mirror of
https://github.com/CloverHackyColor/CloverBootloader.git
synced 2024-12-03 13:13:30 +01:00
98 lines
3.4 KiB
Plaintext
98 lines
3.4 KiB
Plaintext
=pod
|
|
|
|
=head1 NAME
|
|
|
|
SSL_connect - initiate the TLS/SSL handshake with an TLS/SSL server
|
|
|
|
=head1 SYNOPSIS
|
|
|
|
#include <openssl/ssl.h>
|
|
|
|
int SSL_connect(SSL *ssl);
|
|
|
|
=head1 DESCRIPTION
|
|
|
|
SSL_connect() initiates the TLS/SSL handshake with a server. The communication
|
|
channel must already have been set and assigned to the B<ssl> by setting an
|
|
underlying B<BIO>.
|
|
|
|
=head1 NOTES
|
|
|
|
The behaviour of SSL_connect() depends on the underlying BIO.
|
|
|
|
If the underlying BIO is B<blocking>, SSL_connect() will only return once the
|
|
handshake has been finished or an error occurred.
|
|
|
|
If the underlying BIO is B<nonblocking>, SSL_connect() will also return
|
|
when the underlying BIO could not satisfy the needs of SSL_connect()
|
|
to continue the handshake, indicating the problem by the return value -1.
|
|
In this case a call to SSL_get_error() with the
|
|
return value of SSL_connect() will yield B<SSL_ERROR_WANT_READ> or
|
|
B<SSL_ERROR_WANT_WRITE>. The calling process then must repeat the call after
|
|
taking appropriate action to satisfy the needs of SSL_connect().
|
|
The action depends on the underlying BIO. When using a nonblocking 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.
|
|
|
|
Many systems implement Nagle's algorithm by default which means that it will
|
|
buffer outgoing TCP data if a TCP packet has already been sent for which no
|
|
corresponding ACK has been received yet from the peer. This can have performance
|
|
impacts after a successful TLSv1.3 handshake or a successful TLSv1.2 (or below)
|
|
resumption handshake, because the last peer to communicate in the handshake is
|
|
the client. If the client is also the first to send application data (as is
|
|
typical for many protocols) then this data could be buffered until an ACK has
|
|
been received for the final handshake message.
|
|
|
|
The B<TCP_NODELAY> socket option is often available to disable Nagle's
|
|
algorithm. If an application opts to disable Nagle's algorithm consideration
|
|
should be given to turning it back on again later if appropriate. The helper
|
|
function BIO_set_tcp_ndelay() can be used to turn on or off the B<TCP_NODELAY>
|
|
option.
|
|
|
|
=head1 RETURN VALUES
|
|
|
|
The following return values can occur:
|
|
|
|
=over 4
|
|
|
|
=item Z<>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 B<ret> to find out the reason.
|
|
|
|
=item Z<>1
|
|
|
|
The TLS/SSL handshake was successfully completed, a TLS/SSL connection has been
|
|
established.
|
|
|
|
=item E<lt>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 if action is needed to continue the operation
|
|
for nonblocking BIOs. Call SSL_get_error() with the return value B<ret>
|
|
to find out the reason.
|
|
|
|
=back
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<SSL_get_error(3)>, L<SSL_accept(3)>,
|
|
L<SSL_shutdown(3)>, L<ssl(7)>, L<bio(7)>,
|
|
L<SSL_set_connect_state(3)>,
|
|
L<SSL_do_handshake(3)>,
|
|
L<SSL_CTX_new(3)>
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2000-2020 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
|