Fix: loading of live session within userspace domains

[lttng-tools.git] / src / lib / lttng-ctl / lttng-ctl.c

/*
 * liblttngctl.c
 *
 * Linux Trace Toolkit Control Library
 *
 * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License, version 2.1 only,
 * as published by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#define _GNU_SOURCE
#define _LGPL_SOURCE
#include <assert.h>
#include <grp.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <common/common.h>
#include <common/defaults.h>
#include <common/sessiond-comm/sessiond-comm.h>
#include <common/uri.h>
#include <common/utils.h>
#include <lttng/lttng.h>
#include <lttng/health-internal.h>

#include "filter/filter-ast.h"
#include "filter/filter-parser.h"
#include "filter/filter-bytecode.h"
#include "filter/memstream.h"
#include "lttng-ctl-helper.h"

#ifdef DEBUG
static const int print_xml = 1;
#define dbg_printf(fmt, args...)        \
        printf("[debug liblttng-ctl] " fmt, ## args)
#else
static const int print_xml = 0;
#define dbg_printf(fmt, args...)                                \
do {                                                            \
        /* do nothing but check printf format */                \
        if (0)                                                  \
                printf("[debug liblttnctl] " fmt, ## args);     \
} while (0)
#endif


/* Socket to session daemon for communication */
static int sessiond_socket;
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.
 */
int lttng_opt_quiet;
int lttng_opt_verbose;
int lttng_opt_mi;

/*
 * Copy string from src to dst and enforce null terminated byte.
 */
LTTNG_HIDDEN
void lttng_ctl_copy_string(char *dst, const char *src, size_t len)
{
        if (src && dst) {
                strncpy(dst, src, len);
                /* Enforce the NULL terminated byte */
                dst[len - 1] = '\0';
        } else if (dst) {
                dst[0] = '\0';
        }
}

/*
 * Copy domain to lttcomm_session_msg domain.
 *
 * If domain is unknown, default domain will be the kernel.
 */
LTTNG_HIDDEN
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 : %d", 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(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;
}

/*
 * Receive data from the sessiond socket.
 *
 * On success, returns the number of bytes received (>=0)
 * On error, returns -1 (recvmsg() error) or -ENOTCONN
 */
static int recv_data_sessiond(void *buf, size_t len)
{
        int ret;

        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;
        }

end:
        return ret;
}

/*
 *  Check if we are in the specified group.
 *
 *  If yes return 1, else return -1.
 */
LTTNG_HIDDEN
int lttng_check_tracing_group(void)
{
        struct group *grp_tracing;      /* no free(). See getgrnam(3) */
        gid_t *grp_list;
        int grp_list_size, grp_id, i;
        int ret = -1;
        const char *grp_name = tracing_group;

        /* Get GID of group 'tracing' */
        grp_tracing = getgrnam(grp_name);
        if (!grp_tracing) {
                /* 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 = 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] == grp_tracing->gr_gid) {
                        ret = 1;
                        break;
                }
        }

free_list:
        free(grp_list);

end:
        return ret;
}

/*
 * 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) {
                lttng_ctl_copy_string(sessiond_sock_path,
                                DEFAULT_GLOBAL_CLIENT_UNIX_SOCK, sizeof(sessiond_sock_path));
        }

        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 0. On error, return -1.
 */
static int connect_sessiond(void)
{
        int ret;

        /* Don't try to connect if already connected. */
        if (connected) {
                return 0;
        }

        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;
        }

        sessiond_socket = ret;
        connected = 1;

        return 0;

error:
        return -1;
}

/*
 *  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);
                sessiond_socket = 0;
                connected = 0;
        }

        return ret;
}

/*
 * Ask the session daemon a specific command and put the data into buf.
 * Takes extra var. len. data as input to send to the session daemon.
 *
 * Return size of data (only payload, not header) or a negative error code.
 */
LTTNG_HIDDEN
int lttng_ctl_ask_sessiond_varlen(struct lttcomm_session_msg *lsm,
                void *vardata, size_t varlen, void **buf)
{
        int ret;
        size_t size;
        void *data = NULL;
        struct lttcomm_lttng_msg llm;

        ret = connect_sessiond();
        if (ret < 0) {
                ret = -LTTNG_ERR_NO_SESSIOND;
                goto end;
        }

