1: =pod
    2: 
    3: =head1 NAME
    4: 
    5: SSL_get_error - obtain result code for TLS/SSL I/O operation
    6: 
    7: =head1 SYNOPSIS
    8: 
    9:  #include <openssl/ssl.h>
   10: 
   11:  int SSL_get_error(const SSL *ssl, int ret);
   12: 
   13: =head1 DESCRIPTION
   14: 
   15: SSL_get_error() returns a result code (suitable for the C "switch"
   16: statement) for a preceding call to SSL_connect(), SSL_accept(), SSL_do_handshake(),
   17: SSL_read(), SSL_peek(), or SSL_write() on B<ssl>.  The value returned by
   18: that TLS/SSL I/O function must be passed to SSL_get_error() in parameter
   19: B<ret>.
   20: 
   21: In addition to B<ssl> and B<ret>, SSL_get_error() inspects the
   22: current thread's OpenSSL error queue.  Thus, SSL_get_error() must be
   23: used in the same thread that performed the TLS/SSL I/O operation, and no
   24: other OpenSSL function calls should appear in between.  The current
   25: thread's error queue must be empty before the TLS/SSL I/O operation is
   26: attempted, or SSL_get_error() will not work reliably.
   27: 
   28: =head1 RETURN VALUES
   29: 
   30: The following return values can currently occur:
   31: 
   32: =over 4
   33: 
   34: =item SSL_ERROR_NONE
   35: 
   36: The TLS/SSL I/O operation completed.  This result code is returned
   37: if and only if B<ret E<gt> 0>.
   38: 
   39: =item SSL_ERROR_ZERO_RETURN
   40: 
   41: The TLS/SSL connection has been closed.  If the protocol version is SSL 3.0
   42: or TLS 1.0, this result code is returned only if a closure
   43: alert has occurred in the protocol, i.e. if the connection has been
   44: closed cleanly. Note that in this case B<SSL_ERROR_ZERO_RETURN>
   45: does not necessarily indicate that the underlying transport
   46: has been closed.
   47: 
   48: =item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
   49: 
   50: The operation did not complete; the same TLS/SSL I/O function should be
   51: called again later.  If, by then, the underlying B<BIO> has data
   52: available for reading (if the result code is B<SSL_ERROR_WANT_READ>)
   53: or allows writing data (B<SSL_ERROR_WANT_WRITE>), then some TLS/SSL
   54: protocol progress will take place, i.e. at least part of an TLS/SSL
   55: record will be read or written.  Note that the retry may again lead to
   56: a B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE> condition.
   57: There is no fixed upper limit for the number of iterations that
   58: may be necessary until progress becomes visible at application
   59: protocol level.
   60: 
   61: For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or
   62: poll() on the underlying socket can be used to find out when the
   63: TLS/SSL I/O function should be retried.
   64: 
   65: Caveat: Any TLS/SSL I/O function can lead to either of
   66: B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>.  In particular,
   67: SSL_read() or SSL_peek() may want to write data and SSL_write() may want
   68: to read data.  This is mainly because TLS/SSL handshakes may occur at any
   69: time during the protocol (initiated by either the client or the server);
   70: SSL_read(), SSL_peek(), and SSL_write() will handle any pending handshakes.
   71: 
   72: =item SSL_ERROR_WANT_CONNECT, SSL_ERROR_WANT_ACCEPT
   73: 
   74: The operation did not complete; the same TLS/SSL I/O function should be
   75: called again later. The underlying BIO was not connected yet to the peer
   76: and the call would block in connect()/accept(). The SSL function should be
   77: called again when the connection is established. These messages can only
   78: appear with a BIO_s_connect() or BIO_s_accept() BIO, respectively.
   79: In order to find out, when the connection has been successfully established,
   80: on many platforms select() or poll() for writing on the socket file descriptor
   81: can be used.
   82: 
   83: =item SSL_ERROR_WANT_X509_LOOKUP
   84: 
   85: The operation did not complete because an application callback set by
   86: SSL_CTX_set_client_cert_cb() has asked to be called again.
   87: The TLS/SSL I/O function should be called again later.
   88: Details depend on the application.
   89: 
   90: =item SSL_ERROR_SYSCALL
   91: 
   92: Some I/O error occurred.  The OpenSSL error queue may contain more
   93: information on the error.  If the error queue is empty
   94: (i.e. ERR_get_error() returns 0), B<ret> can be used to find out more
   95: about the error: If B<ret == 0>, an EOF was observed that violates
   96: the protocol.  If B<ret == -1>, the underlying B<BIO> reported an
   97: I/O error (for socket I/O on Unix systems, consult B<errno> for details).
   98: 
   99: =item SSL_ERROR_SSL
  100: 
  101: A failure in the SSL library occurred, usually a protocol error.  The
  102: OpenSSL error queue contains more information on the error.
  103: 
  104: =back
  105: 
  106: =head1 SEE ALSO
  107: 
  108: L<ssl(3)|ssl(3)>, L<err(3)|err(3)>
  109: 
  110: =head1 HISTORY
  111: 
  112: SSL_get_error() was added in SSLeay 0.8.
  113: 
  114: =cut