src/lib/lttng-ctl/channel.c

   1 /*
   2  * Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * This library is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU Lesser General Public License, version 2.1 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This library is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  11  * for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this library; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18 #include <lttng/notification/notification-internal.h>
  19 #include <lttng/notification/channel-internal.h>
  20 #include <lttng/condition/condition-internal.h>
  21 #include <lttng/endpoint.h>
  22 #include <common/defaults.h>
  23 #include <common/error.h>
  24 #include <common/dynamic-buffer.h>
  25 #include <common/utils.h>
  26 #include <common/defaults.h>
  27 #include <assert.h>
  28 #include "lttng-ctl-helper.h"
  29 #include <common/compat/poll.h>
  30
  31 static
  32 int handshake(struct lttng_notification_channel *channel);
  33
  34 /*
  35  * Populates the reception buffer with the next complete message.
  36  * The caller must acquire the channel's lock.
  37  */
  38 static
  39 int receive_message(struct lttng_notification_channel *channel)
  40 {
  41         ssize_t ret;
  42         struct lttng_notification_channel_message msg;
  43
  44         if (lttng_dynamic_buffer_set_size(&channel->reception_buffer, 0)) {
  45                 ret = -1;
  46                 goto end;
  47         }
  48
  49         ret = lttcomm_recv_unix_sock(channel->socket, &msg, sizeof(msg));
  50         if (ret <= 0) {
  51                 ret = -1;
  52                 goto error;
  53         }
  54
  55         if (msg.size > DEFAULT_MAX_NOTIFICATION_CLIENT_MESSAGE_PAYLOAD_SIZE) {
  56                 ret = -1;
  57                 goto error;
  58         }
  59
  60         /* Add message header at buffer's start. */
  61         ret = lttng_dynamic_buffer_append(&channel->reception_buffer, &msg,
  62                         sizeof(msg));
  63         if (ret) {
  64                 goto error;
  65         }
  66
  67         /* Reserve space for the payload. */
  68         ret = lttng_dynamic_buffer_set_size(&channel->reception_buffer,
  69                         channel->reception_buffer.size + msg.size);
  70         if (ret) {
  71                 goto error;
  72         }
  73
  74         /* Receive message payload. */
  75         ret = lttcomm_recv_unix_sock(channel->socket,
  76                         channel->reception_buffer.data + sizeof(msg), msg.size);
  77         if (ret < (ssize_t) msg.size) {
  78                 ret = -1;
  79                 goto error;
  80         }
  81         ret = 0;
  82 end:
  83         return ret;
  84 error:
  85         if (lttng_dynamic_buffer_set_size(&channel->reception_buffer, 0)) {
  86                 ret = -1;
  87         }
  88         goto end;
  89 }
  90
  91 static
  92 enum lttng_notification_channel_message_type get_current_message_type(
  93                 struct lttng_notification_channel *channel)
  94 {
  95         struct lttng_notification_channel_message *msg;
  96
  97         assert(channel->reception_buffer.size >= sizeof(*msg));
  98
  99         msg = (struct lttng_notification_channel_message *)
 100                         channel->reception_buffer.data;
 101         return (enum lttng_notification_channel_message_type) msg->type;
 102 }
 103
 104 static
 105 struct lttng_notification *create_notification_from_current_message(
 106                 struct lttng_notification_channel *channel)
 107 {
 108         ssize_t ret;
 109         struct lttng_notification *notification = NULL;
 110         struct lttng_buffer_view view;
 111
 112         if (channel->reception_buffer.size <=
 113                         sizeof(struct lttng_notification_channel_message)) {
 114                 goto end;
 115         }
 116
 117         view = lttng_buffer_view_from_dynamic_buffer(&channel->reception_buffer,
 118                         sizeof(struct lttng_notification_channel_message), -1);
 119
 120         ret = lttng_notification_create_from_buffer(&view, &notification);
 121         if (ret != channel->reception_buffer.size -
 122                         sizeof(struct lttng_notification_channel_message)) {
 123                 lttng_notification_destroy(notification);
 124                 notification = NULL;
 125                 goto end;
 126         }
 127 end:
 128         return notification;
 129 }
 130
 131 struct lttng_notification_channel *lttng_notification_channel_create(
