source3/smbd/notify_inotify.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    Copyright (C) Andrew Tridgell 2006
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 /*
  21   notify implementation using inotify
  22 */
  23
  24 #include "includes.h"
  25 #include "../librpc/gen_ndr/notify.h"
  26 #include "smbd/smbd.h"
  27 #include "lib/util/sys_rw_data.h"
  28
  29 #include <sys/inotify.h>
  30
  31 /* glibc < 2.5 headers don't have these defines */
  32 #ifndef IN_ONLYDIR
  33 #define IN_ONLYDIR 0x01000000
  34 #endif
  35 #ifndef IN_MASK_ADD
  36 #define IN_MASK_ADD 0x20000000
  37 #endif
  38
  39 struct inotify_private {
  40         struct sys_notify_context *ctx;
  41         int fd;
  42         struct inotify_watch_context *watches;
  43 };
  44
  45 struct inotify_watch_context {
  46         struct inotify_watch_context *next, *prev;
  47         struct inotify_private *in;
  48         int wd;
  49         void (*callback)(struct sys_notify_context *ctx,
  50                          void *private_data,
  51                          struct notify_event *ev,
  52                          uint32_t filter);
  53         void *private_data;
  54         uint32_t mask; /* the inotify mask */
  55         uint32_t filter; /* the windows completion filter */
  56         const char *path;
  57 };
  58
  59
  60 /*
  61   map from a change notify mask to a inotify mask. Remove any bits
  62   which we can handle
  63 */
  64 static const struct {
  65         uint32_t notify_mask;
  66         uint32_t inotify_mask;
  67 } inotify_mapping[] = {
  68         {FILE_NOTIFY_CHANGE_FILE_NAME,   IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO},
  69         {FILE_NOTIFY_CHANGE_DIR_NAME,    IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO},
  70         {FILE_NOTIFY_CHANGE_ATTRIBUTES,  IN_ATTRIB|IN_MOVED_TO|IN_MOVED_FROM|IN_MODIFY},
  71         {FILE_NOTIFY_CHANGE_LAST_WRITE,  IN_ATTRIB},
  72         {FILE_NOTIFY_CHANGE_LAST_ACCESS, IN_ATTRIB},
  73         {FILE_NOTIFY_CHANGE_EA,          IN_ATTRIB},
  74         {FILE_NOTIFY_CHANGE_SECURITY,    IN_ATTRIB}
  75 };
  76
  77 static uint32_t inotify_map(uint32_t *filter)
  78 {
  79         size_t i;
  80         uint32_t out=0;
  81         for (i=0;i<ARRAY_SIZE(inotify_mapping);i++) {
  82                 if (inotify_mapping[i].notify_mask & *filter) {
  83                         out |= inotify_mapping[i].inotify_mask;
  84                         *filter &= ~inotify_mapping[i].notify_mask;
  85                 }
  86         }
  87         return out;
  88 }
  89
  90 /*
  91  * Map inotify mask back to filter. This returns all filters that
  92  * could have created the inotify watch.
