| .\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk> |
| .\" |
| .\" SPDX-License-Identifier: LGPL-2.0-or-later |
| .\" |
| .TH io_uring_prep_sendmsg 3 "March 12, 2022" "liburing-2.2" "liburing Manual" |
| .SH NAME |
| io_uring_prep_sendmsg - prepare a sendmsg request |
| .fi |
| .SH SYNOPSIS |
| .nf |
| .BR "#include <sys/types.h>" |
| .BR "#include <sys/socket.h>" |
| .BR "#include <liburing.h>" |
| .PP |
| .BI "void io_uring_prep_sendmsg(struct io_uring_sqe *" sqe "," |
| .BI " int " fd "," |
| .BI " const struct msghdr *" msg "," |
| .BI " unsigned " flags ");" |
| .PP |
| .SH DESCRIPTION |
| .PP |
| The io_uring_prep_sendmsg() function prepares a sendmsg request. The submission |
| queue entry |
| .I sqe |
| is setup to use the file descriptor |
| .I fd |
| to start sending the data indicated by |
| .I msg |
| with the |
| .BR sendmsg (2) |
| defined flags in the |
| .I flags |
| argument. |
| |
| This function prepares an async |
| .BR sendmsg (2) |
| request. See that man page for details. |
| |
| .SH RETURN VALUE |
| None |
| .SH ERRORS |
| The CQE |
| .I 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 |
| .B -1 |
| on failure and set |
| .I errno |
| to the actual error value, io_uring never uses |
| .I errno. |
| Instead it returns the negated |
| .I errno |
| directly in the CQE |
| .I res |
| field. |
| .SH NOTES |
| 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 |
| .B IORING_FEAT_SUBMIT_STABLE |
| flag passed back from |
| .BR io_uring_queue_init_params (3). |
| .SH SEE ALSO |
| .BR io_uring_get_sqe (3), io_uring_submit (3), sendmsg (2) |