src/lib/lttng-ctl/lttng-ctl.c

   1 /*
   2  * liblttngctl.c
   3  *
   4  * Linux Trace Toolkit Control Library
   5  *
   6  * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #define _GNU_SOURCE
  24 #include <grp.h>
  25 #include <errno.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <string.h>
  29 #include <unistd.h>
  30
  31 #include <common/common.h>
  32 #include <common/defaults.h>
  33 #include <common/sessiond-comm/sessiond-comm.h>
  34 #include <lttng/lttng.h>
  35
  36 /* Socket to session daemon for communication */
  37 static int sessiond_socket;
  38 static char sessiond_sock_path[PATH_MAX];
  39
  40 /* Variables */
  41 static char *tracing_group;
  42 static int connected;
  43
  44 /*
  45  * Copy string from src to dst and enforce null terminated byte.
  46  */
  47 static void copy_string(char *dst, const char *src, size_t len)
  48 {
  49         if (src && dst) {
  50                 strncpy(dst, src, len);
  51                 /* Enforce the NULL terminated byte */
  52                 dst[len - 1] = '\0';
  53         } else if (dst) {
  54                 dst[0] = '\0';
  55         }
  56 }
  57
  58 /*
  59  * Copy domain to lttcomm_session_msg domain.
  60  *
  61  * If domain is unknown, default domain will be the kernel.
  62  */
  63 static void copy_lttng_domain(struct lttng_domain *dst, struct lttng_domain *src)
  64 {
  65         if (src && dst) {
  66                 switch (src->type) {
  67                         case LTTNG_DOMAIN_KERNEL:
  68                         case LTTNG_DOMAIN_UST:
  69                         /*
  70                         case LTTNG_DOMAIN_UST_EXEC_NAME:
  71                         case LTTNG_DOMAIN_UST_PID:
  72                         case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
  73                         */
  74                                 memcpy(dst, src, sizeof(struct lttng_domain));
  75                                 break;
  76                         default:
  77                                 memset(dst, 0, sizeof(struct lttng_domain));
  78                                 dst->type = LTTNG_DOMAIN_KERNEL;
  79                                 break;
  80                 }
  81         }
  82 }
  83
  84 /*
  85  * Send lttcomm_session_msg to the session daemon.
  86  *
  87  * On success, returns the number of bytes sent (>=0)
  88  * On error, returns -1
  89  */
  90 static int send_session_msg(struct lttcomm_session_msg *lsm)
  91 {
  92         int ret;
  93
  94         if (!connected) {
  95                 ret = -ENOTCONN;
  96                 goto end;
  97         }
  98
  99         ret = lttcomm_send_creds_unix_sock(sessiond_socket, lsm,
 100                         sizeof(struct lttcomm_session_msg));
 101
 102 end:
 103         return ret;
 104 }
 105
 106 /*
 107  * Receive data from the sessiond socket.
 108  *
 109  * On success, returns the number of bytes received (>=0)
 110  * On error, returns -1 (recvmsg() error) or -ENOTCONN
 111  */
 112 static int recv_data_sessiond(void *buf, size_t len)
 113 {
 114         int ret;
 115
 116         if (!connected) {
 117                 ret = -ENOTCONN;
 118                 goto end;
 119         }
 120
 121         ret = lttcomm_recv_unix_sock(sessiond_socket, buf, len);
 122
 123 end:
 124         return ret;
 125 }
 126
 127 /*
 128  *  Check if we are in the specified group.
 129  *
 130  *  If yes return 1, else return -1.
 131  */
 132 static int check_tracing_group(const char *grp_name)
 133 {
 134         struct group *grp_tracing;      /* no free(). See getgrnam(3) */
 135         gid_t *grp_list;
 136         int grp_list_size, grp_id, i;
 137         int ret = -1;
 138
 139         /* Get GID of group 'tracing' */
 140         grp_tracing = getgrnam(grp_name);
 141         if (!grp_tracing) {
 142                 /* If grp_tracing is NULL, the group does not exist. */
 143                 goto end;
 144         }
 145
 146         /* Get number of supplementary group IDs */
 147         grp_list_size = getgroups(0, NULL);
 148         if (grp_list_size < 0) {
 149                 perror("getgroups");
 150                 goto end;
 151         }
 152
 153         /* Alloc group list of the right size */
 154         grp_list = malloc(grp_list_size * sizeof(gid_t));
 155         if (!grp_list) {
 156                 perror("malloc");
 157                 goto end;
 158         }
 159         grp_id = getgroups(grp_list_size, grp_list);
 160         if (grp_id < 0) {
 161                 perror("getgroups");
 162                 goto free_list;
 163         }
 164
 165         for (i = 0; i < grp_list_size; i++) {
 166                 if (grp_list[i] == grp_tracing->gr_gid) {
 167                         ret = 1;
 168                         break;
 169                 }
 170         }
 171
 172 free_list:
 173         free(grp_list);
 174
 175 end:
 176         return ret;
 177 }
 178
 179 /*
 180  * Try connect to session daemon with sock_path.