        /* Send command to session daemon */
        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, varlen);
        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;
        }

        size = llm.data_size;
        if (size == 0) {
                /* If client free with size 0 */
                if (buf != NULL) {
                        *buf = NULL;
                }
                ret = 0;
                goto end;
        }

        data = zmalloc(size);
        if (!data) {
                ret = -ENOMEM;
                goto end;
        }

        /* Get payload data */
        ret = recv_data_sessiond(data, size);
        if (ret < 0) {
                free(data);
                goto end;
        }

        /*
         * Extra protection not to dereference a NULL pointer. If buf is NULL at
         * this point, an error is returned and data is freed.
         */
        if (buf == NULL) {
                ret = -LTTNG_ERR_INVALID;
                free(data);
                goto end;
        }

        *buf = data;
        ret = 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)
{
        struct lttng_handle *handle = NULL;

        handle = zmalloc(sizeof(struct lttng_handle));
        if (handle == NULL) {
                PERROR("malloc handle");
                goto end;
        }

        /* Copy session name */
        lttng_ctl_copy_string(handle->session_name, session_name,
                        sizeof(handle->session_name));

        /* Copy lttng domain or leave initialized to 0. */
        if (domain) {
                lttng_ctl_copy_lttng_domain(&handle->domain, domain);
        }

end:
        return handle;
}

/*
 * 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)
{
        struct lttcomm_session_msg lsm;

        if (handle == NULL || socket_path == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_REGISTER_CONSUMER;
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        lttng_ctl_copy_string(lsm.u.reg.path, socket_path, sizeof(lsm.u.reg.path));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 *  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)
{
        struct lttcomm_session_msg lsm;

        if (session_name == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_START_TRACE;

        lttng_ctl_copy_string(lsm.session.name, session_name,
                        sizeof(lsm.session.name));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 * 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) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_STOP_TRACE;

        lttng_ctl_copy_string(lsm.session.name, session_name,
                        sizeof(lsm.session.name));

        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);
                }
        } 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)
{
        struct lttcomm_session_msg lsm;

        /* Safety check. Both are mandatory */
        if (handle == NULL || ctx == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        lsm.cmd_type = LTTNG_ADD_CONTEXT;

        /* If no channel name, send empty string. */
        if (channel_name == NULL) {
                lttng_ctl_copy_string(lsm.u.context.channel_name, "",
                                sizeof(lsm.u.context.channel_name));
        } else {
                lttng_ctl_copy_string(lsm.u.context.channel_name, channel_name,
                                sizeof(lsm.u.context.channel_name));
        }

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        memcpy(&lsm.u.context.ctx, ctx, sizeof(struct lttng_event_context));

        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 *  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;

        assert(ev);

        /* Don't add filter for the '*' event. */
        if (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) {
                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;
}

/*
 * Generate the filter bytecode from a give filter expression string. Put the
 * newly allocated parser context in ctxp and populate the lsm object with the
 * expression len.
 *
 * Return 0 on success else a LTTNG_ERR_* code and ctxp is untouched.
 */
static int generate_filter(char *filter_expression,
                struct lttcomm_session_msg *lsm, struct filter_parser_ctx **ctxp)
{
        int ret;
        struct filter_parser_ctx *ctx = NULL;
        FILE *fmem = NULL;

        assert(filter_expression);
        assert(lsm);
        assert(ctxp);

