lib/tevent/tevent_select.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    main select loop and event handling
   4    Copyright (C) Andrew Tridgell        2003-2005
   5    Copyright (C) Stefan Metzmacher      2005-2009
   6
   7      ** NOTE! The following LGPL license applies to the tevent
   8      ** library. This does NOT imply that all of Samba is released
   9      ** under the LGPL
  10
  11    This library is free software; you can redistribute it and/or
  12    modify it under the terms of the GNU Lesser General Public
  13    License as published by the Free Software Foundation; either
  14    version 3 of the License, or (at your option) any later version.
  15
  16    This library is distributed in the hope that it will be useful,
  17    but WITHOUT ANY WARRANTY; without even the implied warranty of
  18    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19    Lesser General Public License for more details.
  20
  21    You should have received a copy of the GNU Lesser General Public
  22    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  23 */
  24
  25 #include "replace.h"
  26 #include "system/filesys.h"
  27 #include "system/select.h"
  28 #include "tevent.h"
  29 #include "tevent_util.h"
  30 #include "tevent_internal.h"
  31
  32 struct select_event_context {
  33         /* a pointer back to the generic event_context */
  34         struct tevent_context *ev;
  35
  36         /* the maximum file descriptor number in fd_events */
  37         int maxfd;
  38
  39         /* information for exiting from the event loop */
  40         int exit_code;
  41 };
  42
  43 /*
  44   create a select_event_context structure.
  45 */
  46 static int select_event_context_init(struct tevent_context *ev)
  47 {
  48         struct select_event_context *select_ev;
  49
  50         select_ev = talloc_zero(ev, struct select_event_context);
  51         if (!select_ev) return -1;
  52         select_ev->ev = ev;
  53
  54         ev->additional_data = select_ev;
  55         return 0;
  56 }
  57
  58 /*
  59   recalculate the maxfd
  60 */
  61 static void calc_maxfd(struct select_event_context *select_ev)
  62 {
  63         struct tevent_fd *fde;
  64
  65         select_ev->maxfd = 0;
  66         for (fde = select_ev->ev->fd_events; fde; fde = fde->next) {
  67                 if (fde->fd > select_ev->maxfd) {
  68                         select_ev->maxfd = fde->fd;
  69                 }
  70         }
  71 }
  72
  73
  74 /* to mark the ev->maxfd invalid
  75  * this means we need to recalculate it
  76  */
  77 #define EVENT_INVALID_MAXFD (-1)
  78
  79 /*
  80   destroy an fd_event
  81 */
  82 static int select_event_fd_destructor(struct tevent_fd *fde)
  83 {
  84         struct tevent_context *ev = fde->event_ctx;
  85         struct select_event_context *select_ev = NULL;
  86
  87         if (ev) {
  88                 select_ev = talloc_get_type(ev->additional_data,
  89                                             struct select_event_context);
  90
  91                 if (select_ev->maxfd == fde->fd) {
  92                         select_ev->maxfd = EVENT_INVALID_MAXFD;
  93                 }
  94         }
  95
  96         return tevent_common_fd_destructor(fde);
  97 }
  98
  99 /*
 100   add a fd based event
 101   return NULL on failure (memory allocation error)
 102 */
 103 static struct tevent_fd *select_event_add_fd(struct tevent_context *ev, TALLOC_CTX *mem_ctx,
 104                                              int fd, uint16_t flags,
 105                                              tevent_fd_handler_t handler,
 106                                              void *private_data,
 107                                              const char *handler_name,
 108                                              const char *location)
 109 {
 110         struct select_event_context *select_ev = talloc_get_type(ev->additional_data,
 111                                                            struct select_event_context);
 112         struct tevent_fd *fde;
 113
 114         fde = tevent_common_add_fd(ev, mem_ctx, fd, flags,
 115                                    handler, private_data,
 116                                    handler_name, location);
 117         if (!fde) return NULL;
 118
 119         if ((select_ev->maxfd != EVENT_INVALID_MAXFD)
 120             && (fde->fd > select_ev->maxfd)) {
 121                 select_ev->maxfd = fde->fd;
 122         }
 123         talloc_set_destructor(fde, select_event_fd_destructor);
 124
 125         return fde;
 126 }
 127
 128 /*
 129   event loop handling using select()
 130 */
 131 static int select_event_loop_select(struct select_event_context *select_ev, struct timeval *tvalp)
