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io_uring_prep_msg_ring_fd(3) — Linux manual page

io_uring_prep_msg_ring_fd(3) liburing Manualio_uring_prep_msg_ring_fd(3)

NAME        top

       io_uring_prep_msg_ring_fd - send a direct descriptor to another       ring

SYNOPSIS        top

#include <liburing.h>void io_uring_prep_msg_ring_fd(struct io_uring_sqe *sqe,intfd,intsource_fd,inttarget_fd,__u64data,unsigned intflags);void io_uring_prep_msg_ring_fd_alloc(struct io_uring_sqe *sqe,intfd,intsource_fd,__u64data,unsigned intflags);

DESCRIPTION        top

io_uring_prep_msg_ring_fd(3) prepares an SQE to send a direct file       descriptor to another ring. The submission queue entrysqe is       setup to use the file descriptorfd, which must identify a target       io_uring context, to send the locally registered file descriptor       with valuesource_fd to the destination ring into indextarget_fd       and passingdata as the user data in the target CQE with the       request modifier flags set byflags.  Currently there are no valid       flag modifiers, this field must contain0.io_uring_prep_msg_ring_fd_alloc(3) is similar toio_uring_prep_msg_ring_fd(3), but doesn't specify a target index       for the direct descriptor. Instead, this index is allocated in the       target ring and returned in the CQEres field.

RETURN VALUE        top

       None

ERRORS        top

       These are the errors that are reported in the CQEres field.-ENOMEM              The kernel was unable to allocate memory for the request.-EINVAL              One of the fields set in the SQE was invalid.-EINVAL              Target ring is identical to the source ring.-EBADFD              The descriptor passed infd does not refer to an io_uring              file descriptor, or the ring is in a disabled state.-EOVERFLOW              The kernel was unable to fill a CQE on the target ring.              This can happen if the target CQ ring is in an overflow              state and the kernel wasn't able to allocate memory for a              new CQE entry.-ENFILE              The direct descriptor table in the target ring was full, no              new descriptors could be successfully allocated.

COLOPHON        top

       This page is part of theliburing (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 isnot part of the original manual page), send a mail to       man-pages@man7.orgliburing-2.4                   Mar 16, 2023io_uring_prep_msg_ring_fd(3)

Pages that refer to this page:io_uring_prep_msg_ring_fd(3), io_uring_prep_msg_ring_fd_alloc(3), io_uring_register_sync_msg(3)

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