  93  */
  94 static uint32_t inotify_map_mask_to_filter(uint32_t mask)
  95 {
  96         size_t i;
  97         uint32_t filter = 0;
  98
  99         for (i = 0; i < ARRAY_SIZE(inotify_mapping); i++) {
 100                 if (inotify_mapping[i].inotify_mask & mask) {
 101                         filter |= inotify_mapping[i].notify_mask;
 102                 }
 103         }
 104
 105         if (mask & IN_ISDIR) {
 106                 filter &= ~FILE_NOTIFY_CHANGE_FILE_NAME;
 107         } else {
 108                 filter &= ~FILE_NOTIFY_CHANGE_DIR_NAME;
 109         }
 110
 111         return filter;
 112 }
 113
 114 /*
 115   destroy the inotify private context
 116 */
 117 static int inotify_destructor(struct inotify_private *in)
 118 {
 119         close(in->fd);
 120         return 0;
 121 }
 122
 123
 124 /*
 125   see if a particular event from inotify really does match a requested
 126   notify event in SMB
 127 */
 128 static bool filter_match(struct inotify_watch_context *w,
 129                          struct inotify_event *e)
 130 {
 131         bool ok;
 132
 133         DEBUG(10, ("filter_match: e->mask=%x, w->mask=%x, w->filter=%x\n",
 134                    e->mask, w->mask, w->filter));
 135
 136         if ((e->mask & w->mask) == 0) {
 137                 /* this happens because inotify_add_watch() coalesces watches on the same
 138                    path, oring their masks together */
 139                 return False;
 140         }
 141
 142         /* SMB separates the filters for files and directories */
 143         if (e->mask & IN_ISDIR) {
 144                 ok = ((w->filter & FILE_NOTIFY_CHANGE_DIR_NAME) != 0);
 145                 return ok;
 146         }
 147
 148         if ((e->mask & IN_ATTRIB) &&
 149             (w->filter & (FILE_NOTIFY_CHANGE_ATTRIBUTES|
 150                           FILE_NOTIFY_CHANGE_LAST_WRITE|
 151                           FILE_NOTIFY_CHANGE_LAST_ACCESS|
 152                           FILE_NOTIFY_CHANGE_EA|
 153                           FILE_NOTIFY_CHANGE_SECURITY))) {
 154                 return True;
 155         }
 156         if ((e->mask & IN_MODIFY) &&
 157             (w->filter & FILE_NOTIFY_CHANGE_ATTRIBUTES)) {
 158                 return True;
 159         }
 160
 161         ok = ((w->filter & FILE_NOTIFY_CHANGE_FILE_NAME) != 0);
 162         return ok;
 163 }
 164
 165
 166
 167 /*
 168   dispatch one inotify event
 169
 170   the cookies are used to correctly handle renames
 171 */
 172 static void inotify_dispatch(struct inotify_private *in,
 173                              struct inotify_event *e,
 174                              int prev_wd,
 175                              uint32_t prev_cookie,
 176                              struct inotify_event *e2)
 177 {
 178         struct inotify_watch_context *w, *next;
 179         struct notify_event ne;
 180         uint32_t filter;
 181
 182         DEBUG(10, ("inotify_dispatch called with mask=%x, name=[%s]\n",
 183                    e->mask, e->len ? e->name : ""));
 184
 185         /* ignore extraneous events, such as unmount and IN_IGNORED events */
 186         if ((e->mask & (IN_ATTRIB|IN_MODIFY|IN_CREATE|IN_DELETE|
 187                         IN_MOVED_FROM|IN_MOVED_TO)) == 0) {
 188                 return;
 189         }
 190
 191         /* map the inotify mask to a action. This gets complicated for
 192            renames */
 193         if (e->mask & IN_CREATE) {
 194                 ne.action = NOTIFY_ACTION_ADDED;
 195         } else if (e->mask & IN_DELETE) {
 196                 ne.action = NOTIFY_ACTION_REMOVED;
 197         } else if (e->mask & IN_MOVED_FROM) {
 198                 if (e2 != NULL && e2->cookie == e->cookie &&
 199                     e2->wd == e->wd) {
 200                         ne.action = NOTIFY_ACTION_OLD_NAME;
 201                 } else {
 202                         ne.action = NOTIFY_ACTION_REMOVED;
 203                 }
 204         } else if (e->mask & IN_MOVED_TO) {
 205                 if ((e->cookie == prev_cookie) && (e->wd == prev_wd)) {
 206                         ne.action = NOTIFY_ACTION_NEW_NAME;
 207                 } else {
 208                         ne.action = NOTIFY_ACTION_ADDED;
 209                 }
 210         } else {
 211                 ne.action = NOTIFY_ACTION_MODIFIED;
 212         }
 213         ne.path = e->name;
 214
 215         filter = inotify_map_mask_to_filter(e->mask);
 216
 217         DBG_DEBUG("ne.action = %d, ne.path = %s, filter = %d\n",
 218                   ne.action, ne.path, filter);
 219
 220         /* find any watches that have this watch descriptor */
 221         for (w=in->watches;w;w=next) {
 222                 next = w->next;
 223                 if (w->wd == e->wd && filter_match(w, e)) {
 224                         ne.dir = w->path;
 225                         w->callback(in->ctx, w->private_data, &ne, filter);
 226                 }
 227         }
 228
 229         if ((ne.action == NOTIFY_ACTION_NEW_NAME) &&
 230             ((e->mask & IN_ISDIR) == 0)) {
 231
 232                 /*
 233                  * SMB expects a file rename to generate three events, two for
 234                  * the rename and the other for a modify of the
 235                  * destination. Strange!