 132                 struct lttng_endpoint *endpoint)
 133 {
 134         int fd, ret;
 135         bool is_in_tracing_group = false, is_root = false;
 136         char *sock_path = NULL;
 137         struct lttng_notification_channel *channel = NULL;
 138
 139         if (!endpoint ||
 140                         endpoint != lttng_session_daemon_notification_endpoint) {
 141                 goto end;
 142         }
 143
 144         sock_path = zmalloc(LTTNG_PATH_MAX);
 145         if (!sock_path) {
 146                 goto end;
 147         }
 148
 149         channel = zmalloc(sizeof(struct lttng_notification_channel));
 150         if (!channel) {
 151                 goto end;
 152         }
 153         channel->socket = -1;
 154         pthread_mutex_init(&channel->lock, NULL);
 155         lttng_dynamic_buffer_init(&channel->reception_buffer);
 156         CDS_INIT_LIST_HEAD(&channel->pending_notifications.list);
 157
 158         is_root = (getuid() == 0);
 159         if (!is_root) {
 160                 is_in_tracing_group = lttng_check_tracing_group();
 161         }
 162
 163         if (is_root || is_in_tracing_group) {
 164                 lttng_ctl_copy_string(sock_path,
 165                                 DEFAULT_GLOBAL_NOTIFICATION_CHANNEL_UNIX_SOCK,
 166                                 LTTNG_PATH_MAX);
 167                 ret = lttcomm_connect_unix_sock(sock_path);
 168                 if (ret >= 0) {
 169                         fd = ret;
 170                         goto set_fd;
 171                 }
 172         }
 173
 174         /* Fallback to local session daemon. */
 175         ret = snprintf(sock_path, LTTNG_PATH_MAX,
 176                         DEFAULT_HOME_NOTIFICATION_CHANNEL_UNIX_SOCK,
 177                         utils_get_home_dir());
 178         if (ret < 0 || ret >= LTTNG_PATH_MAX) {
 179                 goto error;
 180         }
 181
 182         ret = lttcomm_connect_unix_sock(sock_path);
 183         if (ret < 0) {
 184                 goto error;
 185         }
 186         fd = ret;
 187
 188 set_fd:
 189         channel->socket = fd;
 190
 191         ret = handshake(channel);
 192         if (ret) {
 193                 goto error;
 194         }
 195 end:
 196         free(sock_path);
 197         return channel;
 198 error:
 199         lttng_notification_channel_destroy(channel);
 200         channel = NULL;
 201         goto end;
 202 }
 203
 204 enum lttng_notification_channel_status
 205 lttng_notification_channel_get_next_notification(
 206                 struct lttng_notification_channel *channel,
 207                 struct lttng_notification **_notification)
 208 {
 209         int ret;
 210         struct lttng_notification *notification = NULL;
 211         enum lttng_notification_channel_status status =
 212                         LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
 213         struct lttng_poll_event events;
 214
 215         if (!channel || !_notification) {
 216                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID;
 217                 goto end;
 218         }
 219
 220         pthread_mutex_lock(&channel->lock);
 221
 222         if (channel->pending_notifications.count) {
 223                 struct pending_notification *pending_notification;
 224
 225                 assert(!cds_list_empty(&channel->pending_notifications.list));
 226
 227                 /* Deliver one of the pending notifications. */
 228                 pending_notification = cds_list_first_entry(
 229                                 &channel->pending_notifications.list,
 230                                 struct pending_notification,
 231                                 node);
 232                 notification = pending_notification->notification;
 233                 if (!notification) {
 234                         status = LTTNG_NOTIFICATION_CHANNEL_STATUS_NOTIFICATIONS_DROPPED;
 235                 }
 236                 cds_list_del(&pending_notification->node);
 237                 channel->pending_notifications.count--;
 238                 free(pending_notification);
 239                 goto end_unlock;
 240         }
 241
 242         /*
 243          * Block on interruptible epoll/poll() instead of the message reception
 244          * itself as the recvmsg() wrappers always restart on EINTR. We choose
 245          * to wait using interruptible epoll/poll() in order to:
 246          *   1) Return if a signal occurs,
 247          *   2) Not deal with partially received messages.
