source/lib/messages_local.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Samba internal messaging functions
   4    Copyright (C) 2007 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 /**
  21   @defgroup messages Internal messaging framework
  22   @{
  23   @file messages.c
  24
  25   @brief  Module for internal messaging between Samba daemons.
  26
  27    The idea is that if a part of Samba wants to do communication with
  28    another Samba process then it will do a message_register() of a
  29    dispatch function, and use message_send_pid() to send messages to
  30    that process.
  31
  32    The dispatch function is given the pid of the sender, and it can
  33    use that to reply by message_send_pid().  See ping_message() for a
  34    simple example.
  35
  36    @caution Dispatch functions must be able to cope with incoming
  37    messages on an *odd* byte boundary.
  38
  39    This system doesn't have any inherent size limitations but is not
  40    very efficient for large messages or when messages are sent in very
  41    quick succession.
  42
  43 */
  44
  45 #include "includes.h"
  46 #include "librpc/gen_ndr/messaging.h"
  47 #include "librpc/gen_ndr/ndr_messaging.h"
  48
  49 static sig_atomic_t received_signal;
  50
  51 static NTSTATUS messaging_tdb_send(struct messaging_context *msg_ctx,
  52                                    struct server_id pid, int msg_type,
  53                                    const DATA_BLOB *data,
  54                                    struct messaging_backend *backend);
  55
  56 /****************************************************************************
  57  Notifications come in as signals.
  58 ****************************************************************************/
  59
  60 static void sig_usr1(void)
  61 {
  62         received_signal = 1;
  63         sys_select_signal(SIGUSR1);
  64 }
  65
  66 static int messaging_tdb_destructor(struct messaging_backend *tdb_ctx)
  67 {
  68         struct tdb_wrap *tdb = (struct tdb_wrap *)tdb_ctx->private_data;
  69         TALLOC_FREE(tdb);
  70         return 0;
  71 }
  72
  73 /****************************************************************************
  74  Initialise the messaging functions.
  75 ****************************************************************************/
  76
  77 NTSTATUS messaging_tdb_init(struct messaging_context *msg_ctx,
  78                             TALLOC_CTX *mem_ctx,
  79                             struct messaging_backend **presult)
  80 {
  81         struct messaging_backend *result;
  82         struct tdb_wrap *tdb;
  83
  84         if (!(result = TALLOC_P(mem_ctx, struct messaging_backend))) {
  85                 DEBUG(0, ("talloc failed\n"));
  86                 return NT_STATUS_NO_MEMORY;
  87         }
  88
  89         tdb = tdb_wrap_open(result, lock_path("messages.tdb"),
  90                             0, TDB_CLEAR_IF_FIRST|TDB_DEFAULT,
  91                             O_RDWR|O_CREAT,0600);
  92
  93         if (!tdb) {
  94                 NTSTATUS status = map_nt_error_from_unix(errno);
  95                 DEBUG(0, ("ERROR: Failed to initialise messages database: "
  96                           "%s\n", strerror(errno)));
  97                 TALLOC_FREE(result);
  98                 return status;
  99         }
 100
 101         sec_init();
 102
 103         /* Activate the per-hashchain freelist */
 104         tdb_set_max_dead(tdb->tdb, 5);
 105
 106         CatchSignal(SIGUSR1, SIGNAL_CAST sig_usr1);
 107
 108         result->private_data = (void *)tdb;
 109         result->send_fn = messaging_tdb_send;
 110
 111         talloc_set_destructor(result, messaging_tdb_destructor);
 112
 113         *presult = result;
 114         return NT_STATUS_OK;