        /*
         * Casting const to non-const, as the underlying function will use it in
         * read-only mode.
         */
        fmem = lttng_fmemopen((void *) filter_expression,
                        strlen(filter_expression), "r");
        if (!fmem) {
                fprintf(stderr, "Error opening memory as stream\n");
                ret = -LTTNG_ERR_FILTER_NOMEM;
                goto error;
        }
        ctx = filter_parser_ctx_alloc(fmem);
        if (!ctx) {
                fprintf(stderr, "Error allocating parser\n");
                ret = -LTTNG_ERR_FILTER_NOMEM;
                goto filter_alloc_error;
        }
        ret = filter_parser_ctx_append_ast(ctx);
        if (ret) {
                fprintf(stderr, "Parse error\n");
                ret = -LTTNG_ERR_FILTER_INVAL;
                goto parse_error;
        }
        ret = filter_visitor_set_parent(ctx);
        if (ret) {
                fprintf(stderr, "Set parent error\n");
                ret = -LTTNG_ERR_FILTER_INVAL;
                goto parse_error;
        }
        if (print_xml) {
                ret = filter_visitor_print_xml(ctx, stdout, 0);
                if (ret) {
                        fflush(stdout);
                        fprintf(stderr, "XML print error\n");
                        ret = -LTTNG_ERR_FILTER_INVAL;
                        goto parse_error;
                }
        }

        dbg_printf("Generating IR... ");
        fflush(stdout);
        ret = filter_visitor_ir_generate(ctx);
        if (ret) {
                fprintf(stderr, "Generate IR error\n");
                ret = -LTTNG_ERR_FILTER_INVAL;
                goto parse_error;
        }
        dbg_printf("done\n");

        dbg_printf("Validating IR... ");
        fflush(stdout);
        ret = filter_visitor_ir_check_binary_op_nesting(ctx);
        if (ret) {
                ret = -LTTNG_ERR_FILTER_INVAL;
                goto parse_error;
        }
        /* Validate strings used as literals in the expression */
        ret = filter_visitor_ir_validate_string(ctx);
        if (ret) {
                ret = -LTTNG_ERR_FILTER_INVAL;
                goto parse_error;
        }
        dbg_printf("done\n");

        dbg_printf("Generating bytecode... ");
        fflush(stdout);
        ret = filter_visitor_bytecode_generate(ctx);
        if (ret) {
                fprintf(stderr, "Generate bytecode error\n");
                ret = -LTTNG_ERR_FILTER_INVAL;
                goto parse_error;
        }
        dbg_printf("done\n");
        dbg_printf("Size of bytecode generated: %u bytes.\n",
                        bytecode_get_len(&ctx->bytecode->b));

        lsm->u.enable.bytecode_len = sizeof(ctx->bytecode->b)
                + bytecode_get_len(&ctx->bytecode->b);
        lsm->u.enable.expression_len = strlen(filter_expression) + 1;

        /* No need to keep the memory stream. */
        if (fclose(fmem) != 0) {
                PERROR("fclose");
        }

        *ctxp = ctx;
        return 0;

parse_error:
        filter_ir_free(ctx);
        filter_parser_ctx_free(ctx);
filter_alloc_error:
        if (fclose(fmem) != 0) {
                PERROR("fclose");
        }
error:
        return ret;
}

/*
 * 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;
        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. */
        if (channel_name == NULL) {
                lttng_ctl_copy_string(lsm.u.enable.channel_name, "",
                                sizeof(lsm.u.enable.channel_name));
        } else {
                lttng_ctl_copy_string(lsm.u.enable.channel_name, channel_name,
                                sizeof(lsm.u.enable.channel_name));
        }

        lsm.cmd_type = LTTNG_ENABLE_EVENT;
        if (ev->name[0] == '\0') {
                /* Enable all events */
                lttng_ctl_copy_string(ev->name, "*", sizeof(ev->name));
        }

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
        /* FIXME: copying non-packed struct to packed struct. */
        memcpy(&lsm.u.enable.event, ev, sizeof(lsm.u.enable.event));

        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
        lsm.u.enable.exclusion_count = exclusion_count;
        lsm.u.enable.bytecode_len = 0;

