70 lines
1.8 KiB
Groff
70 lines
1.8 KiB
Groff
.\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk>
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.\"
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.\" SPDX-License-Identifier: LGPL-2.0-or-later
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.\"
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.TH io_uring_prep_sendmsg 3 "March 12, 2022" "liburing-2.2" "liburing Manual"
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.SH NAME
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io_uring_prep_sendmsg \- prepare a sendmsg request
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.SH SYNOPSIS
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.nf
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.B #include <sys/types.h>
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.B #include <sys/socket.h>
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.B #include <liburing.h>
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.PP
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.BI "void io_uring_prep_sendmsg(struct io_uring_sqe *" sqe ","
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.BI " int " fd ","
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.BI " const struct msghdr *" msg ","
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.BI " unsigned " flags ");"
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.fi
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.SH DESCRIPTION
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.PP
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The
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.BR io_uring_prep_sendmsg (3)
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function prepares a sendmsg request. The submission queue entry
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.I sqe
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is setup to use the file descriptor
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.I fd
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to start sending the data indicated by
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.I msg
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with the
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.BR sendmsg (2)
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defined flags in the
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.I flags
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argument.
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This function prepares an async
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.BR sendmsg (2)
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request. See that man page for details.
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.SH RETURN VALUE
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None
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.SH ERRORS
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The CQE
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.I res
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field will contain the result of the operation. See the related man page for
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details on possible values. Note that where synchronous system calls will return
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.B -1
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on failure and set
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.I errno
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to the actual error value, io_uring never uses
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.IR errno .
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Instead it returns the negated
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.I errno
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directly in the CQE
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.I res
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field.
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.SH NOTES
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As with any request that passes in data in a struct, that data must remain
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valid until the request has been successfully submitted. It need not remain
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valid until completion. Once a request has been submitted, the in-kernel
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state is stable. Very early kernels (5.4 and earlier) required state to be
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stable until the completion occurred. Applications can test for this
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behavior by inspecting the
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.B IORING_FEAT_SUBMIT_STABLE
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flag passed back from
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.BR io_uring_queue_init_params (3).
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.SH SEE ALSO
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.BR io_uring_get_sqe (3),
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.BR io_uring_submit (3),
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.BR sendmsg (2)
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