lib: compile liblttng-ctl as C++
[lttng-tools.git] / src / lib / lttng-ctl / lttng-ctl.cpp
diff --git a/src/lib/lttng-ctl/lttng-ctl.cpp b/src/lib/lttng-ctl/lttng-ctl.cpp
new file mode 100644 (file)
index 0000000..3622987
--- /dev/null
@@ -0,0 +1,3519 @@
+/*
+ * lttng-ctl.c
+ *
+ * Linux Trace Toolkit Control Library
+ *
+ * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
+ * Copyright (C) 2016 Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ *
+ * SPDX-License-Identifier: LGPL-2.1-only
+ *
+ */
+
+#define _LGPL_SOURCE
+#include <grp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <common/bytecode/bytecode.h>
+#include <common/align.h>
+#include <common/common.h>
+#include <common/compat/errno.h>
+#include <common/compat/string.h>
+#include <common/defaults.h>
+#include <common/dynamic-array.h>
+#include <common/dynamic-buffer.h>
+#include <common/payload-view.h>
+#include <common/payload.h>
+#include <common/sessiond-comm/sessiond-comm.h>
+#include <common/tracker.h>
+#include <common/unix.h>
+#include <common/uri.h>
+#include <common/utils.h>
+#include <lttng/channel-internal.h>
+#include <lttng/destruction-handle.h>
+#include <lttng/endpoint.h>
+#include <lttng/error-query-internal.h>
+#include <lttng/event-internal.h>
+#include <lttng/health-internal.h>
+#include <lttng/lttng-error.h>
+#include <lttng/lttng.h>
+#include <lttng/session-descriptor-internal.h>
+#include <lttng/session-internal.h>
+#include <lttng/trigger/trigger-internal.h>
+#include <lttng/userspace-probe-internal.h>
+
+#include "lttng-ctl-helper.h"
+#include <common/filter/filter-ast.h>
+#include <common/filter/filter-parser.h>
+#include <common/filter/memstream.h>
+
+#define COPY_DOMAIN_PACKED(dst, src)                           \
+do {                                                           \
+       struct lttng_domain _tmp_domain;                        \
+                                                               \
+       lttng_ctl_copy_lttng_domain(&_tmp_domain, &src);        \
+       dst = _tmp_domain;                                      \
+} while (0)
+
+/* Socket to session daemon for communication */
+static int sessiond_socket = -1;
+static char sessiond_sock_path[PATH_MAX];
+
+/* Variables */
+static char *tracing_group;
+static int connected;
+
+/* Global */
+
+/*
+ * Those two variables are used by error.h to silent or control the verbosity of
+ * error message. They are global to the library so application linking with it
+ * are able to compile correctly and also control verbosity of the library.
+ */
+LTTNG_EXPORT int lttng_opt_quiet;
+LTTNG_EXPORT int lttng_opt_verbose;
+LTTNG_EXPORT int lttng_opt_mi;
+
+/*
+ * Copy domain to lttcomm_session_msg domain.
+ *
+ * If domain is unknown, default domain will be the kernel.
+ */
+void lttng_ctl_copy_lttng_domain(struct lttng_domain *dst,
+               struct lttng_domain *src)
+{
+       if (src && dst) {
+               switch (src->type) {
+               case LTTNG_DOMAIN_KERNEL:
+               case LTTNG_DOMAIN_UST:
+               case LTTNG_DOMAIN_JUL:
+               case LTTNG_DOMAIN_LOG4J:
+               case LTTNG_DOMAIN_PYTHON:
+                       memcpy(dst, src, sizeof(struct lttng_domain));
+                       break;
+               default:
+                       memset(dst, 0, sizeof(struct lttng_domain));
+                       break;
+               }
+       }
+}
+
+/*
+ * Send lttcomm_session_msg to the session daemon.
+ *
+ * On success, returns the number of bytes sent (>=0)
+ * On error, returns -1
+ */
+static int send_session_msg(struct lttcomm_session_msg *lsm)
+{
+       int ret;
+
+       if (!connected) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+               goto end;
+       }
+
+       DBG("LSM cmd type: '%s' (%d)", lttcomm_sessiond_command_str((lttcomm_sessiond_command) lsm->cmd_type),
+                       lsm->cmd_type);
+
+       ret = lttcomm_send_creds_unix_sock(sessiond_socket, lsm,
+                       sizeof(struct lttcomm_session_msg));
+       if (ret < 0) {
+               ret = -LTTNG_ERR_FATAL;
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * Send var len data to the session daemon.
+ *
+ * On success, returns the number of bytes sent (>=0)
+ * On error, returns -1
+ */
+static int send_session_varlen(const void *data, size_t len)
+{
+       int ret;
+
+       if (!connected) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+               goto end;
+       }
+
+       if (!data || !len) {
+               ret = 0;
+               goto end;
+       }
+
+       ret = lttcomm_send_unix_sock(sessiond_socket, data, len);
+       if (ret < 0) {
+               ret = -LTTNG_ERR_FATAL;
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * Send file descriptors to the session daemon.
+ *
+ * On success, returns the number of bytes sent (>=0)
+ * On error, returns -1
+ */
+static int send_session_fds(const int *fds, size_t nb_fd)
+{
+       int ret;
+
+       if (!connected) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+               goto end;
+       }
+
+       if (!fds || !nb_fd) {
+               ret = 0;
+               goto end;
+       }
+
+       ret = lttcomm_send_fds_unix_sock(sessiond_socket, fds, nb_fd);
+       if (ret < 0) {
+               ret = -LTTNG_ERR_FATAL;
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * Receive data from the sessiond socket.
+ *
+ * On success, returns the number of bytes received (>=0)
+ * On error, returns a negative lttng_error_code.
+ */
+static int recv_data_sessiond(void *buf, size_t len)
+{
+       int ret;
+
+       LTTNG_ASSERT(len > 0);
+
+       if (!connected) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+               goto end;
+       }
+
+       ret = lttcomm_recv_unix_sock(sessiond_socket, buf, len);
+       if (ret < 0) {
+               ret = -LTTNG_ERR_FATAL;
+       } else if (ret == 0) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * Receive a payload from the session daemon by appending to an existing
+ * payload.
+ * On success, returns the number of bytes received (>=0)
+ * On error, returns a negative lttng_error_code.
+ */
+static int recv_payload_sessiond(struct lttng_payload *payload, size_t len)
+{
+       int ret;
+       const size_t original_payload_size = payload->buffer.size;
+
+       ret = lttng_dynamic_buffer_set_size(
+                       &payload->buffer, payload->buffer.size + len);
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       ret = recv_data_sessiond(
+                       payload->buffer.data + original_payload_size, len);
+end:
+       return ret;
+}
+
+/*
+ * Check if we are in the specified group.
+ *
+ * If yes return 1, else return -1.
+ */
+int lttng_check_tracing_group(void)
+{
+       gid_t *grp_list, tracing_gid;
+       int grp_list_size, grp_id, i;
+       int ret = -1;
+       const char *grp_name = tracing_group;
+
+       /* Get GID of group 'tracing' */
+       if (utils_get_group_id(grp_name, false, &tracing_gid)) {
+               /* If grp_tracing is NULL, the group does not exist. */
+               goto end;
+       }
+
+       /* Get number of supplementary group IDs */
+       grp_list_size = getgroups(0, NULL);
+       if (grp_list_size < 0) {
+               PERROR("getgroups");
+               goto end;
+       }
+
+       /* Alloc group list of the right size */
+       grp_list = (gid_t *) zmalloc(grp_list_size * sizeof(gid_t));
+       if (!grp_list) {
+               PERROR("malloc");
+               goto end;
+       }
+       grp_id = getgroups(grp_list_size, grp_list);
+       if (grp_id < 0) {
+               PERROR("getgroups");
+               goto free_list;
+       }
+
+       for (i = 0; i < grp_list_size; i++) {
+               if (grp_list[i] == tracing_gid) {
+                       ret = 1;
+                       break;
+               }
+       }
+
+free_list:
+       free(grp_list);
+
+end:
+       return ret;
+}
+
+static int check_enough_available_memory(size_t num_bytes_requested_per_cpu)
+{
+       int ret;
+       long num_cpu;
+       size_t best_mem_info;
+       size_t num_bytes_requested_total;
+
+       /*
+        * Get the number of CPU currently online to compute the amount of
+        * memory needed to create a buffer for every CPU.
+        */
+       num_cpu = sysconf(_SC_NPROCESSORS_ONLN);
+       if (num_cpu == -1) {
+               goto error;
+       }
+
+       num_bytes_requested_total = num_bytes_requested_per_cpu * num_cpu;
+
+       /*
+        * Try to get the `MemAvail` field of `/proc/meminfo`. This is the most
+        * reliable estimate we can get but it is only exposed by the kernel
+        * since 3.14. (See Linux kernel commit:
+        * 34e431b0ae398fc54ea69ff85ec700722c9da773)
+        */
+       ret = utils_get_memory_available(&best_mem_info);
+       if (ret >= 0) {
+               goto success;
+       }
+
+       /*
+        * As a backup plan, use `MemTotal` field of `/proc/meminfo`. This
+        * is a sanity check for obvious user error.
+        */
+       ret = utils_get_memory_total(&best_mem_info);
+       if (ret >= 0) {
+               goto success;
+       }
+
+error:
+       return -1;
+success:
+       return best_mem_info >= num_bytes_requested_total;
+}
+
+/*
+ * Try connect to session daemon with sock_path.
+ *
+ * Return 0 on success, else -1
+ */
+static int try_connect_sessiond(const char *sock_path)
+{
+       int ret;
+
+       /* If socket exist, we check if the daemon listens for connect. */
+       ret = access(sock_path, F_OK);
+       if (ret < 0) {
+               /* Not alive */
+               goto error;
+       }
+
+       ret = lttcomm_connect_unix_sock(sock_path);
+       if (ret < 0) {
+               /* Not alive. */
+               goto error;
+       }
+
+       ret = lttcomm_close_unix_sock(ret);
+       if (ret < 0) {
+               PERROR("lttcomm_close_unix_sock");
+       }
+
+       return 0;
+
+error:
+       return -1;
+}
+
+/*
+ * Set sessiond socket path by putting it in the global sessiond_sock_path
+ * variable.
+ *
+ * Returns 0 on success, negative value on failure (the sessiond socket path
+ * is somehow too long or ENOMEM).
+ */
+static int set_session_daemon_path(void)
+{
+       int in_tgroup = 0;      /* In tracing group. */
+       uid_t uid;
+
+       uid = getuid();
+
+       if (uid != 0) {
+               /* Are we in the tracing group ? */
+               in_tgroup = lttng_check_tracing_group();
+       }
+
+       if ((uid == 0) || in_tgroup == 1) {
+               const int ret = lttng_strncpy(sessiond_sock_path,
+                               DEFAULT_GLOBAL_CLIENT_UNIX_SOCK,
+                               sizeof(sessiond_sock_path));
+
+               if (ret) {
+                       goto error;
+               }
+       }
+
+       if (uid != 0) {
+               int ret;
+
+               if (in_tgroup) {
+                       /* Tracing group. */
+                       ret = try_connect_sessiond(sessiond_sock_path);
+                       if (ret >= 0) {
+                               goto end;
+                       }
+                       /* Global session daemon not available... */
+               }
+               /* ...or not in tracing group (and not root), default */
+
+               /*
+                * With GNU C <  2.1, snprintf returns -1 if the target buffer
+                * is too small;
+                * With GNU C >= 2.1, snprintf returns the required size
+                * (excluding closing null)
+                */
+               ret = snprintf(sessiond_sock_path, sizeof(sessiond_sock_path),
+                               DEFAULT_HOME_CLIENT_UNIX_SOCK, utils_get_home_dir());
+               if ((ret < 0) || (ret >= sizeof(sessiond_sock_path))) {
+                       goto error;
+               }
+       }
+end:
+       return 0;
+
+error:
+       return -1;
+}
+
+/*
+ * Connect to the LTTng session daemon.
+ *
+ * On success, return the socket's file descriptor. On error, return -1.
