Implements `lttng_event_notifier_notification_{create,destroy}()`
[lttng-tools.git] / src / bin / lttng-sessiond / notification-thread-events.c
index ff810decec454228d7bc594410e811eef9ee211b..823f2a7eb3b2d53a4642844738ebd808445e2f26 100644 (file)
 #include <lttng/condition/buffer-usage-internal.h>
 #include <lttng/condition/session-consumed-size-internal.h>
 #include <lttng/condition/session-rotation-internal.h>
+#include <lttng/condition/event-rule-internal.h>
+#include <lttng/domain-internal.h>
 #include <lttng/notification/channel-internal.h>
+#include <lttng/trigger/trigger-internal.h>
+#include <lttng/event-rule/event-rule-internal.h>
 
 #include <time.h>
 #include <unistd.h>
@@ -34,6 +38,7 @@
 #include <inttypes.h>
 #include <fcntl.h>
 
+#include "condition-internal.h"
 #include "notification-thread.h"
 #include "notification-thread-events.h"
 #include "notification-thread-commands.h"
@@ -110,6 +115,7 @@ struct lttng_session_trigger_list {
 struct lttng_trigger_ht_element {
        struct lttng_trigger *trigger;
        struct cds_lfht_node node;
+       struct cds_lfht_node node_by_name_uid;
        /* call_rcu delayed reclaim. */
        struct rcu_head rcu_node;
 };
@@ -187,6 +193,9 @@ int client_handle_transmission_status(
                enum client_transmission_status transmission_status,
                struct notification_thread_state *state);
 
+static
+void free_lttng_trigger_ht_element_rcu(struct rcu_head *node);
+
 static
 int match_client_socket(struct cds_lfht_node *node, const void *key)
 {
@@ -261,18 +270,26 @@ int match_channel_info(struct cds_lfht_node *node, const void *key)
 }
 
 static
-int match_condition(struct cds_lfht_node *node, const void *key)
+int match_trigger(struct cds_lfht_node *node, const void *key)
 {
-       struct lttng_condition *condition_key = (struct lttng_condition *) key;
-       struct lttng_trigger_ht_element *trigger;
-       struct lttng_condition *condition;
+       struct lttng_trigger *trigger_key = (struct lttng_trigger *) key;
+       struct lttng_trigger_ht_element *trigger_ht_element;
 
-       trigger = caa_container_of(node, struct lttng_trigger_ht_element,
+       trigger_ht_element = caa_container_of(node, struct lttng_trigger_ht_element,
                        node);
-       condition = lttng_trigger_get_condition(trigger->trigger);
-       assert(condition);
 
-       return !!lttng_condition_is_equal(condition_key, condition);
+       return !!lttng_trigger_is_equal(trigger_key, trigger_ht_element->trigger);
+}
+
+static
+int match_trigger_token(struct cds_lfht_node *node, const void *key)
+{
+       const uint64_t *_key = key;
+       struct notification_trigger_tokens_ht_element *element;
+
+       element = caa_container_of(node,
+                       struct notification_trigger_tokens_ht_element, node);
+       return *_key == element->token;
 }
 
 static
@@ -302,102 +319,100 @@ int match_session(struct cds_lfht_node *node, const void *key)
 }
 
 static
-unsigned long lttng_condition_buffer_usage_hash(
-       const struct lttng_condition *_condition)
+const char *notification_command_type_str(
+               enum notification_thread_command_type type)
 {
-       unsigned long hash;
-       unsigned long condition_type;
-       struct lttng_condition_buffer_usage *condition;
-
-       condition = container_of(_condition,
-                       struct lttng_condition_buffer_usage, parent);
-
-       condition_type = (unsigned long) condition->parent.type;
-       hash = hash_key_ulong((void *) condition_type, lttng_ht_seed);
-       if (condition->session_name) {
-               hash ^= hash_key_str(condition->session_name, lttng_ht_seed);
-       }
-       if (condition->channel_name) {
-               hash ^= hash_key_str(condition->channel_name, lttng_ht_seed);
-       }
-       if (condition->domain.set) {
-               hash ^= hash_key_ulong(
-                               (void *) condition->domain.type,
-                               lttng_ht_seed);
-       }
-       if (condition->threshold_ratio.set) {
-               uint64_t val;
-
-               val = condition->threshold_ratio.value * (double) UINT32_MAX;
-               hash ^= hash_key_u64(&val, lttng_ht_seed);
-       } else if (condition->threshold_bytes.set) {
-               uint64_t val;
-
-               val = condition->threshold_bytes.value;
-               hash ^= hash_key_u64(&val, lttng_ht_seed);
+       switch (type) {
+       case NOTIFICATION_COMMAND_TYPE_REGISTER_TRIGGER:
+               return "REGISTER_TRIGGER";
+       case NOTIFICATION_COMMAND_TYPE_UNREGISTER_TRIGGER:
+               return "UNREGISTER_TRIGGER";
+       case NOTIFICATION_COMMAND_TYPE_ADD_CHANNEL:
+               return "ADD_CHANNEL";
+       case NOTIFICATION_COMMAND_TYPE_REMOVE_CHANNEL:
+               return "REMOVE_CHANNEL";
+       case NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING:
+               return "SESSION_ROTATION_ONGOING";
+       case NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_COMPLETED:
+               return "SESSION_ROTATION_COMPLETED";
+       case NOTIFICATION_COMMAND_TYPE_ADD_TRACER_EVENT_SOURCE:
+               return "ADD_TRACER_EVENT_SOURCE";
+       case NOTIFICATION_COMMAND_TYPE_REMOVE_TRACER_EVENT_SOURCE:
+               return "REMOVE_TRACER_EVENT_SOURCE";
+       case NOTIFICATION_COMMAND_TYPE_LIST_TRIGGERS:
+               return "LIST_TRIGGERS";
+       case NOTIFICATION_COMMAND_TYPE_QUIT:
+               return "QUIT";
+       case NOTIFICATION_COMMAND_TYPE_CLIENT_COMMUNICATION_UPDATE:
+               return "CLIENT_COMMUNICATION_UPDATE";
+       default:
+               abort();
        }
-       return hash;
 }
 
+/*
+ * Match trigger based on name and credentials only.
+ * Name duplication is NOT allowed for the same uid.
+ */
 static
-unsigned long lttng_condition_session_consumed_size_hash(
-       const struct lttng_condition *_condition)
+int match_trigger_by_name_uid(struct cds_lfht_node *node,
+               const void *key)
 {
-       unsigned long hash;
-       unsigned long condition_type =
-                       (unsigned long) LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE;
-       struct lttng_condition_session_consumed_size *condition;
-       uint64_t val;
-
-       condition = container_of(_condition,
-                       struct lttng_condition_session_consumed_size, parent);
-
-       hash = hash_key_ulong((void *) condition_type, lttng_ht_seed);
-       if (condition->session_name) {
-               hash ^= hash_key_str(condition->session_name, lttng_ht_seed);
+       bool match = false;
+       const char *name;
+       const char *key_name;
+       enum lttng_trigger_status status;
+       const struct lttng_credentials *key_creds;
+       const struct lttng_credentials *node_creds;
+       const struct lttng_trigger *trigger_key =
+                       (const struct lttng_trigger *) key;
+       const struct lttng_trigger_ht_element *trigger_ht_element =
+                       caa_container_of(node,
+                               struct lttng_trigger_ht_element,
+                               node_by_name_uid);
+
+       status = lttng_trigger_get_name(trigger_ht_element->trigger, &name);
+       assert(status == LTTNG_TRIGGER_STATUS_OK);
+
+       status = lttng_trigger_get_name(trigger_key, &key_name);
+       assert(status == LTTNG_TRIGGER_STATUS_OK);
+
+       /* Compare the names. */
+       if (strcmp(name, key_name) != 0) {
+               goto end;
        }
-       val = condition->consumed_threshold_bytes.value;
-       hash ^= hash_key_u64(&val, lttng_ht_seed);
-       return hash;
-}
 
-static
-unsigned long lttng_condition_session_rotation_hash(
-       const struct lttng_condition *_condition)
-{
-       unsigned long hash, condition_type;
-       struct lttng_condition_session_rotation *condition;
+       /* Compare the owners' UIDs. */
+       key_creds = lttng_trigger_get_credentials(trigger_key);
+       node_creds = lttng_trigger_get_credentials(trigger_ht_element->trigger);
 
