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      1 =pod
      2 
      3 =head1 NAME
      4 
      5 SSL_accept - wait for a TLS/SSL client to initiate a TLS/SSL handshake
      6 
      7 =head1 SYNOPSIS
      8 
      9  #include <openssl/ssl.h>
     10 
     11  int SSL_accept(SSL *ssl);
     12 
     13 =head1 DESCRIPTION
     14 
     15 SSL_accept() waits for a TLS/SSL client to initiate the TLS/SSL handshake.
     16 The communication channel must already have been set and assigned to the
     17 B<ssl> by setting an underlying B<BIO>.
     18 
     19 =head1 NOTES
     20 
     21 The behaviour of SSL_accept() depends on the underlying BIO.
     22 
     23 If the underlying BIO is B<blocking>, SSL_accept() will only return once the
     24 handshake has been finished or an error occurred.
     25 
     26 If the underlying BIO is B<nonblocking>, SSL_accept() will also return
     27 when the underlying BIO could not satisfy the needs of SSL_accept()
     28 to continue the handshake, indicating the problem by the return value -1.
     29 In this case a call to SSL_get_error() with the
     30 return value of SSL_accept() will yield B<SSL_ERROR_WANT_READ> or
     31 B<SSL_ERROR_WANT_WRITE>. The calling process then must repeat the call after
     32 taking appropriate action to satisfy the needs of SSL_accept().
     33 The action depends on the underlying BIO. When using a nonblocking socket,
     34 nothing is to be done, but select() can be used to check for the required
     35 condition. When using a buffering BIO, like a BIO pair, data must be written
     36 into or retrieved out of the BIO before being able to continue.
     37 
     38 =head1 RETURN VALUES
     39 
     40 The following return values can occur:
     41 
     42 =over 4
     43 
     44 =item Z<>0
     45 
     46 The TLS/SSL handshake was not successful but was shut down controlled and
     47 by the specifications of the TLS/SSL protocol. Call SSL_get_error() with the
     48 return value B<ret> to find out the reason.
     49 
     50 =item Z<>1
     51 
     52 The TLS/SSL handshake was successfully completed, a TLS/SSL connection has been
     53 established.
     54 
     55 =item E<lt>0
     56 
     57 The TLS/SSL handshake was not successful because a fatal error occurred either
     58 at the protocol level or a connection failure occurred. The shutdown was
     59 not clean. It can also occur if action is needed to continue the operation
     60 for nonblocking BIOs. Call SSL_get_error() with the return value B<ret>
     61 to find out the reason.
     62 
     63 =back
     64 
     65 =head1 SEE ALSO
     66 
     67 L<SSL_get_error(3)>, L<SSL_connect(3)>,
     68 L<SSL_shutdown(3)>, L<ssl(7)>, L<bio(7)>,
     69 L<SSL_set_connect_state(3)>,
     70 L<SSL_do_handshake(3)>,
     71 L<SSL_CTX_new(3)>
     72 
     73 =head1 COPYRIGHT
     74 
     75 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
     76 
     77 Licensed under the OpenSSL license (the "License").  You may not use
     78 this file except in compliance with the License.  You can obtain a copy
     79 in the file LICENSE in the source distribution or at
     80 L<https://www.openssl.org/source/license.html>.
     81 
     82 =cut
     83