source3/lib/g_lock.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    global locks based on dbwrap and messaging
   4    Copyright (C) 2009 by Volker Lendecke
   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 #include "includes.h"
  21 #include "system/filesys.h"
  22 #include "dbwrap/dbwrap.h"
  23 #include "dbwrap/dbwrap_open.h"
  24 #include "dbwrap/dbwrap_watch.h"
  25 #include "g_lock.h"
  26 #include "util_tdb.h"
  27 #include "../lib/util/tevent_ntstatus.h"
  28 #include "messages.h"
  29 #include "serverid.h"
  30
  31 struct g_lock_ctx {
  32         struct db_context *db;
  33         struct messaging_context *msg;
  34 };
  35
  36 /*
  37  * The "g_lock.tdb" file contains records, indexed by the 0-terminated
  38  * lockname. The record contains an array of "struct g_lock_rec"
  39  * structures.
  40  */
  41
  42 struct g_lock_rec {
  43         enum g_lock_type lock_type;
  44         struct server_id pid;
  45 };
  46
  47 struct g_lock_ctx *g_lock_ctx_init(TALLOC_CTX *mem_ctx,
  48                                    struct messaging_context *msg)
  49 {
  50         struct g_lock_ctx *result;
  51         struct db_context *backend;
  52         char *db_path;
  53
  54         result = talloc(mem_ctx, struct g_lock_ctx);
  55         if (result == NULL) {
  56                 return NULL;
  57         }
  58         result->msg = msg;
  59
  60         db_path = lock_path("g_lock.tdb");
  61         if (db_path == NULL) {
  62                 TALLOC_FREE(result);
  63                 return NULL;
  64         }
  65
  66         backend = db_open(result, db_path, 0,
  67                           TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH,
  68                           O_RDWR|O_CREAT, 0600,
  69                           DBWRAP_LOCK_ORDER_2,
  70                           DBWRAP_FLAG_NONE);
  71         TALLOC_FREE(db_path);
  72         if (backend == NULL) {
  73                 DEBUG(1, ("g_lock_init: Could not open g_lock.tdb\n"));
  74                 TALLOC_FREE(result);
  75                 return NULL;
  76         }
  77
  78         result->db = db_open_watched(result, backend, msg);
  79         if (result->db == NULL) {
  80                 DBG_WARNING("g_lock_init: db_open_watched failed\n");
  81                 TALLOC_FREE(result);
  82                 return NULL;
  83         }
  84         return result;
  85 }
  86
  87 static bool g_lock_conflicts(enum g_lock_type l1, enum g_lock_type l2)
  88 {
  89         /*
  90          * Only tested write locks so far. Very likely this routine
  91          * needs to be fixed for read locks....
  92          */
  93         if ((l1 == G_LOCK_READ) && (l2 == G_LOCK_READ)) {
  94                 return false;
  95         }
  96         return true;
  97 }
  98
  99 static bool g_lock_parse(TALLOC_CTX *mem_ctx, TDB_DATA data,
 100                          unsigned *pnum_locks, struct g_lock_rec **plocks)
 101 {
 102         unsigned num_locks;
 103         struct g_lock_rec *locks;
 104
 105         if ((data.dsize % sizeof(struct g_lock_rec)) != 0) {
 106                 DEBUG(1, ("invalid lock record length %zu\n", data.dsize));
 107                 return false;
 108         }
 109         num_locks = data.dsize / sizeof(struct g_lock_rec);
 110         locks = talloc_memdup(mem_ctx, data.dptr, data.dsize);
 111         if (locks == NULL) {
 112                 DEBUG(1, ("talloc_memdup failed\n"));
 113                 return false;
 114         }
 115         *plocks = locks;
 116         *pnum_locks = num_locks;
 117         return true;
 118 }
 119
 120 static NTSTATUS g_lock_trylock(struct db_record *rec, struct server_id self,
 121                                enum g_lock_type type,
 122                                struct server_id *blocker)
 123 {
 124         TDB_DATA data;
 125         unsigned i, num_locks;
 126         struct g_lock_rec *locks, *tmp;
 127         NTSTATUS status;
 128         bool modified = false;
 129
 130         data = dbwrap_record_get_value(rec);
 131
 132         if (!g_lock_parse(talloc_tos(), data, &num_locks, &locks)) {
