lib/tevent/tevent_epoll.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    main select loop and event handling - epoll implementation
   5
   6    Copyright (C) Andrew Tridgell        2003-2005
   7    Copyright (C) Stefan Metzmacher      2005-2013
   8    Copyright (C) Jeremy Allison         2013
   9
  10      ** NOTE! The following LGPL license applies to the tevent
  11      ** library. This does NOT imply that all of Samba is released
  12      ** under the LGPL
  13
  14    This library is free software; you can redistribute it and/or
  15    modify it under the terms of the GNU Lesser General Public
  16    License as published by the Free Software Foundation; either
  17    version 3 of the License, or (at your option) any later version.
  18
  19    This library is distributed in the hope that it will be useful,
  20    but WITHOUT ANY WARRANTY; without even the implied warranty of
  21    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22    Lesser General Public License for more details.
  23
  24    You should have received a copy of the GNU Lesser General Public
  25    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  26 */
  27
  28 #include "replace.h"
  29 #include "system/filesys.h"
  30 #include "system/select.h"
  31 #include "tevent.h"
  32 #include "tevent_internal.h"
  33 #include "tevent_util.h"
  34
  35 struct epoll_event_context {
  36         /* a pointer back to the generic event_context */
  37         struct tevent_context *ev;
  38
  39         /* when using epoll this is the handle from epoll_create */
  40         int epoll_fd;
  41
  42         pid_t pid;
  43
  44         bool panic_force_replay;
  45         bool *panic_state;
  46         bool (*panic_fallback)(struct tevent_context *ev, bool replay);
  47 };
  48
  49 #define EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT      (1<<0)
  50 #define EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR   (1<<1)
  51 #define EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR      (1<<2)
  52 #define EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX        (1<<3)
  53
  54 #ifdef TEST_PANIC_FALLBACK
  55
  56 static int epoll_create_panic_fallback(struct epoll_event_context *epoll_ev,
  57                                        int size)
  58 {
  59         if (epoll_ev->panic_fallback == NULL) {
  60                 return epoll_create(size);
  61         }
  62
  63         /* 50% of the time, fail... */
  64         if ((random() % 2) == 0) {
  65                 errno = EINVAL;
  66                 return -1;
  67         }
  68
  69         return epoll_create(size);
  70 }
  71
  72 static int epoll_ctl_panic_fallback(struct epoll_event_context *epoll_ev,
  73                                     int epfd, int op, int fd,
  74                                     struct epoll_event *event)
  75 {
  76         if (epoll_ev->panic_fallback == NULL) {
  77                 return epoll_ctl(epfd, op, fd, event);
  78         }
  79
  80         /* 50% of the time, fail... */
  81         if ((random() % 2) == 0) {
  82                 errno = EINVAL;
  83                 return -1;
  84         }
  85
  86         return epoll_ctl(epfd, op, fd, event);
  87 }
  88
  89 static int epoll_wait_panic_fallback(struct epoll_event_context *epoll_ev,
  90                                      int epfd,
  91                                      struct epoll_event *events,
  92                                      int maxevents,
  93                                      int timeout)
  94 {
  95         if (epoll_ev->panic_fallback == NULL) {
  96                 return epoll_wait(epfd, events, maxevents, timeout);
  97         }
  98
  99         /* 50% of the time, fail... */
 100         if ((random() % 2) == 0) {
 101                 errno = EINVAL;
 102                 return -1;
 103         }
 104
 105         return epoll_wait(epfd, events, maxevents, timeout);
 106 }
 107
 108 #define epoll_create(_size) \
 109         epoll_create_panic_fallback(epoll_ev, _size)
 110 #define epoll_ctl(_epfd, _op, _fd, _event) \
 111         epoll_ctl_panic_fallback(epoll_ev,_epfd, _op, _fd, _event)
 112 #define epoll_wait(_epfd, _events, _maxevents, _timeout) \
 113         epoll_wait_panic_fallback(epoll_ev, _epfd, _events, _maxevents, _timeout)
 114 #endif
 115
 116 /*
 117   called to set the panic fallback function.
