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 "lib/util/server_id.h"
  23 #include "dbwrap/dbwrap.h"
  24 #include "dbwrap/dbwrap_open.h"
  25 #include "dbwrap/dbwrap_watch.h"
  26 #include "g_lock.h"
  27 #include "util_tdb.h"
  28 #include "../lib/util/tevent_ntstatus.h"
  29 #include "messages.h"
  30 #include "serverid.h"
  31
  32 struct g_lock_ctx {
  33         struct db_context *db;
  34         struct messaging_context *msg;
  35 };
  36
  37 /*
  38  * The "g_lock.tdb" file contains records, indexed by the 0-terminated
  39  * lockname. The record contains an array of "struct g_lock_rec"
  40  * structures.
  41  */
  42
  43 struct g_lock_rec {
  44         enum g_lock_type lock_type;
  45         struct server_id pid;
  46 };
  47
  48 #define G_LOCK_REC_LENGTH (SERVER_ID_BUF_LENGTH+1)
  49
  50 static void g_lock_rec_put(uint8_t buf[G_LOCK_REC_LENGTH],
  51                            const struct g_lock_rec rec)
  52 {
  53         SCVAL(buf, 0, rec.lock_type);
  54         server_id_put(buf+1, rec.pid);
  55 }
  56
  57 static void g_lock_rec_get(struct g_lock_rec *rec,
  58                            const uint8_t buf[G_LOCK_REC_LENGTH])
  59 {
  60         rec->lock_type = CVAL(buf, 0);
  61         server_id_get(&rec->pid, buf+1);
  62 }
  63
  64 struct g_lock_ctx *g_lock_ctx_init(TALLOC_CTX *mem_ctx,
  65                                    struct messaging_context *msg)
  66 {
  67         struct g_lock_ctx *result;
  68         struct db_context *backend;
  69         char *db_path;
  70
  71         result = talloc(mem_ctx, struct g_lock_ctx);
  72         if (result == NULL) {
  73                 return NULL;
  74         }
  75         result->msg = msg;
  76
  77         db_path = lock_path("g_lock.tdb");
  78         if (db_path == NULL) {
  79                 TALLOC_FREE(result);
  80                 return NULL;
  81         }
  82
  83         backend = db_open(result, db_path, 0,
  84                           TDB_CLEAR_IF_FIRST|TDB_INCOMPATIBLE_HASH,
  85                           O_RDWR|O_CREAT, 0600,
  86                           DBWRAP_LOCK_ORDER_2,
  87                           DBWRAP_FLAG_NONE);
  88         TALLOC_FREE(db_path);
  89         if (backend == NULL) {
  90                 DEBUG(1, ("g_lock_init: Could not open g_lock.tdb\n"));
  91                 TALLOC_FREE(result);
  92                 return NULL;
  93         }
  94
  95         result->db = db_open_watched(result, backend, msg);
  96         if (result->db == NULL) {
  97                 DBG_WARNING("g_lock_init: db_open_watched failed\n");
  98                 TALLOC_FREE(result);
  99                 return NULL;
 100         }
 101         return result;
 102 }
 103
 104 static bool g_lock_conflicts(enum g_lock_type l1, enum g_lock_type l2)
 105 {
 106         /*
 107          * Only tested write locks so far. Very likely this routine
 108          * needs to be fixed for read locks....