 133                 return NT_STATUS_INTERNAL_ERROR;
 134         }
 135
 136         for (i=0; i<num_locks; i++) {
 137                 if (serverid_equal(&self, &locks[i].pid)) {
 138                         status = NT_STATUS_INTERNAL_ERROR;
 139                         goto done;
 140                 }
 141                 if (g_lock_conflicts(type, locks[i].lock_type)) {
 142                         struct server_id pid = locks[i].pid;
 143
 144                         /*
 145                          * As the serverid_exists might recurse into
 146                          * the g_lock code, we use
 147                          * SERVERID_UNIQUE_ID_NOT_TO_VERIFY to avoid the loop
 148                          */
 149                         pid.unique_id = SERVERID_UNIQUE_ID_NOT_TO_VERIFY;
 150
 151                         if (serverid_exists(&pid)) {
 152                                 status = NT_STATUS_LOCK_NOT_GRANTED;
 153                                 *blocker = locks[i].pid;
 154                                 goto done;
 155                         }
 156
 157                         /*
 158                          * Delete stale conflicting entry
 159                          */
 160                         locks[i] = locks[num_locks-1];
 161                         num_locks -= 1;
 162                         modified = true;
 163                 }
 164         }
 165
 166         tmp = talloc_realloc(talloc_tos(), locks, struct g_lock_rec,
 167                              num_locks+1);
 168         if (tmp == NULL) {
 169                 status = NT_STATUS_NO_MEMORY;
 170                 goto done;
 171         }
 172         locks = tmp;
 173
 174         ZERO_STRUCT(locks[num_locks]);
 175         locks[num_locks].pid = self;
 176         locks[num_locks].lock_type = type;
 177         num_locks += 1;
 178         modified = true;
 179
 180         status = NT_STATUS_OK;
 181 done:
 182         if (modified) {
 183                 NTSTATUS store_status;
 184
 185                 data = make_tdb_data((uint8_t *)locks, num_locks * sizeof(*locks));
 186                 store_status = dbwrap_record_store(rec, data, 0);
 187                 if (!NT_STATUS_IS_OK(store_status)) {
 188                         DEBUG(1, ("rec->store failed: %s\n",
 189                                   nt_errstr(store_status)));
 190                         status = store_status;
 191                 }
 192         }
 193         TALLOC_FREE(locks);
 194         return status;
 195 }
 196
 197 struct g_lock_lock_state {
 198         struct tevent_context *ev;
 199         struct g_lock_ctx *ctx;
 200         const char *name;
 201         enum g_lock_type type;
 202 };
 203
 204 static void g_lock_lock_retry(struct tevent_req *subreq);
 205
 206 struct tevent_req *g_lock_lock_send(TALLOC_CTX *mem_ctx,
 207                                     struct tevent_context *ev,
 208                                     struct g_lock_ctx *ctx,
 209                                     const char *name,
 210                                     enum g_lock_type type)
 211 {
 212         struct tevent_req *req, *subreq;
 213         struct g_lock_lock_state *state;
 214         struct db_record *rec;
 215         struct server_id self, blocker;
 216         NTSTATUS status;
 217
 218         req = tevent_req_create(mem_ctx, &state, struct g_lock_lock_state);
 219         if (req == NULL) {
 220                 return NULL;
 221         }
 222         state->ev = ev;
 223         state->ctx = ctx;
 224         state->name = name;
 225         state->type = type;
 226
 227         rec = dbwrap_fetch_locked(ctx->db, talloc_tos(),
 228                                   string_term_tdb_data(state->name));
 229         if (rec == NULL) {
 230                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 231                 tevent_req_nterror(req, NT_STATUS_LOCK_NOT_GRANTED);
 232                 return tevent_req_post(req, ev);
 233         }
 234
 235         self = messaging_server_id(state->ctx->msg);
 236
 237         status = g_lock_trylock(rec, self, state->type, &blocker);
 238         if (NT_STATUS_IS_OK(status)) {
