SSL_CTX_set_session_cache_moOpSSL_CTX_set_session_cache_mode(3)





NAME
       SSL_CTX_set_session_cache_mode, SSL_CTX_get_ses-
       sion_cache_mode - enable/disable session caching

SYNOPSIS
        #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
       SSL_CTX_set_session_cache_mode() enables/disables ses-
       sion caching by setting the operational mode for ctx to
       <mode>.

       SSL_CTX_get_session_cache_mode() returns the currently
       used cache mode.

NOTES
       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 main-
       tained, the sessions are unique for each SSL_CTX object.

       In order to reuse a session, a client must send the ses-
       sion'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 ses-
       sion 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_con-
       text(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 connec-
           tion), 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_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 re-
           use.  Normally a new session is added to the inter-
           nal 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 config-
           ured, any successful session lookups in the external
           cache (ie. for session-resume requests) would nor-
           mally be copied into the local cache before process-
           ing 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.

       The default mode is SSL_SESS_CACHE_SERVER.

RETURN VALUES
       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
       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_con-
       text(3), SSL_CTX_set_timeout(3), SSL_CTX_flush_ses-
       sions(3)

HISTORY
       SSL_SESS_CACHE_NO_INTERNAL_STORE and
       SSL_SESS_CACHE_NO_INTERNAL were introduced in OpenSSL
       0.9.6h.



0.9.7c                     200SSL_CTX_set_session_cache_mode(3)
