linux/tools/lib/bpf/xsk.h

/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */

/*
 * AF_XDP user-space access library.
 *
 * Copyright(c) 2018 - 2019 Intel Corporation.
 *
 * Author(s): Magnus Karlsson <magnus.karlsson@intel.com>
 */

#ifndef __LIBBPF_XSK_H
#define __LIBBPF_XSK_H

#include <stdio.h>
#include <stdint.h>
#include <linux/if_xdp.h>

#include "libbpf.h"
#include "libbpf_util.h"

#ifdef __cplusplus
extern "C" {
#endif

/* Do not access these members directly. Use the functions below. */
#define DEFINE_XSK_RING(name) \
struct name { \
	__u32 cached_prod; \
	__u32 cached_cons; \
	__u32 mask; \
	__u32 size; \
	__u32 *producer; \
	__u32 *consumer; \
	void *ring; \
}

DEFINE_XSK_RING(xsk_ring_prod);
DEFINE_XSK_RING(xsk_ring_cons);

/* For a detailed explanation on the memory barriers associated with the
 * ring, please take a look at net/xdp/xsk_queue.h.
 */

struct xsk_umem;
struct xsk_socket;

static inline __u64 *xsk_ring_prod__fill_addr(struct xsk_ring_prod *fill,
					      __u32 idx)
{
	__u64 *addrs = (__u64 *)fill->ring;

	return &addrs[idx & fill->mask];
}

static inline const __u64 *
xsk_ring_cons__comp_addr(const struct xsk_ring_cons *comp, __u32 idx)
{
	const __u64 *addrs = (const __u64 *)comp->ring;

	return &addrs[idx & comp->mask];
}

static inline struct xdp_desc *xsk_ring_prod__tx_desc(struct xsk_ring_prod *tx,
						      __u32 idx)
{
	struct xdp_desc *descs = (struct xdp_desc *)tx->ring;

	return &descs[idx & tx->mask];
}

static inline const struct xdp_desc *
xsk_ring_cons__rx_desc(const struct xsk_ring_cons *rx, __u32 idx)
{
	const struct xdp_desc *descs = (const struct xdp_desc *)rx->ring;

	return &descs[idx & rx->mask];
}

static inline __u32 xsk_prod_nb_free(struct xsk_ring_prod *r, __u32 nb)
{
	__u32 free_entries = r->cached_cons - r->cached_prod;

	if (free_entries >= nb)
		return free_entries;

	/* Refresh the local tail pointer.
	 * cached_cons is r->size bigger than the real consumer pointer so
	 * that this addition can be avoided in the more frequently
	 * executed code that computs free_entries in the beginning of
	 * this function. Without this optimization it whould have been
	 * free_entries = r->cached_prod - r->cached_cons + r->size.
	 */
	r->cached_cons = *r->consumer + r->size;

	return r->cached_cons - r->cached_prod;
}

static inline __u32 xsk_cons_nb_avail(struct xsk_ring_cons *r, __u32 nb)
{
	__u32 entries = r->cached_prod - r->cached_cons;

	if (entries == 0) {
		r->cached_prod = *r->producer;
		entries = r->cached_prod - r->cached_cons;
	}

	return (entries > nb) ? nb : entries;
}

static inline size_t xsk_ring_prod__reserve(struct xsk_ring_prod *prod,
					    size_t nb, __u32 *idx)
{
	if (xsk_prod_nb_free(prod, nb) < nb)
		return 0;

	*idx = prod->cached_prod;
	prod->cached_prod += nb;

	return nb;
}

static inline void xsk_ring_prod__submit(struct xsk_ring_prod *prod, size_t nb)
{
	/* Make sure everything has been written to the ring before indicating
	 * this to the kernel by writing the producer pointer.
	 */
	libbpf_smp_wmb();

	*prod->producer += nb;
}

static inline size_t xsk_ring_cons__peek(struct xsk_ring_cons *cons,
					 size_t nb, __u32 *idx)
{
	size_t entries = xsk_cons_nb_avail(cons, nb);

	if (entries > 0) {
		/* Make sure we do not speculatively read the data before
		 * we have received the packet buffers from the ring.
		 */
		libbpf_smp_rmb();

		*idx = cons->cached_cons;
		cons->cached_cons += entries;
	}

	return entries;
}

static inline void xsk_ring_cons__release(struct xsk_ring_cons *cons, size_t nb)
{
	/* Make sure data has been read before indicating we are done
	 * with the entries by updating the consumer pointer.
	 */
	libbpf_smp_rwmb();

	*cons->consumer += nb;
}

static inline void *xsk_umem__get_data(void *umem_area, __u64 addr)
{
	return &((char *)umem_area)[addr];
}

LIBBPF_API int xsk_umem__fd(const struct xsk_umem *umem);
LIBBPF_API int xsk_socket__fd(const struct xsk_socket *xsk);

#define XSK_RING_CONS__DEFAULT_NUM_DESCS      2048
#define XSK_RING_PROD__DEFAULT_NUM_DESCS      2048
#define XSK_UMEM__DEFAULT_FRAME_SHIFT    12 /* 4096 bytes */
#define XSK_UMEM__DEFAULT_FRAME_SIZE     (1 << XSK_UMEM__DEFAULT_FRAME_SHIFT)
#define XSK_UMEM__DEFAULT_FRAME_HEADROOM 0

struct xsk_umem_config {
	__u32 fill_size;
	__u32 comp_size;
	__u32 frame_size;
	__u32 frame_headroom;
};

/* Flags for the libbpf_flags field. */
#define XSK_LIBBPF_FLAGS__INHIBIT_PROG_LOAD (1 << 0)

struct xsk_socket_config {
	__u32 rx_size;
	__u32 tx_size;
	__u32 libbpf_flags;
	__u32 xdp_flags;
	__u16 bind_flags;
};

/* Set config to NULL to get the default configuration. */
LIBBPF_API int xsk_umem__create(struct xsk_umem **umem,
				void *umem_area, __u64 size,
				struct xsk_ring_prod *fill,
				struct xsk_ring_cons *comp,
				const struct xsk_umem_config *config);
LIBBPF_API int xsk_socket__create(struct xsk_socket **xsk,
				  const char *ifname, __u32 queue_id,
				  struct xsk_umem *umem,
				  struct xsk_ring_cons *rx,
				  struct xsk_ring_prod *tx,
				  const struct xsk_socket_config *config);

/* Returns 0 for success and -EBUSY if the umem is still in use. */
LIBBPF_API int xsk_umem__delete(struct xsk_umem *umem);
LIBBPF_API void xsk_socket__delete(struct xsk_socket *xsk);

#ifdef __cplusplus
} /* extern "C" */
#endif

#endif /* __LIBBPF_XSK_H */