[lttng-tools.git] / src / bin / lttng-sessiond / cmd.c

/*
 * Copyright (C) 2012 David Goulet <dgoulet@efficios.com>
 * Copyright (C) 2016 Jérémie Galarneau <jeremie.galarneau@efficios.com>
 *
 * SPDX-License-Identifier: GPL-2.0-only
 *
 */

#include "bin/lttng-sessiond/session.h"
#define _LGPL_SOURCE
#include <assert.h>
#include <inttypes.h>
#include <urcu/list.h>
#include <urcu/uatomic.h>
#include <sys/stat.h>
#include <stdio.h>

#include <common/defaults.h>
#include <common/common.h>
#include <common/sessiond-comm/sessiond-comm.h>
#include <common/relayd/relayd.h>
#include <common/utils.h>
#include <common/compat/string.h>
#include <common/kernel-ctl/kernel-ctl.h>
#include <common/dynamic-buffer.h>
#include <common/buffer-view.h>
#include <common/payload.h>
#include <common/payload-view.h>
#include <common/trace-chunk.h>
#include <lttng/location-internal.h>
#include <lttng/trigger/trigger-internal.h>
#include <lttng/condition/condition.h>
#include <lttng/condition/condition-internal.h>
#include <lttng/condition/on-event.h>
#include <lttng/condition/on-event-internal.h>
#include <lttng/event-rule/event-rule.h>
#include <lttng/event-rule/event-rule-internal.h>
#include <lttng/action/action.h>
#include <lttng/channel.h>
#include <lttng/channel-internal.h>
#include <lttng/rotate-internal.h>
#include <lttng/location-internal.h>
#include <lttng/session-internal.h>
#include <lttng/userspace-probe-internal.h>
#include <lttng/session-descriptor-internal.h>
#include <lttng/lttng-error.h>
#include <lttng/tracker.h>
#include <common/string-utils/string-utils.h>

#include "channel.h"
#include "consumer.h"
#include "event.h"
#include "health-sessiond.h"
#include "kernel.h"
#include "kernel-consumer.h"
#include "lttng-sessiond.h"
#include "utils.h"
#include "lttng-syscall.h"
#include "agent.h"
#include "buffer-registry.h"
#include "notification-thread.h"
#include "notification-thread-commands.h"
#include "rotate.h"
#include "rotation-thread.h"
#include "timer.h"
#include "agent-thread.h"
#include "tracker.h"

#include "cmd.h"

/* Sleep for 100ms between each check for the shm path's deletion. */
#define SESSION_DESTROY_SHM_PATH_CHECK_DELAY_US 100000

struct cmd_destroy_session_reply_context {
	int reply_sock_fd;
	bool implicit_rotation_on_destroy;
	/*
	 * Indicates whether or not an error occurred while launching the
	 * destruction of a session.
	 */
	enum lttng_error_code destruction_status;
};

static enum lttng_error_code wait_on_path(void *path);

/*
 * Command completion handler that is used by the destroy command
 * when a session that has a non-default shm_path is being destroyed.
 *
 * See comment in cmd_destroy_session() for the rationale.
 */
static struct destroy_completion_handler {
	struct cmd_completion_handler handler;
	char shm_path[member_sizeof(struct ltt_session, shm_path)];
} destroy_completion_handler = {
	.handler = {
		.run = wait_on_path,
		.data = destroy_completion_handler.shm_path
	},
	.shm_path = { 0 },
};

static struct cmd_completion_handler *current_completion_handler;

/*
 * Used to keep a unique index for each relayd socket created where this value
 * is associated with streams on the consumer so it can match the right relayd
 * to send to. It must be accessed with the relayd_net_seq_idx_lock
 * held.
 */
static pthread_mutex_t relayd_net_seq_idx_lock = PTHREAD_MUTEX_INITIALIZER;
static uint64_t relayd_net_seq_idx;

static int validate_ust_event_name(const char *);
static int cmd_enable_event_internal(struct ltt_session *session,
		const struct lttng_domain *domain,
		char *channel_name, struct lttng_event *event,
		char *filter_expression,
		struct lttng_bytecode *filter,
		struct lttng_event_exclusion *exclusion,
		int wpipe);

/*
 * Create a session path used by list_lttng_sessions for the case that the
 * session consumer is on the network.
 */
static int build_network_session_path(char *dst, size_t size,
		struct ltt_session *session)
{
	int ret, kdata_port, udata_port;
	struct lttng_uri *kuri = NULL, *uuri = NULL, *uri = NULL;
	char tmp_uurl[PATH_MAX], tmp_urls[PATH_MAX];

	assert(session);
	assert(dst);

	memset(tmp_urls, 0, sizeof(tmp_urls));
	memset(tmp_uurl, 0, sizeof(tmp_uurl));

	kdata_port = udata_port = DEFAULT_NETWORK_DATA_PORT;

	if (session->kernel_session && session->kernel_session->consumer) {
		kuri = &session->kernel_session->consumer->dst.net.control;
		kdata_port = session->kernel_session->consumer->dst.net.data.port;
	}

	if (session->ust_session && session->ust_session->consumer) {
		uuri = &session->ust_session->consumer->dst.net.control;
		udata_port = session->ust_session->consumer->dst.net.data.port;
	}

	if (uuri == NULL && kuri == NULL) {
		uri = &session->consumer->dst.net.control;
		kdata_port = session->consumer->dst.net.data.port;
	} else if (kuri && uuri) {
		ret = uri_compare(kuri, uuri);
		if (ret) {
			/* Not Equal */
			uri = kuri;
			/* Build uuri URL string */
			ret = uri_to_str_url(uuri, tmp_uurl, sizeof(tmp_uurl));
			if (ret < 0) {
				goto error;
			}
		} else {
			uri = kuri;
		}
	} else if (kuri && uuri == NULL) {
		uri = kuri;
	} else if (uuri && kuri == NULL) {
		uri = uuri;
	}

	ret = uri_to_str_url(uri, tmp_urls, sizeof(tmp_urls));
	if (ret < 0) {
		goto error;
	}

	/*
	 * Do we have a UST url set. If yes, this means we have both kernel and UST
	 * to print.
	 */
	if (*tmp_uurl != '\0') {
		ret = snprintf(dst, size, "[K]: %s [data: %d] -- [U]: %s [data: %d]",
				tmp_urls, kdata_port, tmp_uurl, udata_port);
	} else {
		int dport;
		if (kuri || (!kuri && !uuri)) {
			dport = kdata_port;
		} else {
			/* No kernel URI, use the UST port. */
			dport = udata_port;
		}
		ret = snprintf(dst, size, "%s [data: %d]", tmp_urls, dport);
	}

error:
	return ret;
}

/*
 * Get run-time attributes if the session has been started (discarded events,
 * lost packets).
 */
static int get_kernel_runtime_stats(struct ltt_session *session,
		struct ltt_kernel_channel *kchan, uint64_t *discarded_events,
		uint64_t *lost_packets)
{
	int ret;

	if (!session->has_been_started) {
		ret = 0;
		*discarded_events = 0;
		*lost_packets = 0;
		goto end;
	}

	ret = consumer_get_discarded_events(session->id, kchan->key,
			session->kernel_session->consumer,
			discarded_events);
	if (ret < 0) {
		goto end;
	}

	ret = consumer_get_lost_packets(session->id, kchan->key,
			session->kernel_session->consumer,
			lost_packets);
	if (ret < 0) {
		goto end;
	}

end:
	return ret;
}

/*
 * Get run-time attributes if the session has been started (discarded events,
 * lost packets).
 */
static int get_ust_runtime_stats(struct ltt_session *session,
		struct ltt_ust_channel *uchan, uint64_t *discarded_events,
		uint64_t *lost_packets)
{
	int ret;
	struct ltt_ust_session *usess;

	if (!discarded_events || !lost_packets) {
		ret = -1;
		goto end;
	}

	usess = session->ust_session;
	assert(discarded_events);
	assert(lost_packets);

	if (!usess || !session->has_been_started) {
		*discarded_events = 0;
		*lost_packets = 0;
		ret = 0;
		goto end;
	}

	if (usess->buffer_type == LTTNG_BUFFER_PER_UID) {
		ret = ust_app_uid_get_channel_runtime_stats(usess->id,
				&usess->buffer_reg_uid_list,
				usess->consumer, uchan->id,
				uchan->attr.overwrite,
				discarded_events,
				lost_packets);
	} else if (usess->buffer_type == LTTNG_BUFFER_PER_PID) {
		ret = ust_app_pid_get_channel_runtime_stats(usess,
				uchan, usess->consumer,
				uchan->attr.overwrite,
				discarded_events,
				lost_packets);
		if (ret < 0) {
			goto end;
		}
		*discarded_events += uchan->per_pid_closed_app_discarded;
		*lost_packets += uchan->per_pid_closed_app_lost;
	} else {
		ERR("Unsupported buffer type");
		assert(0);
		ret = -1;
		goto end;
	}

end:
	return ret;
}

/*
 * Fill lttng_channel array of all channels.
 */
static ssize_t list_lttng_channels(enum lttng_domain_type domain,
		struct ltt_session *session, struct lttng_channel *channels,
		struct lttng_channel_extended *chan_exts)
{
	int i = 0, ret = 0;
	struct ltt_kernel_channel *kchan;

	DBG("Listing channels for session %s", session->name);

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		/* Kernel channels */
		if (session->kernel_session != NULL) {
			cds_list_for_each_entry(kchan,
					&session->kernel_session->channel_list.head, list) {
				uint64_t discarded_events, lost_packets;
				struct lttng_channel_extended *extended;

				extended = (struct lttng_channel_extended *)
						kchan->channel->attr.extended.ptr;

				ret = get_kernel_runtime_stats(session, kchan,
						&discarded_events, &lost_packets);
				if (ret < 0) {
					goto end;
				}
				/* Copy lttng_channel struct to array */
				memcpy(&channels[i], kchan->channel, sizeof(struct lttng_channel));
				channels[i].enabled = kchan->enabled;
				chan_exts[i].discarded_events =
						discarded_events;
				chan_exts[i].lost_packets = lost_packets;
				chan_exts[i].monitor_timer_interval =
						extended->monitor_timer_interval;
				chan_exts[i].blocking_timeout = 0;
				i++;
			}
		}
		break;
	case LTTNG_DOMAIN_UST:
	{
		struct lttng_ht_iter iter;
		struct ltt_ust_channel *uchan;

		rcu_read_lock();
		cds_lfht_for_each_entry(session->ust_session->domain_global.channels->ht,
				&iter.iter, uchan, node.node) {
			uint64_t discarded_events = 0, lost_packets = 0;

			if (lttng_strncpy(channels[i].name, uchan->name,
					LTTNG_SYMBOL_NAME_LEN)) {
				break;
			}
			channels[i].attr.overwrite = uchan->attr.overwrite;
			channels[i].attr.subbuf_size = uchan->attr.subbuf_size;
			channels[i].attr.num_subbuf = uchan->attr.num_subbuf;
			channels[i].attr.switch_timer_interval =
				uchan->attr.switch_timer_interval;
			channels[i].attr.read_timer_interval =
				uchan->attr.read_timer_interval;
			channels[i].enabled = uchan->enabled;
			channels[i].attr.tracefile_size = uchan->tracefile_size;
			channels[i].attr.tracefile_count = uchan->tracefile_count;

