NAME

       SSL_client_version, SSL_get_version, SSL_is_dtls, SSL_version - get the protocol
       information of a connection

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);

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.

RETURN VALUES

       SSL_get_version() returns one of the following strings:

       SSLv3
           The connection uses the SSLv3 protocol.

       TLSv1
           The connection uses the TLSv1.0 protocol.

       TLSv1.1
           The connection uses the TLSv1.1 protocol.

       TLSv1.2
           The connection uses the TLSv1.2 protocol.

       TLSv1.3
           The connection uses the TLSv1.3 protocol.

       unknown
           This indicates an unknown protocol version.

       SSL_version() and SSL_client_version() return an integer which could include any of the
       following:

       SSL3_VERSION
           The connection uses the SSLv3 protocol.

       TLS1_VERSION
           The connection uses the TLSv1.0 protocol.

       TLS1_1_VERSION
           The connection uses the TLSv1.1 protocol.

       TLS1_2_VERSION
           The connection uses the TLSv1.2 protocol.

       TLS1_3_VERSION
           The connection uses the TLSv1.3 protocol (never returned for SSL_client_version()).

SEE ALSO

       ssl(7)

HISTORY

       The SSL_is_dtls() function was added in OpenSSL 1.1.0.

COPYRIGHT

       Copyright 2001-2018 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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 <https://www.openssl.org/source/license.html>.