SSL_SESSION_free(3) OpenSSL SSL_SESSION_free(3)
SSL_SESSION_free - free an allocated SSL_SESSION structure
void SSL_SESSION_free(SSL_SESSION *session);
SSL_SESSION_free() decrements the reference count of session and
removes the SSL_SESSION structure pointed to by session and frees up
the allocated memory, if the the reference count has reached 0.
SSL_SESSION objects are allocated, when a TLS/SSL handshake operation
is successfully completed. Depending on the settings, see
SSL_CTX_set_session_cache_mode(3), the SSL_SESSION objects are inter-
nally referenced by the SSL_CTX and linked into its session cache. SSL
objects may be using the SSL_SESSION object; as a session may be
reused, several SSL objects may be using one SSL_SESSION object at the
same time. It is therefore crucial to keep the reference count (usage
information) correct and not delete a SSL_SESSION object that is still
used, as this may lead to program failures due to dangling pointers.
These failures may also appear delayed, e.g. when an SSL_SESSION
object was completely freed as the reference count incorrectly became
0, but it is still referenced in the internal session cache and the
cache list is processed during a SSL_CTX_flush_sessions(3) operation.
SSL_SESSION_free() must only be called for SSL_SESSION objects, for
which the reference count was explicitly incremented (e.g. by calling
SSL_get1_session(), see SSL_get_session(3)) or when the SSL_SESSION
object was generated outside a TLS handshake operation, e.g. by using
d2i_SSL_SESSION(3). It must not be called on other SSL_SESSION
objects, as this would cause incorrect reference counts and therefore
SSL_SESSION_free() does not provide diagnostic information.
ssl(3), SSL_get_session(3), SSL_CTX_set_session_cache_mode(3),
3rd Berkeley Distribution 0.9.7d SSL_SESSION_free(3)