			/*
			 * Map enum lttng_ust_output to enum lttng_event_output.
			 */
			switch (uchan->attr.output) {
			case LTTNG_UST_ABI_MMAP:
				channels[i].attr.output = LTTNG_EVENT_MMAP;
				break;
			default:
				/*
				 * LTTNG_UST_MMAP is the only supported UST
				 * output mode.
				 */
				assert(0);
				break;
			}

			chan_exts[i].monitor_timer_interval =
					uchan->monitor_timer_interval;
			chan_exts[i].blocking_timeout =
				uchan->attr.u.s.blocking_timeout;

			ret = get_ust_runtime_stats(session, uchan,
					&discarded_events, &lost_packets);
			if (ret < 0) {
				break;
			}
			chan_exts[i].discarded_events = discarded_events;
			chan_exts[i].lost_packets = lost_packets;
			i++;
		}
		rcu_read_unlock();
		break;
	}
	default:
		break;
	}

end:
	if (ret < 0) {
		return -LTTNG_ERR_FATAL;
	} else {
		return LTTNG_OK;
	}
}

static int append_extended_info(const char *filter_expression,
		struct lttng_event_exclusion *exclusion,
		struct lttng_userspace_probe_location *probe_location,
		struct lttng_payload *payload)
{
	int ret = 0;
	size_t filter_len = 0;
	size_t nb_exclusions = 0;
	size_t userspace_probe_location_len = 0;
	struct lttcomm_event_extended_header extended_header = {};
	struct lttcomm_event_extended_header *p_extended_header;
	const size_t original_payload_size = payload->buffer.size;

	ret = lttng_dynamic_buffer_append(&payload->buffer, &extended_header,
			sizeof(extended_header));
	if (ret) {
		goto end;
	}

	if (filter_expression) {
		filter_len = strlen(filter_expression) + 1;
		ret = lttng_dynamic_buffer_append(&payload->buffer,
				filter_expression, filter_len);
		if (ret) {
			goto end;
		}
	}

	if (exclusion) {
		const size_t len = exclusion->count * LTTNG_SYMBOL_NAME_LEN;

		nb_exclusions = exclusion->count;

		ret = lttng_dynamic_buffer_append(
				&payload->buffer, &exclusion->names, len);
		if (ret) {
			goto end;
		}
	}

	if (probe_location) {
		const size_t size_before_probe = payload->buffer.size;

		ret = lttng_userspace_probe_location_serialize(probe_location,
				payload);
		if (ret < 0) {
			ret = -1;
			goto end;
		}

		userspace_probe_location_len =
				payload->buffer.size - size_before_probe;
	}

	/* Set header fields */
	p_extended_header = (struct lttcomm_event_extended_header *)
			(payload->buffer.data + original_payload_size);

	p_extended_header->filter_len = filter_len;
	p_extended_header->nb_exclusions = nb_exclusions;
	p_extended_header->userspace_probe_location_len =
			userspace_probe_location_len;

	ret = 0;
end:
	return ret;
}

/*
 * Create a list of agent domain events.
 *
 * Return number of events in list on success or else a negative value.
 */
static int list_lttng_agent_events(struct agent *agt,
		struct lttng_payload *payload)
{
	int nb_events = 0, ret = 0;
	const struct agent_event *agent_event;
	struct lttng_ht_iter iter;

	assert(agt);

	DBG3("Listing agent events");

	rcu_read_lock();
	cds_lfht_for_each_entry (
			agt->events->ht, &iter.iter, agent_event, node.node) {
		struct lttng_event event = {
			.enabled = AGENT_EVENT_IS_ENABLED(agent_event),
			.loglevel = agent_event->loglevel_value,
			.loglevel_type = agent_event->loglevel_type,
		};

		ret = lttng_strncpy(event.name, agent_event->name, sizeof(event.name));
		if (ret) {
			/* Internal error, invalid name. */
			ERR("Invalid event name while listing agent events: '%s' exceeds the maximal allowed length of %zu bytes",
					agent_event->name, sizeof(event.name));
			ret = -LTTNG_ERR_UNK;
			goto end;
		}

		ret = lttng_dynamic_buffer_append(
				&payload->buffer, &event, sizeof(event));
		if (ret) {
			ERR("Failed to append event to payload");
			ret = -LTTNG_ERR_NOMEM;
			goto end;
		}

		nb_events++;
	}

	cds_lfht_for_each_entry (
		agt->events->ht, &iter.iter, agent_event, node.node) {
		/* Append extended info. */
		ret = append_extended_info(agent_event->filter_expression, NULL,
				NULL, payload);
		if (ret) {
			ERR("Failed to append extended event info to payload");
			ret = -LTTNG_ERR_NOMEM;
			goto end;
		}
	}

	ret = nb_events;
end:
	rcu_read_unlock();
	return ret;
}

/*
 * Create a list of ust global domain events.
 */
static int list_lttng_ust_global_events(char *channel_name,
		struct ltt_ust_domain_global *ust_global,
		struct lttng_payload *payload)
{
	int ret = 0;
	unsigned int nb_events = 0;
	struct lttng_ht_iter iter;
	const struct lttng_ht_node_str *node;
	const struct ltt_ust_channel *uchan;
	const struct ltt_ust_event *uevent;

	DBG("Listing UST global events for channel %s", channel_name);

	rcu_read_lock();

	lttng_ht_lookup(ust_global->channels, (void *) channel_name, &iter);
	node = lttng_ht_iter_get_node_str(&iter);
	if (node == NULL) {
		ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
		goto end;
	}

	uchan = caa_container_of(&node->node, struct ltt_ust_channel, node.node);

	DBG3("Listing UST global events");

	cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent, node.node) {
		struct lttng_event event = {};

		if (uevent->internal) {
			continue;
		}

		ret = lttng_strncpy(event.name, uevent->attr.name, sizeof(event.name));
		if (ret) {
			/* Internal error, invalid name. */
			ERR("Invalid event name while listing user space tracer events: '%s' exceeds the maximal allowed length of %zu bytes",
					uevent->attr.name, sizeof(event.name));
			ret = -LTTNG_ERR_UNK;
			goto end;
		}

		event.enabled = uevent->enabled;

		switch (uevent->attr.instrumentation) {
		case LTTNG_UST_ABI_TRACEPOINT:
			event.type = LTTNG_EVENT_TRACEPOINT;
			break;
		case LTTNG_UST_ABI_PROBE:
			event.type = LTTNG_EVENT_PROBE;
			break;
		case LTTNG_UST_ABI_FUNCTION:
			event.type = LTTNG_EVENT_FUNCTION;
			break;
		}

		event.loglevel = uevent->attr.loglevel;
		switch (uevent->attr.loglevel_type) {
		case LTTNG_UST_ABI_LOGLEVEL_ALL:
			event.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
			break;
		case LTTNG_UST_ABI_LOGLEVEL_RANGE:
			event.loglevel_type = LTTNG_EVENT_LOGLEVEL_RANGE;
			break;
		case LTTNG_UST_ABI_LOGLEVEL_SINGLE:
			event.loglevel_type = LTTNG_EVENT_LOGLEVEL_SINGLE;
			break;
		}

		if (uevent->filter) {
			event.filter = 1;
		}

		if (uevent->exclusion) {
			event.exclusion = 1;
		}

		ret = lttng_dynamic_buffer_append(&payload->buffer, &event, sizeof(event));
		if (ret) {
			ERR("Failed to append event to payload");
			ret = -LTTNG_ERR_NOMEM;
			goto end;
		}

		nb_events++;
	}

	cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent, node.node) {
		/* Append extended info. */
		ret = append_extended_info(uevent->filter_expression,
				uevent->exclusion, NULL, payload);
		if (ret) {
			ERR("Failed to append extended event info to payload");
			ret = -LTTNG_ERR_FATAL;
			goto end;
		}
	}

	ret = nb_events;
end:
	rcu_read_unlock();
	return ret;
}

/*
 * Fill lttng_event array of all kernel events in the channel.
 */
static int list_lttng_kernel_events(char *channel_name,
		struct ltt_kernel_session *kernel_session,
		struct lttng_payload *payload)
{
	int ret;
	unsigned int nb_event;
	const struct ltt_kernel_event *kevent;
	const struct ltt_kernel_channel *kchan;

	kchan = trace_kernel_get_channel_by_name(channel_name, kernel_session);
	if (kchan == NULL) {
		ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
		goto error;
	}

	nb_event = kchan->event_count;

	DBG("Listing events for channel %s", kchan->channel->name);

	/* Kernel channels */
	cds_list_for_each_entry(kevent, &kchan->events_list.head , list) {
		struct lttng_event event = {};

		ret = lttng_strncpy(event.name, kevent->event->name, sizeof(event.name));
		if (ret) {
			/* Internal error, invalid name. */
			ERR("Invalid event name while listing kernel events: '%s' exceeds the maximal allowed length of %zu bytes",
					kevent->event->name,
					sizeof(event.name));
			ret = -LTTNG_ERR_UNK;
			goto end;
		}

		event.enabled = kevent->enabled;
		event.filter = (unsigned char) !!kevent->filter_expression;

		switch (kevent->event->instrumentation) {
		case LTTNG_KERNEL_TRACEPOINT:
			event.type = LTTNG_EVENT_TRACEPOINT;
			break;
		case LTTNG_KERNEL_KRETPROBE:
			event.type = LTTNG_EVENT_FUNCTION;
			memcpy(&event.attr.probe, &kevent->event->u.kprobe,
					sizeof(struct lttng_kernel_kprobe));
			break;
		case LTTNG_KERNEL_KPROBE:
			event.type = LTTNG_EVENT_PROBE;
			memcpy(&event.attr.probe, &kevent->event->u.kprobe,
					sizeof(struct lttng_kernel_kprobe));
			break;
		case LTTNG_KERNEL_UPROBE:
			event.type = LTTNG_EVENT_USERSPACE_PROBE;
			break;
		case LTTNG_KERNEL_FUNCTION:
			event.type = LTTNG_EVENT_FUNCTION;
			memcpy(&event.attr.ftrace, &kevent->event->u.ftrace,
					sizeof(struct lttng_kernel_function));
			break;
		case LTTNG_KERNEL_NOOP:
			event.type = LTTNG_EVENT_NOOP;
			break;
		case LTTNG_KERNEL_SYSCALL:
			event.type = LTTNG_EVENT_SYSCALL;
			break;
		case LTTNG_KERNEL_ALL:
			/* fall-through. */
		default:
			assert(0);
			break;
		}

		ret = lttng_dynamic_buffer_append(
				&payload->buffer, &event, sizeof(event));
		if (ret) {
			ERR("Failed to append event to payload");
			ret = -LTTNG_ERR_NOMEM;
			goto end;
		}
	}

	cds_list_for_each_entry(kevent, &kchan->events_list.head , list) {
		/* Append extended info. */
		ret = append_extended_info(kevent->filter_expression, NULL,
				kevent->userspace_probe_location, payload);
		if (ret) {
			DBG("Error appending extended info message");
			ret = -LTTNG_ERR_FATAL;
			goto error;
		}
	}

end:
	return nb_event;
error:
	return ret;
}

/*
 * Add URI so the consumer output object. Set the correct path depending on the
 * domain adding the default trace directory.
 */
static enum lttng_error_code add_uri_to_consumer(
		const struct ltt_session *session,
		struct consumer_output *consumer,
		struct lttng_uri *uri, enum lttng_domain_type domain)
{
	int ret;
	enum lttng_error_code ret_code = LTTNG_OK;

	assert(uri);

	if (consumer == NULL) {
		DBG("No consumer detected. Don't add URI. Stopping.");
		ret_code = LTTNG_ERR_NO_CONSUMER;
		goto error;
	}

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		ret = lttng_strncpy(consumer->domain_subdir,
				DEFAULT_KERNEL_TRACE_DIR,
				sizeof(consumer->domain_subdir));
		break;
	case LTTNG_DOMAIN_UST:
		ret = lttng_strncpy(consumer->domain_subdir,
				DEFAULT_UST_TRACE_DIR,
				sizeof(consumer->domain_subdir));
		break;
	default:
		/*
		 * This case is possible is we try to add the URI to the global
		 * tracing session consumer object which in this case there is
		 * no subdir.
		 */
		memset(consumer->domain_subdir, 0,
				sizeof(consumer->domain_subdir));
		ret = 0;
	}
	if (ret) {
		ERR("Failed to initialize consumer output domain subdirectory");
		ret_code = LTTNG_ERR_FATAL;
		goto error;
	}

	switch (uri->dtype) {
	case LTTNG_DST_IPV4:
	case LTTNG_DST_IPV6:
		DBG2("Setting network URI to consumer");

		if (consumer->type == CONSUMER_DST_NET) {
			if ((uri->stype == LTTNG_STREAM_CONTROL &&
				consumer->dst.net.control_isset) ||
				(uri->stype == LTTNG_STREAM_DATA &&
				consumer->dst.net.data_isset)) {
				ret_code = LTTNG_ERR_URL_EXIST;
				goto error;
			}
		} else {
			memset(&consumer->dst, 0, sizeof(consumer->dst));
		}