 118 */
 119 _PRIVATE_ bool tevent_epoll_set_panic_fallback(struct tevent_context *ev,
 120                                 bool (*panic_fallback)(struct tevent_context *ev,
 121                                                        bool replay))
 122 {
 123         struct epoll_event_context *epoll_ev;
 124
 125         if (ev->additional_data == NULL) {
 126                 return false;
 127         }
 128
 129         epoll_ev = talloc_get_type(ev->additional_data,
 130                                 struct epoll_event_context);
 131         if (epoll_ev == NULL) {
 132                 return false;
 133         }
 134         epoll_ev->panic_fallback = panic_fallback;
 135         return true;
 136 }
 137
 138 /*
 139   called when a epoll call fails
 140 */
 141 static void epoll_panic(struct epoll_event_context *epoll_ev,
 142                         const char *reason, bool replay)
 143 {
 144         struct tevent_context *ev = epoll_ev->ev;
 145         bool (*panic_fallback)(struct tevent_context *ev, bool replay);
 146
 147         panic_fallback = epoll_ev->panic_fallback;
 148
 149         if (epoll_ev->panic_state != NULL) {
 150                 *epoll_ev->panic_state = true;
 151         }
 152
 153         if (epoll_ev->panic_force_replay) {
 154                 replay = true;
 155         }
 156
 157         TALLOC_FREE(ev->additional_data);
 158
 159         if (panic_fallback == NULL) {
 160                 tevent_debug(ev, TEVENT_DEBUG_FATAL,
 161                         "%s (%s) replay[%u] - calling abort()\n",
 162                         reason, strerror(errno), (unsigned)replay);
 163                 abort();
 164         }
 165
 166         tevent_debug(ev, TEVENT_DEBUG_WARNING,
 167                      "%s (%s) replay[%u] - calling panic_fallback\n",
 168                      reason, strerror(errno), (unsigned)replay);
 169
 170         if (!panic_fallback(ev, replay)) {
 171                 /* Fallback failed. */
 172                 tevent_debug(ev, TEVENT_DEBUG_FATAL,
 173                         "%s (%s) replay[%u] - calling abort()\n",
 174                         reason, strerror(errno), (unsigned)replay);
 175                 abort();
 176         }
 177 }
 178
 179 /*
 180   map from TEVENT_FD_* to EPOLLIN/EPOLLOUT
 181 */
 182 static uint32_t epoll_map_flags(uint16_t flags)
 183 {
 184         uint32_t ret = 0;
 185         if (flags & TEVENT_FD_READ) ret |= (EPOLLIN | EPOLLERR | EPOLLHUP);
 186         if (flags & TEVENT_FD_WRITE) ret |= (EPOLLOUT | EPOLLERR | EPOLLHUP);
 187         return ret;
 188 }
 189
 190 /*
 191  free the epoll fd
 192 */
 193 static int epoll_ctx_destructor(struct epoll_event_context *epoll_ev)
 194 {
 195         close(epoll_ev->epoll_fd);
 196         epoll_ev->epoll_fd = -1;
 197         return 0;
 198 }
 199
 200 /*
 201  init the epoll fd
 202 */
 203 static int epoll_init_ctx(struct epoll_event_context *epoll_ev)
 204 {
 205         epoll_ev->epoll_fd = epoll_create(64);
 206         if (epoll_ev->epoll_fd == -1) {
 207                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
 208                              "Failed to create epoll handle.\n");
 209                 return -1;
 210         }
 211
 212         if (!ev_set_close_on_exec(epoll_ev->epoll_fd)) {
 213                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_WARNING,
 214                              "Failed to set close-on-exec, file descriptor may be leaked to children.\n");
 215         }
 216
 217         epoll_ev->pid = getpid();
 218         talloc_set_destructor(epoll_ev, epoll_ctx_destructor);
 219
 220         return 0;
 221 }
 222
 223 static void epoll_update_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde);
 224
 225 /*
 226   reopen the epoll handle when our pid changes
 227   see http://junkcode.samba.org/ftp/unpacked/junkcode/epoll_fork.c for an
 228   demonstration of why this is needed
 229  */
 230 static void epoll_check_reopen(struct epoll_event_context *epoll_ev)
 231 {
 232         struct tevent_fd *fde;
 233         bool *caller_panic_state = epoll_ev->panic_state;
 234         bool panic_triggered = false;
 235
 236         if (epoll_ev->pid == getpid()) {
 237                 return;
 238         }
 239
 240         close(epoll_ev->epoll_fd);
 241         epoll_ev->epoll_fd = epoll_create(64);
 242         if (epoll_ev->epoll_fd == -1) {
 243                 epoll_panic(epoll_ev, "epoll_create() failed", false);
 244                 return;
 245         }
 246
 247         if (!ev_set_close_on_exec(epoll_ev->epoll_fd)) {
 248                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_WARNING,
 249                              "Failed to set close-on-exec, file descriptor may be leaked to children.\n");
 250         }
 251
 252         epoll_ev->pid = getpid();
 253         epoll_ev->panic_state = &panic_triggered;
 254         for (fde=epoll_ev->ev->fd_events;fde;fde=fde->next) {
 255                 fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 256                 epoll_update_event(epoll_ev, fde);
 257
 258                 if (panic_triggered) {
 259                         if (caller_panic_state != NULL) {
 260                                 *caller_panic_state = true;
 261                         }
 262                         return;
 263                 }
 264         }
 265         epoll_ev->panic_state = NULL;
 266 }
 267
 268 /*
 269  epoll cannot add the same file descriptor twice, once
 270  with read, once with write which is allowed by the
 271  tevent backend. Multiplex the existing fde, flag it
 272  as such so we can search for the correct fde on
 273  event triggering.