+ */
+int connect_sessiond(void)
+{
+       int ret;
+
+       ret = set_session_daemon_path();
+       if (ret < 0) {
+               goto error;
+       }
+
+       /* Connect to the sesssion daemon. */
+       ret = lttcomm_connect_unix_sock(sessiond_sock_path);
+       if (ret < 0) {
+               goto error;
+       }
+
+       return ret;
+
+error:
+       return -1;
+}
+
+static void reset_global_sessiond_connection_state(void)
+{
+       sessiond_socket = -1;
+       connected = 0;
+}
+
+/*
+ *  Clean disconnect from the session daemon.
+ *
+ *  On success, return 0. On error, return -1.
+ */
+static int disconnect_sessiond(void)
+{
+       int ret = 0;
+
+       if (connected) {
+               ret = lttcomm_close_unix_sock(sessiond_socket);
+               reset_global_sessiond_connection_state();
+       }
+
+       return ret;
+}
+
+static int recv_sessiond_optional_data(size_t len, void **user_buf,
+       size_t *user_len)
+{
+       int ret = 0;
+       void *buf = NULL;
+
+       if (len) {
+               if (!user_len) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+
+               buf = zmalloc(len);
+               if (!buf) {
+                       ret = -ENOMEM;
+                       goto end;
+               }
+
+               ret = recv_data_sessiond(buf, len);
+               if (ret < 0) {
+                       goto end;
+               }
+
+               if (!user_buf) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+
+               /* Move ownership of command header buffer to user. */
+               *user_buf = buf;
+               buf = NULL;
+               *user_len = len;
+       } else {
+               /* No command header. */
+               if (user_len) {
+                       *user_len = 0;
+               }
+
+               if (user_buf) {
+                       *user_buf = NULL;
+               }
+       }
+
+end:
+       free(buf);
+       return ret;
+}
+
+/*
+ * Ask the session daemon a specific command and put the data into buf.
+ * Takes extra var. len. data and file descriptors as input to send to the
+ * session daemon.
+ *
+ * Return size of data (only payload, not header) or a negative error code.
+ */
+int lttng_ctl_ask_sessiond_fds_varlen(struct lttcomm_session_msg *lsm,
+               const int *fds, size_t nb_fd, const void *vardata,
+               size_t vardata_len, void **user_payload_buf,
+               void **user_cmd_header_buf, size_t *user_cmd_header_len)
+{
+       int ret;
+       size_t payload_len;
+       struct lttcomm_lttng_msg llm;
+
+       ret = connect_sessiond();
+       if (ret < 0) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+               goto end;
+       } else {
+               sessiond_socket = ret;
+               connected = 1;
+       }
+
+       ret = send_session_msg(lsm);
+       if (ret < 0) {
+               /* Ret value is a valid lttng error code. */
+               goto end;
+       }
+       /* Send var len data */
+       ret = send_session_varlen(vardata, vardata_len);
+       if (ret < 0) {
+               /* Ret value is a valid lttng error code. */
+               goto end;
+       }
+
+       /* Send fds */
+       ret = send_session_fds(fds, nb_fd);
+       if (ret < 0) {
+               /* Ret value is a valid lttng error code. */
+               goto end;
+       }
+
+       /* Get header from data transmission */
+       ret = recv_data_sessiond(&llm, sizeof(llm));
+       if (ret < 0) {
+               /* Ret value is a valid lttng error code. */
+               goto end;
+       }
+
+       /* Check error code if OK */
+       if (llm.ret_code != LTTNG_OK) {
+               ret = -llm.ret_code;
+               goto end;
+       }
+
+       /* Get command header from data transmission */
+       ret = recv_sessiond_optional_data(llm.cmd_header_size,
+               user_cmd_header_buf, user_cmd_header_len);
+       if (ret < 0) {
+               goto end;
+       }
+
+       /* Get payload from data transmission */
+       ret = recv_sessiond_optional_data(llm.data_size, user_payload_buf,
+               &payload_len);
+       if (ret < 0) {
+               goto end;
+       }
+
+       ret = llm.data_size;
+
+end:
+       disconnect_sessiond();
+       return ret;
+}
+
+int lttng_ctl_ask_sessiond_payload(struct lttng_payload_view *message,
+       struct lttng_payload *reply)
+{
+       int ret;
+       struct lttcomm_lttng_msg llm;
+       const int fd_count = lttng_payload_view_get_fd_handle_count(message);
+
+       LTTNG_ASSERT(reply->buffer.size == 0);
+       LTTNG_ASSERT(lttng_dynamic_pointer_array_get_count(&reply->_fd_handles) == 0);
+
+       ret = connect_sessiond();
+       if (ret < 0) {
+               ret = -LTTNG_ERR_NO_SESSIOND;
+               goto end;
+       } else {
+               sessiond_socket = ret;
+               connected = 1;
+       }
+
+       /* Send command to session daemon */
+       ret = lttcomm_send_creds_unix_sock(sessiond_socket, message->buffer.data,
+                       message->buffer.size);
+       if (ret < 0) {
+               ret = -LTTNG_ERR_FATAL;
+               goto end;
+       }
+
+       if (fd_count > 0) {
+               ret = lttcomm_send_payload_view_fds_unix_sock(sessiond_socket,
+                               message);
+               if (ret < 0) {
+                       ret = -LTTNG_ERR_FATAL;
+                       goto end;
+               }
+       }
+
+       /* Get header from data transmission */
+       ret = recv_payload_sessiond(reply, sizeof(llm));
+       if (ret < 0) {
+               /* Ret value is a valid lttng error code. */
+               goto end;
+       }
+
+       llm = *((typeof(llm) *) reply->buffer.data);
+
+       /* Check error code if OK */
+       if (llm.ret_code != LTTNG_OK) {
+               if (llm.ret_code < LTTNG_OK || llm.ret_code >= LTTNG_ERR_NR) {
+                       /* Invalid error code received. */
+                       ret = -LTTNG_ERR_UNK;
+               } else {
+                       ret = -llm.ret_code;
+               }
+               goto end;
+       }
+
+       if (llm.cmd_header_size > 0) {
+               ret = recv_payload_sessiond(reply, llm.cmd_header_size);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
+       /* Get command header from data transmission */
+       if (llm.data_size > 0) {
+               ret = recv_payload_sessiond(reply, llm.data_size);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
+       if (llm.fd_count > 0) {
+               ret = lttcomm_recv_payload_fds_unix_sock(
+                               sessiond_socket, llm.fd_count, reply);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
+       /* Don't return the llm header to the caller. */
+       memmove(reply->buffer.data, reply->buffer.data + sizeof(llm),
+                       reply->buffer.size - sizeof(llm));
+       ret = lttng_dynamic_buffer_set_size(
+                       &reply->buffer, reply->buffer.size - sizeof(llm));
+       if (ret) {
+               /* Can't happen as size is reduced. */
+               abort();
+       }
+
+       ret = reply->buffer.size;
+
+end:
+       disconnect_sessiond();
+       return ret;
+}
+
+/*
+ * Create lttng handle and return pointer.
+ *
+ * The returned pointer will be NULL in case of malloc() error.
+ */
+struct lttng_handle *lttng_create_handle(const char *session_name,
+               struct lttng_domain *domain)
+{
+       int ret;
+       struct lttng_handle *handle = NULL;
+
+       handle = (lttng_handle *) zmalloc(sizeof(struct lttng_handle));
+       if (handle == NULL) {
+               PERROR("malloc handle");
+               goto end;
+       }
+
+       /* Copy session name */
+       ret = lttng_strncpy(handle->session_name, session_name ? : "",
+                           sizeof(handle->session_name));
+       if (ret) {
+               goto error;
+       }
+
+       /* Copy lttng domain or leave initialized to 0. */
+       if (domain) {
+               lttng_ctl_copy_lttng_domain(&handle->domain, domain);
+       }
+
+end:
+       return handle;
+error:
+       free(handle);
+       return NULL;
+}
+
+/*
+ * Destroy handle by free(3) the pointer.
+ */
+void lttng_destroy_handle(struct lttng_handle *handle)
+{
+       free(handle);
+}
+
+/*
+ * Register an outside consumer.
+ *
+ * Returns size of returned session payload data or a negative error code.
+ */
+int lttng_register_consumer(struct lttng_handle *handle,
+               const char *socket_path)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (handle == NULL || socket_path == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_REGISTER_CONSUMER;
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+
+       ret = lttng_strncpy(lsm.u.reg.path, socket_path,
+                           sizeof(lsm.u.reg.path));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+end:
+       return ret;
+}
+
+/*
+ * Start tracing for all traces of the session.
+ *
+ * Returns size of returned session payload data or a negative error code.
+ */
+int lttng_start_tracing(const char *session_name)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (session_name == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_START_TRACE;
+
+       ret = lttng_strncpy(lsm.session.name, session_name,
+                           sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+end:
+       return ret;
+}
+
+/*
+ * Stop tracing for all traces of the session.
+ */
+static int _lttng_stop_tracing(const char *session_name, int wait)
+{
+       int ret, data_ret;
+       struct lttcomm_session_msg lsm;
+
+       if (session_name == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_STOP_TRACE;
+
+       ret = lttng_strncpy(lsm.session.name, session_name,
+                           sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+       if (ret < 0 && ret != -LTTNG_ERR_TRACE_ALREADY_STOPPED) {
+               goto error;
+       }
+
+       if (!wait) {
+               goto end;
+       }
+
+       /* Check for data availability */
+       do {
+               data_ret = lttng_data_pending(session_name);
+               if (data_ret < 0) {
+                       /* Return the data available call error. */
+                       ret = data_ret;
+                       goto error;
+               }
+
+               /*
+                * Data sleep time before retrying (in usec). Don't sleep if the
+                * call returned value indicates availability.
+                */
+               if (data_ret) {
+                       usleep(DEFAULT_DATA_AVAILABILITY_WAIT_TIME_US);
+               }
+       } while (data_ret != 0);
+
+end:
+error:
+       return ret;
+}
+
+/*
+ * Stop tracing and wait for data availability.
+ */
+int lttng_stop_tracing(const char *session_name)
+{
+       return _lttng_stop_tracing(session_name, 1);
+}
+
+/*
+ * Stop tracing but _don't_ wait for data availability.
+ */
+int lttng_stop_tracing_no_wait(const char *session_name)
+{
+       return _lttng_stop_tracing(session_name, 0);
+}
+
+/*
+ * Add context to a channel.
+ *
+ * If the given channel is NULL, add the contexts to all channels.
+ * The event_name param is ignored.
+ *
+ * Returns the size of the returned payload data or a negative error code.
+ */
+int lttng_add_context(struct lttng_handle *handle,
+               struct lttng_event_context *ctx, const char *event_name,
+               const char *channel_name)
+{
+       int ret;
+       size_t len = 0;
+       char *buf = NULL;
+       struct lttcomm_session_msg lsm;
+
+       /* Safety check. Both are mandatory. */
+       if (handle == NULL || ctx == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_ADD_CONTEXT;
+
+       /* If no channel name, send empty string. */
+       ret = lttng_strncpy(lsm.u.context.channel_name, channel_name ?: "",
+                       sizeof(lsm.u.context.channel_name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       if (ctx->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT) {
+               size_t provider_len, ctx_len;
+               const char *provider_name = ctx->u.app_ctx.provider_name;
+               const char *ctx_name = ctx->u.app_ctx.ctx_name;
+
+               if (!provider_name || !ctx_name) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+
+               provider_len = strlen(provider_name);
+               if (provider_len == 0) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+               lsm.u.context.provider_name_len = provider_len;
+
+               ctx_len = strlen(ctx_name);
+               if (ctx_len == 0) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+               lsm.u.context.context_name_len = ctx_len;
+
+               len = provider_len + ctx_len;
+               buf = (char *) zmalloc(len);
+               if (!buf) {
+                       ret = -LTTNG_ERR_NOMEM;
+                       goto end;
+               }
+
+               memcpy(buf, provider_name, provider_len);
+               memcpy(buf + provider_len, ctx_name, ctx_len);
+       }
+       memcpy(&lsm.u.context.ctx, ctx, sizeof(struct lttng_event_context));
+
+       if (ctx->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT) {
+               /*
+                * Don't leak application addresses to the sessiond.
+                * This is only necessary when ctx is for an app ctx otherwise
+                * the values inside the union (type & config) are overwritten.