-       condition = container_of(_condition,
-                       struct lttng_condition_session_rotation, parent);
-       condition_type = (unsigned long) condition->parent.type;
-       hash = hash_key_ulong((void *) condition_type, lttng_ht_seed);
-       assert(condition->session_name);
-       hash ^= hash_key_str(condition->session_name, lttng_ht_seed);
-       return hash;
+       match = lttng_credentials_is_equal_uid(key_creds, node_creds);
+
+end:
+       return match;
 }
 
 /*
- * The lttng_condition hashing code is kept in this file (rather than
- * condition.c) since it makes use of GPLv2 code (hashtable utils), which we
- * don't want to link in liblttng-ctl.
+ * Hash trigger based on name and credentials only.
  */
 static
-unsigned long lttng_condition_hash(const struct lttng_condition *condition)
+unsigned long hash_trigger_by_name_uid(const struct lttng_trigger *trigger)
 {
-       switch (condition->type) {
-       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
-       case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
-               return lttng_condition_buffer_usage_hash(condition);
-       case LTTNG_CONDITION_TYPE_SESSION_CONSUMED_SIZE:
-               return lttng_condition_session_consumed_size_hash(condition);
-       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
-       case LTTNG_CONDITION_TYPE_SESSION_ROTATION_COMPLETED:
-               return lttng_condition_session_rotation_hash(condition);
-       default:
-               ERR("[notification-thread] Unexpected condition type caught");
-               abort();
+       unsigned long hash = 0;
+       const struct lttng_credentials *trigger_creds;
+       const char *trigger_name;
+       enum lttng_trigger_status status;
+
+       status = lttng_trigger_get_name(trigger, &trigger_name);
+       if (status == LTTNG_TRIGGER_STATUS_OK) {
+               hash = hash_key_str(trigger_name, lttng_ht_seed);
        }
+
+       trigger_creds = lttng_trigger_get_credentials(trigger);
+       hash ^= hash_key_ulong((void *) (unsigned long) LTTNG_OPTIONAL_GET(trigger_creds->uid),
+                       lttng_ht_seed);
+
+       return hash;
 }
 
 static
@@ -442,6 +457,8 @@ enum lttng_object_type get_condition_binding_object(
        case LTTNG_CONDITION_TYPE_SESSION_ROTATION_ONGOING:
        case LTTNG_CONDITION_TYPE_SESSION_ROTATION_COMPLETED:
                return LTTNG_OBJECT_TYPE_SESSION;
+       case LTTNG_CONDITION_TYPE_EVENT_RULE_HIT:
+               return LTTNG_OBJECT_TYPE_NONE;
        default:
                return LTTNG_OBJECT_TYPE_UNKNOWN;
        }
@@ -952,6 +969,7 @@ int evaluate_condition_for_client(const struct lttng_trigger *trigger,
                                &evaluation, &object_uid, &object_gid);
                break;
        case LTTNG_OBJECT_TYPE_NONE:
+               DBG("[notification-thread] Newly subscribed-to condition not bound to object, nothing to evaluate");
                ret = 0;
                goto end;
        case LTTNG_OBJECT_TYPE_UNKNOWN:
@@ -1184,8 +1202,8 @@ void notification_client_destroy(struct notification_client *client,
                client->socket = -1;
        }
        client->communication.active = false;
-       lttng_dynamic_buffer_reset(&client->communication.inbound.buffer);
-       lttng_dynamic_buffer_reset(&client->communication.outbound.buffer);
+       lttng_payload_reset(&client->communication.inbound.payload);
+       lttng_payload_reset(&client->communication.outbound.payload);
        pthread_mutex_destroy(&client->lock);
        call_rcu(&client->rcu_node, free_notification_client_rcu);
 }
@@ -1623,7 +1641,7 @@ int handle_notification_thread_command_add_channel(
 
        DBG("[notification-thread] Adding channel %s from session %s, channel key = %" PRIu64 " in %s domain",
                        channel_name, session_name, channel_key_int,
-                       channel_domain == LTTNG_DOMAIN_KERNEL ? "kernel" : "user space");
+                       lttng_domain_type_str(channel_domain));
 
        CDS_INIT_LIST_HEAD(&trigger_list);
 
@@ -1724,7 +1742,7 @@ int handle_notification_thread_command_remove_channel(
        struct channel_info *channel_info;
 
        DBG("[notification-thread] Removing channel key = %" PRIu64 " in %s domain",
-                       channel_key, domain == LTTNG_DOMAIN_KERNEL ? "kernel" : "user space");
+                       channel_key, lttng_domain_type_str(domain));
 
        rcu_read_lock();
 
@@ -1807,8 +1825,8 @@ int handle_notification_thread_command_session_rotation(
        struct lttng_trigger_list_element *trigger_list_element;
        struct session_info *session_info;
        const struct lttng_credentials session_creds = {
-               .uid = session_uid,
-               .gid = session_gid,
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(session_uid),
+               .gid = LTTNG_OPTIONAL_INIT_VALUE(session_gid),
        };
 
        rcu_read_lock();
@@ -1918,25 +1936,198 @@ end:
 }
 
 static
-int condition_is_supported(struct lttng_condition *condition)
+int handle_notification_thread_command_add_tracer_event_source(
+               struct notification_thread_state *state,
+               int tracer_event_source_fd,
+               enum lttng_domain_type domain_type,
+               enum lttng_error_code *_cmd_result)
+{
+       int ret = 0;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct notification_event_tracer_event_source_element *element = NULL;
+
+       element = zmalloc(sizeof(*element));
+       if (!element) {
+               cmd_result = LTTNG_ERR_NOMEM;
+               ret = -1;
+               goto end;
+       }
+
+       element->fd = tracer_event_source_fd;
+       element->domain = domain_type;
+
+       cds_list_add(&element->node, &state->tracer_event_sources_list);
+
+       DBG3("[notification-thread] Adding tracer event source fd to poll set: tracer_event_source_fd = %d, domain = '%s'",
+                       tracer_event_source_fd,
+                       lttng_domain_type_str(domain_type));
+
+       /* Adding the read side pipe to the event poll. */
+       ret = lttng_poll_add(&state->events, tracer_event_source_fd, LPOLLIN | LPOLLERR);
+       if (ret < 0) {
+               ERR("[notification-thread] Failed to add tracer event source to poll set: tracer_event_source_fd = %d, domain = '%s'",
+                               tracer_event_source_fd,
+                               lttng_domain_type_str(element->domain));
+               cds_list_del(&element->node);
+               free(element);
+               goto end;
+       }
+
+       element->is_fd_in_poll_set = true;
+
+end:
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+static
+int handle_notification_thread_command_remove_tracer_event_source(
+               struct notification_thread_state *state,
+               int tracer_event_source_fd,
+               enum lttng_error_code *_cmd_result)
+{
+       int ret = 0;
+       bool found = false;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct notification_event_tracer_event_source_element *source_element = NULL, *tmp;
+
+       cds_list_for_each_entry_safe(source_element, tmp,
+                       &state->tracer_event_sources_list, node) {
+               if (source_element->fd != tracer_event_source_fd) {
+                       continue;
+               }
+
+               DBG("[notification-thread] Removed tracer event source from poll set: tracer_event_source_fd = %d, domain = '%s'",
+                               tracer_event_source_fd,
+                               lttng_domain_type_str(source_element->domain));
+               cds_list_del(&source_element->node);
+               found = true;
+               break;
+       }
+
+       if (!found) {
+               /*
+                * This is temporarily allowed since the poll activity set is
+                * not properly cleaned-up for the moment. This is adressed in
+                * an upcoming fix.
+                */
+               source_element = NULL;
+               goto end;
+       }
+
+       if (!source_element->is_fd_in_poll_set) {
+               /* Skip the poll set removal. */
+               goto end;
+       }
+
+       DBG3("[notification-thread] Removing tracer event source from poll set: tracer_event_source_fd = %d, domain = '%s'",
+                       tracer_event_source_fd,
+                       lttng_domain_type_str(source_element->domain));
+
+       /* Removing the fd from the event poll set. */
+       ret = lttng_poll_del(&state->events, tracer_event_source_fd);
+       if (ret < 0) {
+               ERR("[notification-thread] Failed to remove tracer event source from poll set: tracer_event_source_fd = %d, domain = '%s'",
+                               tracer_event_source_fd,
+                               lttng_domain_type_str(source_element->domain));
+               cmd_result = LTTNG_ERR_FATAL;
+               goto end;
+       }
+
+       source_element->is_fd_in_poll_set = false;
+
+end:
+       free(source_element);
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+int handle_notification_thread_remove_tracer_event_source_no_result(
+               struct notification_thread_state *state,
+               int tracer_event_source_fd)
 {
        int ret;
+       enum lttng_error_code cmd_result;
+
+       ret = handle_notification_thread_command_remove_tracer_event_source(
+                       state, tracer_event_source_fd, &cmd_result);
+       (void) cmd_result;
+       return ret;
+}
+
+static int handle_notification_thread_command_list_triggers(
+               struct notification_thread_handle *handle,
+               struct notification_thread_state *state,
+               uid_t client_uid,
+               struct lttng_triggers **triggers,
+               enum lttng_error_code *_cmd_result)
+{
+       int ret = 0;
+       enum lttng_error_code cmd_result = LTTNG_OK;
+       struct cds_lfht_iter iter;
+       struct lttng_trigger_ht_element *trigger_ht_element;
+       struct lttng_triggers *local_triggers = NULL;
+       const struct lttng_credentials *creds;
+
+       rcu_read_lock();
+
+       local_triggers = lttng_triggers_create();
+       if (!local_triggers) {
+               /* Not a fatal error. */
+               cmd_result = LTTNG_ERR_NOMEM;
+               goto end;
+       }
+
+       cds_lfht_for_each_entry(state->triggers_ht, &iter,
+                       trigger_ht_element, node) {
+               /*
+                * Only return the triggers to which the client has access.
+                * The root user has visibility over all triggers.
+                */
+               creds = lttng_trigger_get_credentials(trigger_ht_element->trigger);
+               if (client_uid != lttng_credentials_get_uid(creds) && client_uid != 0) {
+                       continue;
+               }
+
+               ret = lttng_triggers_add(local_triggers,
+                               trigger_ht_element->trigger);
+               if (ret < 0) {
+                       /* Not a fatal error. */
+                       ret = 0;
+                       cmd_result = LTTNG_ERR_NOMEM;
+                       goto end;
+               }
+       }
+
+       /* Transferring ownership to the caller. */
+       *triggers = local_triggers;
+       local_triggers = NULL;
+
+end:
+       rcu_read_unlock();
+       lttng_triggers_destroy(local_triggers);
+       *_cmd_result = cmd_result;
+       return ret;
+}
+
+static
+bool condition_is_supported(struct lttng_condition *condition)
+{
+       bool is_supported;
 