 181  *
 182  * Return 0 on success, else -1
 183  */
 184 static int try_connect_sessiond(const char *sock_path)
 185 {
 186         int ret;
 187
 188         /* If socket exist, we check if the daemon listens for connect. */
 189         ret = access(sock_path, F_OK);
 190         if (ret < 0) {
 191                 /* Not alive */
 192                 return -1;
 193         }
 194
 195         ret = lttcomm_connect_unix_sock(sock_path);
 196         if (ret < 0) {
 197                 /* Not alive */
 198                 return -1;
 199         }
 200
 201         ret = lttcomm_close_unix_sock(ret);
 202         if (ret < 0) {
 203                 perror("lttcomm_close_unix_sock");
 204         }
 205
 206         return 0;
 207 }
 208
 209 /*
 210  * Set sessiond socket path by putting it in the global
 211  * sessiond_sock_path variable.
 212  * Returns 0 on success,
 213  * -ENOMEM on failure (the sessiond socket path is somehow too long)
 214  */
 215 static int set_session_daemon_path(void)
 216 {
 217         int ret;
 218         int in_tgroup = 0;      /* In tracing group */
 219         uid_t uid;
 220
 221         uid = getuid();
 222
 223         if (uid != 0) {
 224                 /* Are we in the tracing group ? */
 225                 in_tgroup = check_tracing_group(tracing_group);
 226         }
 227
 228         if ((uid == 0) || in_tgroup) {
 229                 copy_string(sessiond_sock_path, DEFAULT_GLOBAL_CLIENT_UNIX_SOCK,
 230                                 sizeof(sessiond_sock_path));
 231         }
 232
 233         if (uid != 0) {
 234                 if (in_tgroup) {
 235                         /* Tracing group */
 236                         ret = try_connect_sessiond(sessiond_sock_path);
 237                         if (ret >= 0) {
 238                                 goto end;
 239                         }
 240                         /* Global session daemon not available... */
 241                 }
 242                 /* ...or not in tracing group (and not root), default */
 243
 244                 /*
 245                  * With GNU C <  2.1, snprintf returns -1 if the target buffer is too small;
 246                  * With GNU C >= 2.1, snprintf returns the required size (excluding closing null)
 247                  */
 248                 ret = snprintf(sessiond_sock_path, sizeof(sessiond_sock_path),
 249                                 DEFAULT_HOME_CLIENT_UNIX_SOCK, getenv("HOME"));
 250                 if ((ret < 0) || (ret >= sizeof(sessiond_sock_path))) {
 251                         return -ENOMEM;
 252                 }
 253         }
 254 end:
 255         return 0;
 256 }
 257
 258 /*
 259  *  Connect to the LTTng session daemon.
 260  *
 261  *  On success, return 0. On error, return -1.
 262  */
 263 static int connect_sessiond(void)
 264 {
 265         int ret;
 266
 267         ret = set_session_daemon_path();
 268         if (ret < 0) {
 269                 return -1; /* set_session_daemon_path() returns -ENOMEM */
 270         }
 271
 272         /* Connect to the sesssion daemon */
 273         ret = lttcomm_connect_unix_sock(sessiond_sock_path);
 274         if (ret < 0) {
 275                 return ret;
 276         }
 277
 278         sessiond_socket = ret;
 279         connected = 1;
 280
 281         return 0;
 282 }
 283
 284 /*
 285  *  Clean disconnect from the session daemon.
 286  *  On success, return 0. On error, return -1.
 287  */
 288 static int disconnect_sessiond(void)
 289 {
 290         int ret = 0;
 291
 292         if (connected) {
 293                 ret = lttcomm_close_unix_sock(sessiond_socket);
 294                 sessiond_socket = 0;
 295                 connected = 0;
 296         }
 297
 298         return ret;
 299 }
 300
 301 /*
 302  * Ask the session daemon a specific command and put the data into buf.
