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

=pod

=head1 NAME

SSL_SESSION_free - free an allocated SSL_SESSION structure

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 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 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.

=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)>

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