        switch (lttng_condition_get_type(condition)) {
        case LTTNG_CONDITION_TYPE_BUFFER_USAGE_LOW:
        case LTTNG_CONDITION_TYPE_BUFFER_USAGE_HIGH:
        {
+               int ret;
                enum lttng_domain_type domain;
 
                ret = lttng_condition_buffer_usage_get_domain_type(condition,
                                &domain);
-               if (ret) {
-                       ret = -1;
-                       goto end;
-               }
+               assert(ret == 0);
 
                if (domain != LTTNG_DOMAIN_KERNEL) {
-                       ret = 1;
+                       is_supported = true;
                        goto end;
                }
 
@@ -1944,15 +2135,43 @@ int condition_is_supported(struct lttng_condition *condition)
                 * Older kernel tracers don't expose the API to monitor their
                 * buffers. Therefore, we reject triggers that require that
                 * mechanism to be available to be evaluated.
+                *
+                * Assume unsupported on error.
+                */
+               is_supported = kernel_supports_ring_buffer_snapshot_sample_positions() == 1;
+               break;
+       }
+       case LTTNG_CONDITION_TYPE_EVENT_RULE_HIT:
+       {
+               const struct lttng_event_rule *event_rule;
+               enum lttng_domain_type domain;
+               const enum lttng_condition_status status =
+                               lttng_condition_event_rule_get_rule(
+                                               condition, &event_rule);
+
+               assert(status == LTTNG_CONDITION_STATUS_OK);
+
+               domain = lttng_event_rule_get_domain_type(event_rule);
+               if (domain != LTTNG_DOMAIN_KERNEL) {
+                       is_supported = true;
+                       goto end;
+               }
+
+               /*
+                * Older kernel tracers can't emit notification. Therefore, we
+                * reject triggers that require that mechanism to be available
+                * to be evaluated.
+                *
+                * Assume unsupported on error.
                 */
-               ret = kernel_supports_ring_buffer_snapshot_sample_positions();
+               is_supported = kernel_supports_event_notifiers() == 1;
                break;
        }
        default:
-               ret = 1;
+               is_supported = true;
        }
 end:
-       return ret;
+       return is_supported;
 }
 
 /* Must be called with RCU read lock held. */
@@ -2058,7 +2277,7 @@ bool is_trigger_action_notify(const struct lttng_trigger *trigger)
        enum lttng_action_type action_type;
 
        assert(action);
-       action_type = lttng_action_get_type_const(action);
+       action_type = lttng_action_get_type(action);
        if (action_type == LTTNG_ACTION_TYPE_NOTIFY) {
                is_notify = true;
                goto end;
@@ -2074,7 +2293,7 @@ bool is_trigger_action_notify(const struct lttng_trigger *trigger)
                                lttng_action_group_get_at_index(
                                                action, i);
 
-               action_type = lttng_action_get_type_const(inner_action);
+               action_type = lttng_action_get_type(inner_action);
                if (action_type == LTTNG_ACTION_TYPE_NOTIFY) {
                        is_notify = true;
                        goto end;
@@ -2085,6 +2304,50 @@ end:
        return is_notify;
 }
 
+static bool trigger_name_taken(struct notification_thread_state *state,
+               const struct lttng_trigger *trigger)
+{
+       struct cds_lfht_iter iter;
+
+       /*
+        * No duplicata is allowed in the triggers_by_name_uid_ht.
+        * The match is done against the trigger name and uid.
+        */
+       cds_lfht_lookup(state->triggers_by_name_uid_ht,
+                       hash_trigger_by_name_uid(trigger),
+                       match_trigger_by_name_uid,
+                       trigger,
+                       &iter);
+       return !!cds_lfht_iter_get_node(&iter);
+}
+
+static
+enum lttng_error_code generate_trigger_name(
+               struct notification_thread_state *state,
+               struct lttng_trigger *trigger, const char **name)
+{
+       enum lttng_error_code ret_code = LTTNG_OK;
+       bool taken = false;
+       enum lttng_trigger_status status;
+
+       do {
+               const int ret = lttng_trigger_generate_name(trigger,
+                               state->trigger_id.name_offset++);
+               if (ret) {
+                       /* The only reason this can fail right now. */
+                       ret_code = LTTNG_ERR_NOMEM;
+                       break;
+               }
+
+               status = lttng_trigger_get_name(trigger, name);
+               assert(status == LTTNG_TRIGGER_STATUS_OK);
+
+               taken = trigger_name_taken(state, trigger);
+       } while (taken || state->trigger_id.name_offset == UINT64_MAX);
+
+       return ret_code;
+}
+
 /*
  * FIXME A client's credentials are not checked when registering a trigger.
  *
@@ -2112,27 +2375,49 @@ int handle_notification_thread_command_register_trigger(
        struct notification_client_list *client_list = NULL;
        struct lttng_trigger_ht_element *trigger_ht_element = NULL;
        struct notification_client_list_element *client_list_element;
+       struct notification_trigger_tokens_ht_element *trigger_tokens_ht_element = NULL;
        struct cds_lfht_node *node;
        struct cds_lfht_iter iter;
+       const char* trigger_name;
        bool free_trigger = true;
        struct lttng_evaluation *evaluation = NULL;
        struct lttng_credentials object_creds;
+       uid_t object_uid;
+       gid_t object_gid;
        enum action_executor_status executor_status;
+       const uint64_t trigger_tracer_token =
+                       state->trigger_id.next_tracer_token++;
 
        rcu_read_lock();
 
