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# Conflicts:
#	README.md
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Zhi Guan
2017-02-14 16:12:29 +08:00
parent d2254170b8
commit 43fed1108d
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77
doc/ssl/SSL_read.pod
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@@ -2,7 +2,7 @@
=head1 NAME
SSL_read - read bytes from a TLS/SSL connection.
SSL_read - read bytes from a TLS/SSL connection
=head1 SYNOPSIS
@@ -18,16 +18,16 @@ buffer B<buf>.
=head1 NOTES
If necessary, SSL_read() will negotiate a TLS/SSL session, if
not already explicitly performed by L<SSL_connect(3)|SSL_connect(3)> or
L<SSL_accept(3)|SSL_accept(3)>. If the
not already explicitly performed by L<SSL_connect(3)> or
L<SSL_accept(3)>. If the
peer requests a re-negotiation, it will be performed transparently during
the SSL_read() operation. The behaviour of SSL_read() depends on the
underlying BIO.
underlying BIO.
For the transparent negotiation to succeed, the B<ssl> must have been
initialized to client or server mode. This is being done by calling
L<SSL_set_connect_state(3)|SSL_set_connect_state(3)> or SSL_set_accept_state()
before the first call to an SSL_read() or L<SSL_write(3)|SSL_write(3)>
L<SSL_set_connect_state(3)> or SSL_set_accept_state()
before the first call to an SSL_read() or L<SSL_write(3)>
function.
SSL_read() works based on the SSL/TLS records. The data are received in
@@ -47,14 +47,14 @@ record is complete and SSL_read() can succeed.
If the underlying BIO is B<blocking>, SSL_read() will only return, once the
read operation has been finished or an error occurred, except when a
renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur.
renegotiation take place, in which case a SSL_ERROR_WANT_READ may occur.
This behaviour can be controlled with the SSL_MODE_AUTO_RETRY flag of the
L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)> call.
L<SSL_CTX_set_mode(3)> call.
If the underlying BIO is B<non-blocking>, SSL_read() will also return
when the underlying BIO could not satisfy the needs of SSL_read()
to continue the operation. In this case a call to
L<SSL_get_error(3)|SSL_get_error(3)> with the
L<SSL_get_error(3)> with the
return value of SSL_read() will yield B<SSL_ERROR_WANT_READ> or
B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
call to SSL_read() can also cause write operations! The calling process
@@ -64,7 +64,7 @@ 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.
L<SSL_pending(3)|SSL_pending(3)> can be used to find out whether there
L<SSL_pending(3)> can be used to find out whether there
are buffered bytes available for immediate retrieval. In this case
SSL_read() can be called without blocking or actually receiving new
data from the underlying socket.
@@ -81,44 +81,41 @@ The following return values can occur:
=over 4
=item E<gt>0
=item E<gt> 0
The read operation was successful; the return value is the number of
bytes actually read from the TLS/SSL connection.
The read operation was successful.
The return value is the number of bytes actually read from the TLS/SSL
connection.
=item Z<>0
=item Z<><= 0
The read operation was not successful. The reason may either be a clean
shutdown due to a "close notify" alert sent by the peer (in which case
the SSL_RECEIVED_SHUTDOWN flag in the ssl shutdown state is set
(see L<SSL_shutdown(3)|SSL_shutdown(3)>,
L<SSL_set_shutdown(3)|SSL_set_shutdown(3)>). It is also possible, that
the peer simply shut down the underlying transport and the shutdown is
incomplete. Call SSL_get_error() with the return value B<ret> to find out,
whether an error occurred or the connection was shut down cleanly
(SSL_ERROR_ZERO_RETURN).
The read operation was not successful, because either the connection was closed,
an error occurred or action must be taken by the calling process.
Call L<SSL_get_error(3)> with the return value B<ret> to find out the reason.
SSLv2 (deprecated) does not support a shutdown alert protocol, so it can
only be detected, whether the underlying connection was closed. It cannot
be checked, whether the closure was initiated by the peer or by something
else.
=item E<lt>0
The read operation was not successful, because either an error occurred
or action must be taken by the calling process. Call SSL_get_error() with the
return value B<ret> to find out the reason.
Old documentation indicated a difference between 0 and -1, and that -1 was
retryable.
You should instead call SSL_get_error() to find out if it's retryable.
=back
=head1 SEE ALSO
L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_write(3)|SSL_write(3)>,
L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)|SSL_CTX_new(3)>,
L<SSL_connect(3)|SSL_connect(3)>, L<SSL_accept(3)|SSL_accept(3)>
L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>,
L<SSL_pending(3)|SSL_pending(3)>,
L<SSL_shutdown(3)|SSL_shutdown(3)>, L<SSL_set_shutdown(3)|SSL_set_shutdown(3)>,
L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>
L<SSL_get_error(3)>, L<SSL_write(3)>,
L<SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)>,
L<SSL_connect(3)>, L<SSL_accept(3)>
L<SSL_set_connect_state(3)>,
L<SSL_pending(3)>,
L<SSL_shutdown(3)>, L<SSL_set_shutdown(3)>,
L<ssl(3)>, L<bio(3)>
=head1 COPYRIGHT
Copyright 2000-2016 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
L<https://www.openssl.org/source/license.html>.
=cut