- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- SEE ALSO
- HISTORY
- COPYRIGHT

# 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 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 https://www.openssl.org/source/license.html.