 303  *
 304  * Return size of data (only payload, not header) or a negative error code.
 305  */
 306 static int ask_sessiond(struct lttcomm_session_msg *lsm, void **buf)
 307 {
 308         int ret;
 309         size_t size;
 310         void *data = NULL;
 311         struct lttcomm_lttng_msg llm;
 312
 313         ret = connect_sessiond();
 314         if (ret < 0) {
 315                 goto end;
 316         }
 317
 318         /* Send command to session daemon */
 319         ret = send_session_msg(lsm);
 320         if (ret < 0) {
 321                 goto end;
 322         }
 323
 324         /* Get header from data transmission */
 325         ret = recv_data_sessiond(&llm, sizeof(llm));
 326         if (ret < 0) {
 327                 goto end;
 328         }
 329
 330         /* Check error code if OK */
 331         if (llm.ret_code != LTTCOMM_OK) {
 332                 ret = -llm.ret_code;
 333                 goto end;
 334         }
 335
 336         size = llm.data_size;
 337         if (size == 0) {
 338                 /* If client free with size 0 */
 339                 if (buf != NULL) {
 340                         *buf = NULL;
 341                 }
 342                 ret = 0;
 343                 goto end;
 344         }
 345
 346         data = (void*) malloc(size);
 347
 348         /* Get payload data */
 349         ret = recv_data_sessiond(data, size);
 350         if (ret < 0) {
 351                 free(data);
 352                 goto end;
 353         }
 354
 355         /*
 356          * Extra protection not to dereference a NULL pointer. If buf is NULL at
 357          * this point, an error is returned and data is freed.
 358          */
 359         if (buf == NULL) {
 360                 ret = -1;
 361                 free(data);
 362                 goto end;
 363         }
 364
 365         *buf = data;
 366         ret = size;
 367
 368 end:
 369         disconnect_sessiond();
 370         return ret;
 371 }
 372
 373 /*
 374  * Create lttng handle and return pointer.
 375  * The returned pointer will be NULL in case of malloc() error.
 376  */
 377 struct lttng_handle *lttng_create_handle(const char *session_name,
 378                 struct lttng_domain *domain)
 379 {
 380         struct lttng_handle *handle;
 381
 382         handle = malloc(sizeof(struct lttng_handle));
 383         if (handle == NULL) {
 384                 perror("malloc handle");
 385                 goto end;
 386         }
 387
 388         /* Copy session name */
 389         copy_string(handle->session_name, session_name,
 390                         sizeof(handle->session_name));
 391
 392         /* Copy lttng domain */
 393         copy_lttng_domain(&handle->domain, domain);
 394
 395 end:
 396         return handle;
 397 }
 398
 399 /*
 400  * Destroy handle by free(3) the pointer.
 401  */
 402 void lttng_destroy_handle(struct lttng_handle *handle)
 403 {
 404         if (handle) {
 405                 free(handle);
 406         }
 407 }
 408
 409 /*
 410  * Register an outside consumer.
 411  * Returns size of returned session payload data or a negative error code.
 412  */
 413 int lttng_register_consumer(struct lttng_handle *handle,
 414                 const char *socket_path)
 415 {
 416         struct lttcomm_session_msg lsm;
 417
 418         lsm.cmd_type = LTTNG_REGISTER_CONSUMER;
 419         copy_string(lsm.session.name, handle->session_name,
 420                         sizeof(lsm.session.name));
 421         copy_lttng_domain(&lsm.domain, &handle->domain);
 422
 423         copy_string(lsm.u.reg.path, socket_path, sizeof(lsm.u.reg.path));
 424
 425         return ask_sessiond(&lsm, NULL);
 426 }
 427
 428 /*
 429  *  Start tracing for all traces of the session.
 430  *  Returns size of returned session payload data or a negative error code.
 431  */
 432 int lttng_start_tracing(const char *session_name)
 433 {
 434         struct lttcomm_session_msg lsm;
 435
 436         if (session_name == NULL) {
 437                 return -1;
 438         }
 439
 440         lsm.cmd_type = LTTNG_START_TRACE;
 441
 442         copy_string(lsm.session.name, session_name, sizeof(lsm.session.name));
 443
 444         return ask_sessiond(&lsm, NULL);
 445 }
 446
 447 /*
 448  *  Stop tracing for all traces of the session.