 274 */
 275
 276 static int epoll_add_multiplex_fd(struct epoll_event_context *epoll_ev,
 277                                   struct tevent_fd *add_fde)
 278 {
 279         struct epoll_event event;
 280         struct tevent_fd *mpx_fde;
 281         int ret;
 282
 283         /* Find the existing fde that caused the EEXIST error. */
 284         for (mpx_fde = epoll_ev->ev->fd_events; mpx_fde; mpx_fde = mpx_fde->next) {
 285                 if (mpx_fde->fd != add_fde->fd) {
 286                         continue;
 287                 }
 288
 289                 if (mpx_fde == add_fde) {
 290                         continue;
 291                 }
 292
 293                 break;
 294         }
 295         if (mpx_fde == NULL) {
 296                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
 297                              "can't find multiplex fde for fd[%d]",
 298                              add_fde->fd);
 299                 return -1;
 300         }
 301
 302         if (mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
 303                 /* Logic error. Can't have more than 2 multiplexed fde's. */
 304                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
 305                              "multiplex fde for fd[%d] is already multiplexed\n",
 306                              mpx_fde->fd);
 307                 return -1;
 308         }
 309
 310         /*
 311          * The multiplex fde must have the same fd, and also
 312          * already have an epoll event attached.
 313          */
 314         if (!(mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT)) {
 315                 /* Logic error. Can't have more than 2 multiplexed fde's. */
 316                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_FATAL,
 317                              "multiplex fde for fd[%d] has no event\n",
 318                              mpx_fde->fd);
 319                 return -1;
 320         }
 321
 322         /* Modify the mpx_fde to add in the new flags. */
 323         ZERO_STRUCT(event);
 324         event.events = epoll_map_flags(mpx_fde->flags);
 325         event.events |= epoll_map_flags(add_fde->flags);
 326         event.data.ptr = mpx_fde;
 327         ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_MOD, mpx_fde->fd, &event);
 328         if (ret != 0 && errno == EBADF) {
 329                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_ERROR,
 330                              "EPOLL_CTL_MOD EBADF for "
 331                              "add_fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
 332                              add_fde, mpx_fde, add_fde->fd);
 333                 DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
 334                 mpx_fde->event_ctx = NULL;
 335                 DLIST_REMOVE(epoll_ev->ev->fd_events, add_fde);
 336                 add_fde->event_ctx = NULL;
 337                 return 0;
 338         } else if (ret != 0) {
 339                 return ret;
 340         }
 341
 342         /*
 343          * Make each fde->additional_data pointers point at each other
 344          * so we can look them up from each other. They are now paired.
 345          */
 346         mpx_fde->additional_data = (struct tevent_fd *)add_fde;
 347         add_fde->additional_data = (struct tevent_fd *)mpx_fde;
 348
 349         /* Now flag both fde's as being multiplexed. */
 350         mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX;
 351         add_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX;
 352
 353         /* we need to keep the GOT_ERROR flag */
 354         if (mpx_fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR) {
 355                 add_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR;
 356         }
 357
 358         return 0;
 359 }
 360
 361 /*
 362  add the epoll event to the given fd_event
 363 */
 364 static void epoll_add_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde)
 365 {
 366         struct epoll_event event;
 367         int ret;
 368         struct tevent_fd *mpx_fde = NULL;
 369
 370         fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 371         fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 372
 373         if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
 374                 /*
 375                  * This is a multiplexed fde, we need to include both
 376                  * flags in the modified event.
