NAME

       io_uring_prep_sendmsg - prepare a sendmsg request

SYNOPSIS

       #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);

DESCRIPTION

       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.

       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.

RETURN VALUE

       None

ERRORS

       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.

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  IORING_FEAT_SUBMIT_STABLE  flag passed back from
       io_uring_queue_init_params(3).

SEE ALSO

       io_uring_get_sqe(3), io_uring_submit(3), sendmsg(2)