 236                  */
 237
 238                 ne.action = NOTIFY_ACTION_MODIFIED;
 239                 e->mask = IN_ATTRIB;
 240
 241                 for (w=in->watches;w;w=next) {
 242                         next = w->next;
 243                         if (w->wd == e->wd && filter_match(w, e) &&
 244                             !(w->filter & FILE_NOTIFY_CHANGE_CREATION)) {
 245                                 ne.dir = w->path;
 246                                 w->callback(in->ctx, w->private_data, &ne,
 247                                             filter);
 248                         }
 249                 }
 250         }
 251 }
 252
 253 /*
 254   called when the kernel has some events for us
 255 */
 256 static void inotify_handler(struct tevent_context *ev, struct tevent_fd *fde,
 257                             uint16_t flags, void *private_data)
 258 {
 259         struct inotify_private *in = talloc_get_type(private_data,
 260                                                      struct inotify_private);
 261         int bufsize = 0;
 262         struct inotify_event *e0, *e;
 263         uint32_t prev_cookie=0;
 264         int prev_wd = -1;
 265         ssize_t ret;
 266
 267         /*
 268           we must use FIONREAD as we cannot predict the length of the
 269           filenames, and thus can't know how much to allocate
 270           otherwise
 271         */
 272         if (ioctl(in->fd, FIONREAD, &bufsize) != 0 ||
 273             bufsize == 0) {
 274                 DEBUG(0,("No data on inotify fd?!\n"));
 275                 TALLOC_FREE(fde);
 276                 return;
 277         }
 278
 279         e0 = e = (struct inotify_event *)TALLOC_SIZE(in, bufsize + 1);
 280         if (e == NULL) return;
 281         ((uint8_t *)e)[bufsize] = '\0';
 282
 283         ret = read_data(in->fd, e0, bufsize);
 284         if (ret != bufsize) {
 285                 DEBUG(0, ("Failed to read all inotify data - %s\n",
 286                           strerror(errno)));
 287                 talloc_free(e0);
 288                 /* the inotify fd will now be out of sync,
 289                  * can't keep reading data off it */
 290                 TALLOC_FREE(fde);
 291                 return;
 292         }
 293
 294         /* we can get more than one event in the buffer */
 295         while (e && (bufsize >= sizeof(*e))) {
 296                 struct inotify_event *e2 = NULL;
 297                 bufsize -= e->len + sizeof(*e);
 298                 if (bufsize >= sizeof(*e)) {
 299                         e2 = (struct inotify_event *)(e->len + sizeof(*e) + (char *)e);
 300                 }
 301                 inotify_dispatch(in, e, prev_wd, prev_cookie, e2);
 302                 prev_wd = e->wd;
 303                 prev_cookie = e->cookie;
 304                 e = e2;
 305         }
 306
 307         talloc_free(e0);
 308 }
 309
 310 /*
 311   setup the inotify handle - called the first time a watch is added on
 312   this context
 313 */
 314 static int inotify_setup(struct sys_notify_context *ctx)
 315 {
 316         struct inotify_private *in;
 317         struct tevent_fd *fde;
 318
 319         in = talloc(ctx, struct inotify_private);
 320         if (in == NULL) {
 321                 return ENOMEM;
 322         }
 323
 324         in->fd = inotify_init();
 325         if (in->fd == -1) {
 326                 int ret = errno;
 327                 DEBUG(0, ("Failed to init inotify - %s\n", strerror(ret)));
 328                 talloc_free(in);
 329                 return ret;
 330         }
 331         in->ctx = ctx;
 332         in->watches = NULL;
 333
 334         ctx->private_data = in;
 335         talloc_set_destructor(in, inotify_destructor);
 336
 337         /* add a event waiting for the inotify fd to be readable */
 338         fde = tevent_add_fd(ctx->ev, in, in->fd, TEVENT_FD_READ,
 339                             inotify_handler, in);
 340         if (fde == NULL) {
 341                 ctx->private_data = NULL;