 377                  */
 378                 mpx_fde = talloc_get_type_abort(fde->additional_data,
 379                                                 struct tevent_fd);
 380
 381                 mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 382                 mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 383         }
 384
 385         ZERO_STRUCT(event);
 386         event.events = epoll_map_flags(fde->flags);
 387         if (mpx_fde != NULL) {
 388                 event.events |= epoll_map_flags(mpx_fde->flags);
 389         }
 390         event.data.ptr = fde;
 391         ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_ADD, fde->fd, &event);
 392         if (ret != 0 && errno == EBADF) {
 393                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_ERROR,
 394                              "EPOLL_CTL_ADD EBADF for "
 395                              "fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
 396                              fde, mpx_fde, fde->fd);
 397                 DLIST_REMOVE(epoll_ev->ev->fd_events, fde);
 398                 fde->event_ctx = NULL;
 399                 if (mpx_fde != NULL) {
 400                         DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
 401                         mpx_fde->event_ctx = NULL;
 402                 }
 403                 return;
 404         } else if (ret != 0) {
 405                 epoll_panic(epoll_ev, "EPOLL_CTL_ADD failed", false);
 406                 return;
 407         }
 408
 409         fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 410         /* only if we want to read we want to tell the event handler about errors */
 411         if (fde->flags & TEVENT_FD_READ) {
 412                 fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 413         }
 414
 415         if (mpx_fde == NULL) {
 416                 return;
 417         }
 418
 419         mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 420         /* only if we want to read we want to tell the event handler about errors */
 421         if (mpx_fde->flags & TEVENT_FD_READ) {
 422                 mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 423         }
 424 }
 425
 426 /*
 427  delete the epoll event for given fd_event
 428 */
 429 static void epoll_del_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde)
 430 {
 431         struct epoll_event event;
 432         int ret;
 433         struct tevent_fd *mpx_fde = NULL;
 434
 435         fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 436         fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 437
 438         if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
 439                 /*
 440                  * This is a multiplexed fde, we need to modify both events.
 441                  */
 442                 mpx_fde = talloc_get_type_abort(fde->additional_data,
 443                                                 struct tevent_fd);
 444
 445                 mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 446                 mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 447         }
 448
 449         ZERO_STRUCT(event);
 450         ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_DEL, fde->fd, &event);
 451         if (ret != 0 && errno == ENOENT) {
 452                 /*
 453                  * This can happen after a epoll_check_reopen
 454                  * within epoll_event_fd_destructor.
 455                  */
 456                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_TRACE,
 457                              "EPOLL_CTL_DEL ignoring ENOENT for fd[%d]\n",
 458                              fde->fd);
 459                 return;
 460         } else if (ret != 0 && errno == EBADF) {
 461                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_WARNING,
 462                              "EPOLL_CTL_DEL EBADF for "
 463                              "fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
 464                              fde, mpx_fde, fde->fd);
 465                 DLIST_REMOVE(epoll_ev->ev->fd_events, fde);
 466                 fde->event_ctx = NULL;
 467                 if (mpx_fde != NULL) {
 468                         DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
 469                         mpx_fde->event_ctx = NULL;
 470                 }
 471                 return;
 472         } else if (ret != 0) {
 473                 epoll_panic(epoll_ev, "EPOLL_CTL_DEL failed", false);
 474                 return;
 475         }
 476 }
 477
 478 /*
 479  change the epoll event to the given fd_event
 480 */
 481 static void epoll_mod_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde)
 482 {
 483         struct tevent_fd *mpx_fde = NULL;
 484         struct epoll_event event;
 485         int ret;
 486
 487         fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 488         fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 489
 490         if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_MPX) {
 491                 /*
 492                  * This is a multiplexed fde, we need to include both
 493                  * flags in the modified event.
