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/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         void *private_data;
  53         uint32_t mask; /* the inotify mask */
  54         uint32_t filter; /* the windows completion filter */
  55         const char *path;
  56 };
  57
  58
  59 /*
  60   destroy the inotify private context
  61 */
  62 static int inotify_destructor(struct inotify_private *in)
  63 {
  64         close(in->fd);
  65         return 0;
  66 }
  67
  68
  69 /*
  70   see if a particular event from inotify really does match a requested
  71   notify event in SMB
  72 */
  73 static bool filter_match(struct inotify_watch_context *w,
  74                          struct inotify_event *e)
  75 {
  76         bool ok;
  77
  78         DEBUG(10, ("filter_match: e->mask=%x, w->mask=%x, w->filter=%x\n",
  79                    e->mask, w->mask, w->filter));
  80
  81         if ((e->mask & w->mask) == 0) {
  82                 /* this happens because inotify_add_watch() coalesces watches on the same
  83                    path, oring their masks together */
  84                 return False;
  85         }
  86
  87         /* SMB separates the filters for files and directories */
  88         if (e->mask & IN_ISDIR) {
  89                 ok = ((w->filter & FILE_NOTIFY_CHANGE_DIR_NAME) != 0);
  90                 return ok;
  91         }
  92
  93         if ((e->mask & IN_ATTRIB) &&
  94             (w->filter & (FILE_NOTIFY_CHANGE_ATTRIBUTES|
  95                           FILE_NOTIFY_CHANGE_LAST_WRITE|
  96                           FILE_NOTIFY_CHANGE_LAST_ACCESS|
  97                           FILE_NOTIFY_CHANGE_EA|
  98                           FILE_NOTIFY_CHANGE_SECURITY))) {
  99                 return True;
 100         }
 101         if ((e->mask & IN_MODIFY) &&
 102             (w->filter & FILE_NOTIFY_CHANGE_ATTRIBUTES)) {
 103                 return True;
 104         }
 105
 106         ok = ((w->filter & FILE_NOTIFY_CHANGE_FILE_NAME) != 0);
 107         return ok;
 108 }
 109
 110
 111
 112 /*
 113   dispatch one inotify event
 114
 115   the cookies are used to correctly handle renames
 116 */
 117 static void inotify_dispatch(struct inotify_private *in,
 118                              struct inotify_event *e,
 119                              int prev_wd,
 120                              uint32_t prev_cookie,
 121                              struct inotify_event *e2)
 122 {
 123         struct inotify_watch_context *w, *next;
 124         struct notify_event ne;
 125
 126         DEBUG(10, ("inotify_dispatch called with mask=%x, name=[%s]\n",
 127                    e->mask, e->len ? e->name : ""));
 128
 129         /* ignore extraneous events, such as unmount and IN_IGNORED events */
 130         if ((e->mask & (IN_ATTRIB|IN_MODIFY|IN_CREATE|IN_DELETE|
 131                         IN_MOVED_FROM|IN_MOVED_TO)) == 0) {
 132                 return;
 133         }
 134
 135         /* map the inotify mask to a action. This gets complicated for
 136            renames */
 137         if (e->mask & IN_CREATE) {
 138                 ne.action = NOTIFY_ACTION_ADDED;
 139         } else if (e->mask & IN_DELETE) {
 140                 ne.action = NOTIFY_ACTION_REMOVED;
 141         } else if (e->mask & IN_MOVED_FROM) {
 142                 if (e2 != NULL && e2->cookie == e->cookie &&
 143                     e2->wd == e->wd) {
 144                         ne.action = NOTIFY_ACTION_OLD_NAME;
 145                 } else {
 146                         ne.action = NOTIFY_ACTION_REMOVED;
 147                 }
 148         } else if (e->mask & IN_MOVED_TO) {
 149                 if ((e->cookie == prev_cookie) && (e->wd == prev_wd)) {
 150                         ne.action = NOTIFY_ACTION_NEW_NAME;
 151                 } else {
 152                         ne.action = NOTIFY_ACTION_ADDED;
 153                 }
 154         } else {
 155                 ne.action = NOTIFY_ACTION_MODIFIED;
 156         }
 157         ne.path = e->name;
 158
 159         DEBUG(10, ("inotify_dispatch: ne.action = %d, ne.path = %s\n",
 160                    ne.action, ne.path));
 161
 162         /* find any watches that have this watch descriptor */
 163         for (w=in->watches;w;w=next) {
 164                 next = w->next;
 165                 if (w->wd == e->wd && filter_match(w, e)) {
 166                         ne.dir = w->path;
 167                         w->callback(in->ctx, w->private_data, &ne);
 168                 }
 169         }
 170
 171         if ((ne.action == NOTIFY_ACTION_NEW_NAME) &&
 172             ((e->mask & IN_ISDIR) == 0)) {
 173
 174                 /*
 175                  * SMB expects a file rename to generate three events, two for
 176                  * the rename and the other for a modify of the
 177                  * destination. Strange!