 248          *
 249          * The drawback to this approach is that we assume that messages
 250          * are complete/well formed. If a message is shorter than its
 251          * announced length, receive_message() will block on recvmsg()
 252          * and never return (even if a signal is received).
 253          */
 254         ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
 255         if (ret < 0) {
 256                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 257                 goto end_unlock;
 258         }
 259         ret = lttng_poll_add(&events, channel->socket, LPOLLIN | LPOLLERR);
 260         if (ret < 0) {
 261                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 262                 goto end_clean_poll;
 263         }
 264         ret = lttng_poll_wait_interruptible(&events, -1);
 265         if (ret <= 0) {
 266                 status = (ret == -1 && errno == EINTR) ?
 267                         LTTNG_NOTIFICATION_CHANNEL_STATUS_INTERRUPTED :
 268                         LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 269                 goto end_clean_poll;
 270         }
 271
 272         ret = receive_message(channel);
 273         if (ret) {
 274                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 275                 goto end_clean_poll;
 276         }
 277
 278         switch (get_current_message_type(channel)) {
 279         case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION:
 280                 notification = create_notification_from_current_message(
 281                                 channel);
 282                 if (!notification) {
 283                         status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 284                         goto end_clean_poll;
 285                 }
 286                 break;
 287         case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION_DROPPED:
 288                 /* No payload to consume. */
 289                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_NOTIFICATIONS_DROPPED;
 290                 break;
 291         default:
 292                 /* Protocol error. */
 293                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 294                 goto end_clean_poll;
 295         }
 296
 297 end_clean_poll:
 298         lttng_poll_clean(&events);
 299 end_unlock:
 300         pthread_mutex_unlock(&channel->lock);
 301         *_notification = notification;
 302 end:
 303         return status;
 304 }
 305
 306 static
 307 int enqueue_dropped_notification(
 308                 struct lttng_notification_channel *channel)
 309 {
 310         int ret = 0;
 311         struct pending_notification *pending_notification;
 312         struct cds_list_head *last_element =
 313                         channel->pending_notifications.list.prev;
 314
 315         pending_notification = caa_container_of(last_element,
 316                         struct pending_notification, node);
 317         if (!pending_notification->notification) {
 318                 /*
 319                  * The last enqueued notification indicates dropped
 320                  * notifications; there is nothing to do as we group
 321                  * dropped notifications together.
 322                  */
 323                 goto end;
 324         }
 325
 326         if (channel->pending_notifications.count >=
 327                         DEFAULT_CLIENT_MAX_QUEUED_NOTIFICATIONS_COUNT &&
 328                         pending_notification->notification) {
 329                 /*
 330                  * Discard the last enqueued notification to indicate
 331                  * that notifications were dropped at this point.
