xdp-project-bpf-examples/AF_XDP-interaction/common_user_bpf_xdp.c

#include <bpf/libbpf.h> /* bpf_get_link_xdp_id + bpf_set_link_xdp_id */
#include <string.h>     /* strerror */
#include <net/if.h>     /* IF_NAMESIZE */
#include <stdlib.h>     /* exit(3) */
#include <errno.h>

#include <bpf/bpf.h>
#include <bpf/libbpf.h>

#include <linux/if_link.h> /* Need XDP flags */
#include <linux/err.h>

#include "common_defines.h"

#ifndef PATH_MAX
#define PATH_MAX	4096
#endif

int xdp_link_attach(int ifindex, __u32 xdp_flags, int prog_fd)
{
	int err;

	/* libbpf provide the XDP net_device link-level hook attach helper */
	err = bpf_set_link_xdp_fd(ifindex, prog_fd, xdp_flags);
	if (err == -EEXIST && !(xdp_flags & XDP_FLAGS_UPDATE_IF_NOEXIST)) {
		/* Force mode didn't work, probably because a program of the
		 * opposite type is loaded. Let's unload that and try loading
		 * again.
		 */

		__u32 old_flags = xdp_flags;

		xdp_flags &= ~XDP_FLAGS_MODES;
		xdp_flags |= (old_flags & XDP_FLAGS_SKB_MODE) ? XDP_FLAGS_DRV_MODE : XDP_FLAGS_SKB_MODE;
		err = bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
		if (!err)
			err = bpf_set_link_xdp_fd(ifindex, prog_fd, old_flags);
	}
	if (err < 0) {
		fprintf(stderr, "ERR: "
			"ifindex(%d) link set xdp fd failed (%d): %s\n",
			ifindex, -err, strerror(-err));

		switch (-err) {
		case EBUSY:
		case EEXIST:
			fprintf(stderr, "Hint: XDP already loaded on device"
				" use --force to swap/replace\n");
			break;
		case EOPNOTSUPP:
			fprintf(stderr, "Hint: Native-XDP not supported"
				" use --skb-mode or --auto-mode\n");
			break;
		default:
			break;
		}
		return EXIT_FAIL_XDP;
	}

	return EXIT_OK;
}

int xdp_link_detach(int ifindex, __u32 xdp_flags, __u32 expected_prog_id)
{
	__u32 curr_prog_id;
	int err;

	err = bpf_get_link_xdp_id(ifindex, &curr_prog_id, xdp_flags);
	if (err) {
		fprintf(stderr, "ERR: get link xdp id failed (err=%d): %s\n",
			-err, strerror(-err));
		return EXIT_FAIL_XDP;
	}

	if (!curr_prog_id) {
		if (verbose)
			printf("INFO: %s() no curr XDP prog on ifindex:%d\n",
			       __func__, ifindex);
		return EXIT_OK;
	}

	if (expected_prog_id && curr_prog_id != expected_prog_id) {
		fprintf(stderr, "ERR: %s() "
			"expected prog ID(%d) no match(%d), not removing\n",
			__func__, expected_prog_id, curr_prog_id);
		return EXIT_FAIL;
	}

	if ((err = bpf_set_link_xdp_fd(ifindex, -1, xdp_flags)) < 0) {
		fprintf(stderr, "ERR: %s() link set xdp failed (err=%d): %s\n",
			__func__, err, strerror(-err));
		return EXIT_FAIL_XDP;
	}

	if (verbose)
		printf("INFO: %s() removed XDP prog ID:%d on ifindex:%d\n",
		       __func__, curr_prog_id, ifindex);

	return EXIT_OK;
}

struct bpf_object *load_bpf_object_file(const char *filename, int ifindex)
{
	int first_prog_fd = -1;
	struct bpf_object *obj;
	int err;

	/* This struct allow us to set ifindex, this features is used for
	 * hardware offloading XDP programs (note this sets libbpf
	 * bpf_program->prog_ifindex and foreach bpf_map->map_ifindex).
	 */
	struct bpf_prog_load_attr prog_load_attr = {
		.prog_type = BPF_PROG_TYPE_XDP,
		.ifindex   = ifindex,
	};
	prog_load_attr.file = filename;

	/* Use libbpf for extracting BPF byte-code from BPF-ELF object, and
	 * loading this into the kernel via bpf-syscall
	 */
	err = bpf_prog_load_xattr(&prog_load_attr, &obj, &first_prog_fd);
	if (err) {
		fprintf(stderr, "ERR: loading BPF-OBJ file(%s) (%d): %s\n",
			filename, err, strerror(-err));
		return NULL;
	}

	/* Notice how a pointer to a libbpf bpf_object is returned */
	return obj;
}

static struct bpf_object *open_bpf_object(const char *file, int ifindex)
{
	int err;
	struct bpf_object *obj;
	struct bpf_map *map;
	struct bpf_program *prog, *first_prog = NULL;

	struct bpf_object_open_attr open_attr = {
		.file = file,
		.prog_type = BPF_PROG_TYPE_XDP,
	};

	obj = bpf_object__open_xattr(&open_attr);
	if (IS_ERR_OR_NULL(obj)) {
		err = -PTR_ERR(obj);
		fprintf(stderr, "ERR: opening BPF-OBJ file(%s) (%d): %s\n",
			file, err, strerror(-err));
		return NULL;
	}

	bpf_object__for_each_program(prog, obj) {
		bpf_program__set_type(prog, BPF_PROG_TYPE_XDP);
		bpf_program__set_ifindex(prog, ifindex);
		if (!first_prog)
			first_prog = prog;
	}

	bpf_object__for_each_map(map, obj) {
		if (!bpf_map__is_offload_neutral(map))
			bpf_map__set_ifindex(map, ifindex);
	}

