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129.\" ========================================================================
130.\"
131.IX Title "SSL_CTX_sess_set_get_cb 3"
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133.\" For nroff, turn off justification. Always turn off hyphenation; it makes
134.\" way too many mistakes in technical documents.
135.if n .ad l
136.nh
137.SH "NAME"
138SSL_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
139.SH "SYNOPSIS"
140.IX Header "SYNOPSIS"
141.Vb 1
142\& #include <openssl/ssl.h>
143\&
144\& void SSL_CTX_sess_set_new_cb(SSL_CTX *ctx,
145\& int (*new_session_cb)(SSL *, SSL_SESSION *));
146\& void SSL_CTX_sess_set_remove_cb(SSL_CTX *ctx,
147\& void (*remove_session_cb)(SSL_CTX *ctx, SSL_SESSION *));
148\& void SSL_CTX_sess_set_get_cb(SSL_CTX *ctx,
149\& SSL_SESSION (*get_session_cb)(SSL *, unsigned char *, int, int *));
150\&
151\& int (*SSL_CTX_sess_get_new_cb(SSL_CTX *ctx))(struct ssl_st *ssl, SSL_SESSION *sess);
152\& void (*SSL_CTX_sess_get_remove_cb(SSL_CTX *ctx))(struct ssl_ctx_st *ctx, SSL_SESSION *sess);
153\& SSL_SESSION *(*SSL_CTX_sess_get_get_cb(SSL_CTX *ctx))(struct ssl_st *ssl, unsigned char *data, int len, int *copy);
154\&
155\& int (*new_session_cb)(struct ssl_st *ssl, SSL_SESSION *sess);
156\& void (*remove_session_cb)(struct ssl_ctx_st *ctx, SSL_SESSION *sess);
157\& SSL_SESSION *(*get_session_cb)(struct ssl_st *ssl, unsigned char *data,
158\& int len, int *copy);
159.Ve
160.SH "DESCRIPTION"
161.IX Header "DESCRIPTION"
162\&\fISSL_CTX_sess_set_new_cb()\fR sets the callback function, which is automatically
163called whenever a new session was negotiated.
164.PP
165\&\fISSL_CTX_sess_set_remove_cb()\fR sets the callback function, which is
166automatically called whenever a session is removed by the \s-1SSL\s0 engine,
167because it is considered faulty or the session has become obsolete because
168of exceeding the timeout value.
169.PP
170\&\fISSL_CTX_sess_set_get_cb()\fR sets the callback function which is called,
171whenever a \s-1SSL/TLS\s0 client proposed to resume a session but the session
172could not be found in the internal session cache (see
173\&\fISSL_CTX_set_session_cache_mode\fR\|(3)).
174(\s-1SSL/TLS\s0 server only.)
175.PP
176\&\fISSL_CTX_sess_get_new_cb()\fR, \fISSL_CTX_sess_get_remove_cb()\fR, and
177\&\fISSL_CTX_sess_get_get_cb()\fR allow to retrieve the function pointers of the
178provided callback functions. If a callback function has not been set,
179the \s-1NULL\s0 pointer is returned.
180.SH "NOTES"
181.IX Header "NOTES"
182In order to allow external session caching, synchronization with the internal
183session cache is realized via callback functions. Inside these callback
184functions, session can be saved to disk or put into a database using the
185\&\fId2i_SSL_SESSION\fR\|(3) interface.
186.PP
187The \fInew_session_cb()\fR is called, whenever a new session has been negotiated
188and session caching is enabled (see
189\&\fISSL_CTX_set_session_cache_mode\fR\|(3)).
190The \fInew_session_cb()\fR is passed the \fBssl\fR connection and the ssl session
191\&\fBsess\fR. If the callback returns \fB0\fR, the session will be immediately
192removed again.
193.PP
194The \fIremove_session_cb()\fR is called, whenever the \s-1SSL\s0 engine removes a session
195from the internal cache. This happens when the session is removed because
196it is expired or when a connection was not shutdown cleanly. It also happens
197for all sessions in the internal session cache when
198\&\fISSL_CTX_free\fR\|(3) is called. The \fIremove_session_cb()\fR is passed
199the \fBctx\fR and the ssl session \fBsess\fR. It does not provide any feedback.
200.PP
201The \fIget_session_cb()\fR is only called on \s-1SSL/TLS\s0 servers with the session id
202proposed by the client. The \fIget_session_cb()\fR is always called, also when
203session caching was disabled. The \fIget_session_cb()\fR is passed the
204\&\fBssl\fR connection, the session id of length \fBlength\fR at the memory location
205\&\fBdata\fR. With the parameter \fBcopy\fR the callback can require the
206\&\s-1SSL\s0 engine to increment the reference count of the \s-1SSL_SESSION\s0 object,
207Normally the reference count is not incremented and therefore the
208session must not be explicitly freed with
209\&\fISSL_SESSION_free\fR\|(3).
210.SH "SEE ALSO"
211.IX Header "SEE ALSO"
212\&\fIssl\fR\|(3), \fId2i_SSL_SESSION\fR\|(3),
213\&\fISSL_CTX_set_session_cache_mode\fR\|(3),
214\&\fISSL_CTX_flush_sessions\fR\|(3),
215\&\fISSL_SESSION_free\fR\|(3),
216\&\fISSL_CTX_free\fR\|(3)
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