 239                 TALLOC_FREE(rec);
 240                 tevent_req_done(req);
 241                 return tevent_req_post(req, ev);
 242         }
 243         if (!NT_STATUS_EQUAL(status, NT_STATUS_LOCK_NOT_GRANTED)) {
 244                 TALLOC_FREE(rec);
 245                 tevent_req_nterror(req, status);
 246                 return tevent_req_post(req, ev);
 247         }
 248         subreq = dbwrap_watched_watch_send(state, state->ev, rec, blocker);
 249         TALLOC_FREE(rec);
 250         if (tevent_req_nomem(subreq, req)) {
 251                 return tevent_req_post(req, ev);
 252         }
 253         if (!tevent_req_set_endtime(
 254                     subreq, state->ev,
 255                     timeval_current_ofs(5 + sys_random() % 5, 0))) {
 256                 tevent_req_oom(req);
 257                 return tevent_req_post(req, ev);
 258         }
 259         tevent_req_set_callback(subreq, g_lock_lock_retry, req);
 260         return req;
 261 }
 262
 263 static void g_lock_lock_retry(struct tevent_req *subreq)
 264 {
 265         struct tevent_req *req = tevent_req_callback_data(
 266                 subreq, struct tevent_req);
 267         struct g_lock_lock_state *state = tevent_req_data(
 268                 req, struct g_lock_lock_state);
 269         struct server_id self = messaging_server_id(state->ctx->msg);
 270         struct server_id blocker;
 271         struct db_record *rec;
 272         NTSTATUS status;
 273
 274         status = dbwrap_watched_watch_recv(subreq, talloc_tos(), &rec, NULL,
 275                                            NULL);
 276         TALLOC_FREE(subreq);
 277
 278         if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT)) {
 279                 rec = dbwrap_fetch_locked(
 280                         state->ctx->db, talloc_tos(),
 281                         string_term_tdb_data(state->name));
 282                 if (rec == NULL) {
 283                         status = map_nt_error_from_unix(errno);
 284                 } else {
 285                         status = NT_STATUS_OK;
 286                 }
 287         }
 288
 289         if (tevent_req_nterror(req, status)) {
 290                 return;
 291         }
 292         status = g_lock_trylock(rec, self, state->type, &blocker);
 293         if (NT_STATUS_IS_OK(status)) {
 294                 TALLOC_FREE(rec);
 295                 tevent_req_done(req);
 296                 return;
 297         }
 298         if (!NT_STATUS_EQUAL(status, NT_STATUS_LOCK_NOT_GRANTED)) {
 299                 TALLOC_FREE(rec);
 300                 tevent_req_nterror(req, status);
 301                 return;
 302         }
 303         subreq = dbwrap_watched_watch_send(state, state->ev, rec, blocker);
 304         TALLOC_FREE(rec);
 305         if (tevent_req_nomem(subreq, req)) {
 306                 return;
 307         }
 308         if (!tevent_req_set_endtime(
 309                     subreq, state->ev,
 310                     timeval_current_ofs(5 + sys_random() % 5, 0))) {
 311                 tevent_req_oom(req);
 312                 return;
 313         }
 314         tevent_req_set_callback(subreq, g_lock_lock_retry, req);
 315         return;
 316
 317 }
 318
 319 NTSTATUS g_lock_lock_recv(struct tevent_req *req)
 320 {
 321         return tevent_req_simple_recv_ntstatus(req);
 322 }
 323
 324 NTSTATUS g_lock_lock(struct g_lock_ctx *ctx, const char *name,
 325                      enum g_lock_type type, struct timeval timeout)
 326 {
 327         TALLOC_CTX *frame = talloc_stackframe();
 328         struct tevent_context *ev;
 329         struct tevent_req *req;
 330         struct timeval end;
 331         NTSTATUS status = NT_STATUS_NO_MEMORY;
 332
 333         ev = samba_tevent_context_init(frame);
 334         if (ev == NULL) {
 335                 goto fail;
 336         }
 337         req = g_lock_lock_send(frame, ev, ctx, name, type);
 338         if (req == NULL) {
 339                 goto fail;
 340         }
 341         end = timeval_current_ofs(timeout.tv_sec, timeout.tv_usec);
 342         if (!tevent_req_set_endtime(req, ev, end)) {
