 }
 167
 168 static int tevent_wrapper_glue_loop_once(struct tevent_context *ev, const char *location)
 169 {
 170         tevent_abort(ev, "tevent_wrapper_glue_loop_once() called");
 171         errno = ENOSYS;
 172         return -1;
 173 }
 174
 175 static int tevent_wrapper_glue_loop_wait(struct tevent_context *ev, const char *location)
 176 {
 177         tevent_abort(ev, "tevent_wrapper_glue_loop_wait() called");
 178         errno = ENOSYS;
 179         return -1;
 180 }
 181
 182 static const struct tevent_ops tevent_wrapper_glue_ops = {
 183         .context_init           = tevent_wrapper_glue_context_init,
 184         .add_fd                 = tevent_wrapper_glue_add_fd,
 185         .set_fd_close_fn        = tevent_common_fd_set_close_fn,
 186         .get_fd_flags           = tevent_common_fd_get_flags,
 187         .set_fd_flags           = tevent_common_fd_set_flags,
 188         .add_timer              = tevent_wrapper_glue_add_timer,
 189         .schedule_immediate     = tevent_wrapper_glue_schedule_immediate,
 190         .add_signal             = tevent_wrapper_glue_add_signal,
 191         .loop_once              = tevent_wrapper_glue_loop_once,
 192         .loop_wait              = tevent_wrapper_glue_loop_wait,
 193 };
 194
 195 static int tevent_wrapper_context_destructor(struct tevent_context *wrap_ev)
 196 {
 197         struct tevent_wrapper_glue *glue = wrap_ev->wrapper.glue;
 198         struct tevent_context *main_ev = NULL;
 199         struct tevent_fd *fd = NULL, *fn = NULL;
 200         struct tevent_timer *te = NULL, *tn = NULL;
 201         struct tevent_immediate *ie = NULL, *in = NULL;
 202         struct tevent_signal *se = NULL, *sn = NULL;
 203 #ifdef HAVE_PTHREAD
 204         struct tevent_threaded_context *tctx = NULL, *tctxn = NULL;
 205 #endif
 206
 207         if (glue == NULL) {
 208                 tevent_abort(wrap_ev,
 209                         "tevent_wrapper_context_destructor() active on main");
 210         }
 211
 212         if (glue->destroyed && glue->busy) {
 213                 tevent_common_check_double_free(wrap_ev,
 214                         "tevent_context wrapper double free");
 215         }
 216         glue->destroyed = true;
 217
 218         if (glue->busy) {
 219                 return -1;
 220         }
 221
 222         main_ev = glue->main_ev;
 223         if (main_ev == NULL) {
 224                 return 0;
 225         }
 226
 227         tevent_debug(wrap_ev, TEVENT_DEBUG_TRACE,
 228                      "Destroying wrapper context %p \"%s\"\n",
 229                      wrap_ev, talloc_get_name(glue->private_state));
 230
 231         glue->main_ev = NULL;
 232         DLIST_REMOVE(main_ev->wrapper.list, glue);
 233
 234 #ifdef HAVE_PTHREAD
 235         for (tctx = main_ev->threaded_contexts; tctx != NULL; tctx = tctxn) {
 236                 int ret;
 237
 238                 tctxn = tctx->next;
 239
 240                 if (tctx->event_ctx != glue->wrap_ev) {
 241                         continue;
 242                 }
 243
 244                 ret = pthread_mutex_lock(&tctx->event_ctx_mutex);
 245                 if (ret != 0) {
 246                         abort();
 247                 }
 248
 249                 /*
 250                  * Indicate to the thread that the tevent_context is
 251                  * gone. The counterpart of this is in
 252                  * _tevent_threaded_schedule_immediate, there we read
 253                  * this under the threaded_context's mutex.