 332                  */
 333                 lttng_notification_destroy(
 334                                 pending_notification->notification);
 335                 pending_notification->notification = NULL;
 336                 goto end;
 337         }
 338
 339         pending_notification = zmalloc(sizeof(*pending_notification));
 340         if (!pending_notification) {
 341                 ret = -1;
 342                 goto end;
 343         }
 344         CDS_INIT_LIST_HEAD(&pending_notification->node);
 345         cds_list_add(&pending_notification->node,
 346                         &channel->pending_notifications.list);
 347         channel->pending_notifications.count++;
 348 end:
 349         return ret;
 350 }
 351
 352 static
 353 int enqueue_notification_from_current_message(
 354                 struct lttng_notification_channel *channel)
 355 {
 356         int ret = 0;
 357         struct lttng_notification *notification;
 358         struct pending_notification *pending_notification;
 359
 360         if (channel->pending_notifications.count >=
 361                         DEFAULT_CLIENT_MAX_QUEUED_NOTIFICATIONS_COUNT) {
 362                 /* Drop the notification. */
 363                 ret = enqueue_dropped_notification(channel);
 364                 goto end;
 365         }
 366
 367         pending_notification = zmalloc(sizeof(*pending_notification));
 368         if (!pending_notification) {
 369                 ret = -1;
 370                 goto error;
 371         }
 372         CDS_INIT_LIST_HEAD(&pending_notification->node);
 373
 374         notification = create_notification_from_current_message(channel);
 375         if (!notification) {
 376                 ret = -1;
 377                 goto error;
 378         }
 379
 380         pending_notification->notification = notification;
 381         cds_list_add(&pending_notification->node,
 382                         &channel->pending_notifications.list);
 383         channel->pending_notifications.count++;
 384 end:
 385         return ret;
 386 error:
 387         free(pending_notification);
 388         goto end;
 389 }
 390
 391 enum lttng_notification_channel_status
 392 lttng_notification_channel_has_pending_notification(
 393                 struct lttng_notification_channel *channel,
 394                 bool *_notification_pending)
 395 {
 396         int ret;
 397         enum lttng_notification_channel_status status =
 398                         LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
 399         struct lttng_poll_event events;
 400
 401         if (!channel || !_notification_pending) {
 402                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID;
 403                 goto end;
 404         }
 405
 406         pthread_mutex_lock(&channel->lock);
 407
 408         if (channel->pending_notifications.count) {
 409                 *_notification_pending = true;
 410                 goto end_unlock;
 411         }
 412
 413         if (channel->socket < 0) {
 414                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_CLOSED;
 415                 goto end_unlock;
 416         }
 417
 418         /*
 419          * Check, without blocking, if data is available on the channel's
 420          * socket. If there is data available, it is safe to read (blocking)
 421          * on the socket for a message from the session daemon.
 422          *
 423          * Since all commands wait for the session daemon's reply before
 424          * releasing the channel's lock, the protocol only allows for
 425          * notifications and "notification dropped" messages to come
 426          * through. If we receive a different message type, it is
 427          * considered a protocol error.
 428          *
 429          * Note that this function is not guaranteed not to block. This
 430          * will block until our peer (the session daemon) has sent a complete
 431          * message if we see data available on the socket. If the peer does
 432          * not respect the protocol, this may block indefinitely.
