NAME

       SSL_do_handshake - perform a TLS/SSL handshake

SYNOPSIS

        #include <openssl/ssl.h>

        int SSL_do_handshake(SSL *ssl);

DESCRIPTION

       SSL_do_handshake() will wait for a SSL/TLS handshake to take place. If the connection is in client mode,
       the handshake will be started. The handshake routines may have to be explicitly set in advance using
       either SSL_set_connect_state(3) or SSL_set_accept_state(3).

NOTES

       The behaviour of SSL_do_handshake() depends on the underlying BIO.

       If the underlying BIO is blocking, SSL_do_handshake() will only return once the handshake has been
       finished or an error occurred.

       If the underlying BIO is non-blocking, SSL_do_handshake() will also return when the underlying BIO could
       not satisfy the needs of SSL_do_handshake() to continue the handshake. In this case a call to
       SSL_get_error() with the return value of SSL_do_handshake() will yield SSL_ERROR_WANT_READ or
       SSL_ERROR_WANT_WRITE. The calling process then must repeat the call after taking appropriate action to
       satisfy the needs of SSL_do_handshake().  The action depends on the underlying BIO. When using a non-
       blocking socket, nothing is to be done, but select() can be used to check for the required condition.
       When using a buffering BIO, like a BIO pair, data must be written into or retrieved out of the BIO before
       being able to continue.

RETURN VALUES

       The following return values can occur:

       0   The TLS/SSL handshake was not successful but was shut down controlled and by the specifications of
           the TLS/SSL protocol. Call SSL_get_error() with the return value ret to find out the reason.

       1   The TLS/SSL handshake was successfully completed, a TLS/SSL connection has been established.

       <0  The TLS/SSL handshake was not successful because a fatal error occurred either at the protocol level
           or a connection failure occurred. The shutdown was not clean. It can also occur of action is need to
           continue the operation for non-blocking BIOs. Call SSL_get_error() with the return value ret to find
           out the reason.

SEE ALSO

       SSL_get_error(3), SSL_connect(3), SSL_accept(3), ssl(7), bio(7), SSL_set_connect_state(3)

COPYRIGHT

       Copyright 2002-2016 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>.