=pod

=head1 NAME

SSL_get_session - retrieve TLS/SSL session data

=head1 SYNOPSIS

 #include <openssl/ssl.h>

 SSL_SESSION *SSL_get_session(const SSL *ssl);
 SSL_SESSION *SSL_get0_session(const SSL *ssl);
 SSL_SESSION *SSL_get1_session(SSL *ssl);

=head1 DESCRIPTION

SSL_get_session() returns a pointer to the B<SSL_SESSION> actually used in
B<ssl>. The reference count of the B<SSL_SESSION> is not incremented, so
that the pointer can become invalid by other operations.

SSL_get0_session() is the same as SSL_get_session().

SSL_get1_session() is the same as SSL_get_session(), but the reference
count of the B<SSL_SESSION> is incremented by one.

=head1 NOTES

The ssl session contains all information required to re-establish the
connection without a new handshake.

A session will be automatically removed from the session cache and marked as
non-resumable if the connection is not closed down cleanly, e.g. if a fatal
error occurs on the connection or L<SSL_shutdown(3)> is not called prior to
L<SSL_free(3)>.

SSL_get0_session() returns a pointer to the actual session. As the
reference counter is not incremented, the pointer is only valid while
the connection is in use. If L<SSL_clear(3)|SSL_clear(3)> or
L<SSL_free(3)|SSL_free(3)> is called, the session may be removed completely
(if considered bad), and the pointer obtained will become invalid. Even
if the session is valid, it can be removed at any time due to timeout
during L<SSL_CTX_flush_sessions(3)|SSL_CTX_flush_sessions(3)>.

If the data is to be kept, SSL_get1_session() will increment the reference
count, so that the session will not be implicitly removed by other operations
but stays in memory. In order to remove the session
L<SSL_SESSION_free(3)|SSL_SESSION_free(3)> must be explicitly called once
to decrement the reference count again.

SSL_SESSION objects keep internal link information about the session cache
list, when being inserted into one SSL_CTX object's session cache.
One SSL_SESSION object, regardless of its reference count, must therefore
only be used with one SSL_CTX object (and the SSL objects created
from this SSL_CTX object).

=head1 RETURN VALUES

The following return values can occur:

=over 4

=item NULL

There is no session available in B<ssl>.

=item Pointer to an SSL

The return value points to the data of an SSL session.

=back

=head1 SEE ALSO

L<ssl(3)|ssl(3)>, L<SSL_free(3)|SSL_free(3)>,
L<SSL_clear(3)|SSL_clear(3)>,
L<SSL_SESSION_free(3)|SSL_SESSION_free(3)>

=cut
