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, except for SGC (Server
   25: Gated Cryptography). For SGC, SSL_accept() may return with -1, but
   26: SSL_get_error() will yield B<SSL_ERROR_WANT_READ/WRITE> and SSL_accept()
   27: should be called again.
   28: 
   29: If the underlying BIO is B<non-blocking>, SSL_accept() will also return
   30: when the underlying BIO could not satisfy the needs of SSL_accept()
   31: to continue the handshake, indicating the problem by the return value -1.
   32: In this case a call to SSL_get_error() with the
   33: return value of SSL_accept() will yield B<SSL_ERROR_WANT_READ> or
   34: B<SSL_ERROR_WANT_WRITE>. The calling process then must repeat the call after
   35: taking appropriate action to satisfy the needs of SSL_accept().
   36: The action depends on the underlying BIO. When using a non-blocking socket,
   37: nothing is to be done, but select() can be used to check for the required
   38: condition. When using a buffering BIO, like a BIO pair, data must be written
   39: into or retrieved out of the BIO before being able to continue.
   40: 
   41: =head1 RETURN VALUES
   42: 
   43: The following return values can occur:
   44: 
   45: =over 4
   46: 
   47: =item 1
   48: 
   49: The TLS/SSL handshake was successfully completed, a TLS/SSL connection has been
   50: established.
   51: 
   52: =item 0
   53: 
   54: The TLS/SSL handshake was not successful but was shut down controlled and
   55: by the specifications of the TLS/SSL protocol. Call SSL_get_error() with the
   56: return value B<ret> to find out the reason.
   57: 
   58: =item E<lt>0
   59: 
   60: The TLS/SSL handshake was not successful because a fatal error occurred either
   61: at the protocol level or a connection failure occurred. The shutdown was
   62: not clean. It can also occur of action is need to continue the operation
   63: for non-blocking BIOs. Call SSL_get_error() with the return value B<ret>
   64: to find out the reason.
   65: 
   66: =back
   67: 
   68: =head1 SEE ALSO
   69: 
   70: L<SSL_get_error(3)|SSL_get_error(3)>, L<SSL_connect(3)|SSL_connect(3)>,
   71: L<SSL_shutdown(3)|SSL_shutdown(3)>, L<ssl(3)|ssl(3)>, L<bio(3)|bio(3)>,
   72: L<SSL_set_connect_state(3)|SSL_set_connect_state(3)>,
   73: L<SSL_do_handshake(3)|SSL_do_handshake(3)>,
   74: L<SSL_CTX_new(3)|SSL_CTX_new(3)>
   75: 
   76: =cut