		/* Set URI into consumer output object */
		ret = consumer_set_network_uri(session, consumer, uri);
		if (ret < 0) {
			ret_code = -ret;
			goto error;
		} else if (ret == 1) {
			/*
			 * URI was the same in the consumer so we do not append the subdir
			 * again so to not duplicate output dir.
			 */
			ret_code = LTTNG_OK;
			goto error;
		}
		break;
	case LTTNG_DST_PATH:
		if (*uri->dst.path != '/' || strstr(uri->dst.path, "../")) {
			ret_code = LTTNG_ERR_INVALID;
			goto error;
		}
		DBG2("Setting trace directory path from URI to %s",
				uri->dst.path);
		memset(&consumer->dst, 0, sizeof(consumer->dst));

		ret = lttng_strncpy(consumer->dst.session_root_path,
				uri->dst.path,
				sizeof(consumer->dst.session_root_path));
		if (ret) {
			ret_code = LTTNG_ERR_FATAL;
			goto error;
		}
		consumer->type = CONSUMER_DST_LOCAL;
		break;
	}

	ret_code = LTTNG_OK;
error:
	return ret_code;
}

/*
 * Init tracing by creating trace directory and sending fds kernel consumer.
 */
static int init_kernel_tracing(struct ltt_kernel_session *session)
{
	int ret = 0;
	struct lttng_ht_iter iter;
	struct consumer_socket *socket;

	assert(session);

	rcu_read_lock();

	if (session->consumer_fds_sent == 0 && session->consumer != NULL) {
		cds_lfht_for_each_entry(session->consumer->socks->ht, &iter.iter,
				socket, node.node) {
			pthread_mutex_lock(socket->lock);
			ret = kernel_consumer_send_session(socket, session);
			pthread_mutex_unlock(socket->lock);
			if (ret < 0) {
				ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
				goto error;
			}
		}
	}

error:
	rcu_read_unlock();
	return ret;
}

/*
 * Create a socket to the relayd using the URI.
 *
 * On success, the relayd_sock pointer is set to the created socket.
 * Else, it remains untouched and an LTTng error code is returned.
 */
static enum lttng_error_code create_connect_relayd(struct lttng_uri *uri,
		struct lttcomm_relayd_sock **relayd_sock,
		struct consumer_output *consumer)
{
	int ret;
	enum lttng_error_code status = LTTNG_OK;
	struct lttcomm_relayd_sock *rsock;

	rsock = lttcomm_alloc_relayd_sock(uri, RELAYD_VERSION_COMM_MAJOR,
			RELAYD_VERSION_COMM_MINOR);
	if (!rsock) {
		status = LTTNG_ERR_FATAL;
		goto error;
	}

	/*
	 * Connect to relayd so we can proceed with a session creation. This call
	 * can possibly block for an arbitrary amount of time to set the health
	 * state to be in poll execution.
	 */
	health_poll_entry();
	ret = relayd_connect(rsock);
	health_poll_exit();
	if (ret < 0) {
		ERR("Unable to reach lttng-relayd");
		status = LTTNG_ERR_RELAYD_CONNECT_FAIL;
		goto free_sock;
	}

	/* Create socket for control stream. */
	if (uri->stype == LTTNG_STREAM_CONTROL) {
		uint64_t result_flags;

		DBG3("Creating relayd stream socket from URI");

		/* Check relayd version */
		ret = relayd_version_check(rsock);
		if (ret == LTTNG_ERR_RELAYD_VERSION_FAIL) {
			status = LTTNG_ERR_RELAYD_VERSION_FAIL;
			goto close_sock;
		} else if (ret < 0) {
			ERR("Unable to reach lttng-relayd");
			status = LTTNG_ERR_RELAYD_CONNECT_FAIL;
			goto close_sock;
		}
		consumer->relay_major_version = rsock->major;
		consumer->relay_minor_version = rsock->minor;
		ret = relayd_get_configuration(rsock, 0,
				&result_flags);
		if (ret < 0) {
			ERR("Unable to get relayd configuration");
			status = LTTNG_ERR_RELAYD_CONNECT_FAIL;
			goto close_sock;
		}
		if (result_flags & LTTCOMM_RELAYD_CONFIGURATION_FLAG_CLEAR_ALLOWED) {
			consumer->relay_allows_clear = true;
		}
	} else if (uri->stype == LTTNG_STREAM_DATA) {
		DBG3("Creating relayd data socket from URI");
	} else {
		/* Command is not valid */
		ERR("Relayd invalid stream type: %d", uri->stype);
		status = LTTNG_ERR_INVALID;
		goto close_sock;
	}

	*relayd_sock = rsock;

	return status;

close_sock:
	/* The returned value is not useful since we are on an error path. */
	(void) relayd_close(rsock);
free_sock:
	free(rsock);
error:
	return status;
}

/*
 * Connect to the relayd using URI and send the socket to the right consumer.
 *
 * The consumer socket lock must be held by the caller.
 *
 * Returns LTTNG_OK on success or an LTTng error code on failure.
 */
static enum lttng_error_code send_consumer_relayd_socket(
		unsigned int session_id,
		struct lttng_uri *relayd_uri,
		struct consumer_output *consumer,
		struct consumer_socket *consumer_sock,
		const char *session_name, const char *hostname,
		const char *base_path, int session_live_timer,
		const uint64_t *current_chunk_id,
		time_t session_creation_time,
		bool session_name_contains_creation_time)
{
	int ret;
	struct lttcomm_relayd_sock *rsock = NULL;
	enum lttng_error_code status;

	/* Connect to relayd and make version check if uri is the control. */
	status = create_connect_relayd(relayd_uri, &rsock, consumer);
	if (status != LTTNG_OK) {
		goto relayd_comm_error;
	}
	assert(rsock);

	/* Set the network sequence index if not set. */
	if (consumer->net_seq_index == (uint64_t) -1ULL) {
		pthread_mutex_lock(&relayd_net_seq_idx_lock);
		/*
		 * Increment net_seq_idx because we are about to transfer the
		 * new relayd socket to the consumer.
		 * Assign unique key so the consumer can match streams.
		 */
		consumer->net_seq_index = ++relayd_net_seq_idx;
		pthread_mutex_unlock(&relayd_net_seq_idx_lock);
	}

	/* Send relayd socket to consumer. */
	ret = consumer_send_relayd_socket(consumer_sock, rsock, consumer,
			relayd_uri->stype, session_id,
			session_name, hostname, base_path,
			session_live_timer, current_chunk_id,
			session_creation_time, session_name_contains_creation_time);
	if (ret < 0) {
		status = LTTNG_ERR_ENABLE_CONSUMER_FAIL;
		goto close_sock;
	}

	/* Flag that the corresponding socket was sent. */
	if (relayd_uri->stype == LTTNG_STREAM_CONTROL) {
		consumer_sock->control_sock_sent = 1;
	} else if (relayd_uri->stype == LTTNG_STREAM_DATA) {
		consumer_sock->data_sock_sent = 1;
	}

	/*
	 * Close socket which was dup on the consumer side. The session daemon does
	 * NOT keep track of the relayd socket(s) once transfer to the consumer.
	 */

close_sock:
	if (status != LTTNG_OK) {
		/*
		 * The consumer output for this session should not be used anymore
		 * since the relayd connection failed thus making any tracing or/and
		 * streaming not usable.
		 */
		consumer->enabled = 0;
	}
	(void) relayd_close(rsock);
	free(rsock);

relayd_comm_error:
	return status;
}

/*
 * Send both relayd sockets to a specific consumer and domain.  This is a
 * helper function to facilitate sending the information to the consumer for a
 * session.
 *
 * The consumer socket lock must be held by the caller.
 *
 * Returns LTTNG_OK, or an LTTng error code on failure.
 */
static enum lttng_error_code send_consumer_relayd_sockets(
		enum lttng_domain_type domain,
		unsigned int session_id, struct consumer_output *consumer,
		struct consumer_socket *sock, const char *session_name,
		const char *hostname, const char *base_path, int session_live_timer,
		const uint64_t *current_chunk_id, time_t session_creation_time,
		bool session_name_contains_creation_time)
{
	enum lttng_error_code status = LTTNG_OK;

	assert(consumer);
	assert(sock);

	/* Sending control relayd socket. */
	if (!sock->control_sock_sent) {
		status = send_consumer_relayd_socket(session_id,
				&consumer->dst.net.control, consumer, sock,
				session_name, hostname, base_path, session_live_timer,
				current_chunk_id, session_creation_time,
				session_name_contains_creation_time);
		if (status != LTTNG_OK) {
			goto error;
		}
	}

	/* Sending data relayd socket. */
	if (!sock->data_sock_sent) {
		status = send_consumer_relayd_socket(session_id,
				&consumer->dst.net.data, consumer, sock,
				session_name, hostname, base_path, session_live_timer,
				current_chunk_id, session_creation_time,
				session_name_contains_creation_time);
		if (status != LTTNG_OK) {
			goto error;
		}
	}

error:
	return status;
}

/*
 * Setup relayd connections for a tracing session. First creates the socket to
 * the relayd and send them to the right domain consumer. Consumer type MUST be
 * network.
 */
int cmd_setup_relayd(struct ltt_session *session)
{
	int ret = LTTNG_OK;
	struct ltt_ust_session *usess;
	struct ltt_kernel_session *ksess;
	struct consumer_socket *socket;
	struct lttng_ht_iter iter;
	LTTNG_OPTIONAL(uint64_t) current_chunk_id = {};

	assert(session);

	usess = session->ust_session;
	ksess = session->kernel_session;

	DBG("Setting relayd for session %s", session->name);

	rcu_read_lock();
	if (session->current_trace_chunk) {
		enum lttng_trace_chunk_status status = lttng_trace_chunk_get_id(
				session->current_trace_chunk, &current_chunk_id.value);

		if (status == LTTNG_TRACE_CHUNK_STATUS_OK) {
			current_chunk_id.is_set = true;
		} else {
			ERR("Failed to get current trace chunk id");
			ret = LTTNG_ERR_UNK;
			goto error;
		}
	}

	if (usess && usess->consumer && usess->consumer->type == CONSUMER_DST_NET
			&& usess->consumer->enabled) {
		/* For each consumer socket, send relayd sockets */
		cds_lfht_for_each_entry(usess->consumer->socks->ht, &iter.iter,
				socket, node.node) {
			pthread_mutex_lock(socket->lock);
			ret = send_consumer_relayd_sockets(LTTNG_DOMAIN_UST, session->id,
					usess->consumer, socket,
					session->name, session->hostname,
					session->base_path,
					session->live_timer,
					current_chunk_id.is_set ? &current_chunk_id.value : NULL,
					session->creation_time,
					session->name_contains_creation_time);
			pthread_mutex_unlock(socket->lock);
			if (ret != LTTNG_OK) {
				goto error;
			}
			/* Session is now ready for network streaming. */
			session->net_handle = 1;
		}
		session->consumer->relay_major_version =
			usess->consumer->relay_major_version;
		session->consumer->relay_minor_version =
			usess->consumer->relay_minor_version;
		session->consumer->relay_allows_clear =
			usess->consumer->relay_allows_clear;
	}

	if (ksess && ksess->consumer && ksess->consumer->type == CONSUMER_DST_NET
			&& ksess->consumer->enabled) {
		cds_lfht_for_each_entry(ksess->consumer->socks->ht, &iter.iter,
				socket, node.node) {
			pthread_mutex_lock(socket->lock);
			ret = send_consumer_relayd_sockets(LTTNG_DOMAIN_KERNEL, session->id,
					ksess->consumer, socket,
					session->name, session->hostname,
					session->base_path,
					session->live_timer,
					current_chunk_id.is_set ? &current_chunk_id.value : NULL,
					session->creation_time,
					session->name_contains_creation_time);
			pthread_mutex_unlock(socket->lock);
			if (ret != LTTNG_OK) {
				goto error;
			}
			/* Session is now ready for network streaming. */
			session->net_handle = 1;
		}
		session->consumer->relay_major_version =
			ksess->consumer->relay_major_version;
		session->consumer->relay_minor_version =
			ksess->consumer->relay_minor_version;
		session->consumer->relay_allows_clear =
			ksess->consumer->relay_allows_clear;
	}

error:
	rcu_read_unlock();
	return ret;
}

/*
 * Start a kernel session by opening all necessary streams.
 */
int start_kernel_session(struct ltt_kernel_session *ksess)
{
	int ret;
	struct ltt_kernel_channel *kchan;