 494                  */
 495                 mpx_fde = talloc_get_type_abort(fde->additional_data,
 496                                                 struct tevent_fd);
 497
 498                 mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 499                 mpx_fde->additional_flags &= ~EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 500         }
 501
 502         ZERO_STRUCT(event);
 503         event.events = epoll_map_flags(fde->flags);
 504         if (mpx_fde != NULL) {
 505                 event.events |= epoll_map_flags(mpx_fde->flags);
 506         }
 507         event.data.ptr = fde;
 508         ret = epoll_ctl(epoll_ev->epoll_fd, EPOLL_CTL_MOD, fde->fd, &event);
 509         if (ret != 0 && errno == EBADF) {
 510                 tevent_debug(epoll_ev->ev, TEVENT_DEBUG_ERROR,
 511                              "EPOLL_CTL_MOD EBADF for "
 512                              "fde[%p] mpx_fde[%p] fd[%d] - disabling\n",
 513                              fde, mpx_fde, fde->fd);
 514                 DLIST_REMOVE(epoll_ev->ev->fd_events, fde);
 515                 fde->event_ctx = NULL;
 516                 if (mpx_fde != NULL) {
 517                         DLIST_REMOVE(epoll_ev->ev->fd_events, mpx_fde);
 518                         mpx_fde->event_ctx = NULL;
 519                 }
 520                 return;
 521         } else if (ret != 0) {
 522                 epoll_panic(epoll_ev, "EPOLL_CTL_MOD failed", false);
 523                 return;
 524         }
 525
 526         fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 527         /* only if we want to read we want to tell the event handler about errors */
 528         if (fde->flags & TEVENT_FD_READ) {
 529                 fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 530         }
 531
 532         if (mpx_fde == NULL) {
 533                 return;
 534         }
 535
 536         mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT;
 537         /* only if we want to read we want to tell the event handler about errors */
 538         if (mpx_fde->flags & TEVENT_FD_READ) {
 539                 mpx_fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR;
 540         }
 541 }
 542
 543 static void epoll_update_event(struct epoll_event_context *epoll_ev, struct tevent_fd *fde)
 544 {
 545         bool got_error = (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR);
 546         bool want_read = (fde->flags & TEVENT_FD_READ);
 547         bool want_write= (fde->flags & TEVENT_FD_WRITE);
 548
 549         /* there's already an event */
 550         if (fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_HAS_EVENT) {
 551                 if (want_read || (want_write && !got_error)) {
 552                         epoll_mod_event(epoll_ev, fde);
 553                         return;
 554                 }
 555                 /*
 556                  * if we want to match the select behavior, we need to remove the epoll_event
 557                  * when the caller isn't interested in events.
 558                  *
 559                  * this is because epoll reports EPOLLERR and EPOLLHUP, even without asking for them
 560                  */
 561                 epoll_del_event(epoll_ev, fde);
 562                 return;
 563         }
 564
 565         /* there's no epoll_event attached to the fde */
 566         if (want_read || (want_write && !got_error)) {
 567                 epoll_add_event(epoll_ev, fde);
 568                 return;
 569         }
 570 }
 571
 572 /*
 573   event loop handling using epoll
 574 */
 575 static int epoll_event_loop(struct epoll_event_context *epoll_ev, struct timeval *tvalp)
 576 {
 577         int ret, i;
 578 #define MAXEVENTS 1
 579         struct epoll_event events[MAXEVENTS];
 580         int timeout = -1;
 581         int wait_errno;
 582
 583         if (tvalp) {
 584                 /* it's better to trigger timed events a bit later than too early */
 585                 timeout = ((tvalp->tv_usec+999) / 1000) + (tvalp->tv_sec*1000);
 586         }
 587
 588         if (epoll_ev->ev->signal_events &&
 589             tevent_common_check_signal(epoll_ev->ev)) {
 590                 return 0;
 591         }
 592
 593         tevent_trace_point_callback(epoll_ev->ev, TEVENT_TRACE_BEFORE_WAIT);
 594         ret = epoll_wait(epoll_ev->epoll_fd, events, MAXEVENTS, timeout);
 595         wait_errno = errno;
 596         tevent_trace_point_callback(epoll_ev->ev, TEVENT_TRACE_AFTER_WAIT);
