=pod

=head1 NAME

SSL_client_version, SSL_get_version, SSL_is_dtls, SSL_is_tls, SSL_is_quic,
SSL_CTX_is_quic, SSL_CTX_is_server, 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_is_tls(const SSL *ssl);
 int SSL_is_quic(const SSL *ssl);
 int SSL_CTX_is_quic(const SSL_CTX *ctx);
 int SSL_CTX_is_server(const SSL_CTX *ctx);

 int SSL_version(const SSL *s);

=head1 DESCRIPTION

For SSL, TLS and DTLS protocols 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. For QUIC connections it returns OSSL_QUIC1_VERSION.

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 1 if the connection is using DTLS or 0 if not.

SSL_is_tls() returns 1 if the connection is using SSL/TLS or 0 if not.

SSL_is_quic() returns 1 if the connection is using QUIC or 0 if not.

SSL_CTX_is_quic() returns 1 if the ctx creates QUIC SSL objects or 0 if not.

SSL_CTX_is_server() returns 1 if the ctx uses a I<method> that allows it to be
a server (i.e. server-only or generic method) or 0 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 DTLSv0.9

The connection uses an obsolete pre-standardisation DTLS protocol

=item DTLSv1

The connection uses the DTLSv1 protocol

=item DTLSv1.2

The connection uses the DTLSv1.2 protocol

=item QUICv1

The connection uses the QUICv1 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()).

=item  DTLS1_BAD_VER

The connection uses an obsolete pre-standardisation DTLS protocol

=item DTLS1_VERSION

The connection uses the DTLSv1 protocol

=item DTLS1_2_VERSION

The connection uses the DTLSv1.2 protocol

=item OSSL_QUIC1_VERSION

The connection uses the QUICv1 protocol.

=back

=head1 SEE ALSO

L<ssl(7)>

=head1 HISTORY

The SSL_is_dtls() function was added in OpenSSL 1.1.0. The SSL_is_tls() and
SSL_is_quic() functions were added in OpenSSL 3.2.

The SSL_CTX_is_quic() and SSL_CTX_is_server() functions were added in
OpenSSL 4.0

=head1 COPYRIGHT

Copyright 2001-2026 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
L<https://www.openssl.org/source/license.html>.

=cut