+                */
+               lsm.u.context.ctx.u.app_ctx.provider_name = NULL;
+               lsm.u.context.ctx.u.app_ctx.ctx_name = NULL;
+       }
+
+       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, buf, len, NULL);
+end:
+       free(buf);
+       return ret;
+}
+
+/*
+ * Enable event(s) for a channel.
+ *
+ * If no event name is specified, all events are enabled.
+ * If no channel name is specified, the default 'channel0' is used.
+ *
+ * Returns size of returned session payload data or a negative error code.
+ */
+int lttng_enable_event(struct lttng_handle *handle,
+               struct lttng_event *ev, const char *channel_name)
+{
+       return lttng_enable_event_with_exclusions(handle, ev, channel_name,
+                       NULL, 0, NULL);
+}
+
+/*
+ * Create or enable an event with a filter expression.
+ *
+ * Return negative error value on error.
+ * Return size of returned session payload data if OK.
+ */
+int lttng_enable_event_with_filter(struct lttng_handle *handle,
+               struct lttng_event *event, const char *channel_name,
+               const char *filter_expression)
+{
+       return lttng_enable_event_with_exclusions(handle, event, channel_name,
+                       filter_expression, 0, NULL);
+}
+
+/*
+ * Depending on the event, return a newly allocated agent filter expression or
+ * NULL if not applicable.
+ *
+ * An event with NO loglevel and the name is * will return NULL.
+ */
+static char *set_agent_filter(const char *filter, struct lttng_event *ev)
+{
+       int err;
+       char *agent_filter = NULL;
+
+       LTTNG_ASSERT(ev);
+
+       /* Don't add filter for the '*' event. */
+       if (strcmp(ev->name, "*") != 0) {
+               if (filter) {
+                       err = asprintf(&agent_filter, "(%s) && (logger_name == \"%s\")", filter,
+                                       ev->name);
+               } else {
+                       err = asprintf(&agent_filter, "logger_name == \"%s\"", ev->name);
+               }
+               if (err < 0) {
+                       PERROR("asprintf");
+                       goto error;
+               }
+       }
+
+       /* Add loglevel filtering if any for the JUL domain. */
+       if (ev->loglevel_type != LTTNG_EVENT_LOGLEVEL_ALL) {
+               const char *op;
+
+               if (ev->loglevel_type == LTTNG_EVENT_LOGLEVEL_RANGE) {
+                       op = ">=";
+               } else {
+                       op = "==";
+               }
+
+               if (filter || agent_filter) {
+                       char *new_filter;
+
+                       err = asprintf(&new_filter, "(%s) && (int_loglevel %s %d)",
+                                       agent_filter ? agent_filter : filter, op,
+                                       ev->loglevel);
+                       if (agent_filter) {
+                               free(agent_filter);
+                       }
+                       agent_filter = new_filter;
+               } else {
+                       err = asprintf(&agent_filter, "int_loglevel %s %d", op,
+                                       ev->loglevel);
+               }
+               if (err < 0) {
+                       PERROR("asprintf");
+                       goto error;
+               }
+       }
+
+       return agent_filter;
+error:
+       free(agent_filter);
+       return NULL;
+}
+
+/*
+ * Enable event(s) for a channel, possibly with exclusions and a filter.
+ * If no event name is specified, all events are enabled.
+ * If no channel name is specified, the default name is used.
+ * If filter expression is not NULL, the filter is set for the event.
+ * If exclusion count is not zero, the exclusions are set for the event.
+ * Returns size of returned session payload data or a negative error code.
+ */
+int lttng_enable_event_with_exclusions(struct lttng_handle *handle,
+               struct lttng_event *ev, const char *channel_name,
+               const char *original_filter_expression,
+               int exclusion_count, char **exclusion_list)
+{
+       struct lttcomm_session_msg lsm;
+       struct lttng_payload payload;
+       int ret = 0, i;
+       unsigned int free_filter_expression = 0;
+       struct filter_parser_ctx *ctx = NULL;
+
+       /*
+        * We have either a filter or some exclusions, so we need to set up
+        * a variable-length payload from where to send the data.
+        */
+       lttng_payload_init(&payload);
+
+       /*
+        * Cast as non-const since we may replace the filter expression
+        * by a dynamically allocated string. Otherwise, the original
+        * string is not modified.
+        */
+       char *filter_expression = (char *) original_filter_expression;
+
+       if (handle == NULL || ev == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       /*
+        * Empty filter string will always be rejected by the parser
+        * anyway, so treat this corner-case early to eliminate
+        * lttng_fmemopen error for 0-byte allocation.
+        */
+       if (filter_expression && filter_expression[0] == '\0') {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+
+       /* If no channel name, send empty string. */
+       ret = lttng_strncpy(lsm.u.enable.channel_name, channel_name ?: "",
+                       sizeof(lsm.u.enable.channel_name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       lsm.cmd_type = LTTNG_ENABLE_EVENT;
+       if (ev->name[0] == '\0') {
+               /* Enable all events. */
+               ret = lttng_strncpy(ev->name, "*", sizeof(ev->name));
+               LTTNG_ASSERT(ret == 0);
+       }
+
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+       memcpy(&lsm.u.enable.event, ev, sizeof(lsm.u.enable.event));
+
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       lsm.u.enable.exclusion_count = exclusion_count;
+       lsm.u.enable.bytecode_len = 0;
+
+       /* Parse filter expression. */
+       if (filter_expression != NULL || handle->domain.type == LTTNG_DOMAIN_JUL
+                       || handle->domain.type == LTTNG_DOMAIN_LOG4J
+                       || handle->domain.type == LTTNG_DOMAIN_PYTHON) {
+               if (handle->domain.type == LTTNG_DOMAIN_JUL ||
+                               handle->domain.type == LTTNG_DOMAIN_LOG4J ||
+                               handle->domain.type == LTTNG_DOMAIN_PYTHON) {
+                       char *agent_filter;
+
+                       /* Setup JUL filter if needed. */
+                       agent_filter = set_agent_filter(filter_expression, ev);
+                       if (!agent_filter) {
+                               if (!filter_expression) {
+                                       /*
+                                        * No JUL and no filter, just skip
+                                        * everything below.
+                                        */
+                                       goto ask_sessiond;
+                               }
+                       } else {
+                               /*
+                                * With an agent filter, the original filter has
+                                * been added to it thus replace the filter
+                                * expression.
+                                */
+                               filter_expression = agent_filter;
+                               free_filter_expression = 1;
+                       }
+               }
+
+               ret = filter_parser_ctx_create_from_filter_expression(filter_expression, &ctx);
+               if (ret) {
+                       goto filter_error;
+               }
+
+               lsm.u.enable.bytecode_len = sizeof(ctx->bytecode->b)
+                       + bytecode_get_len(&ctx->bytecode->b);
+               lsm.u.enable.expression_len = strlen(filter_expression) + 1;
+       }
+
+       ret = lttng_dynamic_buffer_set_capacity(&payload.buffer,
+                       lsm.u.enable.bytecode_len +
+                                       lsm.u.enable.expression_len +
+                                       LTTNG_SYMBOL_NAME_LEN *
+                                                       exclusion_count);
+       if (ret) {
+               ret = -LTTNG_ERR_EXCLUSION_NOMEM;
+               goto mem_error;
+       }
+
+       /* Put exclusion names first in the data. */
+       for (i = 0; i < exclusion_count; i++) {
+               size_t exclusion_len;
+
+               exclusion_len = lttng_strnlen(exclusion_list[i],
+                               LTTNG_SYMBOL_NAME_LEN);
+               if (exclusion_len == LTTNG_SYMBOL_NAME_LEN) {
+                       /* Exclusion is not NULL-terminated. */
+                       ret = -LTTNG_ERR_INVALID;
+                       goto mem_error;
+               }
+
+               ret = lttng_dynamic_buffer_append(&payload.buffer,
+                               exclusion_list[i], exclusion_len);
+               if (ret) {
+                       goto mem_error;
+               }
+
+               /*
+                * Padding the rest of the entry with zeros. Every exclusion
+                * entries take LTTNG_SYMBOL_NAME_LEN bytes in the buffer.
+                */
+               ret = lttng_dynamic_buffer_set_size(&payload.buffer,
+                               LTTNG_SYMBOL_NAME_LEN * (i + 1));
+               if (ret) {
+                       goto mem_error;
+               }
+       }
+
+       /* Add filter expression next. */
+       if (filter_expression) {
+               ret = lttng_dynamic_buffer_append(&payload.buffer,
+                               filter_expression, lsm.u.enable.expression_len);
+               if (ret) {
+                       goto mem_error;
+               }
+       }
+       /* Add filter bytecode next. */
+       if (ctx && lsm.u.enable.bytecode_len != 0) {
+               ret = lttng_dynamic_buffer_append(&payload.buffer,
+                               &ctx->bytecode->b, lsm.u.enable.bytecode_len);
+               if (ret) {
+                       goto mem_error;
+               }
+       }
+       if (ev->extended.ptr) {
+               struct lttng_event_extended *ev_ext =
+                       (struct lttng_event_extended *) ev->extended.ptr;
+
+               if (ev_ext->probe_location) {
+                       /*
+                        * lttng_userspace_probe_location_serialize returns the
+                        * number of bytes that was appended to the buffer.
+                        */
+                       ret = lttng_userspace_probe_location_serialize(
+                                       ev_ext->probe_location, &payload);
+                       if (ret < 0) {
+                               goto mem_error;
+                       }
+
+                       /*
+                        * Set the size of the userspace probe location element
+                        * of the buffer so that the receiving side knows where
+                        * to split it.
+                        */
+                       lsm.u.enable.userspace_probe_location_len = ret;
+               }
+       }
+
+       {
+               struct lttng_payload_view view = lttng_payload_view_from_payload(
+                       &payload, 0, -1);
+               int fd_count = lttng_payload_view_get_fd_handle_count(&view);
+               int fd_to_send;
+
+               if (fd_count < 0) {
+                       goto mem_error;
+               }
+
+               LTTNG_ASSERT(fd_count == 0 || fd_count == 1);
+               if (fd_count == 1) {
+                       struct fd_handle *h =
+                                       lttng_payload_view_pop_fd_handle(&view);
+
+                       if (!h) {
+                               goto mem_error;
+                       }
+
+                       fd_to_send = fd_handle_get_fd(h);
+                       fd_handle_put(h);
+               }
+
+               ret = lttng_ctl_ask_sessiond_fds_varlen(&lsm,
+                               fd_count ? &fd_to_send : NULL, fd_count,
+                               view.buffer.size ? view.buffer.data : NULL,
+                               view.buffer.size, NULL, NULL, 0);
+       }
+
+mem_error:
+       if (filter_expression && ctx) {
+               filter_bytecode_free(ctx);
+               filter_ir_free(ctx);
+               filter_parser_ctx_free(ctx);
+       }
+filter_error:
+       if (free_filter_expression) {
+               /*
+                * The filter expression has been replaced and must be freed as
+                * it is not the original filter expression received as a
+                * parameter.
+                */
+               free(filter_expression);
+       }
+error:
+       /*
+        * Return directly to the caller and don't ask the sessiond since
+        * something went wrong in the parsing of data above.
+        */
+       lttng_payload_reset(&payload);
+       return ret;
+
+ask_sessiond:
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+       return ret;
+}
+
+int lttng_disable_event_ext(struct lttng_handle *handle,
+               struct lttng_event *ev, const char *channel_name,
+               const char *original_filter_expression)
+{
+       struct lttcomm_session_msg lsm;
+       char *varlen_data;
+       int ret = 0;
+       unsigned int free_filter_expression = 0;
+       struct filter_parser_ctx *ctx = NULL;
+       /*
+        * Cast as non-const since we may replace the filter expression
+        * by a dynamically allocated string. Otherwise, the original
+        * string is not modified.
+        */
+       char *filter_expression = (char *) original_filter_expression;
+
+       if (handle == NULL || ev == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       /*
+        * Empty filter string will always be rejected by the parser
+        * anyway, so treat this corner-case early to eliminate
+        * lttng_fmemopen error for 0-byte allocation.
