NAME
SSL_SESSION_up_ref,
SSL_SESSION_free —
SSL_SESSION reference
counting
SYNOPSIS
#include
<openssl/ssl.h>
int
SSL_SESSION_up_ref(SSL_SESSION
*session);
void
SSL_SESSION_free(SSL_SESSION
*session);
DESCRIPTION
SSL_SESSION_up_ref()
increments the reference count of the given session by
1.
SSL_SESSION_free()
decrements the reference count of the given session by
1. If the reference count reaches 0, it frees the memory used by the
session. If session is a
NULL pointer, no action occurs.
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 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 is completely freed as the reference count incorrectly becomes 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(3); 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 VALUES
SSL_SESSION_up_ref() returns 1 on success
or 0 on error.
SEE ALSO
d2i_SSL_SESSION(3), ssl(3), SSL_CTX_flush_sessions(3), SSL_CTX_set_session_cache_mode(3), SSL_get_session(3), SSL_SESSION_new(3)
HISTORY
SSL_SESSION_free() first appeared in
SSLeay 0.5.2 and has been available since OpenBSD
2.4.
SSL_SESSION_up_ref() first appeared in
OpenSSL 1.1.0 and has been available since OpenBSD
6.3.