	/* Open kernel metadata */
	if (ksess->metadata == NULL && ksess->output_traces) {
		ret = kernel_open_metadata(ksess);
		if (ret < 0) {
			ret = LTTNG_ERR_KERN_META_FAIL;
			goto error;
		}
	}

	/* Open kernel metadata stream */
	if (ksess->metadata && ksess->metadata_stream_fd < 0) {
		ret = kernel_open_metadata_stream(ksess);
		if (ret < 0) {
			ERR("Kernel create metadata stream failed");
			ret = LTTNG_ERR_KERN_STREAM_FAIL;
			goto error;
		}
	}

	/* For each channel */
	cds_list_for_each_entry(kchan, &ksess->channel_list.head, list) {
		if (kchan->stream_count == 0) {
			ret = kernel_open_channel_stream(kchan);
			if (ret < 0) {
				ret = LTTNG_ERR_KERN_STREAM_FAIL;
				goto error;
			}
			/* Update the stream global counter */
			ksess->stream_count_global += ret;
		}
	}

	/* Setup kernel consumer socket and send fds to it */
	ret = init_kernel_tracing(ksess);
	if (ret != 0) {
		ret = LTTNG_ERR_KERN_START_FAIL;
		goto error;
	}

	/* This start the kernel tracing */
	ret = kernel_start_session(ksess);
	if (ret < 0) {
		ret = LTTNG_ERR_KERN_START_FAIL;
		goto error;
	}

	/* Quiescent wait after starting trace */
	kernel_wait_quiescent();

	ksess->active = 1;

	ret = LTTNG_OK;

error:
	return ret;
}

int stop_kernel_session(struct ltt_kernel_session *ksess)
{
	struct ltt_kernel_channel *kchan;
	bool error_occurred = false;
	int ret;

	if (!ksess || !ksess->active) {
		return LTTNG_OK;
	}
	DBG("Stopping kernel tracing");

	ret = kernel_stop_session(ksess);
	if (ret < 0) {
		ret = LTTNG_ERR_KERN_STOP_FAIL;
		goto error;
	}

	kernel_wait_quiescent();

	/* Flush metadata after stopping (if exists) */
	if (ksess->metadata_stream_fd >= 0) {
		ret = kernel_metadata_flush_buffer(ksess->metadata_stream_fd);
		if (ret < 0) {
			ERR("Kernel metadata flush failed");
			error_occurred = true;
		}
	}

	/* Flush all buffers after stopping */
	cds_list_for_each_entry(kchan, &ksess->channel_list.head, list) {
		ret = kernel_flush_buffer(kchan);
		if (ret < 0) {
			ERR("Kernel flush buffer error");
			error_occurred = true;
		}
	}

	ksess->active = 0;
	if (error_occurred) {
		ret = LTTNG_ERR_UNK;
	} else {
		ret = LTTNG_OK;
	}
error:
	return ret;
}

/*
 * Command LTTNG_DISABLE_CHANNEL processed by the client thread.
 */
int cmd_disable_channel(struct ltt_session *session,
		enum lttng_domain_type domain, char *channel_name)
{
	int ret;
	struct ltt_ust_session *usess;

	usess = session->ust_session;

	rcu_read_lock();

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
	{
		ret = channel_kernel_disable(session->kernel_session,
				channel_name);
		if (ret != LTTNG_OK) {
			goto error;
		}

		kernel_wait_quiescent();
		break;
	}
	case LTTNG_DOMAIN_UST:
	{
		struct ltt_ust_channel *uchan;
		struct lttng_ht *chan_ht;

		chan_ht = usess->domain_global.channels;

		uchan = trace_ust_find_channel_by_name(chan_ht, channel_name);
		if (uchan == NULL) {
			ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
			goto error;
		}

		ret = channel_ust_disable(usess, uchan);
		if (ret != LTTNG_OK) {
			goto error;
		}
		break;
	}
	default:
		ret = LTTNG_ERR_UNKNOWN_DOMAIN;
		goto error;
	}

	ret = LTTNG_OK;

error:
	rcu_read_unlock();
	return ret;
}

/*
 * Command LTTNG_ENABLE_CHANNEL processed by the client thread.
 *
 * The wpipe arguments is used as a notifier for the kernel thread.
 */
int cmd_enable_channel(struct ltt_session *session,
		const struct lttng_domain *domain, const struct lttng_channel *_attr, int wpipe)
{
	int ret;
	struct ltt_ust_session *usess = session->ust_session;
	struct lttng_ht *chan_ht;
	size_t len;
	struct lttng_channel attr;

	assert(session);
	assert(_attr);
	assert(domain);

	attr = *_attr;
	len = lttng_strnlen(attr.name, sizeof(attr.name));

	/* Validate channel name */
	if (attr.name[0] == '.' ||
		memchr(attr.name, '/', len) != NULL) {
		ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
		goto end;
	}

	DBG("Enabling channel %s for session %s", attr.name, session->name);

	rcu_read_lock();

	/*
	 * Don't try to enable a channel if the session has been started at
	 * some point in time before. The tracer does not allow it.
	 */
	if (session->has_been_started) {
		ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
		goto error;
	}

	/*
	 * If the session is a live session, remove the switch timer, the
	 * live timer does the same thing but sends also synchronisation
	 * beacons for inactive streams.
	 */
	if (session->live_timer > 0) {
		attr.attr.live_timer_interval = session->live_timer;
		attr.attr.switch_timer_interval = 0;
	}

	/* Check for feature support */
	switch (domain->type) {
	case LTTNG_DOMAIN_KERNEL:
	{
		if (kernel_supports_ring_buffer_snapshot_sample_positions() != 1) {
			/* Sampling position of buffer is not supported */
			WARN("Kernel tracer does not support buffer monitoring. "
					"Setting the monitor interval timer to 0 "
					"(disabled) for channel '%s' of session '%s'",
					attr.name, session->name);
			lttng_channel_set_monitor_timer_interval(&attr, 0);
		}
		break;
	}
	case LTTNG_DOMAIN_UST:
		break;
	case LTTNG_DOMAIN_JUL:
	case LTTNG_DOMAIN_LOG4J:
	case LTTNG_DOMAIN_PYTHON:
		if (!agent_tracing_is_enabled()) {
			DBG("Attempted to enable a channel in an agent domain but the agent thread is not running");
			ret = LTTNG_ERR_AGENT_TRACING_DISABLED;
			goto error;
		}
		break;
	default:
		ret = LTTNG_ERR_UNKNOWN_DOMAIN;
		goto error;
	}

	switch (domain->type) {
	case LTTNG_DOMAIN_KERNEL:
	{
		struct ltt_kernel_channel *kchan;

		kchan = trace_kernel_get_channel_by_name(attr.name,
				session->kernel_session);
		if (kchan == NULL) {
			if (session->snapshot.nb_output > 0 ||
					session->snapshot_mode) {
				/* Enforce mmap output for snapshot sessions. */
				attr.attr.output = LTTNG_EVENT_MMAP;
			}
			ret = channel_kernel_create(session->kernel_session, &attr, wpipe);
			if (attr.name[0] != '\0') {
				session->kernel_session->has_non_default_channel = 1;
			}
		} else {
			ret = channel_kernel_enable(session->kernel_session, kchan);
		}

		if (ret != LTTNG_OK) {
			goto error;
		}

		kernel_wait_quiescent();
		break;
	}
	case LTTNG_DOMAIN_UST:
	case LTTNG_DOMAIN_JUL:
	case LTTNG_DOMAIN_LOG4J:
	case LTTNG_DOMAIN_PYTHON:
	{
		struct ltt_ust_channel *uchan;

		/*
		 * FIXME
		 *
		 * Current agent implementation limitations force us to allow
		 * only one channel at once in "agent" subdomains. Each
		 * subdomain has a default channel name which must be strictly
		 * adhered to.
		 */
		if (domain->type == LTTNG_DOMAIN_JUL) {
			if (strncmp(attr.name, DEFAULT_JUL_CHANNEL_NAME,
					LTTNG_SYMBOL_NAME_LEN)) {
				ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
				goto error;
			}
		} else if (domain->type == LTTNG_DOMAIN_LOG4J) {
			if (strncmp(attr.name, DEFAULT_LOG4J_CHANNEL_NAME,
					LTTNG_SYMBOL_NAME_LEN)) {
				ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
				goto error;
			}
		} else if (domain->type == LTTNG_DOMAIN_PYTHON) {
			if (strncmp(attr.name, DEFAULT_PYTHON_CHANNEL_NAME,
					LTTNG_SYMBOL_NAME_LEN)) {
				ret = LTTNG_ERR_INVALID_CHANNEL_NAME;
				goto error;
			}
		}

		chan_ht = usess->domain_global.channels;

		uchan = trace_ust_find_channel_by_name(chan_ht, attr.name);
		if (uchan == NULL) {
			ret = channel_ust_create(usess, &attr, domain->buf_type);
			if (attr.name[0] != '\0') {
				usess->has_non_default_channel = 1;
			}
		} else {
			ret = channel_ust_enable(usess, uchan);
		}
		break;
	}
	default:
		ret = LTTNG_ERR_UNKNOWN_DOMAIN;
		goto error;
	}

	if (ret == LTTNG_OK && attr.attr.output != LTTNG_EVENT_MMAP) {
		session->has_non_mmap_channel = true;
	}
error:
	rcu_read_unlock();
end:
	return ret;
}

enum lttng_error_code cmd_process_attr_tracker_get_tracking_policy(
		struct ltt_session *session,
		enum lttng_domain_type domain,
		enum lttng_process_attr process_attr,
		enum lttng_tracking_policy *policy)
{
	enum lttng_error_code ret_code = LTTNG_OK;
	const struct process_attr_tracker *tracker;

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		if (!session->kernel_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		tracker = kernel_get_process_attr_tracker(
				session->kernel_session, process_attr);
		break;
	case LTTNG_DOMAIN_UST:
		if (!session->ust_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		tracker = trace_ust_get_process_attr_tracker(
				session->ust_session, process_attr);
		break;
	default:
		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
		goto end;
	}
	if (tracker) {
		*policy = process_attr_tracker_get_tracking_policy(tracker);
	} else {
		ret_code = LTTNG_ERR_INVALID;
	}
end:
	return ret_code;
}

enum lttng_error_code cmd_process_attr_tracker_set_tracking_policy(
		struct ltt_session *session,
		enum lttng_domain_type domain,
		enum lttng_process_attr process_attr,
		enum lttng_tracking_policy policy)
{
	enum lttng_error_code ret_code = LTTNG_OK;

	switch (policy) {
	case LTTNG_TRACKING_POLICY_INCLUDE_SET:
	case LTTNG_TRACKING_POLICY_EXCLUDE_ALL:
	case LTTNG_TRACKING_POLICY_INCLUDE_ALL:
		break;
	default:
		ret_code = LTTNG_ERR_INVALID;
		goto end;
	}

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		if (!session->kernel_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		ret_code = kernel_process_attr_tracker_set_tracking_policy(
				session->kernel_session, process_attr, policy);
		break;
	case LTTNG_DOMAIN_UST:
		if (!session->ust_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		ret_code = trace_ust_process_attr_tracker_set_tracking_policy(
				session->ust_session, process_attr, policy);
		break;
	default:
		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
		break;
	}
end:
	return ret_code;
}

enum lttng_error_code cmd_process_attr_tracker_inclusion_set_add_value(
		struct ltt_session *session,
		enum lttng_domain_type domain,
		enum lttng_process_attr process_attr,
		const struct process_attr_value *value)
{
	enum lttng_error_code ret_code = LTTNG_OK;

