Copyright (C) 2022 Jens Axboe <axboe@kernel.dk>

SPDX-License-Identifier: LGPL-2.0-or-later

io_uring_prep_send_zc - prepare a zerocopy send request

 #include <liburing.h> 

 "void io_uring_prep_send_zc(struct io_uring_sqe *" sqe ","  " int " sockfd ","  " const void *" buf ","  " size_t " len ","  " int " flags ","  " unsigned " zc_flags ");" 

 "void io_uring_prep_send_zc_fixed(struct io_uring_sqe *" sqe ","  " int " sockfd ","  " const void *" buf ","  " size_t " len ","  " int " flags ","  " unsigned " zc_flags ");"  " unsigned " buf_index ");" 

The io_uring_prep_send_zc (3) function prepares a zerocopy send request. The submission queue entry sqe is setup to use the file descriptor sockfd to start sending the data from buf of size len bytes with send modifier flags flags and zerocopy modifier flags zc_flags . The io_uring_prep_send_zc_fixed (3) works just like io_uring_prep_send_zc (3) except it requires the use of buffers that have been registered with io_uring_register_buffers (3). The buf and len arguments must fall within a region specified by buf_index in the previously registered buffer. The buffer need not be aligned with the start of the registered buffer. 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. These functions prepare an async zerocopy send (2) request. See that man page for details. For details on the zerocopy nature of it, see io_uring_enter (2) .

None 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. io_uring_get_sqe (3), io_uring_submit (3), io_uring_prep_send (3), io_uring_enter (2), send (2)