+        */
+       if (filter_expression && filter_expression[0] == '\0') {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+
+       /* If no channel name, send empty string. */
+       ret = lttng_strncpy(lsm.u.disable.channel_name, channel_name ?: "",
+                       sizeof(lsm.u.disable.channel_name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       lsm.cmd_type = LTTNG_DISABLE_EVENT;
+
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+       memcpy(&lsm.u.disable.event, ev, sizeof(lsm.u.disable.event));
+
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       lsm.u.disable.bytecode_len = 0;
+
+       /*
+        * For the JUL domain, a filter is enforced except for the
+        * disable all event. This is done to avoid having the event in
+        * all sessions thus filtering by logger name.
+        */
+       if (filter_expression == NULL &&
+                       (handle->domain.type != LTTNG_DOMAIN_JUL &&
+                               handle->domain.type != LTTNG_DOMAIN_LOG4J &&
+                               handle->domain.type != LTTNG_DOMAIN_PYTHON)) {
+               goto ask_sessiond;
+       }
+
+       /*
+        * We have a filter, so we need to set up a variable-length
+        * memory block from where to send the data.
+        */
+
+       /* Parse filter expression */
+       if (filter_expression != NULL || handle->domain.type == LTTNG_DOMAIN_JUL
+                       || handle->domain.type == LTTNG_DOMAIN_LOG4J
+                       || handle->domain.type == LTTNG_DOMAIN_PYTHON) {
+               if (handle->domain.type == LTTNG_DOMAIN_JUL ||
+                               handle->domain.type == LTTNG_DOMAIN_LOG4J ||
+                               handle->domain.type == LTTNG_DOMAIN_PYTHON) {
+                       char *agent_filter;
+
+                       /* Setup JUL filter if needed. */
+                       agent_filter = set_agent_filter(filter_expression, ev);
+                       if (!agent_filter) {
+                               if (!filter_expression) {
+                                       /*
+                                        * No JUL and no filter, just skip
+                                        * everything below.
+                                        */
+                                       goto ask_sessiond;
+                               }
+                       } else {
+                               /*
+                                * With a JUL filter, the original filter has
+                                * been added to it thus replace the filter
+                                * expression.
+                                */
+                               filter_expression = agent_filter;
+                               free_filter_expression = 1;
+                       }
+               }
+
+               ret = filter_parser_ctx_create_from_filter_expression(filter_expression, &ctx);
+               if (ret) {
+                       goto filter_error;
+               }
+
+               lsm.u.enable.bytecode_len = sizeof(ctx->bytecode->b)
+                       + bytecode_get_len(&ctx->bytecode->b);
+               lsm.u.enable.expression_len = strlen(filter_expression) + 1;
+       }
+
+       varlen_data = (char *) zmalloc(lsm.u.disable.bytecode_len
+                       + lsm.u.disable.expression_len);
+       if (!varlen_data) {
+               ret = -LTTNG_ERR_EXCLUSION_NOMEM;
+               goto mem_error;
+       }
+
+       /* Add filter expression. */
+       if (lsm.u.disable.expression_len != 0) {
+               memcpy(varlen_data,
+                       filter_expression,
+                       lsm.u.disable.expression_len);
+       }
+       /* Add filter bytecode next. */
+       if (ctx && lsm.u.disable.bytecode_len != 0) {
+               memcpy(varlen_data
+                       + lsm.u.disable.expression_len,
+                       &ctx->bytecode->b,
+                       lsm.u.disable.bytecode_len);
+       }
+
+       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, varlen_data,
+                       lsm.u.disable.bytecode_len + lsm.u.disable.expression_len, NULL);
+       free(varlen_data);
+
+mem_error:
+       if (filter_expression && ctx) {
+               filter_bytecode_free(ctx);
+               filter_ir_free(ctx);
+               filter_parser_ctx_free(ctx);
+       }
+filter_error:
+       if (free_filter_expression) {
+               /*
+                * The filter expression has been replaced and must be freed as
+                * it is not the original filter expression received as a
+                * parameter.
+                */
+               free(filter_expression);
+       }
+error:
+       /*
+        * Return directly to the caller and don't ask the sessiond since
+        * something went wrong in the parsing of data above.
+        */
+       return ret;
+
+ask_sessiond:
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+       return ret;
+}
+
+/*
+ * Disable event(s) of a channel and domain.
+ * If no event name is specified, all events are disabled.
+ * If no channel name is specified, the default 'channel0' is used.
+ * Returns size of returned session payload data or a negative error code.
+ */
+int lttng_disable_event(struct lttng_handle *handle, const char *name,
+               const char *channel_name)
+{
+       int ret;
+       struct lttng_event ev;
+
+       memset(&ev, 0, sizeof(ev));
+       ev.loglevel = -1;
+       ev.type = LTTNG_EVENT_ALL;
+       ret = lttng_strncpy(ev.name, name ?: "", sizeof(ev.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_disable_event_ext(handle, &ev, channel_name, NULL);
+end:
+       return ret;
+}
+
+struct lttng_channel *lttng_channel_create(struct lttng_domain *domain)
+{
+       struct lttng_channel *channel = NULL;
+       struct lttng_channel_extended *extended = NULL;
+
+       if (!domain) {
+               goto error;
+       }
+
+       /* Validate domain. */
+       switch (domain->type) {
+       case LTTNG_DOMAIN_UST:
+               switch (domain->buf_type) {
+               case LTTNG_BUFFER_PER_UID:
+               case LTTNG_BUFFER_PER_PID:
+                       break;
+               default:
+                       goto error;
+               }
+               break;
+       case LTTNG_DOMAIN_KERNEL:
+               if (domain->buf_type != LTTNG_BUFFER_GLOBAL) {
+                       goto error;
+               }
+               break;
+       default:
+               goto error;
+       }
+
+       channel = (lttng_channel *) zmalloc(sizeof(*channel));
+       if (!channel) {
+               goto error;
+       }
+
+       extended = (lttng_channel_extended *) zmalloc(sizeof(*extended));
+       if (!extended) {
+               goto error;
+       }
+
+       channel->attr.extended.ptr = extended;
+
+       lttng_channel_set_default_attr(domain, &channel->attr);
+       return channel;
+error:
+       free(channel);
+       free(extended);
+       return NULL;
+}
+
+void lttng_channel_destroy(struct lttng_channel *channel)
+{
+       if (!channel) {
+               return;
+       }
+
+       if (channel->attr.extended.ptr) {
+               free(channel->attr.extended.ptr);
+       }
+       free(channel);
+}
+
+/*
+ * Enable channel per domain
+ * Returns size of returned session payload data or a negative error code.
+ */
+int lttng_enable_channel(struct lttng_handle *handle,
+               struct lttng_channel *in_chan)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+       size_t total_buffer_size_needed_per_cpu = 0;
+
+       /* NULL arguments are forbidden. No default values. */
+       if (handle == NULL || in_chan == NULL) {
+               return -LTTNG_ERR_INVALID;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       memcpy(&lsm.u.channel.chan, in_chan, sizeof(lsm.u.channel.chan));
+       lsm.u.channel.chan.attr.extended.ptr = NULL;
+
+       if (!in_chan->attr.extended.ptr) {
+               struct lttng_channel *channel;
+               struct lttng_channel_extended *extended;
+
+               channel = lttng_channel_create(&handle->domain);
+               if (!channel) {
+                       return -LTTNG_ERR_NOMEM;
+               }
+
+               /*
+                * Create a new channel in order to use default extended
+                * attribute values.
+                */
+               extended = (struct lttng_channel_extended *)
+                               channel->attr.extended.ptr;
+               memcpy(&lsm.u.channel.extended, extended, sizeof(*extended));
+               lttng_channel_destroy(channel);
+       } else {
+               struct lttng_channel_extended *extended;
+
+               extended = (struct lttng_channel_extended *)
+                               in_chan->attr.extended.ptr;
+               memcpy(&lsm.u.channel.extended, extended, sizeof(*extended));
+       }
+
+       /*
+        * Verify that the amount of memory required to create the requested
+        * buffer is available on the system at the moment.
+        */
+       total_buffer_size_needed_per_cpu = lsm.u.channel.chan.attr.num_subbuf *
+               lsm.u.channel.chan.attr.subbuf_size;
+       if (!check_enough_available_memory(total_buffer_size_needed_per_cpu)) {
+               return -LTTNG_ERR_NOMEM;
+       }
+
+       lsm.cmd_type = LTTNG_ENABLE_CHANNEL;
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                                   sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+end:
+       return ret;
+}
+
+/*
+ * All tracing will be stopped for registered events of the channel.
+ * Returns size of returned session payload data or a negative error code.
+ */
+int lttng_disable_channel(struct lttng_handle *handle, const char *name)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       /* Safety check. Both are mandatory. */
+       if (handle == NULL || name == NULL) {
+               return -LTTNG_ERR_INVALID;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+
+       lsm.cmd_type = LTTNG_DISABLE_CHANNEL;
+
+       ret = lttng_strncpy(lsm.u.disable.channel_name, name,
+                       sizeof(lsm.u.disable.channel_name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                           sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+end:
+       return ret;
+}
+
+/*
+ * Lists all available tracepoints of domain.
+ * Sets the contents of the events array.
+ * Returns the number of lttng_event entries in events;
+ * on error, returns a negative value.
+ */
+int lttng_list_tracepoints(struct lttng_handle *handle,
+               struct lttng_event **events)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (handle == NULL) {
+               return -LTTNG_ERR_INVALID;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_LIST_TRACEPOINTS;
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+
+       ret = lttng_ctl_ask_sessiond(&lsm, (void **) events);
+       if (ret < 0) {
+               return ret;
+       }
+
+       return ret / sizeof(struct lttng_event);
+}
+
+/*
+ * Lists all available tracepoint fields of domain.
+ * Sets the contents of the event field array.
+ * Returns the number of lttng_event_field entries in events;
+ * on error, returns a negative value.
+ */
+int lttng_list_tracepoint_fields(struct lttng_handle *handle,
+               struct lttng_event_field **fields)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (handle == NULL) {
+               return -LTTNG_ERR_INVALID;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_LIST_TRACEPOINT_FIELDS;
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+
+       ret = lttng_ctl_ask_sessiond(&lsm, (void **) fields);
+       if (ret < 0) {
+               return ret;
+       }
+
+       return ret / sizeof(struct lttng_event_field);
+}
+
+/*
+ * Lists all available kernel system calls. Allocates and sets the contents of
+ * the events array.
+ *
+ * Returns the number of lttng_event entries in events; on error, returns a
+ * negative value.
+ */
+int lttng_list_syscalls(struct lttng_event **events)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (!events) {
+               return -LTTNG_ERR_INVALID;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_LIST_SYSCALLS;
+       /* Force kernel domain for system calls. */
+       lsm.domain.type = LTTNG_DOMAIN_KERNEL;
+
+       ret = lttng_ctl_ask_sessiond(&lsm, (void **) events);
+       if (ret < 0) {
+               return ret;
+       }
+
+       return ret / sizeof(struct lttng_event);
+}
+
+/*
+ * Returns a human readable string describing
+ * the error code (a negative value).
