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SSL_CTX_set_session_cache_mode(3)
NAME
  SSL_CTX_set_session_cache_mode, SSL_CTX_get_session_cache_mode - Enable or
  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
  The SSL_CTX_set_session_cache_mode() function enables or disables session
  caching by setting the operational mode for ctx to <mode>.

  The SSL_CTX_get_session_cache_mode() function 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 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 one id.  The server then decides whether to reuse
  the session or start the handshake for a new session.

  A server will check the session in its internal session storage. If the
  session is not found in internal storage or internal storage, it is
  deactivated.	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() 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 be reused, the session is looked up in the
	  internal session cache. 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() function. Since
	  this might lead to a delay which cannot be controlled, the
	  automatic flushing can be disabled and the SSL_CTX_flush_sessions()
	  can be called explicitly by the application.

  SSL_SESS_CACHE_NO_INTERNAL_LOOKUP
	  By setting this option, sessions are cached in the internal storage
	  but they are not looked up automatically. If an external session
	  cache is enabled, sessions are looked up in the external cache. As
	  automatic lookup only applies for SSL/TLS servers.  The option has
	  no effect on clients.

  The default mode is SSL_SESS_CACHE_SERVER.

RETURN VALUES
  The SSL_CTX_set_session_cache_mode() function returns the previously set
  cache mode.

  The SSL_CTX_get_session_cache_mode() function returns the currently set
  cache mode.

SEE ALSO
  Functions: ssl(3), SSL_set_session(3), SSL_session_reused(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)

Index for Section 3

Alphabetical listing for S

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