io_uring_prep_msg_ring(3)       liburing Manual      io_uring_prep_msg_ring(3)

NAME
       io_uring_prep_msg_ring_fd - send a direct descriptor to another ring

SYNOPSIS
       #include <liburing.h>

       void io_uring_prep_msg_ring_fd(struct io_uring_sqe *sqe,
                               int fd,
                               int source_fd,
                               int target_fd,
                               __u64 data,
                               unsigned int flags);

       void io_uring_prep_msg_ring_fd_alloc(struct io_uring_sqe *sqe,
                               int fd,
                               int source_fd,
                               __u64 data,
                               unsigned int flags);

DESCRIPTION
       io_uring_prep_msg_ring_fd(3) prepares an SQE to send a direct file
       descriptor to another ring. The submission queue entry sqe is setup to
       use the file descriptor fd, which must identify a target io_uring
       context, to send the locally registered file descriptor with value
       source_fd to the destination ring into index target_fd and passing data
       as the user data in the target CQE with the request modifier flags set
       by flags.  Currently there are no valid flag modifiers, this field must
       contain 0.

       io_uring_prep_msg_ring_fd_alloc(3) is similar to
       io_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 CQE res field.


RETURN VALUE
       None


ERRORS
       These are the errors that are reported in the CQE res 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 in fd 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.

liburing-2.4                    March 16, 2023       io_uring_prep_msg_ring(3)