 449  *  Returns size of returned session payload data or a negative error code.
 450  */
 451 int lttng_stop_tracing(const char *session_name)
 452 {
 453         struct lttcomm_session_msg lsm;
 454
 455         if (session_name == NULL) {
 456                 return -1;
 457         }
 458
 459         lsm.cmd_type = LTTNG_STOP_TRACE;
 460
 461         copy_string(lsm.session.name, session_name, sizeof(lsm.session.name));
 462
 463         return ask_sessiond(&lsm, NULL);
 464 }
 465
 466 /*
 467  * Add context to event and/or channel.
 468  * If event_name is NULL, the context is applied to all events of the channel.
 469  * If channel_name is NULL, a lookup of the event's channel is done.
 470  * If both are NULL, the context is applied to all events of all channels.
 471  *
 472  * Returns the size of the returned payload data or a negative error code.
 473  */
 474 int lttng_add_context(struct lttng_handle *handle,
 475                 struct lttng_event_context *ctx, const char *event_name,
 476                 const char *channel_name)
 477 {
 478         struct lttcomm_session_msg lsm;
 479
 480         /* Safety check. Both are mandatory */
 481         if (handle == NULL || ctx == NULL) {
 482                 return -1;
 483         }
 484
 485         memset(&lsm, 0, sizeof(lsm));
 486
 487         lsm.cmd_type = LTTNG_ADD_CONTEXT;
 488
 489         /* Copy channel name */
 490         copy_string(lsm.u.context.channel_name, channel_name,
 491                         sizeof(lsm.u.context.channel_name));
 492         /* Copy event name */
 493         copy_string(lsm.u.context.event_name, event_name,
 494                         sizeof(lsm.u.context.event_name));
 495
 496         copy_lttng_domain(&lsm.domain, &handle->domain);
 497
 498         memcpy(&lsm.u.context.ctx, ctx, sizeof(struct lttng_event_context));
 499
 500         copy_string(lsm.session.name, handle->session_name,
 501                         sizeof(lsm.session.name));
 502
 503         return ask_sessiond(&lsm, NULL);
 504 }
 505
 506 /*
 507  *  Enable event(s) for a channel.
 508  *  If no event name is specified, all events are enabled.
 509  *  If no channel name is specified, the default 'channel0' is used.
 510  *  Returns size of returned session payload data or a negative error code.
 511  */
 512 int lttng_enable_event(struct lttng_handle *handle,
 513                 struct lttng_event *ev, const char *channel_name)
 514 {
 515         struct lttcomm_session_msg lsm;
 516
 517         if (handle == NULL || ev == NULL) {
 518                 return -1;
 519         }
 520
 521         memset(&lsm, 0, sizeof(lsm));
 522
 523         /* If no channel name, we put the default name */
 524         if (channel_name == NULL) {
 525                 copy_string(lsm.u.enable.channel_name, DEFAULT_CHANNEL_NAME,
 526                                 sizeof(lsm.u.enable.channel_name));
 527         } else {
 528                 copy_string(lsm.u.enable.channel_name, channel_name,
 529                                 sizeof(lsm.u.enable.channel_name));
 530         }
 531
 532         copy_lttng_domain(&lsm.domain, &handle->domain);
 533
 534         if (ev->name[0] != '\0') {
 535                 lsm.cmd_type = LTTNG_ENABLE_EVENT;
 536         } else {
 537                 lsm.cmd_type = LTTNG_ENABLE_ALL_EVENT;
 538         }
 539         memcpy(&lsm.u.enable.event, ev, sizeof(lsm.u.enable.event));
 540
 541         copy_string(lsm.session.name, handle->session_name,
 542                         sizeof(lsm.session.name));
 543
 544         return ask_sessiond(&lsm, NULL);
 545 }
 546
 547 /*
 548  *  Disable event(s) of a channel and domain.
 549  *  If no event name is specified, all events are disabled.
 550  *  If no channel name is specified, the default 'channel0' is used.
 551  *  Returns size of returned session payload data or a negative error code.
