session FEATURE keep refcount (#303)

* referencing of nc-sessions

* do it atomic

Author: frimpler

src/config.h.in

@@ -41,12 +41,14 @@
 # define ATOMIC_STORE(x, val) atomic_store(&(x), (val))
 # define ATOMIC_LOAD(x) atomic_load((atomic_uintptr_t *)&(x))
 # define ATOMIC_INC(x) atomic_fetch_add(&(x), 1)
+# define ATOMIC_DEC(x) atomic_fetch_sub(&(x), 1)
 #else
 # define ATOMIC_UINT32_T uint32_t
 # define ATOMIC_PTR void *
 # define ATOMIC_STORE(x, val) (x) = (val)
 # define ATOMIC_LOAD(x) (x)
 # define ATOMIC_INC(x) __sync_add_and_fetch(&(x), 1)
+# define ATOMIC_DEC(x) __sync_sub_and_fetch(&(x), 1)
 #endif
 
 /*

src/session.c

@@ -469,6 +469,39 @@ nc_session_get_id(const struct nc_session *session)
     return session->id;
 }
 
+API uint32_t
+nc_session_get_refcnt(const struct nc_session *session)
+{
+    if (!session) {
+        ERRARG("session");
+        return -1;
+    }
+
+    return ATOMIC_LOAD(session->opts.server.ref_count);
+}
+
+API void
+nc_session_reference(struct nc_session *session)
+{
+    if (!session) {
+        ERRARG("session");
+    }
+
+    ATOMIC_INC(session->opts.server.ref_count);
+}
+
+API void
+nc_session_dereference(struct nc_session *session)
+{
+    if (!session) {
+        ERRARG("session");
+    }
+
+    if (ATOMIC_LOAD(session->opts.server.ref_count)) {
+        ATOMIC_DEC(session->opts.server.ref_count);
+    }
+}
+
 API int
 nc_session_get_version(const struct nc_session *session)
 {

src/session.h

@@ -143,6 +143,29 @@ uint32_t nc_session_get_killed_by(const struct nc_session *session);
  */
 uint32_t nc_session_get_id(const struct nc_session *session);
 
+/**
+ * @brief Get reference count.
+ *
+ * @param[in] session Session to get the information from.
+ * @return Session ID.
+ */
+uint32_t nc_session_get_refcnt(const struct nc_session *session);
+/**
+ * @brief Put a reference to the session in order to avoid
+ *        unwanted release of session.
+ *
+ * @param[in] session Session to get the information from.
+ * @return Session ID.
+ */
+void nc_session_reference(struct nc_session *session);
+/**
+ * @brief Take reference from the session
+ *
+ * @param[in] session Session to get the information from.
+ * @return Session ID.
+ */
+void nc_session_dereference(struct nc_session *session);
+
 /**
  * @brief Get session NETCONF version.
  *

src/session_p.h

@@ -456,6 +456,7 @@ struct nc_session {
 
             pthread_mutex_t ch_lock;       /**< Call Home thread lock */
             pthread_cond_t ch_cond;        /**< Call Home thread condition */
+            ATOMIC_UINT32_T ref_count;     /**< Reference count: when referenced by SR's event session ncid */
 
             /* server flags */
 #ifdef NC_ENABLED_SSH