 254                  */
 255
 256                 tctx->event_ctx = NULL;
 257
 258                 ret = pthread_mutex_unlock(&tctx->event_ctx_mutex);
 259                 if (ret != 0) {
 260                         abort();
 261                 }
 262
 263                 DLIST_REMOVE(main_ev->threaded_contexts, tctx);
 264         }
 265 #endif
 266
 267         for (fd = main_ev->fd_events; fd; fd = fn) {
 268                 fn = fd->next;
 269
 270                 if (fd->wrapper != glue) {
 271                         continue;
 272                 }
 273
 274                 tevent_fd_set_flags(fd, 0);
 275
 276                 fd->wrapper = NULL;
 277                 fd->event_ctx = NULL;
 278                 DLIST_REMOVE(main_ev->fd_events, fd);
 279         }
 280
 281         for (te = main_ev->timer_events; te; te = tn) {
 282                 tn = te->next;
 283
 284                 if (te->wrapper != glue) {
 285                         continue;
 286                 }
 287
 288                 te->wrapper = NULL;
 289                 te->event_ctx = NULL;
 290
 291                 if (main_ev->last_zero_timer == te) {
 292                         main_ev->last_zero_timer = DLIST_PREV(te);
 293                 }
 294                 DLIST_REMOVE(main_ev->timer_events, te);
 295         }
 296
 297         for (ie = main_ev->immediate_events; ie; ie = in) {
 298                 in = ie->next;
 299
 300                 if (ie->wrapper != glue) {
 301                         continue;
 302                 }
 303
 304                 ie->wrapper = NULL;
 305                 ie->event_ctx = NULL;
 306                 ie->cancel_fn = NULL;
 307                 DLIST_REMOVE(main_ev->immediate_events, ie);
 308         }
 309
 310         for (se = main_ev->signal_events; se; se = sn) {
 311                 sn = se->next;
 312
 313                 if (se->wrapper != glue) {
 314                         continue;
 315                 }
 316
 317                 se->wrapper = NULL;
 318                 tevent_cleanup_pending_signal_handlers(se);
 319         }
 320
 321         return 0;
 322 }
 323
 324 struct tevent_context *_tevent_context_wrapper_create(struct tevent_context *main_ev,
 325                                                 TALLOC_CTX *mem_ctx,
 326                                                 const struct tevent_wrapper_ops *ops,
 327                                                 void *pstate,
 328                                                 size_t psize,
 329                                                 const char *type,
 330                                                 const char *location)
 331 {
 332         void **ppstate = (void **)pstate;
 333         struct tevent_context *ev = NULL;
 334
 335         if (main_ev->wrapper.glue != NULL) {
 336                 /*
 337                  * stacking of wrappers is not supported
 338                  */
 339                 tevent_debug(main_ev->wrapper.glue->main_ev, TEVENT_DEBUG_FATAL,
 340                              "%s: %s() stacking not allowed\n",
 341                              __func__, location);
 342                 errno = EINVAL;
 343                 return NULL;
 344         }
 345
 346         if (main_ev->nesting.allowed) {
 347                 /*
 348                  * wrappers conflict with nesting
 349                  */
 350                 tevent_debug(main_ev->wrapper.glue->main_ev, TEVENT_DEBUG_FATAL,
 351                              "%s: %s() conflicts with nesting\n",
 352                              __func__, location);
 353                 errno = EINVAL;
 354                 return NULL;
 355         }
 356
 357         ev = talloc_zero(mem_ctx, struct tevent_context);
 358         if (ev == NULL) {
 359                 return NULL;
 360         }
 361         ev->ops = &tevent_wrapper_glue_ops;
 362
 363         ev->wrapper.glue = talloc_zero(ev, struct tevent_wrapper_glue);
 364         if (ev->wrapper.glue == NULL) {
 365                 talloc_free(ev);
 366                 return NULL;
 367         }
 368
 369         talloc_set_destructor(ev, tevent_wrapper_context_destructor);
 370
 371         ev->wrapper.glue->wrap_ev = ev;
 372         ev->wrapper.glue->main_ev = main_ev;
 373         ev->wrapper.glue->ops = ops;
 374         ev->wrapper.glue->private_state = talloc_size(ev->wrapper.glue, psize);
 375         if (ev->wrapper.glue->private_state == NULL) {
 376                 talloc_free(ev);
 377                 return NULL;
 378         }
 379         talloc_set_name_const(ev->wrapper.glue->private_state, type);
 380
 381         DLIST_ADD_END(main_ev->wrapper.list, ev->wrapper.glue);
 382
 383         *ppstate = ev->wrapper.glue->private_state;
 384         return ev;
 385 }
 386
 387 bool tevent_context_is_wrapper(struct tevent_context *ev)
 388 {
 389         if (ev->wrapper.glue != NULL) {
 390                 return true;
 391         }
 392
 393         return false;
 394 }
 395
 396 _PRIVATE_
 397 struct tevent_context *tevent_wrapper_main_ev(struct tevent_context *ev)
 398 {
 399         if (ev == NULL) {
 400                 return NULL;
 401         }
 402
 403         if (ev->wrapper.glue == NULL) {
 404                 return ev;
 405         }
 406
 407         return ev->wrapper.glue->main_ev;
 408 }
 409
 410 /*
 411  * 32 stack elements should be more than enough
 412  *
 413  * e.g. Samba uses just 8 elements for [un]become_{root,user}()
 414  */
 415 #define TEVENT_WRAPPER_STACK_SIZE 32
 416
 417 static struct tevent_wrapper_stack {
 418         const void *ev_ptr;
 419         const struct tevent_wrapper_glue *wrapper;
 420 } wrapper_stack[TEVENT_WRAPPER_STACK_SIZE];
 421
 422 static size_t wrapper_stack_idx;
 423
 424 _PRIVATE_
 425 void tevent_wrapper_push_use_internal(struct tevent_context *ev,
 426                                       struct tevent_wrapper_glue *wrapper)
 427 {
 428         /*
 429          * ev and wrapper need to belong together!