 552  */
 553 int lttng_disable_event(struct lttng_handle *handle, const char *name,
 554                 const char *channel_name)
 555 {
 556         struct lttcomm_session_msg lsm;
 557
 558         if (handle == NULL) {
 559                 return -1;
 560         }
 561
 562         memset(&lsm, 0, sizeof(lsm));
 563
 564         if (channel_name) {
 565                 copy_string(lsm.u.disable.channel_name, channel_name,
 566                                 sizeof(lsm.u.disable.channel_name));
 567         } else {
 568                 copy_string(lsm.u.disable.channel_name, DEFAULT_CHANNEL_NAME,
 569                                 sizeof(lsm.u.disable.channel_name));
 570         }
 571
 572         copy_lttng_domain(&lsm.domain, &handle->domain);
 573
 574         if (name != NULL) {
 575                 copy_string(lsm.u.disable.name, name, sizeof(lsm.u.disable.name));
 576                 lsm.cmd_type = LTTNG_DISABLE_EVENT;
 577         } else {
 578                 lsm.cmd_type = LTTNG_DISABLE_ALL_EVENT;
 579         }
 580
 581         copy_string(lsm.session.name, handle->session_name,
 582                         sizeof(lsm.session.name));
 583
 584         return ask_sessiond(&lsm, NULL);
 585 }
 586
 587 /*
 588  *  Enable channel per domain
 589  *  Returns size of returned session payload data or a negative error code.
 590  */
 591 int lttng_enable_channel(struct lttng_handle *handle,
 592                 struct lttng_channel *chan)
 593 {
 594         struct lttcomm_session_msg lsm;
 595
 596         /*
 597          * NULL arguments are forbidden. No default values.
 598          */
 599         if (handle == NULL || chan == NULL) {
 600                 return -1;
 601         }
 602
 603         memset(&lsm, 0, sizeof(lsm));
 604
 605         memcpy(&lsm.u.channel.chan, chan, sizeof(lsm.u.channel.chan));
 606
 607         lsm.cmd_type = LTTNG_ENABLE_CHANNEL;
 608
 609         copy_lttng_domain(&lsm.domain, &handle->domain);
 610
 611         copy_string(lsm.session.name, handle->session_name,
 612                         sizeof(lsm.session.name));
 613
 614         return ask_sessiond(&lsm, NULL);
 615 }
 616
 617 /*
 618  *  All tracing will be stopped for registered events of the channel.
 619  *  Returns size of returned session payload data or a negative error code.
 620  */
 621 int lttng_disable_channel(struct lttng_handle *handle, const char *name)
 622 {
 623         struct lttcomm_session_msg lsm;
 624
 625         /* Safety check. Both are mandatory */
 626         if (handle == NULL || name == NULL) {
 627                 return -1;
 628         }
 629
 630         memset(&lsm, 0, sizeof(lsm));
 631
 632         lsm.cmd_type = LTTNG_DISABLE_CHANNEL;
 633
 634         copy_string(lsm.u.disable.channel_name, name,
 635                         sizeof(lsm.u.disable.channel_name));
 636
 637         copy_lttng_domain(&lsm.domain, &handle->domain);
 638
 639         copy_string(lsm.session.name, handle->session_name,
 640                         sizeof(lsm.session.name));
 641
 642         return ask_sessiond(&lsm, NULL);
 643 }
 644
 645 /*
 646  *  Lists all available tracepoints of domain.
 647  *  Sets the contents of the events array.
 648  *  Returns the number of lttng_event entries in events;
 649  *  on error, returns a negative value.
 650  */
 651 int lttng_list_tracepoints(struct lttng_handle *handle,
 652                 struct lttng_event **events)
 653 {
 654         int ret;
 655         struct lttcomm_session_msg lsm;
 656
 657         if (handle == NULL) {
 658                 return -1;
 659         }
 660
 661         lsm.cmd_type = LTTNG_LIST_TRACEPOINTS;
 662         copy_lttng_domain(&lsm.domain, &handle->domain);
 663
 664         ret = ask_sessiond(&lsm, (void **) events);
 665         if (ret < 0) {
 666                 return ret;
 667         }
 668
 669         return ret / sizeof(struct lttng_event);
 670 }
 671
 672 /*
 673  *  Returns a human readable string describing
 674  *  the error code (a negative value).
 675  */
 676 const char *lttng_strerror(int code)
 677 {
 678         /* lttcomm error codes range from -LTTCOMM_OK down to -LTTCOMM_NR */
 679         if (code > -LTTCOMM_OK) {
 680                 return "Ended with errors";
 681         }
 682
 683         return lttcomm_get_readable_code(code);
 684 }
 685
 686 /*
 687  *  Create a brand new session using name and path.
 688  *  Returns size of returned session payload data or a negative error code.
