+#define LTTNG_UST_ENUM_HT_BITS 12
+#define LTTNG_UST_ENUM_HT_SIZE (1U << LTTNG_UST_ENUM_HT_BITS)
+
+struct lttng_ust_enum_ht {
+ struct cds_hlist_head table[LTTNG_UST_ENUM_HT_SIZE];
+};
+
+/*
+ * IMPORTANT: this structure is part of the ABI between the probe and
+ * UST. Fields need to be only added at the end, never reordered, never
+ * removed.
+ */
+struct lttng_session {
+ int active; /* Is trace session active ? */
+ int been_active; /* Been active ? */
+ int objd; /* Object associated */
+ void *_deprecated1;
+ struct cds_list_head chan_head; /* Channel list head */
+ struct cds_list_head events_head; /* list of events */
+ struct cds_list_head _deprecated2;
+ struct cds_list_head node; /* Session list */
+ int _deprecated3;
+ unsigned int _deprecated4:1;
+
+ /* New UST 2.1 */
+ /* List of enablers */
+ struct cds_list_head enablers_head;
+ struct lttng_ust_event_ht events_ht; /* ht of events */
+ void *owner; /* object owner */
+ int tstate:1; /* Transient enable state */
+
+ /* New UST 2.4 */
+ int statedump_pending:1;
+
+ /* New UST 2.8 */
+ struct lttng_ust_enum_ht enums_ht; /* ht of enumerations */
+ struct cds_list_head enums_head;
+ struct lttng_ctx *ctx; /* contexts for filters. */
+};
+
+struct lttng_transport {