 109          */
 110         if ((l1 == G_LOCK_READ) && (l2 == G_LOCK_READ)) {
 111                 return false;
 112         }
 113         return true;
 114 }
 115
 116 static bool g_lock_get(TALLOC_CTX *mem_ctx, TDB_DATA data,
 117                        unsigned *pnum_locks, struct g_lock_rec **plocks)
 118 {
 119         size_t i, num_locks;
 120         struct g_lock_rec *locks;
 121
 122         if ((data.dsize % G_LOCK_REC_LENGTH) != 0) {
 123                 DEBUG(1, ("invalid lock record length %zu\n", data.dsize));
 124                 return false;
 125         }
 126         num_locks = data.dsize / G_LOCK_REC_LENGTH;
 127
 128         locks = talloc_array(mem_ctx, struct g_lock_rec, num_locks);
 129         if (locks == NULL) {
 130                 DEBUG(1, ("talloc_memdup failed\n"));
 131                 return false;
 132         }
 133
 134         for (i=0; i<num_locks; i++) {
 135                 g_lock_rec_get(&locks[i], data.dptr);
 136                 data.dptr += G_LOCK_REC_LENGTH;
 137         }
 138
 139         *plocks = locks;
 140         *pnum_locks = num_locks;
 141         return true;
 142 }
 143
 144 static ssize_t g_lock_unparse(uint8_t *buf, size_t buflen,
 145                               const struct g_lock_rec *locks,
 146                               size_t num_locks)
 147 {
 148         size_t i, len, ofs;
 149
 150         if (num_locks > UINT32_MAX/G_LOCK_REC_LENGTH) {
 151                 return -1;
 152         }
 153
 154         len = num_locks * G_LOCK_REC_LENGTH;
 155
 156         if (len > buflen) {
 157                 return len;
 158         }
 159
 160         ofs = 0;
 161
 162         for (i=0; i<num_locks; i++) {
 163                 g_lock_rec_put(buf+ofs, locks[i]);
 164                 ofs += G_LOCK_REC_LENGTH;
 165         }
 166
 167         return len;
 168 }
 169
 170 static NTSTATUS g_lock_record_store(struct db_record *rec,
 171                                     const struct g_lock_rec *locks,
 172                                     size_t num_locks)
 173 {
 174         ssize_t len;
 175         uint8_t *buf;
 176         NTSTATUS status;
 177
 178         len = g_lock_unparse(NULL, 0, locks, num_locks);
 179         if (len == -1) {
 180                 return NT_STATUS_BUFFER_TOO_SMALL;
 181         }
 182
 183         buf = talloc_array(rec, uint8_t, len);
 184         if (buf == NULL) {
 185                 return NT_STATUS_NO_MEMORY;
 186         }
 187
 188         g_lock_unparse(buf, len, locks, num_locks);
 189
 190         status = dbwrap_record_store(
 191                 rec, (TDB_DATA) { .dptr = buf, .dsize = len }, 0);
 192
 193         TALLOC_FREE(buf);
 194
 195         return status;
 196 }
 197
 198 static NTSTATUS g_lock_trylock(struct db_record *rec, struct server_id self,
 199                                enum g_lock_type type,
 200                                struct server_id *blocker)
 201 {
 202         TDB_DATA data;
 203         unsigned i, num_locks;
 204         struct g_lock_rec *locks, *tmp;
 205         NTSTATUS status;
 206         bool modified = false;
 207
 208         data = dbwrap_record_get_value(rec);
 209
 210         if (!g_lock_get(talloc_tos(), data, &num_locks, &locks)) {
 211                 return NT_STATUS_INTERNAL_DB_CORRUPTION;
 212         }
 213
 214         for (i=0; i<num_locks; i++) {
 215                 if (serverid_equal(&self, &locks[i].pid)) {
 216                         status = NT_STATUS_INTERNAL_ERROR;
 217                         goto done;
 218                 }
 219                 if (g_lock_conflicts(type, locks[i].lock_type)) {
 220                         struct server_id pid = locks[i].pid;
 221
 222                         /*
 223                          * As the serverid_exists might recurse into
 224                          * the g_lock code, we use
 225                          * SERVERID_UNIQUE_ID_NOT_TO_VERIFY to avoid the loop
 226                          */
 227                         pid.unique_id = SERVERID_UNIQUE_ID_NOT_TO_VERIFY;
 228
 229                         if (serverid_exists(&pid)) {
 230                                 status = NT_STATUS_LOCK_NOT_GRANTED;
 231                                 *blocker = locks[i].pid;
 232                                 goto done;
 233                         }
 234
 235                         /*
 236                          * Delete stale conflicting entry
 237                          */
 238                         locks[i] = locks[num_locks-1];
 239                         num_locks -= 1;
 240                         modified = true;
 241                 }