 178                  */
 179
 180                 ne.action = NOTIFY_ACTION_MODIFIED;
 181                 e->mask = IN_ATTRIB;
 182
 183                 for (w=in->watches;w;w=next) {
 184                         next = w->next;
 185                         if (w->wd == e->wd && filter_match(w, e) &&
 186                             !(w->filter & FILE_NOTIFY_CHANGE_CREATION)) {
 187                                 ne.dir = w->path;
 188                                 w->callback(in->ctx, w->private_data, &ne);
 189                         }
 190                 }
 191         }
 192 }
 193
 194 /*
 195   called when the kernel has some events for us
 196 */
 197 static void inotify_handler(struct tevent_context *ev, struct tevent_fd *fde,
 198                             uint16_t flags, void *private_data)
 199 {
 200         struct inotify_private *in = talloc_get_type(private_data,
 201                                                      struct inotify_private);
 202         int bufsize = 0;
 203         struct inotify_event *e0, *e;
 204         uint32_t prev_cookie=0;
 205         int prev_wd = -1;
 206         ssize_t ret;
 207
 208         /*
 209           we must use FIONREAD as we cannot predict the length of the
 210           filenames, and thus can't know how much to allocate
 211           otherwise
 212         */
 213         if (ioctl(in->fd, FIONREAD, &bufsize) != 0 ||
 214             bufsize == 0) {
 215                 DEBUG(0,("No data on inotify fd?!\n"));
 216                 TALLOC_FREE(fde);
 217                 return;
 218         }
 219
 220         e0 = e = (struct inotify_event *)TALLOC_SIZE(in, bufsize + 1);
 221         if (e == NULL) return;
 222         ((uint8_t *)e)[bufsize] = '\0';
 223
 224         ret = read_data(in->fd, e0, bufsize);
 225         if (ret != bufsize) {
 226                 DEBUG(0, ("Failed to read all inotify data - %s\n",
 227                           strerror(errno)));
 228                 talloc_free(e0);
 229                 /* the inotify fd will now be out of sync,
 230                  * can't keep reading data off it */
 231                 TALLOC_FREE(fde);
 232                 return;
 233         }
 234
 235         /* we can get more than one event in the buffer */
 236         while (e && (bufsize >= sizeof(*e))) {
 237                 struct inotify_event *e2 = NULL;
 238                 bufsize -= e->len + sizeof(*e);
 239                 if (bufsize >= sizeof(*e)) {
 240                         e2 = (struct inotify_event *)(e->len + sizeof(*e) + (char *)e);
 241                 }
 242                 inotify_dispatch(in, e, prev_wd, prev_cookie, e2);
 243                 prev_wd = e->wd;
 244                 prev_cookie = e->cookie;
 245                 e = e2;
 246         }
 247
 248         talloc_free(e0);
 249 }
 250
 251 /*
 252   setup the inotify handle - called the first time a watch is added on
 253   this context
 254 */
 255 static int inotify_setup(struct sys_notify_context *ctx)
 256 {
 257         struct inotify_private *in;
 258         struct tevent_fd *fde;
 259
 260         in = talloc(ctx, struct inotify_private);
 261         if (in == NULL) {
 262                 return ENOMEM;
 263         }
 264
 265         in->fd = inotify_init();
 266         if (in->fd == -1) {
 267                 int ret = errno;
 268                 DEBUG(0, ("Failed to init inotify - %s\n", strerror(ret)));
 269                 talloc_free(in);
 270                 return ret;
 271         }
 272         in->ctx = ctx;
 273         in->watches = NULL;
 274
 275         ctx->private_data = in;
 276         talloc_set_destructor(in, inotify_destructor);
 277
 278         /* add a event waiting for the inotify fd to be readable */
 279         fde = tevent_add_fd(ctx->ev, in, in->fd, TEVENT_FD_READ,
 280                             inotify_handler, in);
 281         if (fde == NULL) {
 282                 ctx->private_data = NULL;
 283                 TALLOC_FREE(in);
 284                 return ENOMEM;
 285         }
 286         return 0;
 287 }
 288
 289
 290 /*
 291   map from a change notify mask to a inotify mask. Remove any bits
 292   which we can handle
 293 */
 294 static const struct {
 295         uint32_t notify_mask;
 296         uint32_t inotify_mask;
 297 } inotify_mapping[] = {
 298         {FILE_NOTIFY_CHANGE_FILE_NAME,   IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO},
 299         {FILE_NOTIFY_CHANGE_DIR_NAME,    IN_CREATE|IN_DELETE|IN_MOVED_FROM|IN_MOVED_TO},
 300         {FILE_NOTIFY_CHANGE_ATTRIBUTES,  IN_ATTRIB|IN_MOVED_TO|IN_MOVED_FROM|IN_MODIFY},