        /*
         * For the JUL domain, a filter is enforced except for the enable all
         * event. This is done to avoid having the event in all sessions thus
         * filtering by logger name.
         */
        if (exclusion_count == 0 && 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 either a filter or some exclusions, 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 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 = generate_filter(filter_expression, &lsm, &ctx);
                if (ret) {
                        goto filter_error;
                }
        }

        varlen_data = zmalloc(lsm.u.enable.bytecode_len
                        + lsm.u.enable.expression_len
                        + LTTNG_SYMBOL_NAME_LEN * exclusion_count);
        if (!varlen_data) {
                ret = -LTTNG_ERR_EXCLUSION_NOMEM;
                goto mem_error;
        }

        /* Put exclusion names first in the data */
        while (exclusion_count--) {
                strncpy(varlen_data + LTTNG_SYMBOL_NAME_LEN * exclusion_count,
                        *(exclusion_list + exclusion_count), LTTNG_SYMBOL_NAME_LEN);
        }
        /* Add filter expression next */
        if (lsm.u.enable.expression_len != 0) {
                memcpy(varlen_data
                        + LTTNG_SYMBOL_NAME_LEN * lsm.u.enable.exclusion_count,
                        filter_expression,
                        lsm.u.enable.expression_len);
        }
        /* Add filter bytecode next */
        if (ctx && lsm.u.enable.bytecode_len != 0) {
                memcpy(varlen_data
                        + LTTNG_SYMBOL_NAME_LEN * lsm.u.enable.exclusion_count
                        + lsm.u.enable.expression_len,
                        &ctx->bytecode->b,
                        lsm.u.enable.bytecode_len);
        }

        ret = lttng_ctl_ask_sessiond_varlen(&lsm, varlen_data,
                        (LTTNG_SYMBOL_NAME_LEN * lsm.u.enable.exclusion_count) +
                        lsm.u.enable.bytecode_len + lsm.u.enable.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;
}

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. */
        if (channel_name == NULL) {
                lttng_ctl_copy_string(lsm.u.disable.channel_name, "",
                                sizeof(lsm.u.disable.channel_name));
        } else {
                lttng_ctl_copy_string(lsm.u.disable.channel_name, channel_name,
                                sizeof(lsm.u.disable.channel_name));
        }

        lsm.cmd_type = LTTNG_DISABLE_EVENT;

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);
        /* FIXME: copying non-packed struct to packed struct. */
        memcpy(&lsm.u.disable.event, ev, sizeof(lsm.u.disable.event));

        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
        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 = generate_filter(filter_expression, &lsm, &ctx);
                if (ret) {
                        goto filter_error;
                }
        }

        varlen_data = 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(&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)
{
        struct lttng_event ev;

        memset(&ev, 0, sizeof(ev));
        ev.loglevel = -1;
        ev.type = LTTNG_EVENT_ALL;
        lttng_ctl_copy_string(ev.name, name, sizeof(ev.name));
        return lttng_disable_event_ext(handle, &ev, channel_name, NULL);
}

/*
 *  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 *chan)
{
        struct lttcomm_session_msg lsm;

        /*
         * NULL arguments are forbidden. No default values.
         */
        if (handle == NULL || chan == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        memcpy(&lsm.u.channel.chan, chan, sizeof(lsm.u.channel.chan));

        lsm.cmd_type = LTTNG_ENABLE_CHANNEL;

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 *  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)
{
        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;

        lttng_ctl_copy_string(lsm.u.disable.channel_name, name,
                        sizeof(lsm.u.disable.channel_name));

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 *  Add PID to session tracker.
 *  Return 0 on success else a negative LTTng error code.
 */
int lttng_track_pid(struct lttng_handle *handle, int pid)
{
        struct lttcomm_session_msg lsm;

        /*
         * NULL arguments are forbidden. No default values.
         */
        if (handle == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        lsm.cmd_type = LTTNG_TRACK_PID;
        lsm.u.pid_tracker.pid = pid;

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 *  Remove PID from session tracker.
 *  Return 0 on success else a negative LTTng error code.
 */
int lttng_untrack_pid(struct lttng_handle *handle, int pid)
{
        struct lttcomm_session_msg lsm;