 242         }
 243
 244         tmp = talloc_realloc(talloc_tos(), locks, struct g_lock_rec,
 245                              num_locks+1);
 246         if (tmp == NULL) {
 247                 status = NT_STATUS_NO_MEMORY;
 248                 goto done;
 249         }
 250         locks = tmp;
 251
 252         ZERO_STRUCT(locks[num_locks]);
 253         locks[num_locks].pid = self;
 254         locks[num_locks].lock_type = type;
 255         num_locks += 1;
 256         modified = true;
 257
 258         status = NT_STATUS_OK;
 259 done:
 260         if (modified) {
 261                 NTSTATUS store_status;
 262                 store_status = g_lock_record_store(rec, locks, num_locks);
 263                 if (!NT_STATUS_IS_OK(store_status)) {
 264                         DBG_WARNING("g_lock_record_store failed: %s\n",
 265                                     nt_errstr(store_status));
 266                         status = store_status;
 267                 }
 268         }
 269         TALLOC_FREE(locks);
 270         return status;
 271 }
 272
 273 struct g_lock_lock_state {
 274         struct tevent_context *ev;
 275         struct g_lock_ctx *ctx;
 276         const char *name;
 277         enum g_lock_type type;
 278 };
 279
 280 static void g_lock_lock_retry(struct tevent_req *subreq);
 281
 282 struct tevent_req *g_lock_lock_send(TALLOC_CTX *mem_ctx,
 283                                     struct tevent_context *ev,
 284                                     struct g_lock_ctx *ctx,
 285                                     const char *name,
 286                                     enum g_lock_type type)
 287 {
 288         struct tevent_req *req, *subreq;
 289         struct g_lock_lock_state *state;
 290         struct db_record *rec;
 291         struct server_id self, blocker;
 292         NTSTATUS status;
 293
 294         req = tevent_req_create(mem_ctx, &state, struct g_lock_lock_state);
 295         if (req == NULL) {
 296                 return NULL;
 297         }
 298         state->ev = ev;
 299         state->ctx = ctx;
 300         state->name = name;
 301         state->type = type;
 302
 303         rec = dbwrap_fetch_locked(ctx->db, talloc_tos(),
 304                                   string_term_tdb_data(state->name));
 305         if (rec == NULL) {
 306                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 307                 tevent_req_nterror(req, NT_STATUS_LOCK_NOT_GRANTED);
 308                 return tevent_req_post(req, ev);
 309         }
 310
 311         self = messaging_server_id(state->ctx->msg);
 312
 313         status = g_lock_trylock(rec, self, state->type, &blocker);
 314         if (NT_STATUS_IS_OK(status)) {
 315                 TALLOC_FREE(rec);
 316                 tevent_req_done(req);
 317                 return tevent_req_post(req, ev);
 318         }
 319         if (!NT_STATUS_EQUAL(status, NT_STATUS_LOCK_NOT_GRANTED)) {
 320                 TALLOC_FREE(rec);
 321                 tevent_req_nterror(req, status);
 322                 return tevent_req_post(req, ev);
 323         }
 324         subreq = dbwrap_watched_watch_send(state, state->ev, rec, blocker);
 325         TALLOC_FREE(rec);
 326         if (tevent_req_nomem(subreq, req)) {
 327                 return tevent_req_post(req, ev);
 328         }
 329         if (!tevent_req_set_endtime(
 330                     subreq, state->ev,
 331                     timeval_current_ofs(5 + sys_random() % 5, 0))) {
 332                 tevent_req_oom(req);
 333                 return tevent_req_post(req, ev);
 334         }
 335         tevent_req_set_callback(subreq, g_lock_lock_retry, req);
 336         return req;
 337 }
 338
 339 static void g_lock_lock_retry(struct tevent_req *subreq)
 340 {
 341         struct tevent_req *req = tevent_req_callback_data(
 342                 subreq, struct tevent_req);
 343         struct g_lock_lock_state *state = tevent_req_data(
 344                 req, struct g_lock_lock_state);
 345         struct server_id self = messaging_server_id(state->ctx->msg);
 346         struct server_id blocker;
 347         struct db_record *rec;
 348         NTSTATUS status;
 349
 350         status = dbwrap_watched_watch_recv(subreq, talloc_tos(), &rec, NULL,
 351                                            NULL);
 352         TALLOC_FREE(subreq);
 353
 354         if (NT_STATUS_EQUAL(status, NT_STATUS_IO_TIMEOUT)) {
 355                 rec = dbwrap_fetch_locked(
 356                         state->ctx->db, talloc_tos(),
 357                         string_term_tdb_data(state->name));
 358                 if (rec == NULL) {
