doc/man3/SSL_write.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 SSL_write_ex, SSL_write, SSL_sendfile - write bytes to a TLS/SSL connection

 =head1 SYNOPSIS

  #include <openssl/ssl.h>

  ossl_ssize_t SSL_sendfile(SSL *s, int fd, off_t offset, size_t size, int flags);
  int SSL_write_ex(SSL *s, const void *buf, size_t num, size_t *written);
  int SSL_write(SSL *ssl, const void *buf, int num);

 =head1 DESCRIPTION

 SSL_write_ex() and SSL_write() write B<num> bytes from the buffer B<buf> into
 the specified B<ssl> connection. On success SSL_write_ex() will store the number
 of bytes written in B<*written>.

 SSL_sendfile() writes B<size> bytes from offset B<offset> in the file
 descriptor B<fd> to the specified SSL connection B<s>. This function provides
 efficient zero-copy semantics. SSL_sendfile() is available only when
 Kernel TLS is enabled, which can be checked by calling BIO_get_ktls_send().
 It is provided here to allow users to maintain the same interface.
 The meaning of B<flags> is platform dependent.
 Currently, under Linux it is ignored.

 =head1 NOTES

 In the paragraphs below a "write function" is defined as one of either
 SSL_write_ex(), or SSL_write().

 If necessary, a write function will negotiate a TLS/SSL session, if not already
 explicitly performed by L<SSL_connect(3)> or L<SSL_accept(3)>. If the peer
 requests a re-negotiation, it will be performed transparently during
 the write function operation. The behaviour of the write functions 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 being done by calling
 L<SSL_set_connect_state(3)> or SSL_set_accept_state()
 before the first call to a write function.

 If the underlying BIO is B<blocking>, the write functions will only return, once
 the write operation has been finished or an error occurred.

 If the underlying BIO is B<nonblocking> the write functions will also return
 when the underlying BIO could not satisfy the needs of the function to continue
 the operation. In this case a call to L<SSL_get_error(3)> with the
 return value of the write function will yield B<SSL_ERROR_WANT_READ>
 or B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
 call to a write function can also cause read operations! The calling process
 then must repeat the call after taking appropriate action to satisfy the needs
 of the write function. The action depends on the underlying BIO. When using a
 nonblocking 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.

 The write functions 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)>. When
 this flag is set the write functions will also return with success when a
 partial write has been successfully completed. In this case the write function
 operation is considered completed. The bytes are sent and a new write call 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.

 =head1 WARNINGS

 When a write function call has to be repeated because L<SSL_get_error(3)>
 returned B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
 with the same arguments.
 The data that was passed might have been partially processed.
 When B<SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER> was set using L<SSL_CTX_set_mode(3)>
 the pointer can be different, but the data and length should still be the same.

 You should not call SSL_write() with num=0, it will return an error.
 SSL_write_ex() can be called with num=0, but will not send application data to
 the peer.

 =head1 RETURN VALUES

 SSL_write_ex() will return 1 for success or 0 for failure. Success means that
 all requested application data bytes have been written to the SSL connection or,
 if SSL_MODE_ENABLE_PARTIAL_WRITE is in use, at least 1 application data byte has
 been written to the SSL connection. Failure means that not all the requested
 bytes have been written yet (if SSL_MODE_ENABLE_PARTIAL_WRITE is not in use) or
 no bytes could be written to the SSL connection (if
 SSL_MODE_ENABLE_PARTIAL_WRITE is in use). Failures can be retryable (e.g. the
 network write buffer has temporarily filled up) or non-retryable (e.g. a fatal
 network error). In the event of a failure call L<SSL_get_error(3)> to find out
 the reason which indicates whether the call is retryable or not.

 For SSL_write() the following return values can occur:

 =over 4

 =item E<gt> 0

 The write operation was successful, the return value is the number of
 bytes actually written to the TLS/SSL connection.

 =item Z<><= 0

 The write operation was not successful, because either the connection was
 closed, an error occurred or action must be taken by the calling process.
 Call SSL_get_error() with the return value B<ret> to find out the reason.

 Old documentation indicated a difference between 0 and -1, and that -1 was
 retryable.
 You should instead call SSL_get_error() to find out if it's retryable.

 =back

 For SSL_sendfile(), the following return values can occur:

 =over 4

 =item Z<>>= 0

 The write operation was successful, the return value is the number
 of bytes of the file written to the TLS/SSL connection. The return
 value can be less than B<size> for a partial write.

 =item E<lt> 0

 The write operation was not successful, because either the connection was
 closed, an error occurred or action must be taken by the calling process.
 Call SSL_get_error() with the return value to find out the reason.

 =back

 =head1 SEE ALSO

 L<SSL_get_error(3)>, L<SSL_read_ex(3)>, L<SSL_read(3)>
 L<SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)>,
 L<SSL_connect(3)>, L<SSL_accept(3)>
 L<SSL_set_connect_state(3)>, L<BIO_ctrl(3)>,
 L<ssl(7)>, L<bio(7)>

 =head1 HISTORY

 The SSL_write_ex() function was added in OpenSSL 1.1.1.
 The SSL_sendfile() function was added in OpenSSL 3.0.

 =head1 COPYRIGHT

 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

 Licensed under the Apache License 2.0 (the "License").  You may not use
 this file except in compliance with the License.  You can obtain a copy
 in the file LICENSE in the source distribution or at
 L<https://www.openssl.org/source/license.html>.

