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         if (fd < 0 || fd >= FD_SETSIZE) {
 115                 errno = EBADF;
 116                 return NULL;
 117         }
 118
 119         fde = tevent_common_add_fd(ev, mem_ctx, fd, flags,
 120                                    handler, private_data,
 121                                    handler_name, location);
 122         if (!fde) return NULL;
 123
 124         if (fde->fd > select_ev->maxfd) {
 125                 select_ev->maxfd = fde->fd;
 126         }
 127         talloc_set_destructor(fde, select_event_fd_destructor);
 128
 129         return fde;
 130 }
 131
 132 /*
 133   event loop handling using select()
 134 */
 135 static int select_event_loop_select(struct select_event_context *select_ev, struct timeval *tvalp)
 136 {
 137         fd_set r_fds, w_fds;
 138         struct tevent_fd *fde;
 139         int selrtn;
 140
 141         /* we maybe need to recalculate the maxfd */
 142         if (select_ev->maxfd == EVENT_INVALID_MAXFD) {
 143                 calc_maxfd(select_ev);
 144         }
 145
 146         FD_ZERO(&r_fds);
 147         FD_ZERO(&w_fds);
 148
 149         /* setup any fd events */
 150         for (fde = select_ev->ev->fd_events; fde; fde = fde->next) {
 151                 if (fde->fd < 0 || fde->fd >= FD_SETSIZE) {
 152                         errno = EBADF;
 153                         return -1;
 154                 }
 155
 156                 if (fde->flags & TEVENT_FD_READ) {
 157                         FD_SET(fde->fd, &r_fds);
 158                 }
 159                 if (fde->flags & TEVENT_FD_WRITE) {
 160                         FD_SET(fde->fd, &w_fds);
 161                 }
 162         }
 163
 164         if (select_ev->ev->signal_events &&
 165             tevent_common_check_signal(select_ev->ev)) {
 166                 return 0;
 167         }
 168
 169         selrtn = select(select_ev->maxfd+1, &r_fds, &w_fds, NULL, tvalp);
 170
 171         if (selrtn == -1 && errno == EINTR &&
 172             select_ev->ev->signal_events) {
 173                 tevent_common_check_signal(select_ev->ev);
 174                 return 0;
 175         }
 176
 177         if (selrtn == -1 && errno == EBADF) {
 178                 /* the socket is dead! this should never
 179                    happen as the socket should have first been
 180                    made readable and that should have removed
 181                    the event, so this must be a bug. This is a
 182                    fatal error. */
 183                 tevent_debug(select_ev->ev, TEVENT_DEBUG_FATAL,
 184                              "ERROR: EBADF on select_event_loop_once\n");
 185                 select_ev->exit_code = EBADF;
 186                 return -1;
 187         }
 188
 189         if (selrtn == 0 && tvalp) {
 190                 /* we don't care about a possible delay here */
 191                 tevent_common_loop_timer_delay(select_ev->ev);
 192                 return 0;
 193         }
 194
 195         if (selrtn > 0) {
 196                 /* at least one file descriptor is ready - check
 197                    which ones and call the handler, being careful to allow
 198                    the handler to remove itself when called */
 199                 for (fde = select_ev->ev->fd_events; fde; fde = fde->next) {
 200                         uint16_t flags = 0;
 201
 202                         if (FD_ISSET(fde->fd, &r_fds)) flags |= TEVENT_FD_READ;
 203                         if (FD_ISSET(fde->fd, &w_fds)) flags |= TEVENT_FD_WRITE;
 204                         if (flags) {
 205                                 fde->handler(select_ev->ev, fde, flags, fde->private_data);
 206                                 break;
 207                         }
 208                 }
 209         }
 210
 211         return 0;
 212 }
 213
 214 /*
 215   do a single event loop using the events defined in ev
 216 */
 217 static int select_event_loop_once(struct tevent_context *ev, const char *location)
 218 {
 219         struct select_event_context *select_ev = talloc_get_type(ev->additional_data,
 220                                                            struct select_event_context);
 221         struct timeval tval;
 222
 223         if (ev->signal_events &&
 224             tevent_common_check_signal(ev)) {
 225                 return 0;
 226         }
 227
 228         if (ev->immediate_events &&
 229             tevent_common_loop_immediate(ev)) {
 230                 return 0;
 231         }
 232
 233         tval = tevent_common_loop_timer_delay(ev);
 234         if (tevent_timeval_is_zero(&tval)) {
 235                 return 0;
 236         }
 237
 238         return select_event_loop_select(select_ev, &tval);
 239 }
 240
 241 static const struct tevent_ops select_event_ops = {
 242         .context_init           = select_event_context_init,
 243         .add_fd                 = select_event_add_fd,
 244         .set_fd_close_fn        = tevent_common_fd_set_close_fn,
 245         .get_fd_flags           = tevent_common_fd_get_flags,
 246         .set_fd_flags           = tevent_common_fd_set_flags,
 247         .add_timer              = tevent_common_add_timer,
 248         .schedule_immediate     = tevent_common_schedule_immediate,
 249         .add_signal             = tevent_common_add_signal,
 250         .loop_once              = select_event_loop_once,
 251         .loop_wait              = tevent_common_loop_wait,
 252 };
 253
 254 bool tevent_select_init(void)
 255 {
 256         return tevent_register_backend("select", &select_event_ops);
 257 }