 342                 TALLOC_FREE(in);
 343                 return ENOMEM;
 344         }
 345         return 0;
 346 }
 347
 348 /*
 349   destroy a watch
 350 */
 351 static int watch_destructor(struct inotify_watch_context *w)
 352 {
 353         struct inotify_private *in = w->in;
 354         int wd = w->wd;
 355         DLIST_REMOVE(w->in->watches, w);
 356
 357         for (w=in->watches;w;w=w->next) {
 358                 if (w->wd == wd) {
 359                         /*
 360                          * Another inotify_watch_context listens on this path,
 361                          * leave the kernel level watch in place
 362                          */
 363                         return 0;
 364                 }
 365         }
 366
 367         DEBUG(10, ("Deleting inotify watch %d\n", wd));
 368         if (inotify_rm_watch(in->fd, wd) == -1) {
 369                 DEBUG(1, ("inotify_rm_watch returned %s\n", strerror(errno)));
 370         }
 371         return 0;
 372 }
 373
 374
 375 /*
 376   add a watch. The watch is removed when the caller calls
 377   talloc_free() on *handle
 378 */
 379 int inotify_watch(TALLOC_CTX *mem_ctx,
 380                   struct sys_notify_context *ctx,
 381                   const char *path,
 382                   uint32_t *filter,
 383                   uint32_t *subdir_filter,
 384                   void (*callback)(struct sys_notify_context *ctx,
 385                                    void *private_data,
 386                                    struct notify_event *ev,
 387                                    uint32_t filter),
 388                   void *private_data,
 389                   void *handle_p)
 390 {
 391         struct inotify_private *in;
 392         uint32_t mask;
 393         struct inotify_watch_context *w;
 394         uint32_t orig_filter = *filter;
 395         void **handle = (void **)handle_p;
 396
 397         /* maybe setup the inotify fd */
 398         if (ctx->private_data == NULL) {
 399                 int ret;
 400                 ret = inotify_setup(ctx);
 401                 if (ret != 0) {
 402                         return ret;
 403                 }
 404         }
 405
 406         in = talloc_get_type(ctx->private_data, struct inotify_private);
 407
 408         mask = inotify_map(filter);
 409         if (mask == 0) {
 410                 /* this filter can't be handled by inotify */
 411                 return EINVAL;
 412         }
 413
 414         /* using IN_MASK_ADD allows us to cope with inotify() returning the same
 415            watch descriptor for multiple watches on the same path */
 416         mask |= (IN_MASK_ADD | IN_ONLYDIR);
 417
 418         w = talloc(mem_ctx, struct inotify_watch_context);
 419         if (w == NULL) {
 420                 *filter = orig_filter;
 421                 return ENOMEM;
 422         }
 423
 424         w->in = in;
 425         w->callback = callback;
 426         w->private_data = private_data;
 427         w->mask = mask;
 428         w->filter = orig_filter;
 429         w->path = talloc_strdup(w, path);
 430         if (w->path == NULL) {
 431                 *filter = orig_filter;
 432                 TALLOC_FREE(w);
 433                 return ENOMEM;
 434         }
 435
 436         /* get a new watch descriptor for this path */
 437         w->wd = inotify_add_watch(in->fd, path, mask);
 438         if (w->wd == -1) {
 439                 int err = errno;
 440                 *filter = orig_filter;
 441                 TALLOC_FREE(w);
 442                 DEBUG(1, ("inotify_add_watch returned %s\n", strerror(err)));
 443                 return err;
 444         }
 445
 446         DEBUG(10, ("inotify_add_watch for %s mask %x returned wd %d\n",
 447                    path, mask, w->wd));
 448
 449         (*handle) = w;
 450
 451         DLIST_ADD(in->watches, w);
 452
 453         /* the caller frees the handle to stop watching */
 454         talloc_set_destructor(w, watch_destructor);
 455
 456         return 0;
 457 }