 689  */
 690 int lttng_create_session(const char *name, const char *path)
 691 {
 692         struct lttcomm_session_msg lsm;
 693
 694         lsm.cmd_type = LTTNG_CREATE_SESSION;
 695         copy_string(lsm.session.name, name, sizeof(lsm.session.name));
 696         copy_string(lsm.session.path, path, sizeof(lsm.session.path));
 697
 698         return ask_sessiond(&lsm, NULL);
 699 }
 700
 701 /*
 702  *  Destroy session using name.
 703  *  Returns size of returned session payload data or a negative error code.
 704  */
 705 int lttng_destroy_session(const char *session_name)
 706 {
 707         struct lttcomm_session_msg lsm;
 708
 709         if (session_name == NULL) {
 710                 return -1;
 711         }
 712
 713         lsm.cmd_type = LTTNG_DESTROY_SESSION;
 714
 715         copy_string(lsm.session.name, session_name, sizeof(lsm.session.name));
 716
 717         return ask_sessiond(&lsm, NULL);
 718 }
 719
 720 /*
 721  *  Ask the session daemon for all available sessions.
 722  *  Sets the contents of the sessions array.
 723  *  Returns the number of lttng_session entries in sessions;
 724  *  on error, returns a negative value.
 725  */
 726 int lttng_list_sessions(struct lttng_session **sessions)
 727 {
 728         int ret;
 729         struct lttcomm_session_msg lsm;
 730
 731         lsm.cmd_type = LTTNG_LIST_SESSIONS;
 732         ret = ask_sessiond(&lsm, (void**) sessions);
 733         if (ret < 0) {
 734                 return ret;
 735         }
 736
 737         return ret / sizeof(struct lttng_session);
 738 }
 739
 740 /*
 741  *  Ask the session daemon for all available domains of a session.
 742  *  Sets the contents of the domains array.
 743  *  Returns the number of lttng_domain entries in domains;
 744  *  on error, returns a negative value.
 745  */
 746 int lttng_list_domains(const char *session_name,
 747                 struct lttng_domain **domains)
 748 {
 749         int ret;
 750         struct lttcomm_session_msg lsm;
 751
 752         if (session_name == NULL) {
 753                 return -1;
 754         }
 755
 756         lsm.cmd_type = LTTNG_LIST_DOMAINS;
 757
 758         copy_string(lsm.session.name, session_name, sizeof(lsm.session.name));
 759
 760         ret = ask_sessiond(&lsm, (void**) domains);
 761         if (ret < 0) {
 762                 return ret;
 763         }
 764
 765         return ret / sizeof(struct lttng_domain);
 766 }
 767
 768 /*
 769  *  Ask the session daemon for all available channels of a session.
 770  *  Sets the contents of the channels array.
 771  *  Returns the number of lttng_channel entries in channels;
 772  *  on error, returns a negative value.
 773  */
 774 int lttng_list_channels(struct lttng_handle *handle,
 775                 struct lttng_channel **channels)
 776 {
 777         int ret;
 778         struct lttcomm_session_msg lsm;
 779
 780         if (handle == NULL) {
 781                 return -1;
 782         }
 783
 784         lsm.cmd_type = LTTNG_LIST_CHANNELS;
 785         copy_string(lsm.session.name, handle->session_name,
 786                         sizeof(lsm.session.name));
 787
 788         copy_lttng_domain(&lsm.domain, &handle->domain);
 789
 790         ret = ask_sessiond(&lsm, (void**) channels);
 791         if (ret < 0) {
 792                 return ret;
 793         }
 794
 795         return ret / sizeof(struct lttng_channel);
 796 }
 797
 798 /*
 799  *  Ask the session daemon for all available events of a session channel.
 800  *  Sets the contents of the events array.
 801  *  Returns the number of lttng_event entries in events;
 802  *  on error, returns a negative value.
 803  */
 804 int lttng_list_events(struct lttng_handle *handle,
 805                 const char *channel_name, struct lttng_event **events)
 806 {
 807         int ret;
 808         struct lttcomm_session_msg lsm;
 809
 810         /* Safety check. An handle and channel name are mandatory */
 811         if (handle == NULL || channel_name == NULL) {
 812                 return -1;
 813         }
 814
 815         lsm.cmd_type = LTTNG_LIST_EVENTS;
 816         copy_string(lsm.session.name, handle->session_name,
 817                         sizeof(lsm.session.name));
 818         copy_string(lsm.u.list.channel_name, channel_name,
 819                         sizeof(lsm.u.list.channel_name));
 820
 821         copy_lttng_domain(&lsm.domain, &handle->domain);
 822
 823         ret = ask_sessiond(&lsm, (void**) events);
 824         if (ret < 0) {
 825                 return ret;
 826         }
 827
 828         return ret / sizeof(struct lttng_event);
 829 }
 830
 831 /*
 832  * Sets the tracing_group variable with name.
