|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | NOTES | SEE ALSO | COLOPHON |
|
|
|
io_uring_prep_sendmsg(3) liburing Manual io_uring_prep_sendmsg(3)
io_uring_prep_sendmsg - prepare a sendmsg request
#include <sys/types.h>
#include <sys/socket.h>
#include <liburing.h>
void io_uring_prep_sendmsg(struct io_uring_sqe *sqe,
int fd,
const struct msghdr *msg,
unsigned flags);
void io_uring_prep_sendmsg_zc(struct io_uring_sqe *sqe,
int fd,
const struct msghdr *msg,
unsigned flags);
The io_uring_prep_sendmsg(3) function prepares a sendmsg request.
The submission queue entry sqe is setup to use the file descriptor
fd to start sending the data indicated by msg with the sendmsg(2)
defined flags in the flags argument.
The io_uring_prep_sendmsg_zc(3) accepts the same parameters as
io_uring_prep_sendmsg(3) but prepares a zerocopy sendmsg request.
See io_uring_prep_send(3) for a description of flags that can be
set in the SQE ioprio field. In addition to those, the zero-copy
send also supports setting IORING_SEND_ZC_REPORT_USAGE . If set,
the notification CQE res field will report the number of bytes
that were copied rather than sent with zero copy. A value of 0
indicates success. If the value is IORING_NOTIF_USAGE_ZC_COPIED ,
then data was copied.
Note that using IOSQE_IO_LINK with this request type requires the
setting of MSG_WAITALL in the flags argument, as a short send
isn't considered an error condition without that being set.
This function prepares an async sendmsg(2) request. See that man
page for details.
None
The CQE res field will contain the result of the operation. See
the related man page for details on possible values. Note that
where synchronous system calls will return -1 on failure and set
errno to the actual error value, io_uring never uses errno.
Instead it returns the negated errno directly in the CQE res
field.
As with any request that passes in data in a struct, that data
must remain valid until the request has been successfully
submitted. It need not remain valid until completion. Once a
request has been submitted, the in-kernel state is stable. Very
early kernels (5.4 and earlier) required state to be stable until
the completion occurred. Applications can test for this behavior
by inspecting the IORING_FEAT_SUBMIT_STABLE flag passed back from
io_uring_queue_init_params(3).
io_uring_get_sqe(3), io_uring_submit(3),
io_uring_buf_ring_init(3), io_uring_buf_ring_add(3), sendmsg(2)
This page is part of the liburing (A library for io_uring)
project. Information about the project can be found at
⟨https://github.com/axboe/liburing⟩. If you have a bug report for
this manual page, send it to io-uring@vger.kernel.org. This page
was obtained from the project's upstream Git repository
⟨https://github.com/axboe/liburing⟩ on 2025-08-11. (At that time,
the date of the most recent commit that was found in the
repository was 2025-08-02.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
liburing-2.2 March 12, 2022 io_uring_prep_sendmsg(3)
Pages that refer to this page: io_uring_prep_sendmsg(3), io_uring_prep_sendmsg_zc(3)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|