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		if (!session->kernel_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		ret_code = kernel_process_attr_tracker_inclusion_set_add_value(
				session->kernel_session, process_attr, value);
		break;
	case LTTNG_DOMAIN_UST:
		if (!session->ust_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		ret_code = trace_ust_process_attr_tracker_inclusion_set_add_value(
				session->ust_session, process_attr, value);
		break;
	default:
		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
		break;
	}
end:
	return ret_code;
}

enum lttng_error_code cmd_process_attr_tracker_inclusion_set_remove_value(
		struct ltt_session *session,
		enum lttng_domain_type domain,
		enum lttng_process_attr process_attr,
		const struct process_attr_value *value)
{
	enum lttng_error_code ret_code = LTTNG_OK;

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		if (!session->kernel_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		ret_code = kernel_process_attr_tracker_inclusion_set_remove_value(
				session->kernel_session, process_attr, value);
		break;
	case LTTNG_DOMAIN_UST:
		if (!session->ust_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		ret_code = trace_ust_process_attr_tracker_inclusion_set_remove_value(
				session->ust_session, process_attr, value);
		break;
	default:
		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
		break;
	}
end:
	return ret_code;
}

enum lttng_error_code cmd_process_attr_tracker_get_inclusion_set(
		struct ltt_session *session,
		enum lttng_domain_type domain,
		enum lttng_process_attr process_attr,
		struct lttng_process_attr_values **values)
{
	enum lttng_error_code ret_code = LTTNG_OK;
	const struct process_attr_tracker *tracker;
	enum process_attr_tracker_status status;

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		if (!session->kernel_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		tracker = kernel_get_process_attr_tracker(
				session->kernel_session, process_attr);
		break;
	case LTTNG_DOMAIN_UST:
		if (!session->ust_session) {
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
		tracker = trace_ust_get_process_attr_tracker(
				session->ust_session, process_attr);
		break;
	default:
		ret_code = LTTNG_ERR_UNSUPPORTED_DOMAIN;
		goto end;
	}

	if (!tracker) {
		ret_code = LTTNG_ERR_INVALID;
		goto end;
	}

	status = process_attr_tracker_get_inclusion_set(tracker, values);
	switch (status) {
	case PROCESS_ATTR_TRACKER_STATUS_OK:
		ret_code = LTTNG_OK;
		break;
	case PROCESS_ATTR_TRACKER_STATUS_INVALID_TRACKING_POLICY:
		ret_code = LTTNG_ERR_PROCESS_ATTR_TRACKER_INVALID_TRACKING_POLICY;
		break;
	case PROCESS_ATTR_TRACKER_STATUS_ERROR:
		ret_code = LTTNG_ERR_NOMEM;
		break;
	default:
		ret_code = LTTNG_ERR_UNK;
		break;
	}

end:
	return ret_code;
}

/*
 * Command LTTNG_DISABLE_EVENT processed by the client thread.
 */
int cmd_disable_event(struct ltt_session *session,
		enum lttng_domain_type domain, const char *channel_name,
		const struct lttng_event *event)
{
	int ret;
	const char *event_name;

	DBG("Disable event command for event \'%s\'", event->name);

	event_name = event->name;

	/* Error out on unhandled search criteria */
	if (event->loglevel_type || event->loglevel != -1 || event->enabled
			|| event->pid || event->filter || event->exclusion) {
		ret = LTTNG_ERR_UNK;
		goto error;
	}

	rcu_read_lock();

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
	{
		struct ltt_kernel_channel *kchan;
		struct ltt_kernel_session *ksess;

		ksess = session->kernel_session;

		/*
		 * If a non-default channel has been created in the
		 * session, explicitely require that -c chan_name needs
		 * to be provided.
		 */
		if (ksess->has_non_default_channel && channel_name[0] == '\0') {
			ret = LTTNG_ERR_NEED_CHANNEL_NAME;
			goto error_unlock;
		}

		kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
		if (kchan == NULL) {
			ret = LTTNG_ERR_KERN_CHAN_NOT_FOUND;
			goto error_unlock;
		}

		switch (event->type) {
		case LTTNG_EVENT_ALL:
		case LTTNG_EVENT_TRACEPOINT:
		case LTTNG_EVENT_SYSCALL:
		case LTTNG_EVENT_PROBE:
		case LTTNG_EVENT_FUNCTION:
		case LTTNG_EVENT_FUNCTION_ENTRY:/* fall-through */
			if (event_name[0] == '\0') {
				ret = event_kernel_disable_event(kchan,
					NULL, event->type);
			} else {
				ret = event_kernel_disable_event(kchan,
					event_name, event->type);
			}
			if (ret != LTTNG_OK) {
				goto error_unlock;
			}
			break;
		default:
			ret = LTTNG_ERR_UNK;
			goto error_unlock;
		}

		kernel_wait_quiescent();
		break;
	}
	case LTTNG_DOMAIN_UST:
	{
		struct ltt_ust_channel *uchan;
		struct ltt_ust_session *usess;

		usess = session->ust_session;

		if (validate_ust_event_name(event_name)) {
			ret = LTTNG_ERR_INVALID_EVENT_NAME;
			goto error_unlock;
		}

		/*
		 * If a non-default channel has been created in the
		 * session, explicitly require that -c chan_name needs
		 * to be provided.
		 */
		if (usess->has_non_default_channel && channel_name[0] == '\0') {
			ret = LTTNG_ERR_NEED_CHANNEL_NAME;
			goto error_unlock;
		}

		uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
				channel_name);
		if (uchan == NULL) {
			ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
			goto error_unlock;
		}

		switch (event->type) {
		case LTTNG_EVENT_ALL:
			/*
			 * An empty event name means that everything
			 * should be disabled.
			 */
			if (event->name[0] == '\0') {
				ret = event_ust_disable_all_tracepoints(usess, uchan);
			} else {
				ret = event_ust_disable_tracepoint(usess, uchan,
						event_name);
			}
			if (ret != LTTNG_OK) {
				goto error_unlock;
			}
			break;
		default:
			ret = LTTNG_ERR_UNK;
			goto error_unlock;
		}

		DBG3("Disable UST event %s in channel %s completed", event_name,
				channel_name);
		break;
	}
	case LTTNG_DOMAIN_LOG4J:
	case LTTNG_DOMAIN_JUL:
	case LTTNG_DOMAIN_PYTHON:
	{
		struct agent *agt;
		struct ltt_ust_session *usess = session->ust_session;

		assert(usess);

		switch (event->type) {
		case LTTNG_EVENT_ALL:
			break;
		default:
			ret = LTTNG_ERR_UNK;
			goto error_unlock;
		}

		agt = trace_ust_find_agent(usess, domain);
		if (!agt) {
			ret = -LTTNG_ERR_UST_EVENT_NOT_FOUND;
			goto error_unlock;
		}
		/*
		 * An empty event name means that everything
		 * should be disabled.
		 */
		if (event->name[0] == '\0') {
			ret = event_agent_disable_all(usess, agt);
		} else {
			ret = event_agent_disable(usess, agt, event_name);
		}
		if (ret != LTTNG_OK) {
			goto error_unlock;
		}

		break;
	}
	default:
		ret = LTTNG_ERR_UND;
		goto error_unlock;
	}

	ret = LTTNG_OK;

error_unlock:
	rcu_read_unlock();
error:
	return ret;
}

/*
 * Command LTTNG_ADD_CONTEXT processed by the client thread.
 */
int cmd_add_context(struct ltt_session *session, enum lttng_domain_type domain,
		char *channel_name, const struct lttng_event_context *ctx, int kwpipe)
{
	int ret, chan_kern_created = 0, chan_ust_created = 0;
	char *app_ctx_provider_name = NULL, *app_ctx_name = NULL;

	/*
	 * Don't try to add a context if the session has been started at
	 * some point in time before. The tracer does not allow it and would
	 * result in a corrupted trace.
	 */
	if (session->has_been_started) {
		ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
		goto end;
	}

	if (ctx->ctx == LTTNG_EVENT_CONTEXT_APP_CONTEXT) {
		app_ctx_provider_name = ctx->u.app_ctx.provider_name;
		app_ctx_name = ctx->u.app_ctx.ctx_name;
	}

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		assert(session->kernel_session);

		if (session->kernel_session->channel_count == 0) {
			/* Create default channel */
			ret = channel_kernel_create(session->kernel_session, NULL, kwpipe);
			if (ret != LTTNG_OK) {
				goto error;
			}
			chan_kern_created = 1;
		}
		/* Add kernel context to kernel tracer */
		ret = context_kernel_add(session->kernel_session, ctx, channel_name);
		if (ret != LTTNG_OK) {
			goto error;
		}
		break;
	case LTTNG_DOMAIN_JUL:
	case LTTNG_DOMAIN_LOG4J:
	{
		/*
		 * Validate channel name.
		 * If no channel name is given and the domain is JUL or LOG4J,
		 * set it to the appropriate domain-specific channel name. If
		 * a name is provided but does not match the expexted channel
		 * name, return an error.
		 */
		if (domain == LTTNG_DOMAIN_JUL && *channel_name &&
				strcmp(channel_name,
				DEFAULT_JUL_CHANNEL_NAME)) {
			ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
			goto error;
		} else if (domain == LTTNG_DOMAIN_LOG4J && *channel_name &&
				strcmp(channel_name,
				DEFAULT_LOG4J_CHANNEL_NAME)) {
			ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
			goto error;
		}
		/* break is _not_ missing here. */
	}
	case LTTNG_DOMAIN_UST:
	{
		struct ltt_ust_session *usess = session->ust_session;
		unsigned int chan_count;

		assert(usess);

		chan_count = lttng_ht_get_count(usess->domain_global.channels);
		if (chan_count == 0) {
			struct lttng_channel *attr;
			/* Create default channel */
			attr = channel_new_default_attr(domain, usess->buffer_type);
			if (attr == NULL) {
				ret = LTTNG_ERR_FATAL;
				goto error;
			}

			ret = channel_ust_create(usess, attr, usess->buffer_type);
			if (ret != LTTNG_OK) {
				free(attr);
				goto error;
			}
			channel_attr_destroy(attr);
			chan_ust_created = 1;
		}

		ret = context_ust_add(usess, domain, ctx, channel_name);
		free(app_ctx_provider_name);
		free(app_ctx_name);
		app_ctx_name = NULL;
		app_ctx_provider_name = NULL;
		if (ret != LTTNG_OK) {
			goto error;
		}
		break;
	}
	default:
		ret = LTTNG_ERR_UND;
		goto error;
	}

	ret = LTTNG_OK;
	goto end;

error:
	if (chan_kern_created) {
		struct ltt_kernel_channel *kchan =
			trace_kernel_get_channel_by_name(DEFAULT_CHANNEL_NAME,
					session->kernel_session);
		/* Created previously, this should NOT fail. */
		assert(kchan);
		kernel_destroy_channel(kchan);
	}

	if (chan_ust_created) {
		struct ltt_ust_channel *uchan =
			trace_ust_find_channel_by_name(
					session->ust_session->domain_global.channels,
					DEFAULT_CHANNEL_NAME);
		/* Created previously, this should NOT fail. */
		assert(uchan);
		/* Remove from the channel list of the session. */
		trace_ust_delete_channel(session->ust_session->domain_global.channels,
				uchan);
		trace_ust_destroy_channel(uchan);
	}
end:
	free(app_ctx_provider_name);
	free(app_ctx_name);
	return ret;
}

static inline bool name_starts_with(const char *name, const char *prefix)
{
	const size_t max_cmp_len = min(strlen(prefix), LTTNG_SYMBOL_NAME_LEN);

	return !strncmp(name, prefix, max_cmp_len);
}

/* Perform userspace-specific event name validation */
static int validate_ust_event_name(const char *name)
{
	int ret = 0;

	if (!name) {
		ret = -1;
		goto end;
	}

	/*
	 * Check name against all internal UST event component namespaces used
	 * by the agents.
	 */
	if (name_starts_with(name, DEFAULT_JUL_EVENT_COMPONENT) ||
		name_starts_with(name, DEFAULT_LOG4J_EVENT_COMPONENT) ||
		name_starts_with(name, DEFAULT_PYTHON_EVENT_COMPONENT)) {
		ret = -1;
	}

end:
	return ret;
}

/*
 * Internal version of cmd_enable_event() with a supplemental
 * "internal_event" flag which is used to enable internal events which should
 * be hidden from clients. Such events are used in the agent implementation to
 * enable the events through which all "agent" events are funeled.
 */
static int _cmd_enable_event(struct ltt_session *session,
		const struct lttng_domain *domain,
		char *channel_name, struct lttng_event *event,
		char *filter_expression,
		struct lttng_bytecode *filter,
		struct lttng_event_exclusion *exclusion,
		int wpipe, bool internal_event)
{
	int ret = 0, channel_created = 0;
	struct lttng_channel *attr = NULL;

	assert(session);
	assert(event);
	assert(channel_name);