 115 }
 116
 117 /*******************************************************************
 118  Form a static tdb key from a pid.
 119 ******************************************************************/
 120
 121 static TDB_DATA message_key_pid(TALLOC_CTX *mem_ctx, struct server_id pid)
 122 {
 123         char *key;
 124         TDB_DATA kbuf;
 125
 126         key = talloc_asprintf(talloc_tos(), "PID/%s", procid_str_static(&pid));
 127
 128         SMB_ASSERT(key != NULL);
 129
 130         kbuf.dptr = (uint8 *)key;
 131         kbuf.dsize = strlen(key)+1;
 132         return kbuf;
 133 }
 134
 135 /*
 136   Fetch the messaging array for a process
 137  */
 138
 139 static NTSTATUS messaging_tdb_fetch(TDB_CONTEXT *msg_tdb,
 140                                     TDB_DATA key,
 141                                     TALLOC_CTX *mem_ctx,
 142                                     struct messaging_array **presult)
 143 {
 144         struct messaging_array *result;
 145         TDB_DATA data;
 146         DATA_BLOB blob;
 147         enum ndr_err_code ndr_err;
 148
 149         if (!(result = TALLOC_ZERO_P(mem_ctx, struct messaging_array))) {
 150                 return NT_STATUS_NO_MEMORY;
 151         }
 152
 153         data = tdb_fetch(msg_tdb, key);
 154
 155         if (data.dptr == NULL) {
 156                 *presult = result;
 157                 return NT_STATUS_OK;
 158         }
 159
 160         blob = data_blob_const(data.dptr, data.dsize);
 161
 162         ndr_err = ndr_pull_struct_blob(
 163                 &blob, result, result,
 164                 (ndr_pull_flags_fn_t)ndr_pull_messaging_array);
 165
 166         SAFE_FREE(data.dptr);
 167
 168         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 169                 TALLOC_FREE(result);
 170                 return ndr_map_error2ntstatus(ndr_err);
 171         }
 172
 173         if (DEBUGLEVEL >= 10) {
 174                 DEBUG(10, ("messaging_tdb_fetch:\n"));
 175                 NDR_PRINT_DEBUG(messaging_array, result);
 176         }
 177
 178         *presult = result;
 179         return NT_STATUS_OK;
 180 }
 181
 182 /*
 183   Store a messaging array for a pid
 184 */
 185
 186 static NTSTATUS messaging_tdb_store(TDB_CONTEXT *msg_tdb,
 187                                     TDB_DATA key,
 188                                     struct messaging_array *array)
 189 {
 190         TDB_DATA data;
 191         DATA_BLOB blob;
 192         enum ndr_err_code ndr_err;
 193         TALLOC_CTX *mem_ctx;
 194         int ret;
 195
 196         if (array->num_messages == 0) {
 197                 tdb_delete(msg_tdb, key);
 198                 return NT_STATUS_OK;
 199         }
 200
 201         if (!(mem_ctx = talloc_new(array))) {
 202                 return NT_STATUS_NO_MEMORY;
 203         }
 204
 205         ndr_err = ndr_push_struct_blob(
 206                 &blob, mem_ctx, array,
 207                 (ndr_push_flags_fn_t)ndr_push_messaging_array);
 208
 209         if (!NDR_ERR_CODE_IS_SUCCESS(ndr_err)) {
 210                 talloc_free(mem_ctx);
 211                 return ndr_map_error2ntstatus(ndr_err);
 212         }
 213
 214         if (DEBUGLEVEL >= 10) {
 215                 DEBUG(10, ("messaging_tdb_store:\n"));
 216                 NDR_PRINT_DEBUG(messaging_array, array);
 217         }
 218
 219         data.dptr = blob.data;
 220         data.dsize = blob.length;
 221
 222         ret = tdb_store(msg_tdb, key, data, TDB_REPLACE);
 223         TALLOC_FREE(mem_ctx);
 224
 225         return (ret == 0) ? NT_STATUS_OK : NT_STATUS_INTERNAL_DB_CORRUPTION;
 226 }
 227
 228 /****************************************************************************
 229  Notify a process that it has a message. If the process doesn't exist
 230  then delete its record in the database.
 231 ****************************************************************************/
 232
 233 static NTSTATUS message_notify(struct server_id procid)
 234 {
 235         pid_t pid = procid.pid;
 236         int ret;
 237         uid_t euid = geteuid();
 238
 239         /*
 240          * Doing kill with a non-positive pid causes messages to be
 241          * sent to places we don't want.
 242          */
 243
 244         SMB_ASSERT(pid > 0);
 245
 246         if (euid != 0) {
 247                 /* If we're not root become so to send the message. */
 248                 save_re_uid();
 249                 set_effective_uid(0);
 250         }
 251
 252         ret = kill(pid, SIGUSR1);
 253
 254         if (euid != 0) {
 255                 /* Go back to who we were. */
 256                 int saved_errno = errno;
 257                 restore_re_uid_fromroot();
 258                 errno = saved_errno;
 259         }
 260
 261         if (ret == 0) {
 262                 return NT_STATUS_OK;
 263         }
 264
 265         /*
 266          * Something has gone wrong
 267          */
 268
 269         DEBUG(2,("message to process %d failed - %s\n", (int)pid,
 270                  strerror(errno)));
 271
 272         /*
 273          * No call to map_nt_error_from_unix -- don't want to link in
 274          * errormap.o into lots of utils.
 275          */
 276
 277         if (errno == ESRCH)  return NT_STATUS_INVALID_HANDLE;
 278         if (errno == EINVAL) return NT_STATUS_INVALID_PARAMETER;
 279         if (errno == EPERM)  return NT_STATUS_ACCESS_DENIED;
 280         return NT_STATUS_UNSUCCESSFUL;
 281 }
 282
 283 /****************************************************************************
 284  Send a message to a particular pid.
 285 ****************************************************************************/
 286
 287 static NTSTATUS messaging_tdb_send(struct messaging_context *msg_ctx,
 288                                    struct server_id pid, int msg_type,
 289                                    const DATA_BLOB *data,
 290                                    struct messaging_backend *backend)
 291 {
 292         struct messaging_array *msg_array;
 293         struct messaging_rec *rec;
 294         NTSTATUS status;
 295         TDB_DATA key;
 296         struct tdb_wrap *tdb = (struct tdb_wrap *)backend->private_data;
 297         TALLOC_CTX *frame = talloc_stackframe();
 298
 299         /* NULL pointer means implicit length zero. */
 300         if (!data->data) {
 301                 SMB_ASSERT(data->length == 0);
 302         }
 303
 304         /*
 305          * Doing kill with a non-positive pid causes messages to be
 306          * sent to places we don't want.
