DESCRIPTIONSSL_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. NOTESSSL_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 internally 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 program failures.
RETURN VALUESSSL_SESSION_free() does not provide diagnostic information. SEE ALSOssl(3) , SSL_get_session(3) , SSL_CTX_set_session_cache_mode(3) , SSL_CTX_flush_sessions(3) , d2i_SSL_SESSION(3)
HP Open Source Security for OpenVMS Volume 2:... 
SSL Application Programming Interface (API) Reference