 433          */
 434         ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
 435         if (ret < 0) {
 436                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 437                 goto end_unlock;
 438         }
 439         ret = lttng_poll_add(&events, channel->socket, LPOLLIN | LPOLLERR);
 440         if (ret < 0) {
 441                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 442                 goto end_clean_poll;
 443         }
 444         /* timeout = 0: return immediately. */
 445         ret = lttng_poll_wait_interruptible(&events, 0);
 446         if (ret == 0) {
 447                 /* No data available. */
 448                 *_notification_pending = false;
 449                 goto end_clean_poll;
 450         } else if (ret < 0) {
 451                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 452                 goto end_clean_poll;
 453         }
 454
 455         /* Data available on socket. */
 456         ret = receive_message(channel);
 457         if (ret) {
 458                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 459                 goto end_clean_poll;
 460         }
 461
 462         switch (get_current_message_type(channel)) {
 463         case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION:
 464                 ret = enqueue_notification_from_current_message(channel);
 465                 if (ret) {
 466                         goto end_clean_poll;
 467                 }
 468                 *_notification_pending = true;
 469                 break;
 470         case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION_DROPPED:
 471                 ret = enqueue_dropped_notification(channel);
 472                 if (ret) {
 473                         goto end_clean_poll;
 474                 }
 475                 *_notification_pending = true;
 476                 break;
 477         default:
 478                 /* Protocol error. */
 479                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 480                 goto end_clean_poll;
 481         }
 482
 483 end_clean_poll:
 484         lttng_poll_clean(&events);
 485 end_unlock:
 486         pthread_mutex_unlock(&channel->lock);
 487 end:
 488         return status;
 489 }
 490
 491 static
 492 int receive_command_reply(struct lttng_notification_channel *channel,
 493                 enum lttng_notification_channel_status *status)
 494 {
 495         int ret;
 496         struct lttng_notification_channel_command_reply *reply;
 497
 498         while (true) {
 499                 enum lttng_notification_channel_message_type msg_type;
 500
 501                 ret = receive_message(channel);
 502                 if (ret) {
 503                         goto end;
 504                 }
 505
 506                 msg_type = get_current_message_type(channel);
 507                 switch (msg_type) {
 508                 case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_COMMAND_REPLY:
 509                         goto exit_loop;
 510                 case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION:
 511                         ret = enqueue_notification_from_current_message(
 512                                         channel);
 513                         if (ret) {
 514                                 goto end;
 515                         }
 516                         break;
 517                 case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION_DROPPED:
 518                         ret = enqueue_dropped_notification(channel);
 519                         if (ret) {
 520                                 goto end;
 521                         }
 522                         break;
 523                 case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE:
 524                 {
 525                         struct lttng_notification_channel_command_handshake *handshake;
 526
 527                         handshake = (struct lttng_notification_channel_command_handshake *)
 528                                         (channel->reception_buffer.data +
 529                                         sizeof(struct lttng_notification_channel_message));
 530                         channel->version.major = handshake->major;
 531                         channel->version.minor = handshake->minor;
 532                         channel->version.set = true;
 533                         break;
 534                 }
 535                 default:
 536                         ret = -1;
 537                         goto end;
 538                 }
 539         }
 540
 541 exit_loop:
 542         if (channel->reception_buffer.size <
 543                         (sizeof(struct lttng_notification_channel_message) +
 544                         sizeof(*reply))) {
 545                 /* Invalid message received. */
 546                 ret = -1;
 547                 goto end;
 548         }
 549
 550         reply = (struct lttng_notification_channel_command_reply *)
 551                         (channel->reception_buffer.data +
 552                         sizeof(struct lttng_notification_channel_message));
 553         *status = (enum lttng_notification_channel_status) reply->status;
 554 end:
 555         return ret;
 556 }
 557
 558 static
 559 int handshake(struct lttng_notification_channel *channel)
 560 {
 561         ssize_t ret;
 562         enum lttng_notification_channel_status status =
 563                         LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
