=item SSL_ERROR_ZERO_RETURN
The TLS/SSL peer has closed the connection for writing by sending the
-"close notify" alert.
+close_notify alert.
No more data can be read.
Note that B<SSL_ERROR_ZERO_RETURN> does not necessarily
indicate that the underlying transport has been closed.
=item SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE
-The operation did not complete; the same TLS/SSL I/O function should be
-called again later. If, by then, the underlying B<BIO> has data
-available for reading (if the result code is B<SSL_ERROR_WANT_READ>)
-or allows writing data (B<SSL_ERROR_WANT_WRITE>), then some TLS/SSL
-protocol progress will take place, i.e. at least part of an TLS/SSL
-record will be read or written. Note that the retry may again lead to
-a B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE> condition.
+The operation did not complete and can be retried later.
+
+B<SSL_ERROR_WANT_READ> is returned when the last operation was a read
+operation from a non-blocking B<BIO>.
+It means that not enough data was available at this time to complete the
+operation.
+If at a later time the underlying B<BIO> has data available for reading the same
+function can be called again.
+
+SSL_read() and SSL_read_ex() can also set B<SSL_ERROR_WANT_READ> when there is
+still unprocessed data available at either the B<SSL> or the B<BIO> layer, even
+for a blocking B<BIO>.
+See L<SSL_read(3)> for more information.
+
+B<SSL_ERROR_WANT_WRITE> is returned when the last operation was a write
+to a non-blocking B<BIO> and it was unable to sent all data to the B<BIO>.
+When the B<BIO> is writeable again, the same function can be called again.
+
+Note that the retry may again lead to an B<SSL_ERROR_WANT_READ> or
+B<SSL_ERROR_WANT_WRITE> condition.
There is no fixed upper limit for the number of iterations that
may be necessary until progress becomes visible at application
protocol level.
+It is safe to call SSL_read() or SSL_read_ex() when more data is available
+even when the call that set this error was an SSL_write() or SSL_write_ex().
+However if the call was an SSL_write() or SSL_write_ex(), it should be called
+again to continue sending the application data.
+
For socket B<BIO>s (e.g. when SSL_set_fd() was used), select() or
poll() on the underlying socket can be used to find out when the
TLS/SSL I/O function should be retried.
Caveat: Any TLS/SSL I/O function can lead to either of
-B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>. In particular,
+B<SSL_ERROR_WANT_READ> and B<SSL_ERROR_WANT_WRITE>.
+In particular,
SSL_read_ex(), SSL_read(), SSL_peek_ex(), or SSL_peek() may want to write data
-and SSL_write() or SSL_write_ex() may want to read data. This is mainly because
+and SSL_write() or SSL_write_ex() may want to read data.
+This is mainly because
TLS/SSL handshakes may occur at any time during the protocol (initiated by
either the client or the server); SSL_read_ex(), SSL_read(), SSL_peek_ex(),
SSL_peek(), SSL_write_ex(), and SSL_write() will handle any pending handshakes.
The OpenSSL error queue may contain more information on the error.
For socket I/O on Unix systems, consult B<errno> for details.
+This value can also be returned for other errors, check the error queue for
+details.
+
=item SSL_ERROR_SSL
A failure in the SSL library occurred, usually a protocol error. The
projects / openssl.git / blobdiff