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SSL_CTX_sess_set_get_cb(3)          OpenSSL         SSL_CTX_sess_set_get_cb(3)

NAME
       SSL_CTX_sess_set_new_cb, SSL_CTX_sess_set_remove_cb,
       SSL_CTX_sess_set_get_cb, SSL_CTX_sess_get_new_cb,
       SSL_CTX_sess_get_remove_cb, SSL_CTX_sess_get_get_cb - provide callback
       functions for server side external session caching

SYNOPSIS
        #include <openssl/ssl.h>

        void SSL_CTX_sess_set_new_cb(SSL_CTX *ctx,
                                     int (*new_session_cb)(SSL *, SSL_SESSION *));
        void SSL_CTX_sess_set_remove_cb(SSL_CTX *ctx,
                  void (*remove_session_cb)(SSL_CTX *ctx, SSL_SESSION *));
        void SSL_CTX_sess_set_get_cb(SSL_CTX *ctx,
                  SSL_SESSION (*get_session_cb)(SSL *, unsigned char *, int, int *));

        int (*SSL_CTX_sess_get_new_cb(SSL_CTX *ctx))(struct ssl_st *ssl, SSL_SESSION *sess);
        void (*SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx))(struct ssl_ctx_st *ctx, SSL_SESSION *sess);
        SSL_SESSION *(*SSL_CTX_sess_get_get_cb(SSL_CTX *ctx))(struct ssl_st *ssl, unsigned char *data, int len, int *copy);

        int (*new_session_cb)(struct ssl_st *ssl, SSL_SESSION *sess);
        void (*remove_session_cb)(struct ssl_ctx_st *ctx, SSL_SESSION *sess);
        SSL_SESSION *(*get_session_cb)(struct ssl_st *ssl, unsigned char *data,
                      int len, int *copy);

DESCRIPTION
       SSL_CTX_sess_set_new_cb() sets the callback function, which is
       automatically called whenever a new session was negotiated.

       SSL_CTX_sess_set_remove_cb() sets the callback function, which is
       automatically called whenever a session is removed by the SSL engine,
       because it is considered faulty or the session has become obsolete
       because of exceeding the timeout value.

       SSL_CTX_sess_set_get_cb() sets the callback function which is called,
       whenever a SSL/TLS client proposed to resume a session but the session
       could not be found in the internal session cache (see
       SSL_CTX_set_session_cache_mode(3)).  (SSL/TLS server only.)

       SSL_CTX_sess_get_new_cb(), SSL_CTX_sess_get_remove_cb(), and
       SSL_CTX_sess_get_get_cb() allow to retrieve the function pointers of
       the provided callback functions. If a callback function has not been
       set, the NULL pointer is returned.

NOTES
       In order to allow external session caching, synchronization with the
       internal session cache is realized via callback functions. Inside these
       callback functions, session can be saved to disk or put into a database
       using the d2i_SSL_SESSION(3) interface.

       The new_session_cb() is called, whenever a new session has been
       negotiated and session caching is enabled (see
       SSL_CTX_set_session_cache_mode(3)).  The new_session_cb() is passed the
       ssl connection and the ssl session sess. If the callback returns 0, the
       session will be immediately removed again.

       The remove_session_cb() is called, whenever the SSL engine removes a
       session from the internal cache. This happens when the session is
       removed because it is expired or when a connection was not shutdown
       cleanly. It also happens for all sessions in the internal session cache
       when SSL_CTX_free(3) is called. The remove_session_cb() is passed the
       ctx and the ssl session sess. It does not provide any feedback.

       The get_session_cb() is only called on SSL/TLS servers with the session
       id proposed by the client. The get_session_cb() is always called, also
       when session caching was disabled. The get_session_cb() is passed the
       ssl connection, the session id of length length at the memory location
       data. With the parameter copy the callback can require the SSL engine
       to increment the reference count of the SSL_SESSION object, Normally
       the reference count is not incremented and therefore the session must
       not be explicitly freed with SSL_SESSION_free(3).

SEE ALSO
       ssl(3), d2i_SSL_SESSION(3), SSL_CTX_set_session_cache_mode(3),
       SSL_CTX_flush_sessions(3), SSL_SESSION_free(3), SSL_CTX_free(3)

1.0.2h                            2016-05-03        SSL_CTX_sess_set_get_cb(3)