 430          * It's also fine to only have a raw ev
 431          * without a wrapper.
 432          */
 433         if (unlikely(ev->wrapper.glue != wrapper)) {
 434                 tevent_abort(ev, "tevent_wrapper_push_use_internal() invalid arguments");
 435                 return;
 436         }
 437
 438         if (wrapper != NULL) {
 439                 if (unlikely(wrapper->busy)) {
 440                         tevent_abort(ev, "wrapper already busy!");
 441                         return;
 442                 }
 443                 wrapper->busy = true;
 444         }
 445
 446         if (unlikely(wrapper_stack_idx >= TEVENT_WRAPPER_STACK_SIZE)) {
 447                 tevent_abort(ev, "TEVENT_WRAPPER_STACK_SIZE overflow");
 448                 return;
 449         }
 450
 451         wrapper_stack[wrapper_stack_idx] = (struct tevent_wrapper_stack) {
 452                 .ev_ptr = ev,
 453                 .wrapper = wrapper,
 454         };
 455         wrapper_stack_idx++;
 456 }
 457
 458 _PRIVATE_
 459 void tevent_wrapper_pop_use_internal(const struct tevent_context *__ev_ptr,
 460                                      struct tevent_wrapper_glue *wrapper)
 461 {
 462         struct tevent_context *main_ev = NULL;
 463
 464         /*
 465          * Note that __ev_ptr might a a stale pointer and should not
 466          * be touched, we just compare the pointer value in order
 467          * to enforce the stack order.
 468          */
 469
 470         if (wrapper != NULL) {
 471                 main_ev = wrapper->main_ev;
 472         }
 473
 474         if (unlikely(wrapper_stack_idx == 0)) {
 475                 tevent_abort(main_ev, "tevent_wrapper stack already empty");
 476                 return;
 477         }
 478         wrapper_stack_idx--;
 479
 480         if (wrapper != NULL) {
 481                 wrapper->busy = false;
 482         }
 483
 484         if (wrapper_stack[wrapper_stack_idx].ev_ptr != __ev_ptr) {
 485                 tevent_abort(main_ev, "tevent_wrapper_pop_use mismatch ev!");
 486                 return;
 487         }
 488         if (wrapper_stack[wrapper_stack_idx].wrapper != wrapper) {
 489                 tevent_abort(main_ev, "tevent_wrapper_pop_use mismatch wrap!");
 490                 return;
 491         }
 492
 493         if (wrapper == NULL) {
 494                 return;
 495         }
 496
 497         if (wrapper->destroyed) {
 498                 /*
 499                  * Notice that we can't use TALLOC_FREE()
 500                  * here because wrapper is a talloc child
 501                  * of wrapper->wrap_ev.
 502                  */
 503                 talloc_free(wrapper->wrap_ev);
 504         }
 505 }
 506
 507 bool _tevent_context_push_use(struct tevent_context *ev,
 508                               const char *location)
 509 {
 510         bool ok;
 511
 512         if (ev->wrapper.glue == NULL) {
 513                 tevent_wrapper_push_use_internal(ev, NULL);
 514                 return true;
 515         }
 516
 517         if (ev->wrapper.glue->main_ev == NULL) {
 518                 return false;
 519         }
 520
 521         tevent_wrapper_push_use_internal(ev, ev->wrapper.glue);
 522         ok = ev->wrapper.glue->ops->before_use(ev->wrapper.glue->wrap_ev,
 523                                                ev->wrapper.glue->private_state,
 524                                                ev->wrapper.glue->main_ev,
 525                                                location);
 526         if (!ok) {
 527                 tevent_wrapper_pop_use_internal(ev, ev->wrapper.glue);
 528                 return false;
 529         }
 530
 531         return true;
 532 }
 533
 534 void _tevent_context_pop_use(struct tevent_context *ev,
 535                              const char *location)
 536 {
 537         tevent_wrapper_pop_use_internal(ev, ev->wrapper.glue);
 538
 539         if (ev->wrapper.glue == NULL) {
 540                 return;
 541         }
 542
 543         if (ev->wrapper.glue->main_ev == NULL) {
 544                 return;
 545         }
 546
 547         ev->wrapper.glue->ops->after_use(ev->wrapper.glue->wrap_ev,
 548                                          ev->wrapper.glue->private_state,
 549                                          ev->wrapper.glue->main_ev,
 550                                          location);
 551 }
 552
 553 bool tevent_context_same_loop(struct tevent_context *ev1,
 554                               struct tevent_context *ev2)
 555 {
 556         struct tevent_context *main_ev1 = tevent_wrapper_main_ev(ev1);
 557         struct tevent_context *main_ev2 = tevent_wrapper_main_ev(ev2);
 558
 559         if (main_ev1 == NULL) {
 560                 return false;
 561         }
 562
 563         if (main_ev1 == main_ev2) {
 564                 return true;
 565         }
 566
 567         return false;
 568 }