        /*
         * NULL arguments are forbidden. No default values.
         */
        if (handle == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        lsm.cmd_type = LTTNG_UNTRACK_PID;
        lsm.u.pid_tracker.pid = pid;

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 *  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;
        lttng_ctl_copy_lttng_domain(&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;
        lttng_ctl_copy_lttng_domain(&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);
}

/*
 * Create a brand new session using name and url for destination.
 *
 * Returns LTTNG_OK on success or a negative error code.
 */
int lttng_create_session(const char *name, const char *url)
{
        int ret;
        ssize_t size;
        struct lttcomm_session_msg lsm;
        struct lttng_uri *uris = NULL;

        if (name == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        lsm.cmd_type = LTTNG_CREATE_SESSION;
        lttng_ctl_copy_string(lsm.session.name, name, sizeof(lsm.session.name));

        /* There should never be a data URL */
        size = uri_parse_str_urls(url, NULL, &uris);
        if (size < 0) {
                return -LTTNG_ERR_INVALID;
        }

        lsm.u.uri.size = size;

        ret = lttng_ctl_ask_sessiond_varlen(&lsm, uris,
                        sizeof(struct lttng_uri) * size, NULL);

        free(uris);
        return ret;
}

/*
 *  Destroy session using name.
 *  Returns size of returned session payload data or a negative error code.
 */
int lttng_destroy_session(const char *session_name)
{
        struct lttcomm_session_msg lsm;

        if (session_name == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_DESTROY_SESSION;

        lttng_ctl_copy_string(lsm.session.name, session_name,
                        sizeof(lsm.session.name));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 *  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 **sessions)
{
        int ret;
        struct lttcomm_session_msg lsm;

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_LIST_SESSIONS;
        ret = lttng_ctl_ask_sessiond(&lsm, (void**) sessions);
        if (ret < 0) {
                return ret;
        }

        return ret / sizeof(struct lttng_session);
}

int lttng_set_session_shm_path(const char *session_name,
                const char *shm_path)
{
        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;

        lttng_ctl_copy_string(lsm.session.name, session_name,
                        sizeof(lsm.session.name));
        lttng_ctl_copy_string(lsm.u.set_shm_path.shm_path, shm_path,
                        sizeof(lsm.u.set_shm_path.shm_path));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 *  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) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_LIST_DOMAINS;

        lttng_ctl_copy_string(lsm.session.name, session_name,
                        sizeof(lsm.session.name));

        ret = lttng_ctl_ask_sessiond(&lsm, (void**) domains);
        if (ret < 0) {
                return ret;
        }

        return ret / sizeof(struct lttng_domain);
}

/*
 *  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;
        struct lttcomm_session_msg lsm;

        if (handle == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_LIST_CHANNELS;
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        ret = lttng_ctl_ask_sessiond(&lsm, (void**) channels);
        if (ret < 0) {
                return ret;
        }

        return ret / sizeof(struct lttng_channel);
}

/*
 *  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;

        /* Safety check. An handle and channel name are mandatory */
        if (handle == NULL || channel_name == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_LIST_EVENTS;
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
        lttng_ctl_copy_string(lsm.u.list.channel_name, channel_name,
                        sizeof(lsm.u.list.channel_name));

        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        ret = lttng_ctl_ask_sessiond(&lsm, (void**) events);
        if (ret < 0) {
                return ret;
        }

        return ret / sizeof(struct lttng_event);
}

/*
 * 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)
{
        if (name == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        if (asprintf(&tracing_group, "%s", name) < 0) {
                return -LTTNG_ERR_FATAL;
        }

        return 0;
}

/*
 * Returns size of returned session payload data or a negative error code.
 */
int lttng_calibrate(struct lttng_handle *handle,
                struct lttng_calibrate *calibrate)
{
        struct lttcomm_session_msg lsm;

        /* Safety check. NULL pointer are forbidden */
        if (handle == NULL || calibrate == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_CALIBRATE;
        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        memcpy(&lsm.u.calibrate, calibrate, sizeof(lsm.u.calibrate));

        return lttng_ctl_ask_sessiond(&lsm, NULL);
}

/*
 * 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)
{
        /* Safety check */
        if (attr == NULL || domain == NULL) {
                return;
        }

