.\" $OpenBSD: SSL_get_version.3,v 1.9 2021/04/15 16:13:22 tb Exp $
.\" full merge up to: OpenSSL e417070c Jun 8 11:37:06 2016 -0400
.\" selective merge up to: OpenSSL df75c2bf Dec 9 01:02:36 2018 +0100
.\"
.\" This file was written by Lutz Jaenicke <jaenicke@openssl.org>.
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.Dd $Mdocdate: April 15 2021 $
.Dt SSL_GET_VERSION 3
.Os
.Sh NAME
.Nm SSL_get_version ,
.Nm SSL_is_dtls ,
.Nm SSL_version
.\" The following are intentionally undocumented because
.\" - the longer term plan is to remove them
.\" - nothing appears to be using them in the wild
.\" - and they have the wrong namespace prefix
.\" Nm TLS1_get_version
.\" Nm TLS1_get_client_version
.Nd get the protocol information of a connection
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft const char *
.Fn SSL_get_version "const SSL *ssl"
.Ft int
.Fn SSL_is_dtls "const SSL *ssl"
.Ft int
.Fn SSL_version "const SSL *ssl"
.Sh DESCRIPTION
.Fn SSL_get_version
returns the name of the protocol used for the connection
.Fa ssl .
.Pp
.Fn SSL_is_dtls
returns 1 if the connection is using DTLS, 0 if not.
.Pp
.Fn SSL_version
returns an integer constant representing that protocol.
.Pp
These functions only return reliable results
after the initial handshake has been completed.
.Sh RETURN VALUES
The following strings or integers can be returned by
.Fn SSL_get_version
and
.Fn SSL_version :
.Bl -tag -width Ds
.It Qo TLSv1 Qc No or Dv TLS1_VERSION
The connection uses the TLSv1.0 protocol.
.It Qo TLSv1.1 Qc No or Dv TLS1_1_VERSION
The connection uses the TLSv1.1 protocol.
.It Qo TLSv1.2 Qc No or Dv TLS1_2_VERSION
The connection uses the TLSv1.2 protocol.
.It Qo TLSv1.3 Qc No or Dv TLS1_3_VERSION
The connection uses the TLSv1.3 protocol.
.It Qo DTLSv1 Qc No or Dv DTLS1_VERSION
The connection uses the Datagram Transport Layer Security 1.0 protocol.
.It Qo DTLSv1.2 Qc No or Dv DTLS1_2_VERSION
The connection uses the Datagram Transport Layer Security 1.2 protocol.
.It Qq unknown
This indicates an unknown protocol version;
it cannot currently happen with LibreSSL.
.El
.Pp
.Fn SSL_is_dtls
returns 1 if the connection uses DTLS, 0 if not.
.Sh SEE ALSO
.Xr ssl 3
.Sh HISTORY
.Fn SSL_get_version
and
.Fn SSL_version
first appeared in SSLeay 0.8.0 and have been available since
.Ox 2.4 .
.Pp
.Fn SSL_is_dtls
first appeared in OpenSSL 1.1.0 and has been available since
.Ox 6.9 .