=pod
=head1 NAME
SSL_client_version, SSL_get_version, SSL_is_dtls, SSL_version - get the
protocol information of a connection
=head1 SYNOPSIS
#include <openssl/ssl.h>
int SSL_client_version(const SSL *s);
const char *SSL_get_version(const SSL *ssl);
int SSL_is_dtls(const SSL *ssl);
int SSL_version(const SSL *s);
=head1 DESCRIPTION
SSL_client_version() returns the numeric protocol version advertised by the
client in the legacy_version field of the ClientHello when initiating the
connection. Note that, for TLS, this value will never indicate a version greater
than TLSv1.2 even if TLSv1.3 is subsequently negotiated. SSL_get_version()
returns the name of the protocol used for the connection. SSL_version() returns
the numeric protocol version used for the connection. They should only be called
after the initial handshake has been completed. Prior to that the results
returned from these functions may be unreliable.
SSL_is_dtls() returns one if the connection is using DTLS, zero if not.
=head1 RETURN VALUES
SSL_get_version() returns one of the following strings:
=over 4
=item SSLv3
The connection uses the SSLv3 protocol.
=item TLSv1
The connection uses the TLSv1.0 protocol.
=item TLSv1.1
The connection uses the TLSv1.1 protocol.
=item TLSv1.2
The connection uses the TLSv1.2 protocol.
=item TLSv1.3
The connection uses the TLSv1.3 protocol.
=item unknown
This indicates an unknown protocol version.
=back
SSL_version() and SSL_client_version() return an integer which could include any
of the following:
=over 4
=item SSL3_VERSION
The connection uses the SSLv3 protocol.
=item TLS1_VERSION
The connection uses the TLSv1.0 protocol.
=item TLS1_1_VERSION
The connection uses the TLSv1.1 protocol.
=item TLS1_2_VERSION
The connection uses the TLSv1.2 protocol.
=item TLS1_3_VERSION
The connection uses the TLSv1.3 protocol (never returned for
SSL_client_version()).
=back
=head1 SEE ALSO
L<ssl(7)>
=head1 HISTORY
The SSL_is_dtls() function was added in OpenSSL 1.1.0.
=head1 COPYRIGHT
Copyright 2001-2018 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