 =cut
	=pod

	=head1 NAME

	SSL_write_ex, SSL_write, SSL_sendfile - write bytes to a TLS/SSL connection

	=head1 SYNOPSIS

	#include <openssl/ssl.h>

	ossl_ssize_t SSL_sendfile(SSL *s, int fd, off_t offset, size_t size, int flags);
	int SSL_write_ex(SSL s, const void buf, size_t num, size_t *written);
	int SSL_write(SSL ssl, const void buf, int num);

	=head1 DESCRIPTION

	SSL_write_ex() and SSL_write() write B<num> bytes from the buffer B<buf> into
	the specified B<ssl> connection. On success SSL_write_ex() will store the number
	of bytes written in B<*written>.

	SSL_sendfile() writes B<size> bytes from offset B<offset> in the file
	descriptor B<fd> to the specified SSL connection B<s>. This function provides
	efficient zero-copy semantics. SSL_sendfile() is available only when
	Kernel TLS is enabled, which can be checked by calling BIO_get_ktls_send().
	It is provided here to allow users to maintain the same interface.
	The meaning of B<flags> is platform dependent.
	Currently, under Linux it is ignored.

	=head1 NOTES

	In the paragraphs below a "write function" is defined as one of either
	SSL_write_ex(), or SSL_write().

	If necessary, a write function will negotiate a TLS/SSL session, if not already
	explicitly performed by L<SSL_connect(3)> or L<SSL_accept(3)>. If the peer
	requests a re-negotiation, it will be performed transparently during
	the write function operation. The behaviour of the write functions 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 being done by calling
	L<SSL_set_connect_state(3)> or SSL_set_accept_state()
	before the first call to a write function.

	If the underlying BIO is B<blocking>, the write functions will only return, once
	the write operation has been finished or an error occurred.

	If the underlying BIO is B<nonblocking> the write functions will also return
	when the underlying BIO could not satisfy the needs of the function to continue
	the operation. In this case a call to L<SSL_get_error(3)> with the
	return value of the write function will yield B<SSL_ERROR_WANT_READ>
	or B<SSL_ERROR_WANT_WRITE>. As at any time a re-negotiation is possible, a
	call to a write function can also cause read operations! The calling process
	then must repeat the call after taking appropriate action to satisfy the needs
	of the write function. The action depends on the underlying BIO. When using a
	nonblocking 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.

	The write functions 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)>. When
	this flag is set the write functions will also return with success when a
	partial write has been successfully completed. In this case the write function
	operation is considered completed. The bytes are sent and a new write call 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.

	=head1 WARNINGS

	When a write function call has to be repeated because L<SSL_get_error(3)>
	returned B<SSL_ERROR_WANT_READ> or B<SSL_ERROR_WANT_WRITE>, it must be repeated
	with the same arguments.
	The data that was passed might have been partially processed.
	When B<SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER> was set using L<SSL_CTX_set_mode(3)>
	the pointer can be different, but the data and length should still be the same.

	You should not call SSL_write() with num=0, it will return an error.
	SSL_write_ex() can be called with num=0, but will not send application data to
	the peer.

	=head1 RETURN VALUES

	SSL_write_ex() will return 1 for success or 0 for failure. Success means that
	all requested application data bytes have been written to the SSL connection or,
	if SSL_MODE_ENABLE_PARTIAL_WRITE is in use, at least 1 application data byte has
	been written to the SSL connection. Failure means that not all the requested
	bytes have been written yet (if SSL_MODE_ENABLE_PARTIAL_WRITE is not in use) or
	no bytes could be written to the SSL connection (if
	SSL_MODE_ENABLE_PARTIAL_WRITE is in use). Failures can be retryable (e.g. the
	network write buffer has temporarily filled up) or non-retryable (e.g. a fatal
	network error). In the event of a failure call L<SSL_get_error(3)> to find out
	the reason which indicates whether the call is retryable or not.

	For SSL_write() the following return values can occur:

	=over 4

	=item E<gt> 0

	The write operation was successful, the return value is the number of
	bytes actually written to the TLS/SSL connection.

	=item Z<><= 0

	The write operation was not successful, because either the connection was
	closed, an error occurred or action must be taken by the calling process.
	Call SSL_get_error() with the return value B<ret> to find out the reason.

	Old documentation indicated a difference between 0 and -1, and that -1 was
	retryable.
	You should instead call SSL_get_error() to find out if it's retryable.

	=back

	For SSL_sendfile(), the following return values can occur:

	=over 4

	=item Z<>>= 0

	The write operation was successful, the return value is the number
	of bytes of the file written to the TLS/SSL connection. The return
	value can be less than B<size> for a partial write.

	=item E<lt> 0

	The write operation was not successful, because either the connection was
	closed, an error occurred or action must be taken by the calling process.
	Call SSL_get_error() with the return value to find out the reason.

	=back

	=head1 SEE ALSO

	L<SSL_get_error(3)>, L<SSL_read_ex(3)>, L<SSL_read(3)>
	L<SSL_CTX_set_mode(3)>, L<SSL_CTX_new(3)>,
	L<SSL_connect(3)>, L<SSL_accept(3)>
	L<SSL_set_connect_state(3)>, L<BIO_ctrl(3)>,
	L<ssl(7)>, L<bio(7)>

	=head1 HISTORY

	The SSL_write_ex() function was added in OpenSSL 1.1.1.
	The SSL_sendfile() function was added in OpenSSL 3.0.

	=head1 COPYRIGHT

	Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

	Licensed under the Apache License 2.0 (the "License"). You may not use
	this file except in compliance with the License. You can obtain a copy
	in the file LICENSE in the source distribution or at
	L<https://www.openssl.org/source/license.html>.

	=cut