 833  * This function allocates memory pointed to by tracing_group.
 834  * On success, returns 0, on error, returns -1 (null name) or -ENOMEM.
 835  */
 836 int lttng_set_tracing_group(const char *name)
 837 {
 838         if (name == NULL) {
 839                 return -1;
 840         }
 841
 842         if (asprintf(&tracing_group, "%s", name) < 0) {
 843                 return -ENOMEM;
 844         }
 845
 846         return 0;
 847 }
 848
 849 /*
 850  * Returns size of returned session payload data or a negative error code.
 851  */
 852 int lttng_calibrate(struct lttng_handle *handle,
 853                 struct lttng_calibrate *calibrate)
 854 {
 855         struct lttcomm_session_msg lsm;
 856
 857         /* Safety check. NULL pointer are forbidden */
 858         if (handle == NULL || calibrate == NULL) {
 859                 return -1;
 860         }
 861
 862         lsm.cmd_type = LTTNG_CALIBRATE;
 863         copy_lttng_domain(&lsm.domain, &handle->domain);
 864
 865         memcpy(&lsm.u.calibrate, calibrate, sizeof(lsm.u.calibrate));
 866
 867         return ask_sessiond(&lsm, NULL);
 868 }
 869
 870 /*
 871  * Set default channel attributes.
 872  * If either or both of the arguments are null, attr content is zeroe'd.
 873  */
 874 void lttng_channel_set_default_attr(struct lttng_domain *domain,
 875                 struct lttng_channel_attr *attr)
 876 {
 877         memset(attr, 0, sizeof(struct lttng_channel_attr));
 878
 879         /* Safety check */
 880         if (attr == NULL || domain == NULL) {
 881                 return;
 882         }
 883
 884         switch (domain->type) {
 885         case LTTNG_DOMAIN_KERNEL:
 886                 attr->overwrite = DEFAULT_CHANNEL_OVERWRITE;
 887                 attr->switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
 888                 attr->read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;
 889
 890                 attr->subbuf_size = DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE;
 891                 attr->num_subbuf = DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM;
 892                 attr->output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
 893                 break;
 894         case LTTNG_DOMAIN_UST:
 895 #if 0
 896         case LTTNG_DOMAIN_UST_EXEC_NAME:
 897         case LTTNG_DOMAIN_UST_PID:
 898         case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
 899 #endif
 900                 attr->overwrite = DEFAULT_CHANNEL_OVERWRITE;
 901                 attr->switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
 902                 attr->read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;
 903
 904                 attr->subbuf_size = DEFAULT_UST_CHANNEL_SUBBUF_SIZE;
 905                 attr->num_subbuf = DEFAULT_UST_CHANNEL_SUBBUF_NUM;
 906                 attr->output = DEFAULT_UST_CHANNEL_OUTPUT;
 907                 break;
 908         default:
 909                 /* Default behavior: leave set to 0. */
 910                 break;
 911         }
 912 }
 913
 914 /*
 915  * Check if session daemon is alive.
 916  *
 917  * Return 1 if alive or 0 if not.
 918  * On error returns a negative value.
 919  */
 920 int lttng_session_daemon_alive(void)
 921 {
 922         int ret;
 923
 924         ret = set_session_daemon_path();
 925         if (ret < 0) {
 926                 /* Error */
 927                 return ret;
 928         }
 929
 930         if (strlen(sessiond_sock_path) == 0) {
 931                 /* No socket path set. Weird error */
 932                 return -1;
 933         }
 934
 935         ret = try_connect_sessiond(sessiond_sock_path);
 936         if (ret < 0) {
 937                 /* Not alive */
 938                 return 0;
 939         }
 940
 941         /* Is alive */
 942         return 1;
 943 }
 944
 945 /*
 946  * lib constructor
 947  */
 948 static void __attribute__((constructor)) init()
 949 {
 950         /* Set default session group */
 951         lttng_set_tracing_group(DEFAULT_TRACING_GROUP);
 952 }