+ */
+const char *lttng_strerror(int code)
+{
+       return error_get_str(code);
+}
+
+enum lttng_error_code lttng_create_session_ext(
+               struct lttng_session_descriptor *session_descriptor)
+{
+       enum lttng_error_code ret_code;
+       struct lttcomm_session_msg lsm = {
+               .cmd_type = LTTNG_CREATE_SESSION_EXT,
+       };
+       void *reply = NULL;
+       struct lttng_buffer_view reply_view;
+       int reply_ret;
+       bool sessiond_must_generate_ouput;
+       struct lttng_dynamic_buffer payload;
+       int ret;
+       size_t descriptor_size;
+       struct lttng_session_descriptor *descriptor_reply = NULL;
+
+       lttng_dynamic_buffer_init(&payload);
+       if (!session_descriptor) {
+               ret_code = LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       sessiond_must_generate_ouput =
+                       !lttng_session_descriptor_is_output_destination_initialized(
+                               session_descriptor);
+       if (sessiond_must_generate_ouput) {
+               const char *home_dir = utils_get_home_dir();
+               size_t home_dir_len = home_dir ? strlen(home_dir) + 1 : 0;
+
+               if (!home_dir || home_dir_len > LTTNG_PATH_MAX) {
+                       ret_code = LTTNG_ERR_FATAL;
+                       goto end;
+               }
+
+               lsm.u.create_session.home_dir_size = (uint16_t) home_dir_len;
+               ret = lttng_dynamic_buffer_append(&payload, home_dir,
+                               home_dir_len);
+               if (ret) {
+                       ret_code = LTTNG_ERR_NOMEM;
+                       goto end;
+               }
+       }
+
+       descriptor_size = payload.size;
+       ret = lttng_session_descriptor_serialize(session_descriptor,
+                       &payload);
+       if (ret) {
+               ret_code = LTTNG_ERR_INVALID;
+               goto end;
+       }
+       descriptor_size = payload.size - descriptor_size;
+       lsm.u.create_session.session_descriptor_size = descriptor_size;
+
+       /* Command returns a session descriptor on success. */
+       reply_ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, payload.data,
+                       payload.size, &reply);
+       if (reply_ret < 0) {
+               ret_code = (lttng_error_code) -reply_ret;
+               goto end;
+       } else if (reply_ret == 0) {
+               /* Socket unexpectedly closed by the session daemon. */
+               ret_code = LTTNG_ERR_FATAL;
+               goto end;
+       }
+
+       reply_view = lttng_buffer_view_init((const char *) reply, 0, reply_ret);
+       ret = lttng_session_descriptor_create_from_buffer(&reply_view,
+                       &descriptor_reply);
+       if (ret < 0) {
+               ret_code = LTTNG_ERR_FATAL;
+               goto end;
+       }
+       ret_code = LTTNG_OK;
+       lttng_session_descriptor_assign(session_descriptor, descriptor_reply);
+end:
+       free(reply);
+       lttng_dynamic_buffer_reset(&payload);
+       lttng_session_descriptor_destroy(descriptor_reply);
+       return ret_code;
+}
+
+/*
+ * Create a new session using name and url for destination.
+ *
+ * Return 0 on success else a negative LTTng error code.
+ */
+int lttng_create_session(const char *name, const char *url)
+{
+       int ret;
+       ssize_t size;
+       struct lttng_uri *uris = NULL;
+       struct lttng_session_descriptor *descriptor = NULL;
+       enum lttng_error_code ret_code;
+
+       if (!name) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       size = uri_parse_str_urls(url, NULL, &uris);
+       if (size < 0) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       switch (size) {
+       case 0:
+               descriptor = lttng_session_descriptor_create(name);
+               break;
+       case 1:
+               if (uris[0].dtype != LTTNG_DST_PATH) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+               descriptor = lttng_session_descriptor_local_create(name,
+                               uris[0].dst.path);
+               break;
+       case 2:
+               descriptor = lttng_session_descriptor_network_create(name, url,
+                               NULL);
+               break;
+       default:
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       if (!descriptor) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       ret_code = lttng_create_session_ext(descriptor);
+       ret = ret_code == LTTNG_OK ? 0 : -ret_code;
+end:
+       lttng_session_descriptor_destroy(descriptor);
+       free(uris);
+       return ret;
+}
+
+/*
+ * Create a session exclusively used for snapshot.
+ *
+ * Return 0 on success else a negative LTTng error code.
+ */
+int lttng_create_session_snapshot(const char *name, const char *snapshot_url)
+{
+       int ret;
+       enum lttng_error_code ret_code;
+       ssize_t size;
+       struct lttng_uri *uris = NULL;
+       struct lttng_session_descriptor *descriptor = NULL;
+
+       if (!name) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       size = uri_parse_str_urls(snapshot_url, NULL, &uris);
+       if (size < 0) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       /*
+        * If the user does not specify a custom subdir, use the session name.
+        */
+       if (size > 0 && uris[0].dtype != LTTNG_DST_PATH &&
+                       strlen(uris[0].subdir) == 0) {
+               ret = snprintf(uris[0].subdir, sizeof(uris[0].subdir), "%s",
+                               name);
+               if (ret < 0) {
+                       PERROR("Failed to set session name as network destination sub-directory");
+                       ret = -LTTNG_ERR_FATAL;
+                       goto end;
+               } else if (ret >= sizeof(uris[0].subdir)) {
+                       /* Truncated output. */
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+       }
+
+       switch (size) {
+       case 0:
+               descriptor = lttng_session_descriptor_snapshot_create(name);
+               break;
+       case 1:
+               if (uris[0].dtype != LTTNG_DST_PATH) {
+                       ret = -LTTNG_ERR_INVALID;
+                       goto end;
+               }
+               descriptor = lttng_session_descriptor_snapshot_local_create(
+                               name,
+                               uris[0].dst.path);
+               break;
+       case 2:
+               descriptor = lttng_session_descriptor_snapshot_network_create(
+                               name,
+                               snapshot_url,
+                               NULL);
+               break;
+       default:
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       if (!descriptor) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       ret_code = lttng_create_session_ext(descriptor);
+       ret = ret_code == LTTNG_OK ? 0 : -ret_code;
+end:
+       lttng_session_descriptor_destroy(descriptor);
+       free(uris);
+       return ret;
+}
+
+/*
+ * Create a session exclusively used for live.
+ *
+ * Return 0 on success else a negative LTTng error code.
+ */
+int lttng_create_session_live(const char *name, const char *url,
+               unsigned int timer_interval)
+{
+       int ret;
+       enum lttng_error_code ret_code;
+       struct lttng_session_descriptor *descriptor = NULL;
+
+       if (!name) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       if (url) {
+               descriptor = lttng_session_descriptor_live_network_create(
+                               name, url, NULL, timer_interval);
+       } else {
+               descriptor = lttng_session_descriptor_live_create(
+                               name, timer_interval);
+       }
+       if (!descriptor) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+       ret_code = lttng_create_session_ext(descriptor);
+       ret = ret_code == LTTNG_OK ? 0 : -ret_code;
+end:
+       lttng_session_descriptor_destroy(descriptor);
+       return ret;
+}
+
+/*
+ * Stop the session and wait for the data before destroying it
+ *
+ * Return 0 on success else a negative LTTng error code.
+ */
+int lttng_destroy_session(const char *session_name)
+{
+       int ret;
+       enum lttng_error_code ret_code;
+       enum lttng_destruction_handle_status status;
+       struct lttng_destruction_handle *handle = NULL;
+
+       /*
+        * Stop the tracing and wait for the data to be
+        * consumed.
+        */
+       ret = _lttng_stop_tracing(session_name, 1);
+       if (ret && ret != -LTTNG_ERR_TRACE_ALREADY_STOPPED) {
+               goto end;
+       }
+
+       ret_code = lttng_destroy_session_ext(session_name, &handle);
+       if (ret_code != LTTNG_OK) {
+               ret = (int) -ret_code;
+               goto end;
+       }
+       LTTNG_ASSERT(handle);
+
+       /* Block until the completion of the destruction of the session. */
+       status = lttng_destruction_handle_wait_for_completion(handle, -1);
+       if (status != LTTNG_DESTRUCTION_HANDLE_STATUS_COMPLETED) {
+               ret = -LTTNG_ERR_UNK;
+               goto end;
+       }
+
+       status = lttng_destruction_handle_get_result(handle, &ret_code);
+       if (status != LTTNG_DESTRUCTION_HANDLE_STATUS_OK) {
+               ret = -LTTNG_ERR_UNK;
+               goto end;
+       }
+       ret = ret_code == LTTNG_OK ? 0 : -ret_code;
+end:
+       lttng_destruction_handle_destroy(handle);
+       return ret;
+}
+
+/*
+ * Destroy the session without waiting for the data.
+ */
+int lttng_destroy_session_no_wait(const char *session_name)
+{
+       enum lttng_error_code ret_code;
+
+       ret_code = lttng_destroy_session_ext(session_name, NULL);
+       return ret_code == LTTNG_OK ? 0 : -ret_code;
+}
+
+/*
+ * Ask the session daemon for all available sessions.
+ * Sets the contents of the sessions array.
+ * Returns the number of lttng_session entries in sessions;
+ * on error, returns a negative value.
+ */
+int lttng_list_sessions(struct lttng_session **out_sessions)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+       const size_t session_size = sizeof(struct lttng_session) +
+                       sizeof(struct lttng_session_extended);
+       size_t session_count, i;
+       struct lttng_session_extended *sessions_extended_begin;
+       struct lttng_session *sessions = NULL;
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_LIST_SESSIONS;
+       ret = lttng_ctl_ask_sessiond(&lsm, (void**) &sessions);
+       if (ret <= 0) {
+               goto end;
+       }
+       if (!sessions) {
+               ret = -LTTNG_ERR_FATAL;
+               goto end;
+       }
+
+       if (ret % session_size) {
+               ret = -LTTNG_ERR_UNK;
+               free(sessions);
+               *out_sessions = NULL;
+               goto end;
+       }
+       session_count = (size_t) ret / session_size;
+       sessions_extended_begin = (struct lttng_session_extended *)
+                       (&sessions[session_count]);
+
+       /* Set extended session info pointers. */
+       for (i = 0; i < session_count; i++) {
+               struct lttng_session *session = &sessions[i];
+               struct lttng_session_extended *extended =
+                               &(sessions_extended_begin[i]);
+
+               session->extended.ptr = extended;
+       }
+
+       ret = (int) session_count;
+       *out_sessions = sessions;
+end:
+       return ret;
+}
+
+enum lttng_error_code lttng_session_get_creation_time(
+               const struct lttng_session *session, uint64_t *creation_time)
+{
+       enum lttng_error_code ret = LTTNG_OK;
+       struct lttng_session_extended *extended;
+
+       if (!session || !creation_time || !session->extended.ptr) {
+               ret = LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       extended = (lttng_session_extended *) session->extended.ptr;
+       if (!extended->creation_time.is_set) {
+               /* Not created on the session daemon yet. */
+               ret = LTTNG_ERR_SESSION_NOT_EXIST;
+               goto end;
+       }
+       *creation_time = extended->creation_time.value;
+end:
+       return ret;
+}
+
+int lttng_set_session_shm_path(const char *session_name,
+               const char *shm_path)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (session_name == NULL) {
+               return -LTTNG_ERR_INVALID;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_SET_SESSION_SHM_PATH;
+
+       ret = lttng_strncpy(lsm.session.name, session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_strncpy(lsm.u.set_shm_path.shm_path, shm_path ?: "",
+                       sizeof(lsm.u.set_shm_path.shm_path));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+end:
+       return ret;
+}
+
+/*
+ * Ask the session daemon for all available domains of a session.
+ * Sets the contents of the domains array.
+ * Returns the number of lttng_domain entries in domains;
+ * on error, returns a negative value.
+ */
+int lttng_list_domains(const char *session_name,
+               struct lttng_domain **domains)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (session_name == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_LIST_DOMAINS;
+
+       ret = lttng_strncpy(lsm.session.name, session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, (void**) domains);
+       if (ret < 0) {
+               goto error;
+       }
+
+       return ret / sizeof(struct lttng_domain);
+error:
+       return ret;
+}
+
+/*
+ * Ask the session daemon for all available channels of a session.
+ * Sets the contents of the channels array.
+ * Returns the number of lttng_channel entries in channels;
+ * on error, returns a negative value.
+ */
+int lttng_list_channels(struct lttng_handle *handle,
+               struct lttng_channel **channels)
+{
+       int ret;
+       size_t channel_count, i;
+       const size_t channel_size = sizeof(struct lttng_channel) +
+                       sizeof(struct lttng_channel_extended);
+       struct lttcomm_session_msg lsm;
+       char *extended_at;
+
+       if (handle == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_LIST_CHANNELS;
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+
+       ret = lttng_ctl_ask_sessiond(&lsm, (void**) channels);
+       if (ret < 0) {
+               goto end;
+       }
+
+       if (ret % channel_size) {
+               ret = -LTTNG_ERR_UNK;
+               free(*channels);
+               *channels = NULL;
+               goto end;
+       }
+       channel_count = (size_t) ret / channel_size;
+
+       /* Set extended info pointers */
+       extended_at = ((char *) *channels) +
+                       channel_count * sizeof(struct lttng_channel);
+       for (i = 0; i < channel_count; i++) {
+               struct lttng_channel *chan = &(*channels)[i];
+
+               chan->attr.extended.ptr = extended_at;
+               extended_at += sizeof(struct lttng_channel_extended);
+       }
+
+       ret = (int) channel_count;
+end:
+       return ret;
+}
+
+/*
+ * Ask the session daemon for all available events of a session channel.