 564         struct lttng_notification_channel_command_handshake handshake = {
 565                 .major = LTTNG_NOTIFICATION_CHANNEL_VERSION_MAJOR,
 566                 .minor = LTTNG_NOTIFICATION_CHANNEL_VERSION_MINOR,
 567         };
 568         struct lttng_notification_channel_message msg_header = {
 569                 .type = LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_HANDSHAKE,
 570                 .size = sizeof(handshake),
 571         };
 572         char send_buffer[sizeof(msg_header) + sizeof(handshake)];
 573
 574         memcpy(send_buffer, &msg_header, sizeof(msg_header));
 575         memcpy(send_buffer + sizeof(msg_header), &handshake, sizeof(handshake));
 576
 577         pthread_mutex_lock(&channel->lock);
 578
 579         ret = lttcomm_send_creds_unix_sock(channel->socket, send_buffer,
 580                         sizeof(send_buffer));
 581         if (ret < 0) {
 582                 goto end_unlock;
 583         }
 584
 585         /* Receive handshake info from the sessiond. */
 586         ret = receive_command_reply(channel, &status);
 587         if (ret < 0) {
 588                 goto end_unlock;
 589         }
 590
 591         if (!channel->version.set) {
 592                 ret = -1;
 593                 goto end_unlock;
 594         }
 595
 596         if (channel->version.major != LTTNG_NOTIFICATION_CHANNEL_VERSION_MAJOR) {
 597                 ret = -1;
 598                 goto end_unlock;
 599         }
 600
 601 end_unlock:
 602         pthread_mutex_unlock(&channel->lock);
 603         return ret;
 604 }
 605
 606 static
 607 enum lttng_notification_channel_status send_condition_command(
 608                 struct lttng_notification_channel *channel,
 609                 enum lttng_notification_channel_message_type type,
 610                 const struct lttng_condition *condition)
 611 {
 612         int socket;
 613         ssize_t ret;
 614         enum lttng_notification_channel_status status =
 615                         LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
 616         struct lttng_dynamic_buffer buffer;
 617         struct lttng_notification_channel_message cmd_header = {
 618                 .type = (int8_t) type,
 619         };
 620
 621         lttng_dynamic_buffer_init(&buffer);
 622
 623         if (!channel) {
 624                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID;
 625                 goto end;
 626         }
 627
 628         assert(type == LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_SUBSCRIBE ||
 629                 type == LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNSUBSCRIBE);
 630
 631         pthread_mutex_lock(&channel->lock);
 632         socket = channel->socket;
 633         if (!lttng_condition_validate(condition)) {
 634                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID;
 635                 goto end_unlock;
 636         }
 637
 638         ret = lttng_dynamic_buffer_append(&buffer, &cmd_header,
 639                         sizeof(cmd_header));
 640         if (ret) {
 641                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 642                 goto end_unlock;
 643         }
 644
 645         ret = lttng_condition_serialize(condition, &buffer);
 646         if (ret) {
 647                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID;
 648                 goto end_unlock;
 649         }
 650
 651         /* Update payload length. */
 652         ((struct lttng_notification_channel_message *) buffer.data)->size =
 653                         (uint32_t) (buffer.size - sizeof(cmd_header));
 654
 655         ret = lttcomm_send_unix_sock(socket, buffer.data, buffer.size);
 656         if (ret < 0) {
 657                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 658                 goto end_unlock;
 659         }
 660
 661         ret = receive_command_reply(channel, &status);
 662         if (ret < 0) {
 663                 status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
 664                 goto end_unlock;
 665         }
 666 end_unlock:
 667         pthread_mutex_unlock(&channel->lock);
 668 end:
 669         lttng_dynamic_buffer_reset(&buffer);
 670         return status;
 671 }
 672
 673 enum lttng_notification_channel_status lttng_notification_channel_subscribe(
 674                 struct lttng_notification_channel *channel,
 675                 const struct lttng_condition *condition)
 676 {
 677         return send_condition_command(channel,
 678                         LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_SUBSCRIBE,
 679                         condition);
 680 }
 681
 682 enum lttng_notification_channel_status lttng_notification_channel_unsubscribe(
 683                 struct lttng_notification_channel *channel,
 684                 const struct lttng_condition *condition)
 685 {
 686         return send_condition_command(channel,
 687                         LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_UNSUBSCRIBE,
 688                         condition);
 689 }
 690
 691 void lttng_notification_channel_destroy(
 692                 struct lttng_notification_channel *channel)
 693 {
 694         if (!channel) {
 695                 return;
 696         }
 697
 698         if (channel->socket >= 0) {
 699                 (void) lttcomm_close_unix_sock(channel->socket);
 700         }
 701         pthread_mutex_destroy(&channel->lock);
 702         lttng_dynamic_buffer_reset(&channel->reception_buffer);
 703         free(channel);
 704 }