 343                 goto fail;
 344         }
 345         if (!tevent_req_poll_ntstatus(req, ev, &status)) {
 346                 goto fail;
 347         }
 348         status = g_lock_lock_recv(req);
 349  fail:
 350         TALLOC_FREE(frame);
 351         return status;
 352 }
 353
 354 NTSTATUS g_lock_unlock(struct g_lock_ctx *ctx, const char *name)
 355 {
 356         struct server_id self = messaging_server_id(ctx->msg);
 357         struct db_record *rec = NULL;
 358         struct g_lock_rec *locks = NULL;
 359         unsigned i, num_locks;
 360         NTSTATUS status;
 361         TDB_DATA value;
 362
 363         rec = dbwrap_fetch_locked(ctx->db, talloc_tos(),
 364                                   string_term_tdb_data(name));
 365         if (rec == NULL) {
 366                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 367                 status = NT_STATUS_INTERNAL_ERROR;
 368                 goto done;
 369         }
 370
 371         value = dbwrap_record_get_value(rec);
 372
 373         if (!g_lock_parse(talloc_tos(), value, &num_locks, &locks)) {
 374                 DEBUG(10, ("g_lock_parse for %s failed\n", name));
 375                 status = NT_STATUS_FILE_INVALID;
 376                 goto done;
 377         }
 378         for (i=0; i<num_locks; i++) {
 379                 if (serverid_equal(&self, &locks[i].pid)) {
 380                         break;
 381                 }
 382         }
 383         if (i == num_locks) {
 384                 DEBUG(10, ("g_lock_force_unlock: Lock not found\n"));
 385                 status = NT_STATUS_NOT_FOUND;
 386                 goto done;
 387         }
 388
 389         locks[i] = locks[num_locks-1];
 390         num_locks -= 1;
 391
 392         if (num_locks == 0) {
 393                 status = dbwrap_record_delete(rec);
 394         } else {
 395                 TDB_DATA data;
 396                 data = make_tdb_data((uint8_t *)locks,
 397                                      sizeof(struct g_lock_rec) * num_locks);
 398                 status = dbwrap_record_store(rec, data, 0);
 399         }
 400         if (!NT_STATUS_IS_OK(status)) {
 401                 DEBUG(1, ("g_lock_force_unlock: Could not store record: %s\n",
 402                           nt_errstr(status)));
 403                 goto done;
 404         }
 405
 406         status = NT_STATUS_OK;
 407 done:
 408         TALLOC_FREE(rec);
 409         TALLOC_FREE(locks);
 410         return status;
 411 }
 412
 413 struct g_lock_locks_state {
 414         int (*fn)(const char *name, void *private_data);
 415         void *private_data;
 416 };
 417
 418 static int g_lock_locks_fn(struct db_record *rec, void *priv)
 419 {
 420         TDB_DATA key;
 421         struct g_lock_locks_state *state = (struct g_lock_locks_state *)priv;
 422
 423         key = dbwrap_record_get_key(rec);
 424         if ((key.dsize == 0) || (key.dptr[key.dsize-1] != 0)) {
 425                 DEBUG(1, ("invalid key in g_lock.tdb, ignoring\n"));
 426                 return 0;
 427         }
 428         return state->fn((char *)key.dptr, state->private_data);
 429 }
 430
 431 int g_lock_locks(struct g_lock_ctx *ctx,
 432                  int (*fn)(const char *name, void *private_data),
 433                  void *private_data)
 434 {
 435         struct g_lock_locks_state state;
 436         NTSTATUS status;
 437         int count;
 438
 439         state.fn = fn;
 440         state.private_data = private_data;
 441
 442         status = dbwrap_traverse_read(ctx->db, g_lock_locks_fn, &state, &count);
 443         if (!NT_STATUS_IS_OK(status)) {
 444                 return -1;
 445         } else {
 446                 return count;
 447         }
 448 }
 449
 450 NTSTATUS g_lock_dump(struct g_lock_ctx *ctx, const char *name,
 451                      int (*fn)(struct server_id pid,
 452                                enum g_lock_type lock_type,
 453                                void *private_data),
 454                      void *private_data)
 455 {
 456         TDB_DATA data;
 457         unsigned i, num_locks;
 458         struct g_lock_rec *locks = NULL;