+ * Sets the contents of the events array.
+ * Returns the number of lttng_event entries in events;
+ * on error, returns a negative value.
+ */
+int lttng_list_events(struct lttng_handle *handle,
+               const char *channel_name, struct lttng_event **events)
+{
+       int ret;
+       struct lttcomm_session_msg lsm = {};
+       const struct lttcomm_event_command_header *cmd_header = NULL;
+       uint32_t nb_events, i;
+       const char *comm_ext_at;
+       struct lttng_dynamic_buffer listing;
+       size_t storage_req;
+       struct lttng_payload payload;
+       struct lttng_payload payload_copy;
+       struct lttng_payload_view lsm_view =
+                       lttng_payload_view_init_from_buffer(
+                               (const char *) &lsm, 0, sizeof(lsm));
+       struct lttng_buffer_view cmd_header_view;
+       struct lttng_buffer_view cmd_payload_view;
+       struct lttng_buffer_view flat_events_view;
+       struct lttng_buffer_view ext_view;
+
+       /* Safety check. An handle and channel name are mandatory */
+       if (handle == NULL || channel_name == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       lttng_payload_init(&payload);
+       lttng_payload_init(&payload_copy);
+
+       lsm.cmd_type = LTTNG_LIST_EVENTS;
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_strncpy(lsm.u.list.channel_name, channel_name,
+                       sizeof(lsm.u.list.channel_name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+
+       ret = lttng_ctl_ask_sessiond_payload(&lsm_view, &payload);
+       if (ret < 0) {
+               goto end;
+       }
+
+       /*
+        * A copy of the payload is performed since it will be
+        * consumed twice. Consuming the same payload twice is invalid since
+        * it will cause any received file descriptor to become "shared"
+        * between different instances of the resulting objects.
+        */
+       ret = lttng_payload_copy(&payload, &payload_copy);
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       cmd_header_view = lttng_buffer_view_from_dynamic_buffer(
+               &payload.buffer, 0, sizeof(*cmd_header));
+       if (!lttng_buffer_view_is_valid(&cmd_header_view)) {
+               ret = -LTTNG_ERR_INVALID_PROTOCOL;
+               goto end;
+       }
+
+       cmd_header = (typeof(cmd_header)) cmd_header_view.data;
+
+       /* Set number of events and free command header */
+       nb_events = cmd_header->nb_events;
+       if (nb_events > INT_MAX) {
+               ret = -LTTNG_ERR_OVERFLOW;
+               goto end;
+       }
+
+       cmd_payload_view = lttng_buffer_view_from_dynamic_buffer(
+                       &payload.buffer, sizeof(*cmd_header), -1);
+
+       /*
+        * The buffer that is returned must contain a "flat" version of
+        * the events that are returned. In other words, all pointers
+        * within an lttng_event must point to a location within the returned
+        * buffer so that the user may free everything by simply calling free()
+        * on the returned buffer. This is needed in order to maintain API
+        * compatibility.
+        *
+        * A first pass is performed to compute the size of the buffer that
+        * must be allocated. A second pass is then performed to setup
+        * the returned events so that their members always point within the
+        * buffer.
+        *
+        * The layout of the returned buffer is as follows:
+        *   - struct lttng_event[nb_events],
+        *   - nb_events times the following:
+        *     - struct lttng_event_extended,
+        *     - flattened version of userspace_probe_location
+        *     - filter_expression
+        *     - exclusions
+        *     - padding to align to 64-bits
+        */
+       ext_view = lttng_buffer_view_from_view(&cmd_payload_view,
+                       nb_events * sizeof(struct lttng_event), -1);
+       comm_ext_at = ext_view.data;
+       storage_req = nb_events * sizeof(struct lttng_event);
+       {
+               struct lttng_payload_view payload_view =
+                               lttng_payload_view_from_payload(&payload, 0, -1);
+
+               for (i = 0; i < nb_events; i++) {
+                       const struct lttcomm_event_extended_header *ext_comm =
+                                       (struct lttcomm_event_extended_header *)
+                                                       comm_ext_at;
+                       int probe_storage_req = 0;
+
+                       comm_ext_at += sizeof(*ext_comm);
+                       comm_ext_at += ext_comm->filter_len;
+                       comm_ext_at += ext_comm->nb_exclusions *
+                                       LTTNG_SYMBOL_NAME_LEN;
+
+                       if (ext_comm->userspace_probe_location_len) {
+                               struct lttng_userspace_probe_location
+                                               *probe_location = NULL;
+                               struct lttng_payload_view probe_location_view = lttng_payload_view_from_view(
+                                               &payload_view,
+                                               (const char *) comm_ext_at -
+                                                               payload_view.buffer.data,
+                                               ext_comm->userspace_probe_location_len);
+
+                               if (!lttng_payload_view_is_valid(&probe_location_view)) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto end;
+                               }
+
+                               /*
+                                * Create a temporary userspace probe location
+                                * to determine the size needed by a "flattened"
+                                * version of that same probe location.
+                                */
+                               ret = lttng_userspace_probe_location_create_from_payload(
+                                               &probe_location_view,
+                                               &probe_location);
+                               if (ret < 0) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto end;
+                               }
+
+                               ret = lttng_userspace_probe_location_flatten(
+                                               probe_location, NULL);
+                               lttng_userspace_probe_location_destroy(
+                                               probe_location);
+                               if (ret < 0) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto end;
+                               }
+
+                               probe_storage_req = ret;
+                               comm_ext_at += ext_comm->userspace_probe_location_len;
+                       }
+
+                       storage_req += sizeof(struct lttng_event_extended);
+                       storage_req += ext_comm->filter_len;
+                       storage_req += ext_comm->nb_exclusions *
+                                       LTTNG_SYMBOL_NAME_LEN;
+                       /* Padding to ensure the flat probe is aligned. */
+                       storage_req = lttng_align_ceil(storage_req, sizeof(uint64_t));
+                       storage_req += probe_storage_req;
+               }
+       }
+
+       lttng_dynamic_buffer_init(&listing);
+       /*
+        * We must ensure that "listing" is never resized so as to preserve
+        * the validity of the flattened objects.
+        */
+       ret = lttng_dynamic_buffer_set_capacity(&listing, storage_req);
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       cmd_payload_view = lttng_buffer_view_from_dynamic_buffer(
+               &payload_copy.buffer, sizeof(*cmd_header), -1);
+       flat_events_view = lttng_buffer_view_from_view(&cmd_payload_view, 0,
+                       nb_events * sizeof(struct lttng_event));
+       ret = lttng_dynamic_buffer_append_view(&listing, &flat_events_view);
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto free_dynamic_buffer;
+       }
+
+       ext_view = lttng_buffer_view_from_view(&cmd_payload_view,
+                       nb_events * sizeof(struct lttng_event), -1);
+       comm_ext_at = ext_view.data;
+
+       {
+               struct lttng_payload_view payload_copy_view =
+                               lttng_payload_view_from_payload(
+                                               &payload_copy, 0, -1);
+
+               for (i = 0; i < nb_events; i++) {
+                       struct lttng_event *event = (typeof(event))(
+                                       listing.data +
+                                       (sizeof(struct lttng_event) * i));
+                       const struct lttcomm_event_extended_header *ext_comm =
+                                       (typeof(ext_comm)) comm_ext_at;
+                       struct lttng_event_extended *event_extended =
+                                       (typeof(event_extended))(listing.data +
+                                                       listing.size);
+
+                       /* Insert struct lttng_event_extended. */
+                       ret = lttng_dynamic_buffer_set_size(&listing,
+                                       listing.size + sizeof(*event_extended));
+                       if (ret) {
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto free_dynamic_buffer;
+                       }
+                       event->extended.ptr = event_extended;
+
+                       comm_ext_at += sizeof(*ext_comm);
+
+                       /* Insert filter expression. */
+                       if (ext_comm->filter_len) {
+                               event_extended->filter_expression =
+                                               listing.data + listing.size;
+                               ret = lttng_dynamic_buffer_append(&listing,
+                                               comm_ext_at,
+                                               ext_comm->filter_len);
+                               if (ret) {
+                                       ret = -LTTNG_ERR_NOMEM;
+                                       goto free_dynamic_buffer;
+                               }
+                               comm_ext_at += ext_comm->filter_len;
+                       }
+
+                       /* Insert exclusions. */
+                       if (ext_comm->nb_exclusions) {
+                               event_extended->exclusions.count =
+                                               ext_comm->nb_exclusions;
+                               event_extended->exclusions.strings =
+                                               listing.data + listing.size;
+
+                               ret = lttng_dynamic_buffer_append(&listing,
+                                               comm_ext_at,
+                                               ext_comm->nb_exclusions *
+                                                               LTTNG_SYMBOL_NAME_LEN);
+                               if (ret) {
+                                       ret = -LTTNG_ERR_NOMEM;
+                                       goto free_dynamic_buffer;
+                               }
+                               comm_ext_at += ext_comm->nb_exclusions *
+                                               LTTNG_SYMBOL_NAME_LEN;
+                       }
+
+                       /* Insert padding to align to 64-bits. */
+                       ret = lttng_dynamic_buffer_set_size(&listing,
+                                       lttng_align_ceil(listing.size,
+                                                       sizeof(uint64_t)));
+                       if (ret) {
+                               ret = -LTTNG_ERR_NOMEM;
+                               goto free_dynamic_buffer;
+                       }
+
+                       /* Insert flattened userspace probe location. */
+                       if (ext_comm->userspace_probe_location_len) {
+                               struct lttng_userspace_probe_location
+                                               *probe_location = NULL;
+                               struct lttng_payload_view probe_location_view = lttng_payload_view_from_view(
+                                               &payload_copy_view,
+                                               (const char *) comm_ext_at -
+                                                               payload_copy_view.buffer.data,
+                                               ext_comm->userspace_probe_location_len);
+
+                               if (!lttng_payload_view_is_valid(&probe_location_view)) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto free_dynamic_buffer;
+                               }
+
+                               ret = lttng_userspace_probe_location_create_from_payload(
+                                               &probe_location_view,
+                                               &probe_location);
+                               if (ret < 0) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto free_dynamic_buffer;
+                               }
+
+                               event_extended->probe_location = (struct lttng_userspace_probe_location
+                                                               *) (listing.data +
+                                               listing.size);
+                               ret = lttng_userspace_probe_location_flatten(
+                                               probe_location, &listing);
+                               lttng_userspace_probe_location_destroy(
+                                               probe_location);
+                               if (ret < 0) {
+                                       ret = -LTTNG_ERR_PROBE_LOCATION_INVAL;
+                                       goto free_dynamic_buffer;
+                               }
+
+                               comm_ext_at += ext_comm->userspace_probe_location_len;
+                       }
+               }
+       }
+
+       /* Don't reset listing buffer as we return its content. */
+       *events = (struct lttng_event *) listing.data;
+       lttng_dynamic_buffer_init(&listing);
+       ret = (int) nb_events;
+free_dynamic_buffer:
+       lttng_dynamic_buffer_reset(&listing);
+end:
+       lttng_payload_reset(&payload);
+       lttng_payload_reset(&payload_copy);
+       return ret;
+}
+
+/*
+ * Sets the tracing_group variable with name.
+ * This function allocates memory pointed to by tracing_group.
+ * On success, returns 0, on error, returns -1 (null name) or -ENOMEM.
+ */
+int lttng_set_tracing_group(const char *name)
+{
+       int ret = 0;
+       char *new_group;
+
+       if (name == NULL) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       new_group = strdup(name);
+       if (!new_group) {
+               ret = -LTTNG_ERR_FATAL;
+               goto end;
+       }
+
+       free(tracing_group);
+       tracing_group = new_group;
+       new_group = NULL;
+
+end:
+       return ret;
+}
+
+int lttng_calibrate(struct lttng_handle *handle,
+               struct lttng_calibrate *calibrate)
+{
+       /*
+        * This command was removed in LTTng 2.9.
+        */
+       return -LTTNG_ERR_UND;
+}
+
+/*
+ * Set default channel attributes.
+ * If either or both of the arguments are null, attr content is zeroe'd.