 359                         status = map_nt_error_from_unix(errno);
 360                 } else {
 361                         status = NT_STATUS_OK;
 362                 }
 363         }
 364
 365         if (tevent_req_nterror(req, status)) {
 366                 return;
 367         }
 368         status = g_lock_trylock(rec, self, state->type, &blocker);
 369         if (NT_STATUS_IS_OK(status)) {
 370                 TALLOC_FREE(rec);
 371                 tevent_req_done(req);
 372                 return;
 373         }
 374         if (!NT_STATUS_EQUAL(status, NT_STATUS_LOCK_NOT_GRANTED)) {
 375                 TALLOC_FREE(rec);
 376                 tevent_req_nterror(req, status);
 377                 return;
 378         }
 379         subreq = dbwrap_watched_watch_send(state, state->ev, rec, blocker);
 380         TALLOC_FREE(rec);
 381         if (tevent_req_nomem(subreq, req)) {
 382                 return;
 383         }
 384         if (!tevent_req_set_endtime(
 385                     subreq, state->ev,
 386                     timeval_current_ofs(5 + sys_random() % 5, 0))) {
 387                 tevent_req_oom(req);
 388                 return;
 389         }
 390         tevent_req_set_callback(subreq, g_lock_lock_retry, req);
 391         return;
 392
 393 }
 394
 395 NTSTATUS g_lock_lock_recv(struct tevent_req *req)
 396 {
 397         return tevent_req_simple_recv_ntstatus(req);
 398 }
 399
 400 NTSTATUS g_lock_lock(struct g_lock_ctx *ctx, const char *name,
 401                      enum g_lock_type type, struct timeval timeout)
 402 {
 403         TALLOC_CTX *frame = talloc_stackframe();
 404         struct tevent_context *ev;
 405         struct tevent_req *req;
 406         struct timeval end;
 407         NTSTATUS status = NT_STATUS_NO_MEMORY;
 408
 409         ev = samba_tevent_context_init(frame);
 410         if (ev == NULL) {
 411                 goto fail;
 412         }
 413         req = g_lock_lock_send(frame, ev, ctx, name, type);
 414         if (req == NULL) {
 415                 goto fail;
 416         }
 417         end = timeval_current_ofs(timeout.tv_sec, timeout.tv_usec);
 418         if (!tevent_req_set_endtime(req, ev, end)) {
 419                 goto fail;
 420         }
 421         if (!tevent_req_poll_ntstatus(req, ev, &status)) {
 422                 goto fail;
 423         }
 424         status = g_lock_lock_recv(req);
 425  fail:
 426         TALLOC_FREE(frame);
 427         return status;
 428 }
 429
 430 NTSTATUS g_lock_unlock(struct g_lock_ctx *ctx, const char *name)
 431 {
 432         struct server_id self = messaging_server_id(ctx->msg);
 433         struct db_record *rec = NULL;
 434         struct g_lock_rec *locks = NULL;
 435         unsigned i, num_locks;
 436         NTSTATUS status;
 437         TDB_DATA value;
 438
 439         rec = dbwrap_fetch_locked(ctx->db, talloc_tos(),
 440                                   string_term_tdb_data(name));
 441         if (rec == NULL) {
 442                 DEBUG(10, ("fetch_locked(\"%s\") failed\n", name));
 443                 status = NT_STATUS_INTERNAL_ERROR;
 444                 goto done;
 445         }
 446
 447         value = dbwrap_record_get_value(rec);
 448
 449         if (!g_lock_get(talloc_tos(), value, &num_locks, &locks)) {
 450                 DEBUG(10, ("g_lock_get for %s failed\n", name));
 451                 status = NT_STATUS_FILE_INVALID;
 452                 goto done;
 453         }
 454         for (i=0; i<num_locks; i++) {
 455                 if (serverid_equal(&self, &locks[i].pid)) {
 456                         break;
 457                 }
 458         }
 459         if (i == num_locks) {
 460                 DBG_DEBUG("Lock not found, num_locks=%u\n", num_locks);
 461                 status = NT_STATUS_NOT_FOUND;
 462                 goto done;
 463         }
 464
 465         locks[i] = locks[num_locks-1];
 466         num_locks -= 1;
 467
 468         if (num_locks == 0) {
 469                 status = dbwrap_record_delete(rec);
 470         } else {
 471                 status = g_lock_record_store(rec, locks, num_locks);
 472         }
 473         if (!NT_STATUS_IS_OK(status)) {
 474                 DBG_WARNING("Could not store record: %s\n", nt_errstr(status));
 475                 goto done;
 476         }
 477
 478         status = NT_STATUS_OK;
 479 done:
 480         TALLOC_FREE(rec);
 481         TALLOC_FREE(locks);
 482         return status;
 483 }
 484
 485 struct g_lock_locks_state {
 486         int (*fn)(const char *name, void *private_data);
 487         void *private_data;
 488 };
 489
