Whitespace cleanup in docs

[openssl.git] / doc / ssl / SSL_SESSION_free.pod

diff --git a/doc/ssl/SSL_SESSION_free.pod b/doc/ssl/SSL_SESSION_free.pod
index 5e104d5f2f5792a4168dd616f479151750d56874..1906510e4168d9be2191e2d4476168fc9ee6ea0f 100644 (file)
--- a/doc/ssl/SSL_SESSION_free.pod
+++ b/doc/ssl/SSL_SESSION_free.pod
@@ -8,18 +8,58 @@ SSL_SESSION_free - free an allocated SSL_SESSION structure
 
  #include <openssl/ssl.h>
 
- void *SSL_SESSION_free(SSL_SESSION *session);
+ void SSL_SESSION_free(SSL_SESSION *session);
 
 =head1 DESCRIPTION
 
 SSL_SESSION_free() decrements the reference count of B<session> and removes
 the B<SSL_SESSION> structure pointed to by B<session> and frees up the allocated
-memory, if the the reference count has reached 0.
+memory, if the reference count has reached 0.
+If B<session> is NULL nothing is done.
+
+=head1 NOTES
+
+SSL_SESSION objects are allocated, when a TLS/SSL handshake operation
+is successfully completed. Depending on the settings, see
+L<SSL_CTX_set_session_cache_mode(3)>,
+the SSL_SESSION objects are internally referenced by the SSL_CTX and
+linked into its session cache. SSL objects may be using the SSL_SESSION object;
+as a session may be reused, several SSL objects may be using one SSL_SESSION
+object at the same time. It is therefore crucial to keep the reference
+count (usage information) correct and not delete a SSL_SESSION object
+that is still used, as this may lead to program failures due to
+dangling pointers. These failures may also appear delayed, e.g.
+when an SSL_SESSION object was completely freed as the reference count
+incorrectly became 0, but it is still referenced in the internal
+session cache and the cache list is processed during a
+L<SSL_CTX_flush_sessions(3)> operation.
+
+SSL_SESSION_free() must only be called for SSL_SESSION objects, for
+which the reference count was explicitly incremented (e.g.
+by calling SSL_get1_session(), see L<SSL_get_session(3)>)
+or when the SSL_SESSION object was generated outside a TLS handshake
+operation, e.g. by using L<d2i_SSL_SESSION(3)>.
+It must not be called on other SSL_SESSION objects, as this would cause
+incorrect reference counts and therefore program failures.
 
 =head1 RETURN VALUES
 
 SSL_SESSION_free() does not provide diagnostic information.
 
-L<ssl(3)|ssl(3)>, L<SSL_get_session(3)|SSL_get_session(3)>
+=head1 SEE ALSO
+
+L<ssl(3)>, L<SSL_get_session(3)>,
+L<SSL_CTX_set_session_cache_mode(3)>,
+L<SSL_CTX_flush_sessions(3)>,
+L<d2i_SSL_SESSION(3)>
+
+=head1 COPYRIGHT
+
+Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the OpenSSL license (the "License").  You may not use
+this file except in compliance with the License.  You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
 
 =cut