        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;
                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;
                        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;
                        break;
                }
        default:
                /* Default behavior: leave set to 0. */
                break;
        }
}

/*
 * 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.
                 */
                assert(0);
        }

        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)) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        lsm.cmd_type = LTTNG_SET_CONSUMER_URI;

        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        size = uri_parse_str_urls(control_url, data_url, &uris);
        if (size < 0) {
                return -LTTNG_ERR_INVALID;
        }

        lsm.u.uri.size = size;

        ret = lttng_ctl_ask_sessiond_varlen(&lsm, uris,
                        sizeof(struct lttng_uri) * size, NULL);

        free(uris);
        return ret;
}

/*
 * [OBSOLETE]
 */
int lttng_enable_consumer(struct lttng_handle *handle)
{
        return -ENOSYS;
}

/*
 * [OBSOLETE]
 */
int lttng_disable_consumer(struct lttng_handle *handle)
{
        return -ENOSYS;
}

/*
 * This is an extension of create session that is ONLY and SHOULD only be used
 * by the lttng command line program. It exists to avoid using URI parsing in
 * the lttng client.
 *
 * We need the date and time for the trace path subdirectory for the case where
 * the user does NOT define one using either -o or -U. Using the normal
 * lttng_create_session API call, we have no clue on the session daemon side if
 * the URL was generated automatically by the client or define by the user.
 *
 * So this function "wrapper" is hidden from the public API, takes the datetime
 * string and appends it if necessary to the URI subdirectory before sending it
 * to the session daemon.
 *
 * With this extra function, the lttng_create_session call behavior is not
 * changed and the timestamp is appended to the URI on the session daemon side
 * if necessary.
 */
int _lttng_create_session_ext(const char *name, const char *url,
                const char *datetime)
{
        int ret;
        ssize_t size;
        struct lttcomm_session_msg lsm;
        struct lttng_uri *uris = NULL;

        if (name == NULL || datetime == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        lsm.cmd_type = LTTNG_CREATE_SESSION;
        lttng_ctl_copy_string(lsm.session.name, name, sizeof(lsm.session.name));

        /* There should never be a data URL */
        size = uri_parse_str_urls(url, NULL, &uris);
        if (size < 0) {
                ret = -LTTNG_ERR_INVALID;
                goto error;
        }

        lsm.u.uri.size = size;

        if (size > 0 && uris[0].dtype != LTTNG_DST_PATH && strlen(uris[0].subdir) == 0) {
                /* Don't append datetime if the name was automatically created. */
                if (strncmp(name, DEFAULT_SESSION_NAME "-",
                                        strlen(DEFAULT_SESSION_NAME) + 1)) {
                        ret = snprintf(uris[0].subdir, sizeof(uris[0].subdir), "%s-%s",
                                        name, datetime);
                } else {
                        ret = snprintf(uris[0].subdir, sizeof(uris[0].subdir), "%s", name);
                }
                if (ret < 0) {
                        PERROR("snprintf uri subdir");
                        ret = -LTTNG_ERR_FATAL;
                        goto error;
                }
        }

        ret = lttng_ctl_ask_sessiond_varlen(&lsm, uris,
                        sizeof(struct lttng_uri) * size, NULL);

error:
        free(uris);
        return ret;
}

/*
 * 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;

        if (session_name == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_DATA_PENDING;

        lttng_ctl_copy_string(lsm.session.name, session_name,
                        sizeof(lsm.session.name));

        ret = lttng_ctl_ask_sessiond(&lsm, NULL);