	/* If we have a filter, we must have its filter expression */
	assert(!(!!filter_expression ^ !!filter));

	/* Normalize event name as a globbing pattern */
	strutils_normalize_star_glob_pattern(event->name);

	/* Normalize exclusion names as globbing patterns */
	if (exclusion) {
		size_t i;

		for (i = 0; i < exclusion->count; i++) {
			char *name = LTTNG_EVENT_EXCLUSION_NAME_AT(exclusion, i);

			strutils_normalize_star_glob_pattern(name);
		}
	}

	DBG("Enable event command for event \'%s\'", event->name);

	rcu_read_lock();

	switch (domain->type) {
	case LTTNG_DOMAIN_KERNEL:
	{
		struct ltt_kernel_channel *kchan;

		/*
		 * If a non-default channel has been created in the
		 * session, explicitely require that -c chan_name needs
		 * to be provided.
		 */
		if (session->kernel_session->has_non_default_channel
				&& channel_name[0] == '\0') {
			ret = LTTNG_ERR_NEED_CHANNEL_NAME;
			goto error;
		}

		kchan = trace_kernel_get_channel_by_name(channel_name,
				session->kernel_session);
		if (kchan == NULL) {
			attr = channel_new_default_attr(LTTNG_DOMAIN_KERNEL,
					LTTNG_BUFFER_GLOBAL);
			if (attr == NULL) {
				ret = LTTNG_ERR_FATAL;
				goto error;
			}
			if (lttng_strncpy(attr->name, channel_name,
					sizeof(attr->name))) {
				ret = LTTNG_ERR_INVALID;
				goto error;
			}

			ret = cmd_enable_channel(session, domain, attr, wpipe);
			if (ret != LTTNG_OK) {
				goto error;
			}
			channel_created = 1;
		}

		/* Get the newly created kernel channel pointer */
		kchan = trace_kernel_get_channel_by_name(channel_name,
				session->kernel_session);
		if (kchan == NULL) {
			/* This sould not happen... */
			ret = LTTNG_ERR_FATAL;
			goto error;
		}

		switch (event->type) {
		case LTTNG_EVENT_ALL:
		{
			char *filter_expression_a = NULL;
			struct lttng_bytecode *filter_a = NULL;

			/*
			 * We need to duplicate filter_expression and filter,
			 * because ownership is passed to first enable
			 * event.
			 */
			if (filter_expression) {
				filter_expression_a = strdup(filter_expression);
				if (!filter_expression_a) {
					ret = LTTNG_ERR_FATAL;
					goto error;
				}
			}
			if (filter) {
				filter_a = zmalloc(sizeof(*filter_a) + filter->len);
				if (!filter_a) {
					free(filter_expression_a);
					ret = LTTNG_ERR_FATAL;
					goto error;
				}
				memcpy(filter_a, filter, sizeof(*filter_a) + filter->len);
			}
			event->type = LTTNG_EVENT_TRACEPOINT;	/* Hack */
			ret = event_kernel_enable_event(kchan, event,
				filter_expression, filter);
			/* We have passed ownership */
			filter_expression = NULL;
			filter = NULL;
			if (ret != LTTNG_OK) {
				if (channel_created) {
					/* Let's not leak a useless channel. */
					kernel_destroy_channel(kchan);
				}
				free(filter_expression_a);
				free(filter_a);
				goto error;
			}
			event->type = LTTNG_EVENT_SYSCALL;	/* Hack */
			ret = event_kernel_enable_event(kchan, event,
				filter_expression_a, filter_a);
			/* We have passed ownership */
			filter_expression_a = NULL;
			filter_a = NULL;
			if (ret != LTTNG_OK) {
				goto error;
			}
			break;
		}
		case LTTNG_EVENT_PROBE:
		case LTTNG_EVENT_USERSPACE_PROBE:
		case LTTNG_EVENT_FUNCTION:
		case LTTNG_EVENT_FUNCTION_ENTRY:
		case LTTNG_EVENT_TRACEPOINT:
			ret = event_kernel_enable_event(kchan, event,
				filter_expression, filter);
			/* We have passed ownership */
			filter_expression = NULL;
			filter = NULL;
			if (ret != LTTNG_OK) {
				if (channel_created) {
					/* Let's not leak a useless channel. */
					kernel_destroy_channel(kchan);
				}
				goto error;
			}
			break;
		case LTTNG_EVENT_SYSCALL:
			ret = event_kernel_enable_event(kchan, event,
				filter_expression, filter);
			/* We have passed ownership */
			filter_expression = NULL;
			filter = NULL;
			if (ret != LTTNG_OK) {
				goto error;
			}
			break;
		default:
			ret = LTTNG_ERR_UNK;
			goto error;
		}

		kernel_wait_quiescent();
		break;
	}
	case LTTNG_DOMAIN_UST:
	{
		struct ltt_ust_channel *uchan;
		struct ltt_ust_session *usess = session->ust_session;

		assert(usess);

		/*
		 * If a non-default channel has been created in the
		 * session, explicitely require that -c chan_name needs
		 * to be provided.
		 */
		if (usess->has_non_default_channel && channel_name[0] == '\0') {
			ret = LTTNG_ERR_NEED_CHANNEL_NAME;
			goto error;
		}

		/* Get channel from global UST domain */
		uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
				channel_name);
		if (uchan == NULL) {
			/* Create default channel */
			attr = channel_new_default_attr(LTTNG_DOMAIN_UST,
					usess->buffer_type);
			if (attr == NULL) {
				ret = LTTNG_ERR_FATAL;
				goto error;
			}
			if (lttng_strncpy(attr->name, channel_name,
					sizeof(attr->name))) {
				ret = LTTNG_ERR_INVALID;
				goto error;
			}

			ret = cmd_enable_channel(session, domain, attr, wpipe);
			if (ret != LTTNG_OK) {
				goto error;
			}

			/* Get the newly created channel reference back */
			uchan = trace_ust_find_channel_by_name(
					usess->domain_global.channels, channel_name);
			assert(uchan);
		}

		if (uchan->domain != LTTNG_DOMAIN_UST && !internal_event) {
			/*
			 * Don't allow users to add UST events to channels which
			 * are assigned to a userspace subdomain (JUL, Log4J,
			 * Python, etc.).
			 */
			ret = LTTNG_ERR_INVALID_CHANNEL_DOMAIN;
			goto error;
		}

		if (!internal_event) {
			/*
			 * Ensure the event name is not reserved for internal
			 * use.
			 */
			ret = validate_ust_event_name(event->name);
			if (ret) {
				WARN("Userspace event name %s failed validation.",
						event->name);
				ret = LTTNG_ERR_INVALID_EVENT_NAME;
				goto error;
			}
		}

		/* At this point, the session and channel exist on the tracer */
		ret = event_ust_enable_tracepoint(usess, uchan, event,
				filter_expression, filter, exclusion,
				internal_event);
		/* We have passed ownership */
		filter_expression = NULL;
		filter = NULL;
		exclusion = NULL;
		if (ret == LTTNG_ERR_UST_EVENT_ENABLED) {
			goto already_enabled;
		} else if (ret != LTTNG_OK) {
			goto error;
		}
		break;
	}
	case LTTNG_DOMAIN_LOG4J:
	case LTTNG_DOMAIN_JUL:
	case LTTNG_DOMAIN_PYTHON:
	{
		const char *default_event_name, *default_chan_name;
		struct agent *agt;
		struct lttng_event uevent;
		struct lttng_domain tmp_dom;
		struct ltt_ust_session *usess = session->ust_session;

		assert(usess);

		if (!agent_tracing_is_enabled()) {
			DBG("Attempted to enable an event in an agent domain but the agent thread is not running");
			ret = LTTNG_ERR_AGENT_TRACING_DISABLED;
			goto error;
		}

		agt = trace_ust_find_agent(usess, domain->type);
		if (!agt) {
			agt = agent_create(domain->type);
			if (!agt) {
				ret = LTTNG_ERR_NOMEM;
				goto error;
			}
			agent_add(agt, usess->agents);
		}

		/* Create the default tracepoint. */
		memset(&uevent, 0, sizeof(uevent));
		uevent.type = LTTNG_EVENT_TRACEPOINT;
		uevent.loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
		default_event_name = event_get_default_agent_ust_name(
				domain->type);
		if (!default_event_name) {
			ret = LTTNG_ERR_FATAL;
			goto error;
		}
		strncpy(uevent.name, default_event_name, sizeof(uevent.name));
		uevent.name[sizeof(uevent.name) - 1] = '\0';

		/*
		 * The domain type is changed because we are about to enable the
		 * default channel and event for the JUL domain that are hardcoded.
		 * This happens in the UST domain.
		 */
		memcpy(&tmp_dom, domain, sizeof(tmp_dom));
		tmp_dom.type = LTTNG_DOMAIN_UST;

		switch (domain->type) {
		case LTTNG_DOMAIN_LOG4J:
			default_chan_name = DEFAULT_LOG4J_CHANNEL_NAME;
			break;
		case LTTNG_DOMAIN_JUL:
			default_chan_name = DEFAULT_JUL_CHANNEL_NAME;
			break;
		case LTTNG_DOMAIN_PYTHON:
			default_chan_name = DEFAULT_PYTHON_CHANNEL_NAME;
			break;
		default:
			/* The switch/case we are in makes this impossible */
			assert(0);
		}

		{
			char *filter_expression_copy = NULL;
			struct lttng_bytecode *filter_copy = NULL;

			if (filter) {
				const size_t filter_size = sizeof(
						struct lttng_bytecode)
						+ filter->len;

				filter_copy = zmalloc(filter_size);
				if (!filter_copy) {
					ret = LTTNG_ERR_NOMEM;
					goto error;
				}
				memcpy(filter_copy, filter, filter_size);

				filter_expression_copy =
						strdup(filter_expression);
				if (!filter_expression) {
					ret = LTTNG_ERR_NOMEM;
				}

				if (!filter_expression_copy || !filter_copy) {
					free(filter_expression_copy);
					free(filter_copy);
					goto error;
				}
			}

			ret = cmd_enable_event_internal(session, &tmp_dom,
					(char *) default_chan_name,
					&uevent, filter_expression_copy,
					filter_copy, NULL, wpipe);
		}

		if (ret == LTTNG_ERR_UST_EVENT_ENABLED) {
			goto already_enabled;
		} else if (ret != LTTNG_OK) {
			goto error;
		}

		/* The wild card * means that everything should be enabled. */
		if (strncmp(event->name, "*", 1) == 0 && strlen(event->name) == 1) {
			ret = event_agent_enable_all(usess, agt, event, filter,
					filter_expression);
		} else {
			ret = event_agent_enable(usess, agt, event, filter,
					filter_expression);
		}
		filter = NULL;
		filter_expression = NULL;
		if (ret != LTTNG_OK) {
			goto error;
		}

		break;
	}
	default:
		ret = LTTNG_ERR_UND;
		goto error;
	}

	ret = LTTNG_OK;

already_enabled:
error:
	free(filter_expression);
	free(filter);
	free(exclusion);
	channel_attr_destroy(attr);
	rcu_read_unlock();
	return ret;
}