 597
 598         if (ret == -1 && wait_errno == EINTR && epoll_ev->ev->signal_events) {
 599                 if (tevent_common_check_signal(epoll_ev->ev)) {
 600                         return 0;
 601                 }
 602         }
 603
 604         if (ret == -1 && wait_errno != EINTR) {
 605                 epoll_panic(epoll_ev, "epoll_wait() failed", true);
 606                 return -1;
 607         }
 608
 609         if (ret == 0 && tvalp) {
 610                 /* we don't care about a possible delay here */
 611                 tevent_common_loop_timer_delay(epoll_ev->ev);
 612                 return 0;
 613         }
 614
 615         for (i=0;i<ret;i++) {
 616                 struct tevent_fd *fde = talloc_get_type(events[i].data.ptr,
 617                                                        struct tevent_fd);
 618                 uint16_t flags = 0;
 619
 620                 if (fde == NULL) {
 621                         epoll_panic(epoll_ev, "epoll_wait() gave bad data", true);
 622                         return -1;
 623                 }
 624                 if (events[i].events & (EPOLLHUP|EPOLLERR)) {
 625                         fde->additional_flags |= EPOLL_ADDITIONAL_FD_FLAG_GOT_ERROR;
 626                         /*
 627                          * if we only wait for TEVENT_FD_WRITE, we should not tell the
 628                          * event handler about it, and remove the epoll_event,
 629                          * as we only report errors when waiting for read events,
 630                          * to match the select() behavior
 631                          */
 632                         if (!(fde->additional_flags & EPOLL_ADDITIONAL_FD_FLAG_REPORT_ERROR)) {
 633                                 epoll_update_event(epoll_ev, fde);
 634                                 continue;
 635                         }
 636                         flags |= TEVENT_FD_READ;
 637                 }
 638                 if (events[i].events & EPOLLIN) flags |= TEVENT_FD_READ;
 639                 if (events[i].events & EPOLLOUT) flags |= TEVENT_FD_WRITE;
 640                 if (flags) {
 641                         fde->handler(epoll_ev->ev, fde, flags, fde->private_data);
 642                         break;
 643                 }
 644         }
 645
 646         return 0;
 647 }
 648
 649 /*
 650   create a epoll_event_context structure.
 651 */
 652 static int epoll_event_context_init(struct tevent_context *ev)
 653 {
 654         int ret;
 655         struct epoll_event_context *epoll_ev;
 656
 657         /*
 658          * We might be called during tevent_re_initialise()
 659          * which means we need to free our old additional_data.
 660          */
 661         TALLOC_FREE(ev->additional_data);
 662
 663         epoll_ev = talloc_zero(ev, struct epoll_event_context);
 664         if (!epoll_ev) return -1;
 665         epoll_ev->ev = ev;
 666         epoll_ev->epoll_fd = -1;
 667
 668         ret = epoll_init_ctx(epoll_ev);
 669         if (ret != 0) {
 670                 talloc_free(epoll_ev);
 671                 return ret;
 672         }
 673
 674         ev->additional_data = epoll_ev;
 675         return 0;
 676 }
 677
 678 /*
 679   destroy an fd_event
 680 */
 681 static int epoll_event_fd_destructor(struct tevent_fd *fde)
 682 {
 683         struct tevent_context *ev = fde->event_ctx;
 684         struct epoll_event_context *epoll_ev = NULL;
 685         bool panic_triggered = false;
 686         int flags = fde->flags;
 687
 688         if (ev == NULL) {
 689                 return tevent_common_fd_destructor(fde);
 690         }
 691
 692         epoll_ev = talloc_get_type_abort(ev->additional_data,
 693                                          struct epoll_event_context);
 694
 695         /*
 696          * we must remove the event from the list
 697          * otherwise a panic fallback handler may
 698          * reuse invalid memory
 699          */
 700         DLIST_REMOVE(ev->fd_events, fde);
 701
 702         epoll_ev->panic_state = &panic_triggered;
 703         epoll_check_reopen(epoll_ev);
 704         if (panic_triggered) {
 705                 return tevent_common_fd_destructor(fde);
 706         }
 707
 708         fde->flags = 0;
 709         epoll_update_event(epoll_ev, fde);
 710         fde->flags = flags;
 711         if (panic_triggered) {
 712                 return tevent_common_fd_destructor(fde);
 713         }