 132 {
 133         fd_set r_fds, w_fds;
 134         struct tevent_fd *fde;
 135         int selrtn;
 136
 137         /* we maybe need to recalculate the maxfd */
 138         if (select_ev->maxfd == EVENT_INVALID_MAXFD) {
 139                 calc_maxfd(select_ev);
 140         }
 141
 142         FD_ZERO(&r_fds);
 143         FD_ZERO(&w_fds);
 144
 145         /* setup any fd events */
 146         for (fde = select_ev->ev->fd_events; fde; fde = fde->next) {
 147                 if (fde->flags & TEVENT_FD_READ) {
 148                         FD_SET(fde->fd, &r_fds);
 149                 }
 150                 if (fde->flags & TEVENT_FD_WRITE) {
 151                         FD_SET(fde->fd, &w_fds);
 152                 }
 153         }
 154
 155         if (select_ev->ev->signal_events &&
 156             tevent_common_check_signal(select_ev->ev)) {
 157                 return 0;
 158         }
 159
 160         selrtn = select(select_ev->maxfd+1, &r_fds, &w_fds, NULL, tvalp);
 161
 162         if (selrtn == -1 && errno == EINTR &&
 163             select_ev->ev->signal_events) {
 164                 tevent_common_check_signal(select_ev->ev);
 165                 return 0;
 166         }
 167
 168         if (selrtn == -1 && errno == EBADF) {
 169                 /* the socket is dead! this should never
 170                    happen as the socket should have first been
 171                    made readable and that should have removed
 172                    the event, so this must be a bug. This is a
 173                    fatal error. */
 174                 tevent_debug(select_ev->ev, TEVENT_DEBUG_FATAL,
 175                              "ERROR: EBADF on select_event_loop_once\n");
 176                 select_ev->exit_code = EBADF;
 177                 return -1;
 178         }
 179
 180         if (selrtn == 0 && tvalp) {
 181                 /* we don't care about a possible delay here */
 182                 tevent_common_loop_timer_delay(select_ev->ev);
 183                 return 0;
 184         }
 185
 186         if (selrtn > 0) {
 187                 /* at least one file descriptor is ready - check
 188                    which ones and call the handler, being careful to allow
 189                    the handler to remove itself when called */
 190                 for (fde = select_ev->ev->fd_events; fde; fde = fde->next) {
 191                         uint16_t flags = 0;
 192
 193                         if (FD_ISSET(fde->fd, &r_fds)) flags |= TEVENT_FD_READ;
 194                         if (FD_ISSET(fde->fd, &w_fds)) flags |= TEVENT_FD_WRITE;
 195                         if (flags) {
 196                                 fde->handler(select_ev->ev, fde, flags, fde->private_data);
 197                                 break;
 198                         }
 199                 }
 200         }
 201
 202         return 0;
 203 }
 204
 205 /*
 206   do a single event loop using the events defined in ev
 207 */
 208 static int select_event_loop_once(struct tevent_context *ev, const char *location)
 209 {
 210         struct select_event_context *select_ev = talloc_get_type(ev->additional_data,
 211                                                            struct select_event_context);
 212         struct timeval tval;
 213
 214         if (ev->signal_events &&
 215             tevent_common_check_signal(ev)) {
 216                 return 0;
 217         }
 218
 219         if (ev->immediate_events &&
 220             tevent_common_loop_immediate(ev)) {
 221                 return 0;
 222         }
 223
 224         tval = tevent_common_loop_timer_delay(ev);
 225         if (tevent_timeval_is_zero(&tval)) {
 226                 return 0;
 227         }
 228
 229         return select_event_loop_select(select_ev, &tval);
 230 }
 231
 232 static const struct tevent_ops select_event_ops = {
 233         .context_init           = select_event_context_init,
 234         .add_fd                 = select_event_add_fd,
 235         .set_fd_close_fn        = tevent_common_fd_set_close_fn,
 236         .get_fd_flags           = tevent_common_fd_get_flags,
 237         .set_fd_flags           = tevent_common_fd_set_flags,
 238         .add_timer              = tevent_common_add_timer,
 239         .schedule_immediate     = tevent_common_schedule_immediate,
 240         .add_signal             = tevent_common_add_signal,
 241         .loop_once              = select_event_loop_once,
 242         .loop_wait              = tevent_common_loop_wait,
 243 };
 244
 245 _PRIVATE_ bool tevent_select_init(void)
 246 {
 247         return tevent_register_backend("select", &select_event_ops);
 248 }