+       /* Set the trigger's tracer token. */
+       lttng_trigger_set_tracer_token(trigger, trigger_tracer_token);
+
+       if (lttng_trigger_get_name(trigger, &trigger_name) ==
+                       LTTNG_TRIGGER_STATUS_UNSET) {
+               const enum lttng_error_code ret_code = generate_trigger_name(
+                               state, trigger, &trigger_name);
+
+               if (ret_code != LTTNG_OK) {
+                       /* Fatal error. */
+                       ret = -1;
+                       *cmd_result = ret_code;
+                       goto error;
+               }
+       } else if (trigger_name_taken(state, trigger)) {
+               /* Not a fatal error. */
+               *cmd_result = LTTNG_ERR_TRIGGER_EXISTS;
+               ret = 0;
+               goto error;
+       }
+
        condition = lttng_trigger_get_condition(trigger);
        assert(condition);
 
-       ret = condition_is_supported(condition);
-       if (ret < 0) {
-               goto error;
-       } else if (ret == 0) {
+       /* Some conditions require tracers to implement a minimal ABI version. */
+       if (!condition_is_supported(condition)) {
                *cmd_result = LTTNG_ERR_NOT_SUPPORTED;
                goto error;
-       } else {
-               /* Feature is supported, continue. */
-               ret = 0;
        }
 
        trigger_ht_element = zmalloc(sizeof(*trigger_ht_element));
@@ -2143,12 +2428,13 @@ int handle_notification_thread_command_register_trigger(
 
        /* Add trigger to the trigger_ht. */
        cds_lfht_node_init(&trigger_ht_element->node);
+       cds_lfht_node_init(&trigger_ht_element->node_by_name_uid);
        trigger_ht_element->trigger = trigger;
 
        node = cds_lfht_add_unique(state->triggers_ht,
                        lttng_condition_hash(condition),
-                       match_condition,
-                       condition,
+                       match_trigger,
+                       trigger,
                        &trigger_ht_element->node);
        if (node != &trigger_ht_element->node) {
                /* Not a fatal error, simply report it to the client. */
@@ -2156,10 +2442,59 @@ int handle_notification_thread_command_register_trigger(
                goto error_free_ht_element;
        }
 
+       node = cds_lfht_add_unique(state->triggers_by_name_uid_ht,
+                       hash_trigger_by_name_uid(trigger),
+                       match_trigger_by_name_uid,
+                       trigger,
+                       &trigger_ht_element->node_by_name_uid);
+       if (node != &trigger_ht_element->node_by_name_uid) {
+               /* Not a fatal error, simply report it to the client. */
+               cds_lfht_del(state->triggers_ht, &trigger_ht_element->node);
+               *cmd_result = LTTNG_ERR_TRIGGER_EXISTS;
+               goto error_free_ht_element;
+       }
+
+       if (lttng_condition_get_type(condition) == LTTNG_CONDITION_TYPE_EVENT_RULE_HIT) {
+               trigger_tokens_ht_element = zmalloc(sizeof(*trigger_tokens_ht_element));
+               if (!trigger_tokens_ht_element) {
+                       /* Fatal error. */
+                       ret = -1;
+                       cds_lfht_del(state->triggers_ht,
+                                       &trigger_ht_element->node);
+                       cds_lfht_del(state->triggers_by_name_uid_ht,
+                                       &trigger_ht_element->node_by_name_uid);
+                       goto error_free_ht_element;
+               }
+
+               /* Add trigger token to the trigger_tokens_ht. */
+               cds_lfht_node_init(&trigger_tokens_ht_element->node);
+               trigger_tokens_ht_element->token =
+                               LTTNG_OPTIONAL_GET(trigger->tracer_token);
+               trigger_tokens_ht_element->trigger = trigger;
+
+               node = cds_lfht_add_unique(state->trigger_tokens_ht,
+                               hash_key_u64(&trigger_tokens_ht_element->token,
+                                               lttng_ht_seed),
+                               match_trigger_token,
+                               &trigger_tokens_ht_element->token,
+                               &trigger_tokens_ht_element->node);
+               if (node != &trigger_tokens_ht_element->node) {
+                       /* Internal corruption, fatal error. */
+                       ret = -1;
+                       *cmd_result = LTTNG_ERR_TRIGGER_EXISTS;
+                       cds_lfht_del(state->triggers_ht,
+                                       &trigger_ht_element->node);
+                       cds_lfht_del(state->triggers_by_name_uid_ht,
+                                       &trigger_ht_element->node_by_name_uid);
+                       goto error_free_ht_element;
+               }
+       }
+
        /*
         * Ownership of the trigger and of its wrapper was transfered to
-        * the triggers_ht.
+        * the triggers_ht. Same for token ht element if necessary.
         */
+       trigger_tokens_ht_element = NULL;
        trigger_ht_element = NULL;
        free_trigger = false;
 
@@ -2260,21 +2595,25 @@ int handle_notification_thread_command_register_trigger(
        switch (get_condition_binding_object(condition)) {
        case LTTNG_OBJECT_TYPE_SESSION:
                ret = evaluate_session_condition_for_client(condition, state,
-                               &evaluation, &object_creds.uid,
-                               &object_creds.gid);
+                               &evaluation, &object_uid,
+                               &object_gid);
+               LTTNG_OPTIONAL_SET(&object_creds.uid, object_uid);
+               LTTNG_OPTIONAL_SET(&object_creds.gid, object_gid);
                break;
        case LTTNG_OBJECT_TYPE_CHANNEL:
                ret = evaluate_channel_condition_for_client(condition, state,
-                               &evaluation, &object_creds.uid,
-                               &object_creds.gid);
+                               &evaluation, &object_uid,
+                               &object_gid);
+               LTTNG_OPTIONAL_SET(&object_creds.uid, object_uid);
+               LTTNG_OPTIONAL_SET(&object_creds.gid, object_gid);
                break;
        case LTTNG_OBJECT_TYPE_NONE:
                ret = 0;
-               goto error_put_client_list;
+               break;
        case LTTNG_OBJECT_TYPE_UNKNOWN:
        default:
                ret = -1;
-               goto error_put_client_list;
+               break;
        }
 
        if (ret) {
@@ -2287,7 +2626,7 @@ int handle_notification_thread_command_register_trigger(
        if (!evaluation) {
                /* Evaluation yielded nothing. Normal exit. */
                ret = 0;
-               goto error_put_client_list;
+               goto end;
        }
 
        /*
@@ -2318,18 +2657,27 @@ int handle_notification_thread_command_register_trigger(
                 */
                WARN("No space left when enqueuing action associated to newly registered trigger");
                ret = 0;
-               goto error_put_client_list;
+               goto end;
        default:
                abort();
        }
 
+end:
        *cmd_result = LTTNG_OK;
+       DBG("Registered trigger: name = `%s`, tracer token = %" PRIu64,
+                       trigger_name, trigger_tracer_token);
 
 error_put_client_list:
        notification_client_list_put(client_list);
 
 error_free_ht_element:
-       free(trigger_ht_element);
+       if (trigger_ht_element) {
+               /* Delayed removal due to RCU constraint on delete. */
+               call_rcu(&trigger_ht_element->rcu_node,
+                               free_lttng_trigger_ht_element_rcu);
+       }
+
+       free(trigger_tokens_ht_element);
 error:
        if (free_trigger) {
                lttng_trigger_destroy(trigger);
@@ -2345,10 +2693,17 @@ void free_lttng_trigger_ht_element_rcu(struct rcu_head *node)
                        rcu_node));
 }
 
+static
+void free_notification_trigger_tokens_ht_element_rcu(struct rcu_head *node)
+{
+       free(caa_container_of(node, struct notification_trigger_tokens_ht_element,
+                       rcu_node));
+}
+
 static
 int handle_notification_thread_command_unregister_trigger(
                struct notification_thread_state *state,
-               struct lttng_trigger *trigger,
+               const struct lttng_trigger *trigger,
                enum lttng_error_code *_cmd_reply)
 {
        struct cds_lfht_iter iter;
@@ -2356,7 +2711,7 @@ int handle_notification_thread_command_unregister_trigger(
        struct lttng_channel_trigger_list *trigger_list;
        struct notification_client_list *client_list;
        struct lttng_trigger_ht_element *trigger_ht_element = NULL;
-       struct lttng_condition *condition = lttng_trigger_get_condition(
+       const struct lttng_condition *condition = lttng_trigger_get_const_condition(
                        trigger);
        enum lttng_error_code cmd_reply;
 