/*
 * Command LTTNG_ENABLE_EVENT processed by the client thread.
 * We own filter, exclusion, and filter_expression.
 */
int cmd_enable_event(struct ltt_session *session,
		const struct lttng_domain *domain,
		char *channel_name, struct lttng_event *event,
		char *filter_expression,
		struct lttng_bytecode *filter,
		struct lttng_event_exclusion *exclusion,
		int wpipe)
{
	return _cmd_enable_event(session, domain, channel_name, event,
			filter_expression, filter, exclusion, wpipe, false);
}

/*
 * Enable an event which is internal to LTTng. An internal should
 * never be made visible to clients and are immune to checks such as
 * reserved names.
 */
static int cmd_enable_event_internal(struct ltt_session *session,
		const struct lttng_domain *domain,
		char *channel_name, struct lttng_event *event,
		char *filter_expression,
		struct lttng_bytecode *filter,
		struct lttng_event_exclusion *exclusion,
		int wpipe)
{
	return _cmd_enable_event(session, domain, channel_name, event,
			filter_expression, filter, exclusion, wpipe, true);
}

/*
 * Command LTTNG_LIST_TRACEPOINTS processed by the client thread.
 */
ssize_t cmd_list_tracepoints(enum lttng_domain_type domain,
		struct lttng_event **events)
{
	int ret;
	ssize_t nb_events = 0;

	switch (domain) {
	case LTTNG_DOMAIN_KERNEL:
		nb_events = kernel_list_events(events);
		if (nb_events < 0) {
			ret = LTTNG_ERR_KERN_LIST_FAIL;
			goto error;
		}
		break;
	case LTTNG_DOMAIN_UST:
		nb_events = ust_app_list_events(events);
		if (nb_events < 0) {
			ret = LTTNG_ERR_UST_LIST_FAIL;
			goto error;
		}
		break;
	case LTTNG_DOMAIN_LOG4J:
	case LTTNG_DOMAIN_JUL:
	case LTTNG_DOMAIN_PYTHON:
		nb_events = agent_list_events(events, domain);
		if (nb_events < 0) {
			ret = LTTNG_ERR_UST_LIST_FAIL;
			goto error;
		}
		break;
	default:
		ret = LTTNG_ERR_UND;
		goto error;
	}

	return nb_events;

error:
	/* Return negative value to differentiate return code */
	return -ret;
}

/*
 * Command LTTNG_LIST_TRACEPOINT_FIELDS processed by the client thread.
 */
ssize_t cmd_list_tracepoint_fields(enum lttng_domain_type domain,
		struct lttng_event_field **fields)
{
	int ret;
	ssize_t nb_fields = 0;

	switch (domain) {
	case LTTNG_DOMAIN_UST:
		nb_fields = ust_app_list_event_fields(fields);
		if (nb_fields < 0) {
			ret = LTTNG_ERR_UST_LIST_FAIL;
			goto error;
		}
		break;
	case LTTNG_DOMAIN_KERNEL:
	default:	/* fall-through */
		ret = LTTNG_ERR_UND;
		goto error;
	}

	return nb_fields;

error:
	/* Return negative value to differentiate return code */
	return -ret;
}

ssize_t cmd_list_syscalls(struct lttng_event **events)
{
	return syscall_table_list(events);
}

/*
 * Command LTTNG_START_TRACE processed by the client thread.
 *
 * Called with session mutex held.
 */
int cmd_start_trace(struct ltt_session *session)
{
	enum lttng_error_code ret;
	unsigned long nb_chan = 0;
	struct ltt_kernel_session *ksession;
	struct ltt_ust_session *usess;
	const bool session_rotated_after_last_stop =
			session->rotated_after_last_stop;
	const bool session_cleared_after_last_stop =
			session->cleared_after_last_stop;

	assert(session);

	/* Ease our life a bit ;) */
	ksession = session->kernel_session;
	usess = session->ust_session;

	/* Is the session already started? */
	if (session->active) {
		ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
		/* Perform nothing */
		goto end;
	}

	if (session->rotation_state == LTTNG_ROTATION_STATE_ONGOING &&
			!session->current_trace_chunk) {
		/*
		 * A rotation was launched while the session was stopped and
		 * it has not been completed yet. It is not possible to start
		 * the session since starting the session here would require a
		 * rotation from "NULL" to a new trace chunk. That rotation
		 * would overlap with the ongoing rotation, which is not
		 * supported.
		 */
		WARN("Refusing to start session \"%s\" as a rotation launched after the last \"stop\" is still ongoing",
				session->name);
		ret = LTTNG_ERR_ROTATION_PENDING;
		goto error;
	}

	/*
	 * Starting a session without channel is useless since after that it's not
	 * possible to enable channel thus inform the client.
	 */
	if (usess && usess->domain_global.channels) {
		nb_chan += lttng_ht_get_count(usess->domain_global.channels);
	}
	if (ksession) {
		nb_chan += ksession->channel_count;
	}
	if (!nb_chan) {
		ret = LTTNG_ERR_NO_CHANNEL;
		goto error;
	}

	session->active = 1;
	session->rotated_after_last_stop = false;
	session->cleared_after_last_stop = false;
	if (session->output_traces && !session->current_trace_chunk) {
		if (!session->has_been_started) {
			struct lttng_trace_chunk *trace_chunk;

			DBG("Creating initial trace chunk of session \"%s\"",
					session->name);
			trace_chunk = session_create_new_trace_chunk(
					session, NULL, NULL, NULL);
			if (!trace_chunk) {
				ret = LTTNG_ERR_CREATE_DIR_FAIL;
				goto error;
			}
			assert(!session->current_trace_chunk);
			ret = session_set_trace_chunk(session, trace_chunk,
					NULL);
			lttng_trace_chunk_put(trace_chunk);
			if (ret) {
				ret = LTTNG_ERR_CREATE_TRACE_CHUNK_FAIL_CONSUMER;
				goto error;
			}
		} else {
			DBG("Rotating session \"%s\" from its current \"NULL\" trace chunk to a new chunk",
					session->name);
			/*
			 * Rotate existing streams into the new chunk.
			 * This is a "quiet" rotation has no client has
			 * explicitly requested this operation.
			 *
			 * There is also no need to wait for the rotation
			 * to complete as it will happen immediately. No data
			 * was produced as the session was stopped, so the
			 * rotation should happen on reception of the command.
			 */
			ret = cmd_rotate_session(session, NULL, true,
					LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION);
			if (ret != LTTNG_OK) {
				goto error;
			}
		}
	}

	/* Kernel tracing */
	if (ksession != NULL) {
		DBG("Start kernel tracing session %s", session->name);
		ret = start_kernel_session(ksession);
		if (ret != LTTNG_OK) {
			goto error;
		}
	}

	/* Flag session that trace should start automatically */
	if (usess) {
		int int_ret = ust_app_start_trace_all(usess);

		if (int_ret < 0) {
			ret = LTTNG_ERR_UST_START_FAIL;
			goto error;
		}
	}

	/*
	 * Open a packet in every stream of the session to ensure that viewers
	 * can correctly identify the boundaries of the periods during which
	 * tracing was active for this session.
	 */
	ret = session_open_packets(session);
	if (ret != LTTNG_OK) {
		goto error;
	}

	/*
	 * Clear the flag that indicates that a rotation was done while the
	 * session was stopped.
	 */
	session->rotated_after_last_stop = false;

	if (session->rotate_timer_period) {
		int int_ret = timer_session_rotation_schedule_timer_start(
				session, session->rotate_timer_period);

		if (int_ret < 0) {
			ERR("Failed to enable rotate timer");
			ret = LTTNG_ERR_UNK;
			goto error;
		}
	}

	ret = LTTNG_OK;

error:
	if (ret == LTTNG_OK) {
		/* Flag this after a successful start. */
		session->has_been_started |= 1;
	} else {
		session->active = 0;
		/* Restore initial state on error. */
		session->rotated_after_last_stop =
				session_rotated_after_last_stop;
		session->cleared_after_last_stop =
				session_cleared_after_last_stop;
	}
end:
	return ret;
}

/*
 * Command LTTNG_STOP_TRACE processed by the client thread.
 */
int cmd_stop_trace(struct ltt_session *session)
{
	int ret;
	struct ltt_kernel_session *ksession;
	struct ltt_ust_session *usess;

	assert(session);

	DBG("Begin stop session \"%s\" (id %" PRIu64 ")", session->name, session->id);
	/* Short cut */
	ksession = session->kernel_session;
	usess = session->ust_session;

	/* Session is not active. Skip everythong and inform the client. */
	if (!session->active) {
		ret = LTTNG_ERR_TRACE_ALREADY_STOPPED;
		goto error;
	}

	ret = stop_kernel_session(ksession);
	if (ret != LTTNG_OK) {
		goto error;
	}

	if (usess && usess->active) {
		ret = ust_app_stop_trace_all(usess);
		if (ret < 0) {
			ret = LTTNG_ERR_UST_STOP_FAIL;
			goto error;
		}
	}

	DBG("Completed stop session \"%s\" (id %" PRIu64 ")", session->name,
			session->id);
	/* Flag inactive after a successful stop. */
	session->active = 0;
	ret = LTTNG_OK;

error:
	return ret;
}

/*
 * Set the base_path of the session only if subdir of a control uris is set.
 * Return LTTNG_OK on success, otherwise LTTNG_ERR_*.
 */
static int set_session_base_path_from_uris(struct ltt_session *session,
		size_t nb_uri,
		struct lttng_uri *uris)
{
	int ret;
	size_t i;

	for (i = 0; i < nb_uri; i++) {
		if (uris[i].stype != LTTNG_STREAM_CONTROL ||
				uris[i].subdir[0] == '\0') {
			/* Not interested in these URIs */
			continue;
		}

		if (session->base_path != NULL) {
			free(session->base_path);
			session->base_path = NULL;
		}

		/* Set session base_path */
		session->base_path = strdup(uris[i].subdir);
		if (!session->base_path) {
			PERROR("Failed to copy base path \"%s\" to session \"%s\"",
					uris[i].subdir, session->name);
			ret = LTTNG_ERR_NOMEM;
			goto error;
		}
		DBG2("Setting base path \"%s\" for session \"%s\"",
				session->base_path, session->name);
	}
	ret = LTTNG_OK;
error:
	return ret;
}

/*
 * Command LTTNG_SET_CONSUMER_URI processed by the client thread.
 */
int cmd_set_consumer_uri(struct ltt_session *session, size_t nb_uri,
		struct lttng_uri *uris)
{
	int ret, i;
	struct ltt_kernel_session *ksess = session->kernel_session;
	struct ltt_ust_session *usess = session->ust_session;

	assert(session);
	assert(uris);
	assert(nb_uri > 0);

	/* Can't set consumer URI if the session is active. */
	if (session->active) {
		ret = LTTNG_ERR_TRACE_ALREADY_STARTED;
		goto error;
	}

	/*
	 * Set the session base path if any. This is done inside
	 * cmd_set_consumer_uri to preserve backward compatibility of the
	 * previous session creation api vs the session descriptor api.
	 */
	ret = set_session_base_path_from_uris(session, nb_uri, uris);
	if (ret != LTTNG_OK) {
		goto error;
	}

	/* Set the "global" consumer URIs */
	for (i = 0; i < nb_uri; i++) {
		ret = add_uri_to_consumer(session, session->consumer, &uris[i],
				LTTNG_DOMAIN_NONE);
		if (ret != LTTNG_OK) {
			goto error;
		}
	}

	/* Set UST session URIs */
	if (session->ust_session) {
		for (i = 0; i < nb_uri; i++) {
			ret = add_uri_to_consumer(session,
					session->ust_session->consumer,
					&uris[i], LTTNG_DOMAIN_UST);
			if (ret != LTTNG_OK) {
				goto error;
			}
		}
	}