        /*
         * The lttng_ctl_ask_sessiond function negate the return code if it's not
         * LTTNG_OK so getting -1 means that the reply ret_code was 1 thus meaning
         * that the data is available. Yes it is hackish but for now this is the
         * only way.
         */
        if (ret == -1) {
                ret = 1;
        }

        return ret;
}

/*
 * Create a session exclusively used for snapshot.
 *
 * Returns LTTNG_OK on success or a negative error code.
 */
int lttng_create_session_snapshot(const char *name, const char *snapshot_url)
{
        int ret;
        ssize_t size;
        struct lttcomm_session_msg lsm;
        struct lttng_uri *uris = NULL;

        if (name == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        lsm.cmd_type = LTTNG_CREATE_SESSION_SNAPSHOT;
        lttng_ctl_copy_string(lsm.session.name, name, sizeof(lsm.session.name));

        size = uri_parse_str_urls(snapshot_url, NULL, &uris);
        if (size < 0) {
                return -LTTNG_ERR_INVALID;
        }

        lsm.u.uri.size = size;

        ret = lttng_ctl_ask_sessiond_varlen(&lsm, uris,
                        sizeof(struct lttng_uri) * size, NULL);

        free(uris);
        return ret;
}

/*
 * Create a session exclusively used for live.
 *
 * Returns LTTNG_OK on success or a negative error code.
 */
int lttng_create_session_live(const char *name, const char *url,
                unsigned int timer_interval)
{
        int ret;
        ssize_t size;
        struct lttcomm_session_msg lsm;
        struct lttng_uri *uris = NULL;

        if (name == NULL || timer_interval == 0) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));

        lsm.cmd_type = LTTNG_CREATE_SESSION_LIVE;
        lttng_ctl_copy_string(lsm.session.name, name, sizeof(lsm.session.name));

        if (url) {
                size = uri_parse_str_urls(url, NULL, &uris);
                if (size <= 0) {
                        ret = -LTTNG_ERR_INVALID;
                        goto end;
                }

                /* file:// is not accepted for live session. */
                if (uris[0].dtype == LTTNG_DST_PATH) {
                        ret = -LTTNG_ERR_INVALID;
                        goto end;
                }
        } else {
                size = 0;
        }

        lsm.u.session_live.nb_uri = size;
        lsm.u.session_live.timer_interval = timer_interval;

        ret = lttng_ctl_ask_sessiond_varlen(&lsm, uris,
                        sizeof(struct lttng_uri) * size, NULL);

end:
        free(uris);
        return ret;
}

/*
 * List PIDs in the tracker.
 *
 * @enabled is set to whether the PID tracker is enabled.
 * @pids is set to an allocated array of PIDs currently tracked. On
 * success, @pids must be freed by the caller.
 * @nr_pids is set to the number of entries contained by the @pids array.
 *
 * Returns 0 on success, else a negative LTTng error code.
 */
int lttng_list_tracker_pids(struct lttng_handle *handle,
                int *_enabled, int32_t **_pids, size_t *_nr_pids)
{
        int ret;
        int enabled = 1;
        struct lttcomm_session_msg lsm;
        size_t nr_pids;
        int32_t *pids;

        if (handle == NULL) {
                return -LTTNG_ERR_INVALID;
        }

        memset(&lsm, 0, sizeof(lsm));
        lsm.cmd_type = LTTNG_LIST_TRACKER_PIDS;
        lttng_ctl_copy_string(lsm.session.name, handle->session_name,
                        sizeof(lsm.session.name));
        lttng_ctl_copy_lttng_domain(&lsm.domain, &handle->domain);

        ret = lttng_ctl_ask_sessiond(&lsm, (void **) &pids);
        if (ret < 0) {
                return ret;
        }
        nr_pids = ret / sizeof(int32_t);
        if (nr_pids == 1 && pids[0] == -1) {
                free(pids);
                pids = NULL;
                enabled = 0;
                nr_pids = 0;
        }
        *_enabled = enabled;
        *_pids = pids;
        *_nr_pids = nr_pids;
        return 0;
}

/*
 * lib constructor
 */
static void __attribute__((constructor)) init()
{
        /* Set default session group */
        lttng_set_tracing_group(DEFAULT_TRACING_GROUP);
}

/*
 * lib destructor
 */
static void __attribute__((destructor)) lttng_ctl_exit()
{
        free(tracing_group);
}