@@ -2364,8 +2719,8 @@ int handle_notification_thread_command_unregister_trigger(
 
        cds_lfht_lookup(state->triggers_ht,
                        lttng_condition_hash(condition),
-                       match_condition,
-                       condition,
+                       match_trigger,
+                       trigger,
                        &iter);
        triggers_ht_node = cds_lfht_iter_get_node(&iter);
        if (!triggers_ht_node) {
@@ -2382,13 +2737,7 @@ int handle_notification_thread_command_unregister_trigger(
 
                cds_list_for_each_entry_safe(trigger_element, tmp,
                                &trigger_list->list, node) {
-                       const struct lttng_condition *current_condition =
-                                       lttng_trigger_get_const_condition(
-                                               trigger_element->trigger);
-
-                       assert(current_condition);
-                       if (!lttng_condition_is_equal(condition,
-                                       current_condition)) {
+                       if (!lttng_trigger_is_equal(trigger, trigger_element->trigger)) {
                                continue;
                        }
 
@@ -2399,21 +2748,46 @@ int handle_notification_thread_command_unregister_trigger(
                }
        }
 
-       /*
-        * Remove and release the client list from
-        * notification_trigger_clients_ht.
-        */
-       client_list = get_client_list_from_condition(state, condition);
-       assert(client_list);
+       if (lttng_condition_get_type(condition) ==
+                       LTTNG_CONDITION_TYPE_EVENT_RULE_HIT) {
+               struct notification_trigger_tokens_ht_element
+                               *trigger_tokens_ht_element;
 
-       /* Put new reference and the hashtable's reference. */
-       notification_client_list_put(client_list);
-       notification_client_list_put(client_list);
-       client_list = NULL;
+               cds_lfht_for_each_entry (state->trigger_tokens_ht, &iter,
+                               trigger_tokens_ht_element, node) {
+                       if (!lttng_trigger_is_equal(trigger,
+                                           trigger_tokens_ht_element->trigger)) {
+                               continue;
+                       }
+
+                       DBG("[notification-thread] Removed trigger from tokens_ht");
+                       cds_lfht_del(state->trigger_tokens_ht,
+                                       &trigger_tokens_ht_element->node);
+                       call_rcu(&trigger_tokens_ht_element->rcu_node,
+                                       free_notification_trigger_tokens_ht_element_rcu);
+
+                       break;
+               }
+       }
+
+       if (is_trigger_action_notify(trigger)) {
+               /*
+                * Remove and release the client list from
+                * notification_trigger_clients_ht.
+                */
+               client_list = get_client_list_from_condition(state, condition);
+               assert(client_list);
+
+               /* Put new reference and the hashtable's reference. */
+               notification_client_list_put(client_list);
+               notification_client_list_put(client_list);
+               client_list = NULL;
+       }
 
        /* Remove trigger from triggers_ht. */
        trigger_ht_element = caa_container_of(triggers_ht_node,
                        struct lttng_trigger_ht_element, node);
+       cds_lfht_del(state->triggers_by_name_uid_ht, &trigger_ht_element->node_by_name_uid);
        cds_lfht_del(state->triggers_ht, triggers_ht_node);
 
        /* Release the ownership of the trigger. */
@@ -2448,21 +2822,22 @@ int handle_notification_thread_command(
                        struct notification_thread_command, cmd_list_node);
        cds_list_del(&cmd->cmd_list_node);
        pthread_mutex_unlock(&handle->cmd_queue.lock);
+
+       DBG("[notification-thread] Received `%s` command",
+                       notification_command_type_str(cmd->type));
        switch (cmd->type) {
        case NOTIFICATION_COMMAND_TYPE_REGISTER_TRIGGER:
-               DBG("[notification-thread] Received register trigger command");
-               ret = handle_notification_thread_command_register_trigger(
-                               state, cmd->parameters.trigger,
+               ret = handle_notification_thread_command_register_trigger(state,
+                               cmd->parameters.register_trigger.trigger,
                                &cmd->reply_code);
                break;
        case NOTIFICATION_COMMAND_TYPE_UNREGISTER_TRIGGER:
-               DBG("[notification-thread] Received unregister trigger command");
                ret = handle_notification_thread_command_unregister_trigger(
-                               state, cmd->parameters.trigger,
+                               state,
+                               cmd->parameters.unregister_trigger.trigger,
                                &cmd->reply_code);
                break;
        case NOTIFICATION_COMMAND_TYPE_ADD_CHANNEL:
-               DBG("[notification-thread] Received add channel command");
                ret = handle_notification_thread_command_add_channel(
                                state,
                                cmd->parameters.add_channel.session.name,
@@ -2475,7 +2850,6 @@ int handle_notification_thread_command(
                                &cmd->reply_code);
                break;
        case NOTIFICATION_COMMAND_TYPE_REMOVE_CHANNEL:
-               DBG("[notification-thread] Received remove channel command");
                ret = handle_notification_thread_command_remove_channel(
                                state, cmd->parameters.remove_channel.key,
                                cmd->parameters.remove_channel.domain,
@@ -2483,9 +2857,6 @@ int handle_notification_thread_command(
                break;
        case NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING:
        case NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_COMPLETED:
-               DBG("[notification-thread] Received session rotation %s command",
-                               cmd->type == NOTIFICATION_COMMAND_TYPE_SESSION_ROTATION_ONGOING ?
-                               "ongoing" : "completed");
                ret = handle_notification_thread_command_session_rotation(
                                state,
                                cmd->type,
@@ -2496,8 +2867,34 @@ int handle_notification_thread_command(
                                cmd->parameters.session_rotation.location,
                                &cmd->reply_code);
                break;
+       case NOTIFICATION_COMMAND_TYPE_ADD_TRACER_EVENT_SOURCE:
+               ret = handle_notification_thread_command_add_tracer_event_source(
+                               state,
+                               cmd->parameters.tracer_event_source.tracer_event_source_fd,
+                               cmd->parameters.tracer_event_source.domain,
+                               &cmd->reply_code);
+               break;
+       case NOTIFICATION_COMMAND_TYPE_REMOVE_TRACER_EVENT_SOURCE:
+               ret = handle_notification_thread_command_remove_tracer_event_source(
+                               state,
+                               cmd->parameters.tracer_event_source.tracer_event_source_fd,
+                               &cmd->reply_code);
+               break;
+       case NOTIFICATION_COMMAND_TYPE_LIST_TRIGGERS:
+       {
+               struct lttng_triggers *triggers = NULL;
+
+               ret = handle_notification_thread_command_list_triggers(
+                               handle,
+                               state,
+                               cmd->parameters.list_triggers.uid,
+                               &triggers,
+                               &cmd->reply_code);
+               cmd->reply.list_triggers.triggers = triggers;
+               ret = 0;
+               break;
+       }
        case NOTIFICATION_COMMAND_TYPE_QUIT:
-               DBG("[notification-thread] Received quit command");
                cmd->reply_code = LTTNG_OK;
                ret = 1;
                goto end;
@@ -2582,9 +2979,8 @@ int client_reset_inbound_state(struct notification_client *client)
 {
        int ret;
 
-       ret = lttng_dynamic_buffer_set_size(
-                       &client->communication.inbound.buffer, 0);
-       assert(!ret);
+
+       lttng_payload_clear(&client->communication.inbound.payload);
 
        client->communication.inbound.bytes_to_receive =
                        sizeof(struct lttng_notification_channel_message);
@@ -2593,8 +2989,9 @@ int client_reset_inbound_state(struct notification_client *client)
        LTTNG_SOCK_SET_UID_CRED(&client->communication.inbound.creds, -1);
        LTTNG_SOCK_SET_GID_CRED(&client->communication.inbound.creds, -1);
        ret = lttng_dynamic_buffer_set_size(
-                       &client->communication.inbound.buffer,
+                       &client->communication.inbound.payload.buffer,
                        client->communication.inbound.bytes_to_receive);
+
        return ret;
 }
 