 714         epoll_ev->panic_state = NULL;
 715
 716         return tevent_common_fd_destructor(fde);
 717 }
 718
 719 /*
 720   add a fd based event
 721   return NULL on failure (memory allocation error)
 722 */
 723 static struct tevent_fd *epoll_event_add_fd(struct tevent_context *ev, TALLOC_CTX *mem_ctx,
 724                                             int fd, uint16_t flags,
 725                                             tevent_fd_handler_t handler,
 726                                             void *private_data,
 727                                             const char *handler_name,
 728                                             const char *location)
 729 {
 730         struct epoll_event_context *epoll_ev = talloc_get_type(ev->additional_data,
 731                                                            struct epoll_event_context);
 732         struct tevent_fd *fde;
 733         bool panic_triggered = false;
 734
 735         fde = tevent_common_add_fd(ev, mem_ctx, fd, flags,
 736                                    handler, private_data,
 737                                    handler_name, location);
 738         if (!fde) return NULL;
 739
 740         talloc_set_destructor(fde, epoll_event_fd_destructor);
 741
 742         epoll_ev->panic_state = &panic_triggered;
 743         epoll_check_reopen(epoll_ev);
 744         if (panic_triggered) {
 745                 return fde;
 746         }
 747         epoll_ev->panic_state = NULL;
 748
 749         epoll_update_event(epoll_ev, fde);
 750
 751         return fde;
 752 }
 753
 754 /*
 755   set the fd event flags
 756 */
 757 static void epoll_event_set_fd_flags(struct tevent_fd *fde, uint16_t flags)
 758 {
 759         struct tevent_context *ev;
 760         struct epoll_event_context *epoll_ev;
 761         bool panic_triggered = false;
 762
 763         if (fde->flags == flags) return;
 764
 765         ev = fde->event_ctx;
 766         epoll_ev = talloc_get_type(ev->additional_data, struct epoll_event_context);
 767
 768         fde->flags = flags;
 769
 770         epoll_ev->panic_state = &panic_triggered;
 771         epoll_check_reopen(epoll_ev);
 772         if (panic_triggered) {
 773                 return;
 774         }
 775         epoll_ev->panic_state = NULL;
 776
 777         epoll_update_event(epoll_ev, fde);
 778 }
 779
 780 /*
 781   do a single event loop using the events defined in ev
 782 */
 783 static int epoll_event_loop_once(struct tevent_context *ev, const char *location)
 784 {
 785         struct epoll_event_context *epoll_ev = talloc_get_type(ev->additional_data,
 786                                                            struct epoll_event_context);
 787         struct timeval tval;
 788         bool panic_triggered = false;
 789
 790         if (ev->signal_events &&
 791             tevent_common_check_signal(ev)) {
 792                 return 0;
 793         }
 794
 795         if (ev->immediate_events &&
 796             tevent_common_loop_immediate(ev)) {
 797                 return 0;
 798         }
 799
 800         tval = tevent_common_loop_timer_delay(ev);
 801         if (tevent_timeval_is_zero(&tval)) {
 802                 return 0;
 803         }
 804
 805         epoll_ev->panic_state = &panic_triggered;
 806         epoll_ev->panic_force_replay = true;
 807         epoll_check_reopen(epoll_ev);
 808         if (panic_triggered) {
 809                 errno = EINVAL;
 810                 return -1;
 811         }
 812         epoll_ev->panic_force_replay = false;
 813         epoll_ev->panic_state = NULL;
 814
 815         return epoll_event_loop(epoll_ev, &tval);
 816 }
 817
 818 static const struct tevent_ops epoll_event_ops = {
 819         .context_init           = epoll_event_context_init,
 820         .add_fd                 = epoll_event_add_fd,
 821         .set_fd_close_fn        = tevent_common_fd_set_close_fn,
 822         .get_fd_flags           = tevent_common_fd_get_flags,
 823         .set_fd_flags           = epoll_event_set_fd_flags,
 824         .add_timer              = tevent_common_add_timer,
 825         .schedule_immediate     = tevent_common_schedule_immediate,
 826         .add_signal             = tevent_common_add_signal,
 827         .loop_once              = epoll_event_loop_once,
 828         .loop_wait              = tevent_common_loop_wait,
 829 };
 830
 831 _PRIVATE_ bool tevent_epoll_init(void)
 832 {
 833         return tevent_register_backend("epoll", &epoll_event_ops);
 834 }