 301         {FILE_NOTIFY_CHANGE_LAST_WRITE,  IN_ATTRIB},
 302         {FILE_NOTIFY_CHANGE_LAST_ACCESS, IN_ATTRIB},
 303         {FILE_NOTIFY_CHANGE_EA,          IN_ATTRIB},
 304         {FILE_NOTIFY_CHANGE_SECURITY,    IN_ATTRIB}
 305 };
 306
 307 static uint32_t inotify_map(uint32_t *filter)
 308 {
 309         int i;
 310         uint32_t out=0;
 311         for (i=0;i<ARRAY_SIZE(inotify_mapping);i++) {
 312                 if (inotify_mapping[i].notify_mask & *filter) {
 313                         out |= inotify_mapping[i].inotify_mask;
 314                         *filter &= ~inotify_mapping[i].notify_mask;
 315                 }
 316         }
 317         return out;
 318 }
 319
 320 /*
 321   destroy a watch
 322 */
 323 static int watch_destructor(struct inotify_watch_context *w)
 324 {
 325         struct inotify_private *in = w->in;
 326         int wd = w->wd;
 327         DLIST_REMOVE(w->in->watches, w);
 328
 329         for (w=in->watches;w;w=w->next) {
 330                 if (w->wd == wd) {
 331                         /*
 332                          * Another inotify_watch_context listens on this path,
 333                          * leave the kernel level watch in place
 334                          */
 335                         return 0;
 336                 }
 337         }
 338
 339         DEBUG(10, ("Deleting inotify watch %d\n", wd));
 340         if (inotify_rm_watch(in->fd, wd) == -1) {
 341                 DEBUG(1, ("inotify_rm_watch returned %s\n", strerror(errno)));
 342         }
 343         return 0;
 344 }
 345
 346
 347 /*
 348   add a watch. The watch is removed when the caller calls
 349   talloc_free() on *handle
 350 */
 351 int inotify_watch(TALLOC_CTX *mem_ctx,
 352                   struct sys_notify_context *ctx,
 353                   const char *path,
 354                   uint32_t *filter,
 355                   uint32_t *subdir_filter,
 356                   void (*callback)(struct sys_notify_context *ctx,
 357                                    void *private_data,
 358                                    struct notify_event *ev),
 359                   void *private_data,
 360                   void *handle_p)
 361 {
 362         struct inotify_private *in;
 363         uint32_t mask;
 364         struct inotify_watch_context *w;
 365         uint32_t orig_filter = *filter;
 366         void **handle = (void **)handle_p;
 367
 368         /* maybe setup the inotify fd */
 369         if (ctx->private_data == NULL) {
 370                 int ret;
 371                 ret = inotify_setup(ctx);
 372                 if (ret != 0) {
 373                         return ret;
 374                 }
 375         }
 376
 377         in = talloc_get_type(ctx->private_data, struct inotify_private);
 378
 379         mask = inotify_map(filter);
 380         if (mask == 0) {
 381                 /* this filter can't be handled by inotify */
 382                 return EINVAL;
 383         }
 384
 385         /* using IN_MASK_ADD allows us to cope with inotify() returning the same
 386            watch descriptor for multiple watches on the same path */
 387         mask |= (IN_MASK_ADD | IN_ONLYDIR);
 388
 389         w = talloc(mem_ctx, struct inotify_watch_context);
 390         if (w == NULL) {
 391                 *filter = orig_filter;
 392                 return ENOMEM;
 393         }
 394
 395         w->in = in;
 396         w->callback = callback;
 397         w->private_data = private_data;
 398         w->mask = mask;
 399         w->filter = orig_filter;
 400         w->path = talloc_strdup(w, path);
 401         if (w->path == NULL) {
 402                 *filter = orig_filter;
 403                 TALLOC_FREE(w);
 404                 return ENOMEM;
 405         }
 406
 407         /* get a new watch descriptor for this path */
 408         w->wd = inotify_add_watch(in->fd, path, mask);
 409         if (w->wd == -1) {
 410                 int err = errno;
 411                 *filter = orig_filter;
 412                 TALLOC_FREE(w);
 413                 DEBUG(1, ("inotify_add_watch returned %s\n", strerror(err)));
 414                 return err;
 415         }
 416
 417         DEBUG(10, ("inotify_add_watch for %s mask %x returned wd %d\n",
 418                    path, mask, w->wd));
 419
 420         (*handle) = w;
 421
 422         DLIST_ADD(in->watches, w);
 423
 424         /* the caller frees the handle to stop watching */
 425         talloc_set_destructor(w, watch_destructor);
 426
 427         return 0;
 428 }