@@ -2616,8 +3013,8 @@ int handle_notification_thread_client_connect(
        pthread_mutex_init(&client->lock, NULL);
        client->id = state->next_notification_client_id++;
        CDS_INIT_LIST_HEAD(&client->condition_list);
-       lttng_dynamic_buffer_init(&client->communication.inbound.buffer);
-       lttng_dynamic_buffer_init(&client->communication.outbound.buffer);
+       lttng_payload_init(&client->communication.inbound.payload);
+       lttng_payload_init(&client->communication.outbound.payload);
        client->communication.inbound.expect_creds = true;
 
        ret = client_reset_inbound_state(client);
@@ -2835,6 +3232,10 @@ enum client_transmission_status client_flush_outgoing_queue(
        ssize_t ret;
        size_t to_send_count;
        enum client_transmission_status status;
+       struct lttng_payload_view pv = lttng_payload_view_from_payload(
+                       &client->communication.outbound.payload, 0, -1);
+       const int fds_to_send_count =
+                       lttng_payload_view_get_fd_handle_count(&pv);
 
        ASSERT_LOCKED(client->lock);
 
@@ -2843,55 +3244,121 @@ enum client_transmission_status client_flush_outgoing_queue(
                goto end;
        }
 
-       assert(client->communication.outbound.buffer.size != 0);
-       to_send_count = client->communication.outbound.buffer.size;
+       if (pv.buffer.size == 0) {
+               /*
+                * If both data and fds are equal to zero, we are in an invalid
+                * state.
+                */
+               assert(fds_to_send_count != 0);
+               goto send_fds;
+       }
+
+       /* Send data. */
+       to_send_count = pv.buffer.size;
        DBG("[notification-thread] Flushing client (socket fd = %i) outgoing queue",
                        client->socket);
 
        ret = lttcomm_send_unix_sock_non_block(client->socket,
-                       client->communication.outbound.buffer.data,
+                       pv.buffer.data,
                        to_send_count);
        if ((ret >= 0 && ret < to_send_count)) {
                DBG("[notification-thread] Client (socket fd = %i) outgoing queue could not be completely flushed",
                                client->socket);
                to_send_count -= max(ret, 0);
 
-               memcpy(client->communication.outbound.buffer.data,
-                               client->communication.outbound.buffer.data +
-                               client->communication.outbound.buffer.size - to_send_count,
+               memmove(client->communication.outbound.payload.buffer.data,
+                               pv.buffer.data +
+                               pv.buffer.size - to_send_count,
                                to_send_count);
                ret = lttng_dynamic_buffer_set_size(
-                               &client->communication.outbound.buffer,
+                               &client->communication.outbound.payload.buffer,
                                to_send_count);
                if (ret) {
                        goto error;
                }
 
                status = CLIENT_TRANSMISSION_STATUS_QUEUED;
+               goto end;
        } else if (ret < 0) {
                /* Generic error, disable the client's communication. */
                ERR("[notification-thread] Failed to flush outgoing queue, disconnecting client (socket fd = %i)",
                                client->socket);
                client->communication.active = false;
                status = CLIENT_TRANSMISSION_STATUS_FAIL;
+               goto end;
        } else {
-               /* No error and flushed the queue completely. */
+               /*
+                * No error and flushed the queue completely.
+                *
+                * The payload buffer size is used later to
+                * check if there is notifications queued. So albeit that the
+                * direct caller knows that the transmission is complete, we
+                * need to set the buffer size to zero.
+                */
                ret = lttng_dynamic_buffer_set_size(
-                               &client->communication.outbound.buffer, 0);
+                               &client->communication.outbound.payload.buffer, 0);
                if (ret) {
                        goto error;
                }
+       }
 
-               client->communication.outbound.queued_command_reply = false;
-               client->communication.outbound.dropped_notification = false;
+send_fds:
+       /* No fds to send, transmission is complete. */
+       if (fds_to_send_count == 0) {
                status = CLIENT_TRANSMISSION_STATUS_COMPLETE;
+               goto end;
        }
+
+       ret = lttcomm_send_payload_view_fds_unix_sock_non_block(
+                       client->socket, &pv);
+       if (ret < 0) {
+               /* Generic error, disable the client's communication. */
+               ERR("[notification-thread] Failed to flush outgoing fds queue, disconnecting client (socket fd = %i)",
+                               client->socket);
+               client->communication.active = false;
+               status = CLIENT_TRANSMISSION_STATUS_FAIL;
+               goto end;
+       } else if (ret == 0) {
+               /* Nothing could be sent. */
+               status = CLIENT_TRANSMISSION_STATUS_QUEUED;
+       } else {
+               /* Fd passing is an all or nothing kind of thing. */
+               status = CLIENT_TRANSMISSION_STATUS_COMPLETE;
+               /*
+                * The payload _fd_array count is used later to
+                * check if there is notifications queued. So although the
+                * direct caller knows that the transmission is complete, we
+                * need to clear the _fd_array for the queuing check.
+                */
+               lttng_dynamic_pointer_array_clear(
+                               &client->communication.outbound.payload
+                                                ._fd_handles);
+       }
+
 end:
+       if (status == CLIENT_TRANSMISSION_STATUS_COMPLETE) {
+               client->communication.outbound.queued_command_reply = false;
+               client->communication.outbound.dropped_notification = false;
+               lttng_payload_clear(&client->communication.outbound.payload);
+       }
+
        return status;
 error:
        return CLIENT_TRANSMISSION_STATUS_ERROR;
 }
 
+static
+bool client_has_outbound_data_left(
+               const struct notification_client *client)
+{
+       const struct lttng_payload_view pv = lttng_payload_view_from_payload(
+                       &client->communication.outbound.payload, 0, -1);
+       const bool has_data = pv.buffer.size != 0;
+       const bool has_fds = lttng_payload_view_get_fd_handle_count(&pv);
+
+       return has_data || has_fds;
+}
+
 /* Client lock must _not_ be held by the caller. */
 static
 int client_send_command_reply(struct notification_client *client,
@@ -2921,14 +3388,15 @@ int client_send_command_reply(struct notification_client *client,
 
        /* Enqueue buffer to outgoing queue and flush it. */
        ret = lttng_dynamic_buffer_append(
-                       &client->communication.outbound.buffer,
+                       &client->communication.outbound.payload.buffer,
                        buffer, sizeof(buffer));
        if (ret) {
                goto error_unlock;
        }
 
        transmission_status = client_flush_outgoing_queue(client);
-       if (client->communication.outbound.buffer.size != 0) {
+
+       if (client_has_outbound_data_left(client)) {
                /* Queue could not be emptied. */
                client->communication.outbound.queued_command_reply = true;
        }
@@ -2959,9 +3427,9 @@ int client_handle_message_unknown(struct notification_client *client,
         */
        const struct lttng_notification_channel_message *msg;
 
-       assert(sizeof(*msg) == client->communication.inbound.buffer.size);
+       assert(sizeof(*msg) == client->communication.inbound.payload.buffer.size);
        msg = (const struct lttng_notification_channel_message *)
-                             client->communication.inbound.buffer.data;
+                             client->communication.inbound.payload.buffer.data;
 
        if (msg->size == 0 ||
                        msg->size > DEFAULT_MAX_NOTIFICATION_CLIENT_MESSAGE_PAYLOAD_SIZE) {
@@ -2983,10 +3451,14 @@ int client_handle_message_unknown(struct notification_client *client,
        }
 
        client->communication.inbound.bytes_to_receive = msg->size;
+       client->communication.inbound.fds_to_receive = msg->fds;
        client->communication.inbound.msg_type =
                        (enum lttng_notification_channel_message_type) msg->type;
        ret = lttng_dynamic_buffer_set_size(
-                       &client->communication.inbound.buffer, msg->size);
+                       &client->communication.inbound.payload.buffer, msg->size);
+
+       /* msg is not valid anymore due to lttng_dynamic_buffer_set_size. */
+       msg = NULL;
 end:
        return ret;
 }
@@ -3015,7 +3487,7 @@ int client_handle_message_handshake(struct notification_client *client,
 
        handshake_client =
                        (struct lttng_notification_channel_command_handshake *)
-                                       client->communication.inbound.buffer
+                                       client->communication.inbound.payload.buffer
                                                        .data;
        client->major = handshake_client->major;
        client->minor = handshake_client->minor;
@@ -3041,7 +3513,7 @@ int client_handle_message_handshake(struct notification_client *client,
        pthread_mutex_lock(&client->lock);
        /* Outgoing queue will be flushed when the command reply is sent. */
        ret = lttng_dynamic_buffer_append(
-                       &client->communication.outbound.buffer, send_buffer,
+                       &client->communication.outbound.payload.buffer, send_buffer,
                        sizeof(send_buffer));
        if (ret) {
                ERR("[notification-thread] Failed to send protocol version to notification channel client");
@@ -3084,8 +3556,8 @@ int client_handle_message_subscription(
        enum lttng_notification_channel_status status =
                        LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
        struct lttng_payload_view condition_view =
-                       lttng_payload_view_from_dynamic_buffer(
-                                       &client->communication.inbound.buffer,
+                       lttng_payload_view_from_payload(
+                                       &client->communication.inbound.payload,
                                        0, -1);
        size_t expected_condition_size;
 