+ */
+void lttng_channel_set_default_attr(struct lttng_domain *domain,
+               struct lttng_channel_attr *attr)
+{
+       struct lttng_channel_extended *extended;
+
+       /* Safety check */
+       if (attr == NULL || domain == NULL) {
+               return;
+       }
+
+       extended = (struct lttng_channel_extended *) attr->extended.ptr;
+       memset(attr, 0, sizeof(struct lttng_channel_attr));
+
+       /* Same for all domains. */
+       attr->overwrite = DEFAULT_CHANNEL_OVERWRITE;
+       attr->tracefile_size = DEFAULT_CHANNEL_TRACEFILE_SIZE;
+       attr->tracefile_count = DEFAULT_CHANNEL_TRACEFILE_COUNT;
+
+       switch (domain->type) {
+       case LTTNG_DOMAIN_KERNEL:
+               attr->switch_timer_interval =
+                               DEFAULT_KERNEL_CHANNEL_SWITCH_TIMER;
+               attr->read_timer_interval = DEFAULT_KERNEL_CHANNEL_READ_TIMER;
+               attr->subbuf_size = default_get_kernel_channel_subbuf_size();
+               attr->num_subbuf = DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM;
+               attr->output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
+               if (extended) {
+                       extended->monitor_timer_interval =
+                                       DEFAULT_KERNEL_CHANNEL_MONITOR_TIMER;
+                       extended->blocking_timeout =
+                                       DEFAULT_KERNEL_CHANNEL_BLOCKING_TIMEOUT;
+               }
+               break;
+       case LTTNG_DOMAIN_UST:
+               switch (domain->buf_type) {
+               case LTTNG_BUFFER_PER_UID:
+                       attr->subbuf_size = default_get_ust_uid_channel_subbuf_size();
+                       attr->num_subbuf = DEFAULT_UST_UID_CHANNEL_SUBBUF_NUM;
+                       attr->output = DEFAULT_UST_UID_CHANNEL_OUTPUT;
+                       attr->switch_timer_interval =
+                                       DEFAULT_UST_UID_CHANNEL_SWITCH_TIMER;
+                       attr->read_timer_interval =
+                                       DEFAULT_UST_UID_CHANNEL_READ_TIMER;
+                       if (extended) {
+                               extended->monitor_timer_interval =
+                                               DEFAULT_UST_UID_CHANNEL_MONITOR_TIMER;
+                               extended->blocking_timeout =
+                                               DEFAULT_UST_UID_CHANNEL_BLOCKING_TIMEOUT;
+                       }
+                       break;
+               case LTTNG_BUFFER_PER_PID:
+               default:
+                       attr->subbuf_size = default_get_ust_pid_channel_subbuf_size();
+                       attr->num_subbuf = DEFAULT_UST_PID_CHANNEL_SUBBUF_NUM;
+                       attr->output = DEFAULT_UST_PID_CHANNEL_OUTPUT;
+                       attr->switch_timer_interval =
+                                       DEFAULT_UST_PID_CHANNEL_SWITCH_TIMER;
+                       attr->read_timer_interval =
+                                       DEFAULT_UST_PID_CHANNEL_READ_TIMER;
+                       if (extended) {
+                               extended->monitor_timer_interval =
+                                               DEFAULT_UST_PID_CHANNEL_MONITOR_TIMER;
+                               extended->blocking_timeout =
+                                               DEFAULT_UST_PID_CHANNEL_BLOCKING_TIMEOUT;
+                       }
+                       break;
+               }
+       default:
+               /* Default behavior: leave set to 0. */
+               break;
+       }
+
+       attr->extended.ptr = extended;
+}
+
+int lttng_channel_get_discarded_event_count(struct lttng_channel *channel,
+               uint64_t *discarded_events)
+{
+       int ret = 0;
+       struct lttng_channel_extended *chan_ext;
+
+       if (!channel || !discarded_events) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       chan_ext = (lttng_channel_extended *) channel->attr.extended.ptr;
+       if (!chan_ext) {
+               /*
+                * This can happen since the lttng_channel structure is
+                * used for other tasks where this pointer is never set.
+                */
+               *discarded_events = 0;
+               goto end;
+       }
+
+       *discarded_events = chan_ext->discarded_events;
+end:
+       return ret;
+}
+
+int lttng_channel_get_lost_packet_count(struct lttng_channel *channel,
+               uint64_t *lost_packets)
+{
+       int ret = 0;
+       struct lttng_channel_extended *chan_ext;
+
+       if (!channel || !lost_packets) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       chan_ext = (lttng_channel_extended *) channel->attr.extended.ptr;
+       if (!chan_ext) {
+               /*
+                * This can happen since the lttng_channel structure is
+                * used for other tasks where this pointer is never set.
+                */
+               *lost_packets = 0;
+               goto end;
+       }
+
+       *lost_packets = chan_ext->lost_packets;
+end:
+       return ret;
+}
+
+int lttng_channel_get_monitor_timer_interval(struct lttng_channel *chan,
+               uint64_t *monitor_timer_interval)
+{
+       int ret = 0;
+
+       if (!chan || !monitor_timer_interval) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       if (!chan->attr.extended.ptr) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       *monitor_timer_interval = ((struct lttng_channel_extended *)
+                       chan->attr.extended.ptr)->monitor_timer_interval;
+end:
+       return ret;
+}
+
+int lttng_channel_set_monitor_timer_interval(struct lttng_channel *chan,
+               uint64_t monitor_timer_interval)
+{
+       int ret = 0;
+
+       if (!chan || !chan->attr.extended.ptr) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ((struct lttng_channel_extended *)
+                       chan->attr.extended.ptr)->monitor_timer_interval =
+                       monitor_timer_interval;
+end:
+       return ret;
+}
+
+int lttng_channel_get_blocking_timeout(struct lttng_channel *chan,
+               int64_t *blocking_timeout)
+{
+       int ret = 0;
+
+       if (!chan || !blocking_timeout) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       if (!chan->attr.extended.ptr) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       *blocking_timeout = ((struct lttng_channel_extended *)
+                       chan->attr.extended.ptr)->blocking_timeout;
+end:
+       return ret;
+}
+
+int lttng_channel_set_blocking_timeout(struct lttng_channel *chan,
+               int64_t blocking_timeout)
+{
+       int ret = 0;
+       int64_t msec_timeout;
+
+       if (!chan || !chan->attr.extended.ptr) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       if (blocking_timeout < 0 && blocking_timeout != -1) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       /*
+        * LTTng-ust's use of poll() to implement this timeout mechanism forces
+        * us to accept a narrower range of values (msecs expressed as a signed
+        * 32-bit integer).
+        */
+       msec_timeout = blocking_timeout / 1000;
+       if (msec_timeout != (int32_t) msec_timeout) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ((struct lttng_channel_extended *)
+                       chan->attr.extended.ptr)->blocking_timeout =
+                       blocking_timeout;
+end:
+       return ret;
+}
+
+/*
+ * Check if session daemon is alive.
+ *
+ * Return 1 if alive or 0 if not.
+ * On error returns a negative value.
+ */
+int lttng_session_daemon_alive(void)
+{
+       int ret;
+
+       ret = set_session_daemon_path();
+       if (ret < 0) {
+               /* Error. */
+               return ret;
+       }
+
+       if (*sessiond_sock_path == '\0') {
+               /*
+                * No socket path set. Weird error which means the constructor
+                * was not called.
+                */
+               abort();
+       }
+
+       ret = try_connect_sessiond(sessiond_sock_path);
+       if (ret < 0) {
+               /* Not alive. */
+               return 0;
+       }
+
+       /* Is alive. */
+       return 1;
+}
+
+/*
+ * Set URL for a consumer for a session and domain.
+ *
+ * Return 0 on success, else a negative value.
+ */
+int lttng_set_consumer_url(struct lttng_handle *handle,
+               const char *control_url, const char *data_url)
+{
+       int ret;
+       ssize_t size;
+       struct lttcomm_session_msg lsm;
+       struct lttng_uri *uris = NULL;
+
+       if (handle == NULL || (control_url == NULL && data_url == NULL)) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+
+       lsm.cmd_type = LTTNG_SET_CONSUMER_URI;
+
+       ret = lttng_strncpy(lsm.session.name, handle->session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       COPY_DOMAIN_PACKED(lsm.domain, handle->domain);
+
+       size = uri_parse_str_urls(control_url, data_url, &uris);
+       if (size < 0) {
+               ret = -LTTNG_ERR_INVALID;
+               goto error;
+       }
+
+       lsm.u.uri.size = size;
+
+       ret = lttng_ctl_ask_sessiond_varlen_no_cmd_header(&lsm, uris,
+                       sizeof(struct lttng_uri) * size, NULL);
+
+       free(uris);
+error:
+       return ret;
+}
+
+/*
+ * [OBSOLETE]
+ */
+extern "C"
+LTTNG_EXPORT int lttng_enable_consumer(struct lttng_handle *handle);
+int lttng_enable_consumer(struct lttng_handle *handle)
+{
+       return -ENOSYS;
+}
+
+/*
+ * [OBSOLETE]
+ */
+extern "C"
+LTTNG_EXPORT int lttng_disable_consumer(struct lttng_handle *handle);
+int lttng_disable_consumer(struct lttng_handle *handle)
+{
+       return -ENOSYS;
+}
+
+/*
+ * [OBSOLETE]
+ */
+extern "C"
+LTTNG_EXPORT int _lttng_create_session_ext(const char *name, const char *url,
+               const char *datetime);
+int _lttng_create_session_ext(const char *name, const char *url,
+               const char *datetime)
+{
+       return -ENOSYS;
+}
+
+/*
+ * For a given session name, this call checks if the data is ready to be read
+ * or is still being extracted by the consumer(s) hence not ready to be used by
+ * any readers.
+ */
+int lttng_data_pending(const char *session_name)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+       uint8_t *pending = NULL;
+
+       if (session_name == NULL) {
+               return -LTTNG_ERR_INVALID;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_DATA_PENDING;
+
+       ret = lttng_strncpy(lsm.session.name, session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, (void **) &pending);
+       if (ret < 0) {
+               goto end;
+       } else if (ret != 1) {
+               /* Unexpected payload size */
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       } else if (!pending) {
+               /* Internal error. */
+               ret = -LTTNG_ERR_UNK;
+               goto end;
+       }
+
+       ret = (int) *pending;
+end:
+       free(pending);
+       return ret;
+}
+
+/*
+ * Regenerate the metadata for a session.
+ * Return 0 on success, a negative error code on error.
+ */
+int lttng_regenerate_metadata(const char *session_name)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (!session_name) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_REGENERATE_METADATA;
+
+       ret = lttng_strncpy(lsm.session.name, session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+       if (ret < 0) {
+               goto end;
+       }
+
+       ret = 0;
+end:
+       return ret;
+}
+
+/*
+ * Deprecated, replaced by lttng_regenerate_metadata.
+ */
+int lttng_metadata_regenerate(const char *session_name)
+{
+       return lttng_regenerate_metadata(session_name);
+}
+
+/*
+ * Regenerate the statedump of a session.
+ * Return 0 on success, a negative error code on error.
+ */
+int lttng_regenerate_statedump(const char *session_name)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+
+       if (!session_name) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_REGENERATE_STATEDUMP;
+
+       ret = lttng_strncpy(lsm.session.name, session_name,
+                       sizeof(lsm.session.name));
+       if (ret) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       ret = lttng_ctl_ask_sessiond(&lsm, NULL);
+       if (ret < 0) {
+               goto end;
+       }
+
+       ret = 0;
+end:
+       return ret;
+}
+
+static
+int _lttng_register_trigger(struct lttng_trigger *trigger, const char *name,
+               bool generate_name)
+{
+       int ret;
+       struct lttcomm_session_msg lsm = {
+               .cmd_type = LTTNG_REGISTER_TRIGGER,
+       };
+       lsm.u.trigger.is_trigger_anonymous = !name && !generate_name;
+       struct lttcomm_session_msg *message_lsm;
+       struct lttng_payload message;
+       struct lttng_payload reply;
+       struct lttng_trigger *reply_trigger = NULL;
+       enum lttng_domain_type domain_type;
+       const struct lttng_credentials user_creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(geteuid()),
+               .gid = LTTNG_OPTIONAL_INIT_UNSET,
+       };
+       const char *unused_trigger_name = NULL;
+       enum lttng_trigger_status trigger_status;
+
+       lttng_payload_init(&message);
+       lttng_payload_init(&reply);
+
+       if (!trigger) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       trigger_status = lttng_trigger_get_name(trigger, &unused_trigger_name);
+       if (trigger_status != LTTNG_TRIGGER_STATUS_UNSET) {
+               /* Re-using already registered trigger. */
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       if (name) {
+               trigger_status = lttng_trigger_set_name(trigger, name);
+               if (trigger_status != LTTNG_TRIGGER_STATUS_OK) {
+                       ret = -LTTNG_ERR_NOMEM;
+                       goto end;
+               }
+       }
+
+       if (!trigger->creds.uid.is_set) {
+               /* Use the client's credentials as the trigger credentials. */
+               lttng_trigger_set_credentials(trigger, &user_creds);
+       } else {
+               /*
+                * Validate that either the current trigger credentials and the
+                * client credentials are identical or that the current user is
+                * root. The root user can register, unregister triggers for
+                * himself and other users.