 490 static int g_lock_locks_fn(struct db_record *rec, void *priv)
 491 {
 492         TDB_DATA key;
 493         struct g_lock_locks_state *state = (struct g_lock_locks_state *)priv;
 494
 495         key = dbwrap_record_get_key(rec);
 496         if ((key.dsize == 0) || (key.dptr[key.dsize-1] != 0)) {
 497                 DEBUG(1, ("invalid key in g_lock.tdb, ignoring\n"));
 498                 return 0;
 499         }
 500         return state->fn((char *)key.dptr, state->private_data);
 501 }
 502
 503 int g_lock_locks(struct g_lock_ctx *ctx,
 504                  int (*fn)(const char *name, void *private_data),
 505                  void *private_data)
 506 {
 507         struct g_lock_locks_state state;
 508         NTSTATUS status;
 509         int count;
 510
 511         state.fn = fn;
 512         state.private_data = private_data;
 513
 514         status = dbwrap_traverse_read(ctx->db, g_lock_locks_fn, &state, &count);
 515         if (!NT_STATUS_IS_OK(status)) {
 516                 return -1;
 517         }
 518         return count;
 519 }
 520
 521 NTSTATUS g_lock_dump(struct g_lock_ctx *ctx, const char *name,
 522                      int (*fn)(struct server_id pid,
 523                                enum g_lock_type lock_type,
 524                                void *private_data),
 525                      void *private_data)
 526 {
 527         TDB_DATA data;
 528         unsigned i, num_locks;
 529         struct g_lock_rec *locks = NULL;
 530         bool ret;
 531         NTSTATUS status;
 532
 533         status = dbwrap_fetch_bystring(ctx->db, talloc_tos(), name, &data);
 534         if (!NT_STATUS_IS_OK(status)) {
 535                 return status;
 536         }
 537
 538         if ((data.dsize == 0) || (data.dptr == NULL)) {
 539                 return NT_STATUS_OK;
 540         }
 541
 542         ret = g_lock_get(talloc_tos(), data, &num_locks, &locks);
 543
 544         TALLOC_FREE(data.dptr);
 545
 546         if (!ret) {
 547                 DEBUG(10, ("g_lock_get for %s failed\n", name));
 548                 return NT_STATUS_INTERNAL_ERROR;
 549         }
 550
 551         for (i=0; i<num_locks; i++) {
 552                 if (fn(locks[i].pid, locks[i].lock_type, private_data) != 0) {
 553                         break;
 554                 }
 555         }
 556         TALLOC_FREE(locks);
 557         return NT_STATUS_OK;
 558 }
 559
 560 static bool g_lock_init_all(TALLOC_CTX *mem_ctx,
 561                             struct tevent_context **pev,
 562                             struct messaging_context **pmsg,
 563                             struct g_lock_ctx **pg_ctx)
 564 {
 565         struct tevent_context *ev = NULL;
 566         struct messaging_context *msg = NULL;
 567         struct g_lock_ctx *g_ctx = NULL;
 568
 569         ev = samba_tevent_context_init(mem_ctx);
 570         if (ev == NULL) {
 571                 d_fprintf(stderr, "ERROR: could not init event context\n");
 572                 goto fail;
 573         }
 574         msg = messaging_init(mem_ctx, ev);
 575         if (msg == NULL) {
 576                 d_fprintf(stderr, "ERROR: could not init messaging context\n");
 577                 goto fail;
 578         }
 579         g_ctx = g_lock_ctx_init(mem_ctx, msg);
 580         if (g_ctx == NULL) {
 581                 d_fprintf(stderr, "ERROR: could not init g_lock context\n");
 582                 goto fail;
 583         }
 584
 585         *pev = ev;
 586         *pmsg = msg;
 587         *pg_ctx = g_ctx;
 588         return true;
 589 fail:
 590         TALLOC_FREE(g_ctx);
 591         TALLOC_FREE(msg);
 592         TALLOC_FREE(ev);
 593         return false;
 594 }
 595
 596 NTSTATUS g_lock_do(const char *name, enum g_lock_type lock_type,
 597                    struct timeval timeout,
 598                    void (*fn)(void *private_data), void *private_data)
 599 {
 600         struct tevent_context *ev = NULL;
 601         struct messaging_context *msg = NULL;
 602         struct g_lock_ctx *g_ctx = NULL;
 603         NTSTATUS status;
 604
 605         if (!g_lock_init_all(talloc_tos(), &ev, &msg, &g_ctx)) {
 606                 status = NT_STATUS_ACCESS_DENIED;
 607                 goto done;
 608         }
 609
 610         status = g_lock_lock(g_ctx, name, lock_type, timeout);
 611         if (!NT_STATUS_IS_OK(status)) {
 612                 goto done;
 613         }
 614         fn(private_data);
 615         g_lock_unlock(g_ctx, name);
 616
 617 done:
 618         TALLOC_FREE(g_ctx);
 619         TALLOC_FREE(msg);
 620         TALLOC_FREE(ev);
 621         return status;
 622 }