SSL_CTX_SET_SESSION_CACHE_MODOpenSSL_CTX_SET_SESSION_CACHE_MODE(3)

NAME    [Toc]    [Back]

       SSL_CTX_set_session_cache_mode, SSL_CTX_get_session_cache_mode
 - enable/disable session caching

SYNOPSIS    [Toc]    [Back]

        #include <openssl/ssl.h>

        long  SSL_CTX_set_session_cache_mode(SSL_CTX  ctx,   long
mode);
        long SSL_CTX_get_session_cache_mode(SSL_CTX ctx);

DESCRIPTION    [Toc]    [Back]

       SSL_CTX_set_session_cache_mode() enables/disables session
       caching by setting the operational mode for ctx to <mode>.

       SSL_CTX_get_session_cache_mode() returns the currently
       used cache mode.

NOTES    [Toc]    [Back]

       The OpenSSL library can store/retrieve SSL/TLS sessions
       for later reuse.  The sessions can be held in memory for
       each ctx, if more than one SSL_CTX object is being maintained,
 the sessions are unique for each SSL_CTX object.

       In order to reuse a session, a client must send the session's
 id to the server. It can only send exactly one  id.
       The server then either agrees to reuse the session or it
       starts a full handshake (to create a new session).

       A server will lookup up the session in its internal session
 storage. If the session is not found in internal
       storage or lookups for the internal storage have been
       deactivated (SSL_SESS_CACHE_NO_INTERNAL_LOOKUP), the
       server will try the external storage if available.

       Since a client may try to reuse a session intended for use
       in a different context, the session id context must be set
       by the server (see SSL_CTX_set_session_id_context(3)).

       The following session cache modes and modifiers are available:


       SSL_SESS_CACHE_OFF
           No session caching for client or server takes place.

       SSL_SESS_CACHE_CLIENT
           Client sessions are added to the session cache. As
           there is no reliable way for the OpenSSL library to
           know whether a session should be reused or which session
 to choose (due to the abstract BIO layer the SSL
           engine does not have details about the connection),
           the application must select the session to be reused
           by using the SSL_set_session(3) function. This option
           is not activated by default.
SSL_CTX_SET_SESSION_CACHE_MODOpenSSL_CTX_SET_SESSION_CACHE_MODE(3)


       SSL_SESS_CACHE_SERVER
           Server sessions are added to the session cache. When a
           client proposes a session to be reused, the server
           looks for the corresponding session in (first) the
           internal session cache (unless
           SSL_SESS_CACHE_NO_INTERNAL_LOOKUP is set), then (second)
 in the external cache if available. If the session
 is found, the server will try to reuse the session.
  This is the default.

       SSL_SESS_CACHE_BOTH
           Enable both SSL_SESS_CACHE_CLIENT and
           SSL_SESS_CACHE_SERVER at the same time.

       SSL_SESS_CACHE_NO_AUTO_CLEAR
           Normally the session cache is checked for expired sessions
 every 255 connections using the
           SSL_CTX_flush_sessions(3) function. Since this may
           lead to a delay which cannot be controlled, the automatic
 flushing may be disabled and
           SSL_CTX_flush_sessions(3) can be called explicitly by
           the application.

       SSL_SESS_CACHE_NO_INTERNAL_LOOKUP
           By setting this flag, session-resume operations in an
           SSL/TLS server will not automatically look up sessions
           in the internal cache, even if sessions are automatically
 stored there. If external session caching callbacks
 are in use, this flag guarantees that all
           lookups are directed to the external cache.  As automatic
 lookup only applies for SSL/TLS servers, the
           flag has no effect on clients.

       SSL_SESS_CACHE_NO_INTERNAL_STORE
           Depending on the presence of SSL_SESS_CACHE_CLIENT
           and/or SSL_SESS_CACHE_SERVER, sessions negotiated in
           an SSL/TLS handshake may be cached for possible reuse.
           Normally a new session is added to the internal cache
           as well as any external session caching (callback)
           that is configured for the SSL_CTX. This flag will
           prevent sessions being stored in the internal cache
           (though the application can add them manually using
           SSL_CTX_add_session(3)). Note: in any SSL/TLS servers
           where external caching is configured, any successful
           session lookups in the external cache (ie. for session-resume
 requests) would normally be copied into
           the local cache before processing continues - this
           flag prevents these additions to the internal cache as
           well.

       SSL_SESS_CACHE_NO_INTERNAL
           Enable both SSL_SESS_CACHE_NO_INTERNAL_LOOKUP and
           SSL_SESS_CACHE_NO_INTERNAL_STORE at the same time.
SSL_CTX_SET_SESSION_CACHE_MODOpenSSL_CTX_SET_SESSION_CACHE_MODE(3)


       The default mode is SSL_SESS_CACHE_SERVER.

RETURN VALUES    [Toc]    [Back]

       SSL_CTX_set_session_cache_mode() returns the previously
       set cache mode.

       SSL_CTX_get_session_cache_mode() returns the currently set
       cache mode.

SEE ALSO    [Toc]    [Back]

       ssl(3), SSL_set_session(3), SSL_session_reused(3),
       SSL_CTX_add_session(3), SSL_CTX_sess_number(3),
       SSL_CTX_sess_set_cache_size(3),
       SSL_CTX_sess_set_get_cb(3),
       SSL_CTX_set_session_id_context(3), SSL_CTX_set_timeout(3),
       SSL_CTX_flush_sessions(3)

HISTORY    [Toc]    [Back]

       SSL_SESS_CACHE_NO_INTERNAL_STORE and
       SSL_SESS_CACHE_NO_INTERNAL were introduced in OpenSSL
       0.9.6h.


OpenBSD 3.6                 2003-05-11                          3