+                *
+                * This check is also present on the sessiond side, using the
+                * credentials passed on the socket. These check are all
+                * "safety" checks.
+                */
+               const struct lttng_credentials *trigger_creds =
+                               lttng_trigger_get_credentials(trigger);
+
+               if (!lttng_credentials_is_equal_uid(trigger_creds, &user_creds)) {
+                       if (lttng_credentials_get_uid(&user_creds) != 0) {
+                               ret = -LTTNG_ERR_EPERM;
+                               goto end_unset_name;
+                       }
+               }
+       }
+
+       if (!lttng_trigger_validate(trigger)) {
+               ret = -LTTNG_ERR_INVALID_TRIGGER;
+               goto end_unset_name;
+       }
+
+       domain_type = lttng_trigger_get_underlying_domain_type_restriction(
+                       trigger);
+
+       lsm.domain.type = domain_type;
+
+       ret = lttng_dynamic_buffer_append(&message.buffer, &lsm, sizeof(lsm));
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto end_unset_name;
+       }
+
+       ret = lttng_trigger_serialize(trigger, &message);
+       if (ret < 0) {
+               ret = -LTTNG_ERR_UNK;
+               goto end_unset_name;
+       }
+
+       /*
+        * This is needed to populate the trigger object size for the command
+        * header.
+        */
+       message_lsm = (struct lttcomm_session_msg *) message.buffer.data;
+
+       message_lsm->u.trigger.length = (uint32_t) message.buffer.size - sizeof(lsm);
+
+       {
+               struct lttng_payload_view message_view =
+                               lttng_payload_view_from_payload(
+                                               &message, 0, -1);
+
+               message_lsm->fd_count = lttng_payload_view_get_fd_handle_count(
+                               &message_view);
+               ret = lttng_ctl_ask_sessiond_payload(&message_view, &reply);
+               if (ret < 0) {
+                       goto end_unset_name;
+               }
+       }
+
+       {
+               struct lttng_payload_view reply_view =
+                               lttng_payload_view_from_payload(
+                                               &reply, 0, reply.buffer.size);
+
+               ret = lttng_trigger_create_from_payload(
+                               &reply_view, &reply_trigger);
+               if (ret < 0) {
+                       ret = -LTTNG_ERR_INVALID_PROTOCOL;
+                       goto end_unset_name;
+               }
+       }
+
+       if (name || generate_name) {
+               ret = lttng_trigger_assign_name(trigger, reply_trigger);
+               if (ret < 0) {
+                       ret = -LTTNG_ERR_NOMEM;
+                       goto end;
+               }
+       }
+
+       ret = 0;
+       goto end;
+
+end_unset_name:
+       trigger_status = lttng_trigger_set_name(trigger, NULL);
+       if (trigger_status != LTTNG_TRIGGER_STATUS_OK) {
+               ret = -LTTNG_ERR_UNK;
+       }
+end:
+       lttng_payload_reset(&message);
+       lttng_payload_reset(&reply);
+       lttng_trigger_destroy(reply_trigger);
+       return ret;
+}
+
+int lttng_register_trigger(struct lttng_trigger *trigger)
+{
+       /* Register an anonymous trigger. */
+       return _lttng_register_trigger(trigger, NULL, false);
+}
+
+enum lttng_error_code lttng_register_trigger_with_name(
+               struct lttng_trigger *trigger, const char *name)
+{
+       const int ret = _lttng_register_trigger(trigger, name, false);
+
+       return ret == 0 ? LTTNG_OK : (enum lttng_error_code) -ret;
+}
+
+enum lttng_error_code lttng_register_trigger_with_automatic_name(
+               struct lttng_trigger *trigger)
+{
+       const int ret =  _lttng_register_trigger(trigger, nullptr, true);
+
+       return ret == 0 ? LTTNG_OK : (enum lttng_error_code) -ret;
+}
+
+enum lttng_error_code lttng_error_query_execute(
+               const struct lttng_error_query *query,
+               const struct lttng_endpoint *endpoint,
+               struct lttng_error_query_results **results)
+{
+       int ret;
+       enum lttng_error_code ret_code;
+       struct lttcomm_session_msg lsm = {
+               .cmd_type = LTTNG_EXECUTE_ERROR_QUERY,
+       };
+       struct lttng_payload message;
+       struct lttng_payload reply;
+       struct lttcomm_session_msg *message_lsm;
+
+       lttng_payload_init(&message);
+       lttng_payload_init(&reply);
+
+       if (!query || !results) {
+               ret_code = LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       if (endpoint != lttng_session_daemon_command_endpoint) {
+               ret_code = LTTNG_ERR_INVALID_ERROR_QUERY_TARGET;
+               goto end;
+       }
+
+       ret = lttng_dynamic_buffer_append(&message.buffer, &lsm, sizeof(lsm));
+       if (ret) {
+               ret_code = LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       ret = lttng_error_query_serialize(query, &message);
+       if (ret) {
+               ret_code = LTTNG_ERR_UNK;
+               goto end;
+       }
+
+       message_lsm = (struct lttcomm_session_msg *) message.buffer.data;
+       message_lsm->u.error_query.length =
+                       (uint32_t) message.buffer.size - sizeof(lsm);
+
+       {
+               struct lttng_payload_view message_view =
+                               lttng_payload_view_from_payload(
+                                               &message, 0, -1);
+
+               message_lsm->fd_count = lttng_payload_view_get_fd_handle_count(
+                               &message_view);
+               ret = lttng_ctl_ask_sessiond_payload(&message_view, &reply);
+               if (ret < 0) {
+                       ret_code =(lttng_error_code) -ret;
+                       goto end;
+               }
+       }
+
+       {
+               ssize_t reply_create_ret;
+               struct lttng_payload_view reply_view =
+                               lttng_payload_view_from_payload(
+                                               &reply, 0, reply.buffer.size);
+
+               reply_create_ret = lttng_error_query_results_create_from_payload(
+                               &reply_view, results);
+               if (reply_create_ret < 0) {
+                       ret_code = LTTNG_ERR_INVALID_PROTOCOL;
+                       goto end;
+               }
+       }
+
+       ret_code = LTTNG_OK;
+end:
+       lttng_payload_reset(&message);
+       lttng_payload_reset(&reply);
+       return ret_code;
+}
+
+int lttng_unregister_trigger(const struct lttng_trigger *trigger)
+{
+       int ret;
+       struct lttcomm_session_msg lsm;
+       struct lttcomm_session_msg *message_lsm;
+       struct lttng_payload message;
+       struct lttng_payload reply;
+       struct lttng_trigger *copy = NULL;
+       const struct lttng_credentials user_creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(geteuid()),
+               .gid = LTTNG_OPTIONAL_INIT_UNSET,
+       };
+
+       lttng_payload_init(&message);
+       lttng_payload_init(&reply);
+
+       if (!trigger) {
+               ret = -LTTNG_ERR_INVALID;
+               goto end;
+       }
+
+       copy = lttng_trigger_copy(trigger);
+       if (!copy) {
+               ret = -LTTNG_ERR_UNK;
+               goto end;
+       }
+
+       if (!copy->creds.uid.is_set) {
+               /* Use the client credentials as the trigger credentials */
+               lttng_trigger_set_credentials(copy, &user_creds);
+       } else {
+               /*
+                * Validate that either the current trigger credentials and the
+                * client credentials are identical or that the current user is
+                * root. The root user can register, unregister triggers for
+                * himself and other users.
+                *
+                * This check is also present on the sessiond side, using the
+                * credentials passed on the socket. These check are all
+                * "safety" checks.
+                */
+               const struct lttng_credentials *trigger_creds =
+                               lttng_trigger_get_credentials(copy);
+               if (!lttng_credentials_is_equal_uid(trigger_creds, &user_creds)) {
+                       if (lttng_credentials_get_uid(&user_creds) != 0) {
+                               ret = -LTTNG_ERR_EPERM;
+                               goto end;
+                       }
+               }
+       }
+
+       if (!lttng_trigger_validate(copy)) {
+               ret = -LTTNG_ERR_INVALID_TRIGGER;
+               goto end;
+       }
+
+       memset(&lsm, 0, sizeof(lsm));
+       lsm.cmd_type = LTTNG_UNREGISTER_TRIGGER;
+
+       ret = lttng_dynamic_buffer_append(&message.buffer, &lsm, sizeof(lsm));
+       if (ret) {
+               ret = -LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       ret = lttng_trigger_serialize(copy, &message);
+       if (ret < 0) {
+               ret = -LTTNG_ERR_UNK;
+               goto end;
+       }
+
+       /*
+        * This is needed to populate the trigger object size for the command
+        * header and number of fds sent.
+       */
+       message_lsm = (struct lttcomm_session_msg *) message.buffer.data;
+
+       message_lsm->u.trigger.length = (uint32_t) message.buffer.size - sizeof(lsm);
+
+       {
+               struct lttng_payload_view message_view =
+                               lttng_payload_view_from_payload(
+                                               &message, 0, -1);
+
+               /*
+                * Update the message header with the number of fd that will be
+                * sent.
+                */
+               message_lsm->fd_count = lttng_payload_view_get_fd_handle_count(
+                               &message_view);
+
+               ret = lttng_ctl_ask_sessiond_payload(&message_view, &reply);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
+       ret = 0;
+end:
+       lttng_trigger_destroy(copy);
+       lttng_payload_reset(&message);
+       lttng_payload_reset(&reply);
+       return ret;
+}
+
+/*
+ * Ask the session daemon for all registered triggers for the current user.
+ *
+ * Allocates and return an lttng_triggers set.
+ * On error, returns a suitable lttng_error_code.
+ */
+enum lttng_error_code lttng_list_triggers(struct lttng_triggers **triggers)
+{
+       int ret;
+       enum lttng_error_code ret_code = LTTNG_OK;
+       struct lttcomm_session_msg lsm = { .cmd_type = LTTNG_LIST_TRIGGERS };
+       struct lttng_triggers *local_triggers = NULL;
+       struct lttng_payload reply;
+       struct lttng_payload_view lsm_view =
+                       lttng_payload_view_init_from_buffer(
+                               (const char *) &lsm, 0, sizeof(lsm));
+
+       lttng_payload_init(&reply);
+
+       ret = lttng_ctl_ask_sessiond_payload(&lsm_view, &reply);
+       if (ret < 0) {
+               ret_code = (enum lttng_error_code) -ret;
+               goto end;
+       }
+
+       {
+               struct lttng_payload_view reply_view =
+                               lttng_payload_view_from_payload(
+                                               &reply, 0, reply.buffer.size);
+
+               ret = lttng_triggers_create_from_payload(
+                               &reply_view, &local_triggers);
+               if (ret < 0) {
+                       ret_code = LTTNG_ERR_FATAL;
+                       goto end;
+               }
+       }
+
+       *triggers = local_triggers;
+       local_triggers = NULL;
+end:
+       lttng_payload_reset(&reply);
+       lttng_triggers_destroy(local_triggers);
+       return ret_code;
+}
+
+/*
+ * lib constructor.
+ */
+static void __attribute__((constructor)) init(void)
+{
+       /* Set default session group */
+       lttng_set_tracing_group(DEFAULT_TRACING_GROUP);
+}
+
+/*
+ * lib destructor.
+ */
+static void __attribute__((destructor)) lttng_ctl_exit(void)
+{
+       free(tracing_group);
+}
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