Extend SSL_CONF

[openssl.git] / doc / ssl / SSL_write.pod

diff --git a/doc/ssl/SSL_write.pod b/doc/ssl/SSL_write.pod
index be1ad76d3b4cf1ac63951ca1c9ca3d2fb1738ac1..e013c12d5254b0d4d08bb0d6ef47972994b72ada 100644 (file)
--- a/doc/ssl/SSL_write.pod
+++ b/doc/ssl/SSL_write.pod
@@ -25,11 +25,9 @@ the SSL_write() operation. The behaviour of SSL_write() depends on the
 underlying BIO. 
 
 For the transparent negotiation to succeed, the B<ssl> must have been
-initialized to client or server mode. This is not the case if a generic
-method is being used (see L<SSL_CTX_new(3)|SSL_CTX_new(3)>, so that
+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()
-must be used before the first call to an L<SSL_read(3)|SSL_read(3)>
-or SSL_write() function.
+before the first call to an L<SSL_read(3)|SSL_read(3)> or SSL_write() function.
 
 If the underlying BIO is B<blocking>, SSL_write() will only return, once the
 write operation has been finished or an error occurred, except when a
@@ -50,12 +48,26 @@ 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.
 
+SSL_write() will only return with success, when the complete contents
+of B<buf> of length B<num> has been written. This default behaviour
+can be changed with the SSL_MODE_ENABLE_PARTIAL_WRITE option of
+L<SSL_CTX_set_mode(3)|SSL_CTX_set_mode(3)>. When this flag is set,
+SSL_write() will also return with success, when a partial write has been
+successfully completed. In this case the SSL_write() operation is considered
+completed. The bytes are sent and a new SSL_write() operation with a new
+buffer (with the already sent bytes removed) must be started.
+A partial write is performed with the size of a message block, which is
+16kB for SSLv3/TLSv1.
+
 =head1 WARNING
 
 When an SSL_write() operation has to be repeated because of
 B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
 with the same arguments.
 
+When calling SSL_write() with num=0 bytes to be sent the behaviour is
+undefined.
+
 =head1 RETURN VALUES
 
 The following return values can occur:
@@ -69,8 +81,14 @@ bytes actually written to the TLS/SSL connection.
 
 =item 0
 
-The write operation was not successful. Call SSL_get_error() with the return
-value B<ret> to find out, whether an error occurred.
+The write operation was not successful. Probably the underlying connection
+was closed. 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).
+
+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, why the closure happened.
 
 =item E<lt>0