@@ -3094,7 +3566,7 @@ int client_handle_message_subscription(
         * other thread accessing clients (action executor) only uses the
         * outbound state.
         */
-       expected_condition_size = client->communication.inbound.buffer.size;
+       expected_condition_size = client->communication.inbound.payload.buffer.size;
        ret = lttng_condition_create_from_payload(&condition_view, &condition);
        if (ret != expected_condition_size) {
                ERR("[notification-thread] Malformed condition received from client");
@@ -3179,7 +3651,6 @@ int handle_notification_thread_client_in(
        struct notification_client *client;
        ssize_t recv_ret;
        size_t offset;
-       bool message_is_complete = false;
 
        rcu_read_lock();
        client = get_client_from_socket(socket, state);
@@ -3189,11 +3660,11 @@ int handle_notification_thread_client_in(
                goto end;
        }
 
-       offset = client->communication.inbound.buffer.size -
+       offset = client->communication.inbound.payload.buffer.size -
                        client->communication.inbound.bytes_to_receive;
        if (client->communication.inbound.expect_creds) {
                recv_ret = lttcomm_recv_creds_unix_sock(socket,
-                               client->communication.inbound.buffer.data + offset,
+                               client->communication.inbound.payload.buffer.data + offset,
                                client->communication.inbound.bytes_to_receive,
                                &client->communication.inbound.creds);
                if (recv_ret > 0) {
@@ -3202,32 +3673,66 @@ int handle_notification_thread_client_in(
                }
        } else {
                recv_ret = lttcomm_recv_unix_sock_non_block(socket,
-                               client->communication.inbound.buffer.data + offset,
+                               client->communication.inbound.payload.buffer.data + offset,
                                client->communication.inbound.bytes_to_receive);
        }
        if (recv_ret >= 0) {
                client->communication.inbound.bytes_to_receive -= recv_ret;
-               message_is_complete = client->communication.inbound
-                                                     .bytes_to_receive == 0;
+       } else {
+               goto error_disconnect_client;
        }
 
-       if (recv_ret < 0) {
-               goto error_disconnect_client;
+       if (client->communication.inbound.bytes_to_receive != 0) {
+               /* Message incomplete wait for more data. */
+               ret = 0;
+               goto end;
        }
 
-       if (message_is_complete) {
-               ret = client_dispatch_message(client, state);
-               if (ret) {
+       assert(client->communication.inbound.bytes_to_receive == 0);
+
+       /* Receive fds. */
+       if (client->communication.inbound.fds_to_receive != 0) {
+               ret = lttcomm_recv_payload_fds_unix_sock_non_block(
+                               client->socket,
+                               client->communication.inbound.fds_to_receive,
+                               &client->communication.inbound.payload);
+               if (ret > 0) {
                        /*
-                        * Only returns an error if this client must be
-                        * disconnected.
+                        * Fds received. non blocking fds passing is all
+                        * or nothing.
                         */
+                       ssize_t expected_size;
+
+                       expected_size = sizeof(int) *
+                                       client->communication.inbound
+                                                       .fds_to_receive;
+                       assert(ret == expected_size);
+                       client->communication.inbound.fds_to_receive = 0;
+               } else if (ret == 0) {
+                       /* Received nothing. */
+                       ret = 0;
+                       goto end;
+               } else {
                        goto error_disconnect_client;
                }
        }
+
+       /* At this point the message is complete.*/
+       assert(client->communication.inbound.bytes_to_receive == 0 &&
+                       client->communication.inbound.fds_to_receive == 0);
+       ret = client_dispatch_message(client, state);
+       if (ret) {
+               /*
+                * Only returns an error if this client must be
+                * disconnected.
+                */
+               goto error_disconnect_client;
+       }
+
 end:
        rcu_read_unlock();
        return ret;
+
 error_disconnect_client:
        ret = notification_thread_client_disconnect(client, state);
        goto end;
@@ -3448,7 +3953,7 @@ int client_notification_overflow(struct notification_client *client)
 
        client->communication.outbound.dropped_notification = true;
        ret = lttng_dynamic_buffer_append(
-                       &client->communication.outbound.buffer, &msg,
+                       &client->communication.outbound.payload.buffer, &msg,
                        sizeof(msg));
        if (ret) {
                PERROR("Failed to enqueue \"dropped notification\" message in client's (socket fd = %i) outgoing queue",
@@ -3474,11 +3979,15 @@ int send_evaluation_to_clients(const struct lttng_trigger *trigger,
                struct notification_thread_state *state,
                uid_t object_uid, gid_t object_gid)
 {
+       const struct lttng_credentials creds = {
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(object_uid),
+               .gid = LTTNG_OPTIONAL_INIT_VALUE(object_gid),
+       };
+
        return notification_client_list_send_evaluation(client_list,
                        lttng_trigger_get_const_condition(trigger), evaluation,
                        lttng_trigger_get_credentials(trigger),
-                       &(struct lttng_credentials){
-                                       .uid = object_uid, .gid = object_gid},
+                       &creds,
                        client_handle_transmission_status_wrapper, state);
 }
 
@@ -3556,6 +4065,16 @@ int notification_client_list_send_evaluation(
                        ->size = (uint32_t)(
                        msg_payload.buffer.size - sizeof(msg_header));
 
+       /* Update the payload number of fds. */
+       {
+               const struct lttng_payload_view pv = lttng_payload_view_from_payload(
+                               &msg_payload, 0, -1);
+
+               ((struct lttng_notification_channel_message *)
+                               msg_payload.buffer.data)->fds = (uint32_t)
+                               lttng_payload_view_get_fd_handle_count(&pv);
+       }
+
        pthread_mutex_lock(&client_list->lock);
        cds_list_for_each_entry_safe(client_list_element, tmp,
                        &client_list->list, node) {
@@ -3575,8 +4094,8 @@ int notification_client_list_send_evaluation(
                }
 
                if (source_object_creds) {
-                       if (client->uid != source_object_creds->uid &&
-                                       client->gid != source_object_creds->gid &&
+                       if (client->uid != lttng_credentials_get_uid(source_object_creds) &&
+                                       client->gid != lttng_credentials_get_gid(source_object_creds) &&
                                        client->uid != 0) {
                                /*
                                 * Client is not allowed to monitor this
@@ -3587,14 +4106,15 @@ int notification_client_list_send_evaluation(
                        }
                }
 
-               if (client->uid != trigger_creds->uid && client->gid != trigger_creds->gid) {
+               if (client->uid != lttng_credentials_get_uid(trigger_creds) && client->gid != lttng_credentials_get_gid(trigger_creds)) {
                        DBG("[notification-thread] Skipping client at it does not have the permission to receive notification for this trigger");
                        goto skip_client;
                }
 
                DBG("[notification-thread] Sending notification to client (fd = %i, %zu bytes)",
                                client->socket, msg_payload.buffer.size);
-               if (client->communication.outbound.buffer.size) {
+
+               if (client_has_outbound_data_left(client)) {
                        /*
                         * Outgoing data is already buffered for this client;
                         * drop the notification and enqueue a "dropped
@@ -3609,9 +4129,7 @@ int notification_client_list_send_evaluation(
                        }
                }
 