 307          */
 308
 309         SMB_ASSERT(procid_to_pid(&pid) > 0);
 310
 311         key = message_key_pid(frame, pid);
 312
 313         if (tdb_chainlock(tdb->tdb, key) == -1) {
 314                 TALLOC_FREE(frame);
 315                 return NT_STATUS_LOCK_NOT_GRANTED;
 316         }
 317
 318         status = messaging_tdb_fetch(tdb->tdb, key, talloc_tos(), &msg_array);
 319
 320         if (!NT_STATUS_IS_OK(status)) {
 321                 goto done;
 322         }
 323
 324         if ((msg_type & MSG_FLAG_LOWPRIORITY)
 325             && (msg_array->num_messages > 1000)) {
 326                 DEBUG(5, ("Dropping message for PID %s\n",
 327                           procid_str_static(&pid)));
 328                 status = NT_STATUS_INSUFFICIENT_RESOURCES;
 329                 goto done;
 330         }
 331
 332         if (!(rec = TALLOC_REALLOC_ARRAY(talloc_tos(), msg_array->messages,
 333                                          struct messaging_rec,
 334                                          msg_array->num_messages+1))) {
 335                 status = NT_STATUS_NO_MEMORY;
 336                 goto done;
 337         }
 338
 339         rec[msg_array->num_messages].msg_version = MESSAGE_VERSION;
 340         rec[msg_array->num_messages].msg_type = msg_type & MSG_TYPE_MASK;
 341         rec[msg_array->num_messages].dest = pid;
 342         rec[msg_array->num_messages].src = procid_self();
 343         rec[msg_array->num_messages].buf = *data;
 344
 345         msg_array->messages = rec;
 346         msg_array->num_messages += 1;
 347
 348         status = messaging_tdb_store(tdb->tdb, key, msg_array);
 349
 350         if (!NT_STATUS_IS_OK(status)) {
 351                 goto done;
 352         }
 353
 354         status = message_notify(pid);
 355
 356         if (NT_STATUS_EQUAL(status, NT_STATUS_INVALID_HANDLE)) {
 357                 DEBUG(2, ("pid %s doesn't exist - deleting messages record\n",
 358                           procid_str_static(&pid)));
 359                 tdb_delete(tdb->tdb, message_key_pid(talloc_tos(), pid));
 360         }
 361
 362  done:
 363         tdb_chainunlock(tdb->tdb, key);
 364         TALLOC_FREE(frame);
 365         return status;
 366 }
 367
 368 /****************************************************************************
 369  Retrieve all messages for the current process.
 370 ****************************************************************************/
 371
 372 static NTSTATUS retrieve_all_messages(TDB_CONTEXT *msg_tdb,
 373                                       TALLOC_CTX *mem_ctx,
 374                                       struct messaging_array **presult)
 375 {
 376         struct messaging_array *result;
 377         TDB_DATA key = message_key_pid(mem_ctx, procid_self());
 378         NTSTATUS status;
 379
 380         if (tdb_chainlock(msg_tdb, key) == -1) {
 381                 TALLOC_FREE(key.dptr);
 382                 return NT_STATUS_LOCK_NOT_GRANTED;
 383         }
 384
 385         status = messaging_tdb_fetch(msg_tdb, key, mem_ctx, &result);
 386
 387         /*
 388          * We delete the record here, tdb_set_max_dead keeps it around
 389          */
 390         tdb_delete(msg_tdb, key);
 391         tdb_chainunlock(msg_tdb, key);
 392
 393         if (NT_STATUS_IS_OK(status)) {
 394                 *presult = result;
 395         }
 396
 397         TALLOC_FREE(key.dptr);
 398
 399         return status;
 400 }
 401
 402 /****************************************************************************
 403  Receive and dispatch any messages pending for this process.
 404  JRA changed Dec 13 2006. Only one message handler now permitted per type.
 405  *NOTE*: Dispatch functions must be able to cope with incoming
 406  messages on an *odd* byte boundary.
 407 ****************************************************************************/
 408
 409 void message_dispatch(struct messaging_context *msg_ctx)
 410 {
 411         struct messaging_array *msg_array = NULL;
 412         struct tdb_wrap *tdb = (struct tdb_wrap *)
 413                 (msg_ctx->local->private_data);
 414         uint32 i;
 415
 416         if (!received_signal)
 417                 return;
 418
 419         DEBUG(10, ("message_dispatch: received_signal = %d\n",
 420                    received_signal));
 421
 422         received_signal = 0;
 423
 424         if (!NT_STATUS_IS_OK(retrieve_all_messages(tdb->tdb, NULL,
 425                                                    &msg_array))) {
 426                 return;
 427         }
 428
 429         for (i=0; i<msg_array->num_messages; i++) {
 430                 messaging_dispatch_rec(msg_ctx, &msg_array->messages[i]);
 431         }
 432
 433         TALLOC_FREE(msg_array);
 434 }
 435
 436 /** @} **/