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