-               ret = lttng_dynamic_buffer_append_buffer(
-                               &client->communication.outbound.buffer,
-                               &msg_payload.buffer);
+               ret = lttng_payload_copy(&msg_payload, &client->communication.outbound.payload);
                if (ret) {
                        /* Fatal error. */
                        goto skip_client;
@@ -3643,6 +4161,199 @@ end:
        return ret;
 }
 
+static struct lttng_event_notifier_notification *receive_notification(
+               int notification_pipe_read_fd, enum lttng_domain_type domain)
+{
+       int ret;
+       uint64_t token;
+       struct lttng_event_notifier_notification *notification = NULL;
+       void *reception_buffer;
+       size_t reception_size;
+
+       struct lttng_ust_event_notifier_notification ust_notification;
+       struct lttng_kernel_event_notifier_notification kernel_notification;
+
+       /* Init lttng_event_notifier_notification */
+       switch(domain) {
+       case LTTNG_DOMAIN_UST:
+               reception_buffer = (void *) &ust_notification;
+               reception_size = sizeof(ust_notification);
+               break;
+       case LTTNG_DOMAIN_KERNEL:
+               reception_buffer = (void *) &kernel_notification;
+               reception_size = sizeof(kernel_notification);
+               break;
+       default:
+               abort();
+       }
+
+       /*
+        * The monitoring pipe only holds messages smaller than PIPE_BUF,
+        * ensuring that read/write of tracer notifications are atomic.
+        */
+       ret = lttng_read(notification_pipe_read_fd, reception_buffer,
+                       reception_size);
+       if (ret != reception_size) {
+               PERROR("Failed to read from event source notification pipe: fd = %d, size to read = %zu, ret = %d",
+                               notification_pipe_read_fd, reception_size, ret);
+               ret = -1;
+               goto end;
+       }
+
+       switch(domain) {
+       case LTTNG_DOMAIN_UST:
+               token = ust_notification.token;
+               break;
+       case LTTNG_DOMAIN_KERNEL:
+               token = kernel_notification.token;
+               break;
+       default:
+               abort();
+       }
+
+       notification = lttng_event_notifier_notification_create(
+                       token, domain);
+end:
+       return notification;
+}
+
+int handle_notification_thread_event_notification(struct notification_thread_state *state,
+               int pipe,
+               enum lttng_domain_type domain)
+{
+       int ret;
+       enum lttng_trigger_status trigger_status;
+       struct cds_lfht_node *node;
+       struct cds_lfht_iter iter;
+       struct notification_trigger_tokens_ht_element *element;
+       struct lttng_evaluation *evaluation = NULL;
+       struct lttng_event_notifier_notification *notification = NULL;
+       enum action_executor_status executor_status;
+       struct notification_client_list *client_list = NULL;
+       const char *trigger_name;
+
+       notification = receive_notification(pipe, domain);
+       if (notification == NULL) {
+               ERR("[notification-thread] Error receiving notification from tracer (fd = %i, domain = %s)",
+                               pipe, lttng_domain_type_str(domain));
+               ret = -1;
+               goto end;
+       }
+
+       /* Find triggers associated with this token. */
+       rcu_read_lock();
+       cds_lfht_lookup(state->trigger_tokens_ht,
+                       hash_key_u64(&notification->tracer_token, lttng_ht_seed),
+                       match_trigger_token, &notification->tracer_token, &iter);
+       node = cds_lfht_iter_get_node(&iter);
+       if (caa_unlikely(!node)) {
+               /*
+                * This is not an error, slow consumption of the tracer
+                * notifications can lead to situations where a trigger is
+                * removed but we still get tracer notifications matching a
+                * trigger that no longer exists.
+                */
+               ret = 0;
+               goto end_unlock;
+       }
+
+       element = caa_container_of(node,
+                       struct notification_trigger_tokens_ht_element,
+                       node);
+
+       if (!lttng_trigger_should_fire(element->trigger)) {
+               ret = 0;
+               goto end_unlock;
+       }
+
+       lttng_trigger_fire(element->trigger);
+
+       trigger_status = lttng_trigger_get_name(element->trigger, &trigger_name);
+       assert(trigger_status == LTTNG_TRIGGER_STATUS_OK);
+
+       evaluation = lttng_evaluation_event_rule_create(
+                       trigger_name);
+       if (evaluation == NULL) {
+               ERR("[notification-thread] Failed to create event rule hit evaluation while creating and enqueuing action executor job");
+               ret = -1;
+               goto end_unlock;
+       }
+
+       client_list = get_client_list_from_condition(state,
+                       lttng_trigger_get_const_condition(element->trigger));
+       executor_status = action_executor_enqueue(state->executor,
+                       element->trigger, evaluation, NULL, client_list);
+       switch (executor_status) {
+       case ACTION_EXECUTOR_STATUS_OK:
+               ret = 0;
+               break;
+       case ACTION_EXECUTOR_STATUS_OVERFLOW:
+       {
+               struct notification_client_list_element *client_list_element,
+                               *tmp;
+
+               /*
+                * Not a fatal error; this is expected and simply means the
+                * executor has too much work queued already.
+                */
+               ret = 0;
+
+               /* No clients subscribed to notifications for this trigger. */
+               if (!client_list) {
+                       break;
+               }
+
+               /* Warn clients that a notification (or more) was dropped. */
+               pthread_mutex_lock(&client_list->lock);
+               cds_list_for_each_entry_safe(client_list_element, tmp,
+                               &client_list->list, node) {
+                       enum client_transmission_status transmission_status;
+                       struct notification_client *client =
+                                       client_list_element->client;
+
+                       pthread_mutex_lock(&client->lock);
+                       ret = client_notification_overflow(client);
+                       if (ret) {
+                               /* Fatal error. */
+                               goto next_client;
+                       }
+
+                       transmission_status =
+                                       client_flush_outgoing_queue(client);
+                       ret = client_handle_transmission_status(
+                                       client, transmission_status, state);
+                       if (ret) {
+                               /* Fatal error. */
+                               goto next_client;
+                       }
+next_client:
+                       pthread_mutex_unlock(&client->lock);
+                       if (ret) {
+                               break;
+                       }
+               }
+
+               pthread_mutex_unlock(&client_list->lock);
+               break;
+       }
+       case ACTION_EXECUTOR_STATUS_ERROR:
+               /* Fatal error, shut down everything. */
+               ERR("Fatal error encoutered while enqueuing action to the action executor");
+               ret = -1;
+               goto end_unlock;
+       default:
+               /* Unhandled error. */
+               abort();
+       }
+
+end_unlock:
+       lttng_event_notifier_notification_destroy(notification);
+       notification_client_list_put(client_list);
+       rcu_read_unlock();
+end:
+       return ret;
+}
+
 int handle_notification_thread_channel_sample(
                struct notification_thread_state *state, int pipe,
                enum lttng_domain_type domain)
@@ -3696,8 +4407,7 @@ int handle_notification_thread_channel_sample(
                 */
                DBG("[notification-thread] Received a sample for an unknown channel from consumerd, key = %" PRIu64 " in %s domain",
                                latest_sample.key.key,
-                               domain == LTTNG_DOMAIN_KERNEL ? "kernel" :
-                                       "user space");
+                               lttng_domain_type_str(domain));
                goto end_unlock;
        }
        channel_info = caa_container_of(node, struct channel_info,
@@ -3777,8 +4487,8 @@ int handle_notification_thread_channel_sample(
        }
 
        channel_creds = (typeof(channel_creds)) {
-               .uid = channel_info->session_info->uid,
-               .gid = channel_info->session_info->gid,
+               .uid = LTTNG_OPTIONAL_INIT_VALUE(channel_info->session_info->uid),
+               .gid = LTTNG_OPTIONAL_INIT_VALUE(channel_info->session_info->gid),
        };
 
        trigger_list = caa_container_of(node, struct lttng_channel_trigger_list,
@@ -3816,6 +4526,12 @@ int handle_notification_thread_channel_sample(
                        goto put_list;
                }
 
+               if (!lttng_trigger_should_fire(trigger)) {
+                       goto put_list;
+               }
+
+               lttng_trigger_fire(trigger);
+
                /*
                 * Ownership of `evaluation` transferred to the action executor
                 * no matter the result.
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