io_uring_prep_cmd_sock3

Usage

#include <liburing.h>

Overview

The io_uring_prep_cmd_sock(3) function prepares an cmd request for a socket. The submission queue entry sqe is setup to use the socket file descriptor pointed to by fd to start an command operation defined by cmd_op.

This is a generic function, and each command has their own individual level, optname, optval values. The optlen defines the size pointed by optval.

Available commands

SOCKET_URING_OP_SIOCINQ

Returns the amount of queued unread data in the receive buffer. The socket must not be in LISTEN state, otherwise an error -EINVAL is returned in the CQE res field. The following arguments are not used for this command level, optname, optval and optlen.

Negative return value means an error.

For more information about this command, please check unix(7).

Available since 6.7.

SOCKET_URING_OP_SIOCOUTQ

Returns the amount of unsent data in the socket send queue. The socket must not be in LISTEN state, otherwise an error -EINVAL is returned in the CQE res. field. The following arguments are not used for this command level, optname, optval and optlen.

Negative return value means an error.

For more information about this command, please check unix(7).

SOCKET_URING_OP_GETSOCKOPT

Command to get options for the socket referred to by the socket file descriptor fd. The arguments are similar to the getsockopt(2) system call.

The SOCKET_URING_OP_GETSOCKOPT command is limited to SOL_SOCKET level.

Differently from the getsockopt(2) system call, the updated optlen value is returned in the CQE res field, on success. On failure, the CQE res contains a negative error number.

SOCKET_URING_OP_SETSOCKOPT

Command to set options for the socket referred to by the socket file descriptor fd. The arguments are similar to the setsockopt(2) system call.

Available since 6.7.

SOCKET_URING_OP_TX_TIMESTAMP

Retrieve transmit timestamps from the socket's error queue. This provides an alternative to the traditional recvmsg(2) error queue interface for obtaining TX timestamps.

The command operates in a polled multishot mode: io_uring will poll the socket and keep posting timestamps as CQEs until the request is cancelled or fails. The ring must be created with IORING_SETUP_CQE32 or IORING_SETUP_CQE_MIXED to provide space for the timestamp data.

The socket must first be configured for timestamping via setsockopt(2) with SO_TIMESTAMPING at the SOL_SOCKET level, specifying the desired timestamp types (e.g. SOF_TIMESTAMPING_TX_SOFTWARE, SOF_TIMESTAMPING_TX_SCHED, SOF_TIMESTAMPING_TX_ACK) along with SOF_TIMESTAMPING_SOFTWARE and SOF_TIMESTAMPING_OPT_TSONLY.

The following arguments are not used for this command: level, optname, optval and optlen.

Each timestamp is delivered as a CQE with IORING_CQE_F_MORE set in cqe->flags to indicate more timestamps may follow. The cqe->res field contains the timestamp key (tskey), which corresponds to the byte offset (for TCP) or packet count (for UDP). The timestamp type (SCM_TSTAMP_SCHED, SCM_TSTAMP_SND or SCM_TSTAMP_ACK) is stored in the upper bits of cqe->flags at offset IORING_TIMESTAMP_TYPE_SHIFT. If the timestamp is a hardware timestamp, the IORING_CQE_F_TSTAMP_HW flag is set.

The actual timestamp value is stored in the extended CQE area as a struct io_timespec (with 64-bit tv_sec and tv_nsec fields), accessible at (cqe + 1).

The final CQE will not have IORING_CQE_F_MORE set, and its cqe->res will contain 0 on success or a negative error code on failure.

Available since 6.17.

SOCKET_URING_OP_GETSOCKNAME

Returns the current address to which the socket is bound. The result is stored in the buffer pointed to by optval, which should be a pointer to a struct sockaddr (or appropriate variant). The optlen argument specifies the size of the buffer. On success, the CQE res field contains the actual size of the socket address. If the buffer is too small, the result is truncated.

This is the io_uring equivalent of getsockname(2).

Available since 6.19.

Notes

The memory block pointed by optval needs to be valid/live until the CQE returns.

Return value

Dependent on the command.

Errors

The CQE res field will contain the result of the operation.