 459         bool ret;
 460         NTSTATUS status;
 461
 462         status = dbwrap_fetch_bystring(ctx->db, talloc_tos(), name, &data);
 463         if (!NT_STATUS_IS_OK(status)) {
 464                 return status;
 465         }
 466
 467         if ((data.dsize == 0) || (data.dptr == NULL)) {
 468                 return NT_STATUS_OK;
 469         }
 470
 471         ret = g_lock_parse(talloc_tos(), data, &num_locks, &locks);
 472
 473         TALLOC_FREE(data.dptr);
 474
 475         if (!ret) {
 476                 DEBUG(10, ("g_lock_parse for %s failed\n", name));
 477                 return NT_STATUS_INTERNAL_ERROR;
 478         }
 479
 480         for (i=0; i<num_locks; i++) {
 481                 if (fn(locks[i].pid, locks[i].lock_type, private_data) != 0) {
 482                         break;
 483                 }
 484         }
 485         TALLOC_FREE(locks);
 486         return NT_STATUS_OK;
 487 }
 488
 489 struct g_lock_get_state {
 490         bool found;
 491         struct server_id *pid;
 492 };
 493
 494 static int g_lock_get_fn(struct server_id pid, enum g_lock_type lock_type,
 495                          void *priv)
 496 {
 497         struct g_lock_get_state *state = (struct g_lock_get_state *)priv;
 498         state->found = true;
 499         *state->pid = pid;
 500         return 1;
 501 }
 502
 503 NTSTATUS g_lock_get(struct g_lock_ctx *ctx, const char *name,
 504                     struct server_id *pid)
 505 {
 506         struct g_lock_get_state state;
 507         NTSTATUS status;
 508
 509         state.found = false;
 510         state.pid = pid;
 511
 512         status = g_lock_dump(ctx, name, g_lock_get_fn, &state);
 513         if (!NT_STATUS_IS_OK(status)) {
 514                 return status;
 515         }
 516         if (!state.found) {
 517                 return NT_STATUS_NOT_FOUND;
 518         }
 519         return NT_STATUS_OK;
 520 }
 521
 522 static bool g_lock_init_all(TALLOC_CTX *mem_ctx,
 523                             struct tevent_context **pev,
 524                             struct messaging_context **pmsg,
 525                             struct g_lock_ctx **pg_ctx)
 526 {
 527         struct tevent_context *ev = NULL;
 528         struct messaging_context *msg = NULL;
 529         struct g_lock_ctx *g_ctx = NULL;
 530
 531         ev = samba_tevent_context_init(mem_ctx);
 532         if (ev == NULL) {
 533                 d_fprintf(stderr, "ERROR: could not init event context\n");
 534                 goto fail;
 535         }
 536         msg = messaging_init(mem_ctx, ev);
 537         if (msg == NULL) {
 538                 d_fprintf(stderr, "ERROR: could not init messaging context\n");
 539                 goto fail;
 540         }
 541         g_ctx = g_lock_ctx_init(mem_ctx, msg);
 542         if (g_ctx == NULL) {
 543                 d_fprintf(stderr, "ERROR: could not init g_lock context\n");
 544                 goto fail;
 545         }
 546
 547         *pev = ev;
 548         *pmsg = msg;
 549         *pg_ctx = g_ctx;
 550         return true;
 551 fail:
 552         TALLOC_FREE(g_ctx);
 553         TALLOC_FREE(msg);
 554         TALLOC_FREE(ev);
 555         return false;
 556 }
 557
 558 NTSTATUS g_lock_do(const char *name, enum g_lock_type lock_type,
 559                    struct timeval timeout,
 560                    void (*fn)(void *private_data), void *private_data)
 561 {
 562         struct tevent_context *ev = NULL;
 563         struct messaging_context *msg = NULL;
 564         struct g_lock_ctx *g_ctx = NULL;
 565         NTSTATUS status;
 566
 567         if (!g_lock_init_all(talloc_tos(), &ev, &msg, &g_ctx)) {
 568                 status = NT_STATUS_ACCESS_DENIED;
 569                 goto done;
 570         }
 571
 572         status = g_lock_lock(g_ctx, name, lock_type, timeout);
 573         if (!NT_STATUS_IS_OK(status)) {
 574                 goto done;
 575         }
 576         fn(private_data);
 577         g_lock_unlock(g_ctx, name);
 578
 579 done:
 580         TALLOC_FREE(g_ctx);
 581         TALLOC_FREE(msg);
 582         TALLOC_FREE(ev);
 583         return status;
 584 }