	/* Set kernel session URIs */
	if (session->kernel_session) {
		for (i = 0; i < nb_uri; i++) {
			ret = add_uri_to_consumer(session,
					session->kernel_session->consumer,
					&uris[i], LTTNG_DOMAIN_KERNEL);
			if (ret != LTTNG_OK) {
				goto error;
			}
		}
	}

	/*
	 * Make sure to set the session in output mode after we set URI since a
	 * session can be created without URL (thus flagged in no output mode).
	 */
	session->output_traces = 1;
	if (ksess) {
		ksess->output_traces = 1;
	}

	if (usess) {
		usess->output_traces = 1;
	}

	/* All good! */
	ret = LTTNG_OK;

error:
	return ret;
}

static
enum lttng_error_code set_session_output_from_descriptor(
		struct ltt_session *session,
		const struct lttng_session_descriptor *descriptor)
{
	int ret;
	enum lttng_error_code ret_code = LTTNG_OK;
	enum lttng_session_descriptor_type session_type =
			lttng_session_descriptor_get_type(descriptor);
	enum lttng_session_descriptor_output_type output_type =
			lttng_session_descriptor_get_output_type(descriptor);
	struct lttng_uri uris[2] = {};
	size_t uri_count = 0;

	switch (output_type) {
	case LTTNG_SESSION_DESCRIPTOR_OUTPUT_TYPE_NONE:
		goto end;
	case LTTNG_SESSION_DESCRIPTOR_OUTPUT_TYPE_LOCAL:
		lttng_session_descriptor_get_local_output_uri(descriptor,
				&uris[0]);
		uri_count = 1;
		break;
	case LTTNG_SESSION_DESCRIPTOR_OUTPUT_TYPE_NETWORK:
		lttng_session_descriptor_get_network_output_uris(descriptor,
				&uris[0], &uris[1]);
		uri_count = 2;
		break;
	default:
		ret_code = LTTNG_ERR_INVALID;
		goto end;
	}

	switch (session_type) {
	case LTTNG_SESSION_DESCRIPTOR_TYPE_SNAPSHOT:
	{
		struct snapshot_output *new_output = NULL;

		new_output = snapshot_output_alloc();
		if (!new_output) {
			ret_code = LTTNG_ERR_NOMEM;
			goto end;
		}

		ret = snapshot_output_init_with_uri(session,
				DEFAULT_SNAPSHOT_MAX_SIZE,
				NULL, uris, uri_count, session->consumer,
				new_output, &session->snapshot);
		if (ret < 0) {
			ret_code = (ret == -ENOMEM) ?
					LTTNG_ERR_NOMEM : LTTNG_ERR_INVALID;
			snapshot_output_destroy(new_output);
			goto end;
		}
		snapshot_add_output(&session->snapshot, new_output);
		break;
	}
	case LTTNG_SESSION_DESCRIPTOR_TYPE_REGULAR:
	case LTTNG_SESSION_DESCRIPTOR_TYPE_LIVE:
	{
		ret_code = cmd_set_consumer_uri(session, uri_count, uris);
		break;
	}
	default:
		ret_code = LTTNG_ERR_INVALID;
		goto end;
	}
end:
	return ret_code;
}

static
enum lttng_error_code cmd_create_session_from_descriptor(
		struct lttng_session_descriptor *descriptor,
		const lttng_sock_cred *creds,
		const char *home_path)
{
	int ret;
	enum lttng_error_code ret_code;
	const char *session_name;
	struct ltt_session *new_session = NULL;
	enum lttng_session_descriptor_status descriptor_status;

	session_lock_list();
	if (home_path) {
		if (*home_path != '/') {
			ERR("Home path provided by client is not absolute");
			ret_code = LTTNG_ERR_INVALID;
			goto end;
		}
	}

	descriptor_status = lttng_session_descriptor_get_session_name(
			descriptor, &session_name);
	switch (descriptor_status) {
	case LTTNG_SESSION_DESCRIPTOR_STATUS_OK:
		break;
	case LTTNG_SESSION_DESCRIPTOR_STATUS_UNSET:
		session_name = NULL;
		break;
	default:
		ret_code = LTTNG_ERR_INVALID;
		goto end;
	}

	ret_code = session_create(session_name, creds->uid, creds->gid,
			&new_session);
	if (ret_code != LTTNG_OK) {
		goto end;
	}

	if (!session_name) {
		ret = lttng_session_descriptor_set_session_name(descriptor,
				new_session->name);
		if (ret) {
			ret_code = LTTNG_ERR_SESSION_FAIL;
			goto end;
		}
	}

	if (!lttng_session_descriptor_is_output_destination_initialized(
			descriptor)) {
		/*
		 * Only include the session's creation time in the output
		 * destination if the name of the session itself was
		 * not auto-generated.
		 */
		ret_code = lttng_session_descriptor_set_default_output(
				descriptor,
				session_name ? &new_session->creation_time : NULL,
				home_path);
		if (ret_code != LTTNG_OK) {
			goto end;
		}
	} else {
		new_session->has_user_specified_directory =
				lttng_session_descriptor_has_output_directory(
					descriptor);
	}

	switch (lttng_session_descriptor_get_type(descriptor)) {
	case LTTNG_SESSION_DESCRIPTOR_TYPE_SNAPSHOT:
		new_session->snapshot_mode = 1;
		break;
	case LTTNG_SESSION_DESCRIPTOR_TYPE_LIVE:
		new_session->live_timer =
				lttng_session_descriptor_live_get_timer_interval(
					descriptor);
		break;
	default:
		break;
	}

	ret_code = set_session_output_from_descriptor(new_session, descriptor);
	if (ret_code != LTTNG_OK) {
		goto end;
	}
	new_session->consumer->enabled = 1;
	ret_code = LTTNG_OK;
end:
	/* Release reference provided by the session_create function. */
	session_put(new_session);
	if (ret_code != LTTNG_OK && new_session) {
		/* Release the global reference on error. */
		session_destroy(new_session);
	}
	session_unlock_list();
	return ret_code;
}

enum lttng_error_code cmd_create_session(struct command_ctx *cmd_ctx, int sock,
		struct lttng_session_descriptor **return_descriptor)
{
	int ret;
	size_t payload_size;
	struct lttng_dynamic_buffer payload;
	struct lttng_buffer_view home_dir_view;
	struct lttng_buffer_view session_descriptor_view;
	struct lttng_session_descriptor *session_descriptor = NULL;
	enum lttng_error_code ret_code;

	lttng_dynamic_buffer_init(&payload);
	if (cmd_ctx->lsm.u.create_session.home_dir_size >=
			LTTNG_PATH_MAX) {
		ret_code = LTTNG_ERR_INVALID;
		goto error;
	}
	if (cmd_ctx->lsm.u.create_session.session_descriptor_size >
			LTTNG_SESSION_DESCRIPTOR_MAX_LEN) {
		ret_code = LTTNG_ERR_INVALID;
		goto error;
	}

	payload_size = cmd_ctx->lsm.u.create_session.home_dir_size +
			cmd_ctx->lsm.u.create_session.session_descriptor_size;
	ret = lttng_dynamic_buffer_set_size(&payload, payload_size);
	if (ret) {
		ret_code = LTTNG_ERR_NOMEM;
		goto error;
	}

	ret = lttcomm_recv_unix_sock(sock, payload.data, payload.size);
	if (ret <= 0) {
		ERR("Reception of session descriptor failed, aborting.");
		ret_code = LTTNG_ERR_SESSION_FAIL;
		goto error;
	}

	home_dir_view = lttng_buffer_view_from_dynamic_buffer(
			&payload,
			0,
			cmd_ctx->lsm.u.create_session.home_dir_size);
	if (cmd_ctx->lsm.u.create_session.home_dir_size > 0 &&
			!lttng_buffer_view_is_valid(&home_dir_view)) {
		ERR("Invalid payload in \"create session\" command: buffer too short to contain home directory");
		ret_code = LTTNG_ERR_INVALID_PROTOCOL;
		goto error;
	}

	session_descriptor_view = lttng_buffer_view_from_dynamic_buffer(
			&payload,
			cmd_ctx->lsm.u.create_session.home_dir_size,
			cmd_ctx->lsm.u.create_session.session_descriptor_size);
	if (!lttng_buffer_view_is_valid(&session_descriptor_view)) {
		ERR("Invalid payload in \"create session\" command: buffer too short to contain session descriptor");
		ret_code = LTTNG_ERR_INVALID_PROTOCOL;
		goto error;
	}

	ret = lttng_session_descriptor_create_from_buffer(
			&session_descriptor_view, &session_descriptor);
	if (ret < 0) {
		ERR("Failed to create session descriptor from payload of \"create session\" command");
		ret_code = LTTNG_ERR_INVALID;
		goto error;
	}

	/*
	 * Sets the descriptor's auto-generated properties (name, output) if
	 * needed.
	 */
	ret_code = cmd_create_session_from_descriptor(session_descriptor,
			&cmd_ctx->creds,
			home_dir_view.size ? home_dir_view.data : NULL);
	if (ret_code != LTTNG_OK) {
		goto error;
	}

	ret_code = LTTNG_OK;
	*return_descriptor = session_descriptor;
	session_descriptor = NULL;
error:
	lttng_dynamic_buffer_reset(&payload);
	lttng_session_descriptor_destroy(session_descriptor);
	return ret_code;
}

static
void cmd_destroy_session_reply(const struct ltt_session *session,
		void *_reply_context)
{
	int ret;
	ssize_t comm_ret;
	const struct cmd_destroy_session_reply_context *reply_context =
			_reply_context;
	struct lttng_dynamic_buffer payload;
	struct lttcomm_session_destroy_command_header cmd_header;
	struct lttng_trace_archive_location *location = NULL;
	struct lttcomm_lttng_msg llm = {
		.cmd_type = LTTNG_DESTROY_SESSION,
		.ret_code = reply_context->destruction_status,
		.pid = UINT32_MAX,
		.cmd_header_size =
			sizeof(struct lttcomm_session_destroy_command_header),
		.data_size = 0,
	};
	size_t payload_size_before_location;

	lttng_dynamic_buffer_init(&payload);

	ret = lttng_dynamic_buffer_append(&payload, &llm, sizeof(llm));
	if (ret) {
		ERR("Failed to append session destruction message");
		goto error;
	}

	cmd_header.rotation_state =
			(int32_t) (reply_context->implicit_rotation_on_destroy ?
				session->rotation_state :
				LTTNG_ROTATION_STATE_NO_ROTATION);
	ret = lttng_dynamic_buffer_append(&payload, &cmd_header,
			sizeof(cmd_header));
	if (ret) {
		ERR("Failed to append session destruction command header");
		goto error;
	}

	if (!reply_context->implicit_rotation_on_destroy) {
		DBG("No implicit rotation performed during the destruction of session \"%s\", sending reply",
				session->name);
		goto send_reply;
	}
	if (session->rotation_state != LTTNG_ROTATION_STATE_COMPLETED) {
		DBG("Rotation state of session \"%s\" is not \"completed\", sending session destruction reply",
				session->name);
		goto send_reply;
	}

	location = session_get_trace_archive_location(session);
	if (!location) {
		ERR("Failed to get the location of the trace archive produced during the destruction of session \"%s\"",
				session->name);
		goto error;
	}

	payload_size_before_location = payload.size;
	comm_ret = lttng_trace_archive_location_serialize(location,
			&payload);
	if (comm_ret < 0) {
		ERR("Failed to serialize the location of the trace archive produced during the destruction of session \"%s\"",
				session->name);
		goto error;
	}
	/* Update the message to indicate the location's length. */
	((struct lttcomm_lttng_msg *) payload.data)->data_size =
			payload.size - payload_size_before_location;
send_reply:
	comm_ret = lttcomm_send_unix_sock(reply_context->reply_sock_fd,
			payload.data, payload.size);
	if (comm_ret != (ssize_t) payload.size) {
		ERR("Failed to send result of the destruction of session \"%s\" to client",
				session->name);
	}
error:
	ret = close(reply_context->reply_sock_fd);
	if (ret) {
		PERROR("Failed to close client socket in deferred session destroy reply");
	}