	if (!first_prog) {
		fprintf(stderr, "ERR: file %s contains no programs\n", file);
		return NULL;
	}

	return obj;
}

static int reuse_maps(struct bpf_object *obj, const char *path)
{
	struct bpf_map *map;

	if (!obj)
		return -ENOENT;

	if (!path)
		return -EINVAL;

	bpf_object__for_each_map(map, obj) {
		int len, err;
		int pinned_map_fd;
		char buf[PATH_MAX];

		len = snprintf(buf, PATH_MAX, "%s/%s", path, bpf_map__name(map));
		if (len < 0) {
			return -EINVAL;
		} else if (len >= PATH_MAX) {
			return -ENAMETOOLONG;
		}

		pinned_map_fd = bpf_obj_get(buf);
		if (pinned_map_fd < 0)
			return pinned_map_fd;

		err = bpf_map__reuse_fd(map, pinned_map_fd);
		if (err)
			return err;
	}

	return 0;
}

struct bpf_object *load_bpf_object_file_reuse_maps(const char *file,
						   int ifindex,
						   const char *pin_dir)
{
	int err;
	struct bpf_object *obj;

	obj = open_bpf_object(file, ifindex);
	if (!obj) {
		fprintf(stderr, "ERR: failed to open object %s\n", file);
		return NULL;
	}

	err = reuse_maps(obj, pin_dir);
	if (err) {
		fprintf(stderr, "ERR: failed to reuse maps for object %s, pin_dir=%s\n",
				file, pin_dir);
		return NULL;
	}

	err = bpf_object__load(obj);
	if (err) {
		fprintf(stderr, "ERR: loading BPF-OBJ file(%s) (%d): %s\n",
			file, err, strerror(-err));
		return NULL;
	}

	return obj;
}

struct bpf_object *load_bpf_and_xdp_attach(struct config *cfg)
{
	struct bpf_program *bpf_prog;
	struct bpf_object *bpf_obj;
	int offload_ifindex = 0;
	int prog_fd = -1;
	size_t len;
	int err;

	/* If flags indicate hardware offload, supply ifindex */
	if (cfg->xdp_flags & XDP_FLAGS_HW_MODE)
		offload_ifindex = cfg->ifindex;

	/* Load the BPF-ELF object file and get back libbpf bpf_object */
	if (cfg->reuse_maps)
		bpf_obj = load_bpf_object_file_reuse_maps(cfg->filename,
							  offload_ifindex,
							  cfg->pin_dir);
	else
		bpf_obj = load_bpf_object_file(cfg->filename, offload_ifindex);
	if (!bpf_obj) {
		fprintf(stderr, "ERR: loading file: %s\n", cfg->filename);
		exit(EXIT_FAIL_BPF);
	}
	/* At this point: All XDP/BPF programs from the cfg->filename have been
	 * loaded into the kernel, and evaluated by the verifier. Only one of
	 * these gets attached to XDP hook, the others will get freed once this
	 * process exit.
	 */

	if (cfg->progsec[0])
		/* Find a matching BPF prog section name */
		bpf_prog = bpf_object__find_program_by_title(bpf_obj, cfg->progsec);
	else
		/* Find the first program */
		bpf_prog = bpf_program__next(NULL, bpf_obj);

	if (!bpf_prog) {
		fprintf(stderr, "ERR: couldn't find a program in ELF section '%s'\n", cfg->progsec);
		exit(EXIT_FAIL_BPF);
	}

	len = sizeof(cfg->progsec) - 1;
	strncpy(cfg->progsec, bpf_program__section_name(bpf_prog), len);
	cfg->progsec[len] = '\0'; /* null terminate string */

	prog_fd = bpf_program__fd(bpf_prog);
	if (prog_fd <= 0) {
		fprintf(stderr, "ERR: bpf_program__fd failed\n");
		exit(EXIT_FAIL_BPF);
	}

	/* At this point: BPF-progs are (only) loaded by the kernel, and prog_fd
	 * is our select file-descriptor handle. Next step is attaching this FD
	 * to a kernel hook point, in this case XDP net_device link-level hook.
	 */
	err = xdp_link_attach(cfg->ifindex, cfg->xdp_flags, prog_fd);
	if (err)
		exit(err);

	return bpf_obj;
}

#define XDP_UNKNOWN	XDP_REDIRECT + 1
#ifndef XDP_ACTION_MAX
#define XDP_ACTION_MAX (XDP_UNKNOWN + 1)
#endif

static const char *xdp_action_names[XDP_ACTION_MAX] = {
	[XDP_ABORTED]   = "XDP_ABORTED",
	[XDP_DROP]      = "XDP_DROP",
	[XDP_PASS]      = "XDP_PASS",
	[XDP_TX]        = "XDP_TX",
	[XDP_REDIRECT]  = "XDP_REDIRECT",
	[XDP_UNKNOWN]	= "XDP_UNKNOWN",
};

const char *action2str(__u32 action)
{
        if (action < XDP_ACTION_MAX)
                return xdp_action_names[action];
        return NULL;
}

int check_map_fd_info(const struct bpf_map_info *info,
		      const struct bpf_map_info *exp)
{
	if (exp->key_size && exp->key_size != info->key_size) {
		fprintf(stderr, "ERR: %s() "
			"Map key size(%d) mismatch expected size(%d)\n",
			__func__, info->key_size, exp->key_size);
		return EXIT_FAIL;
	}
	if (exp->value_size && exp->value_size != info->value_size) {
		fprintf(stderr, "ERR: %s() "
			"Map value size(%d) mismatch expected size(%d)\n",
			__func__, info->value_size, exp->value_size);
		return EXIT_FAIL;
	}
	if (exp->max_entries && exp->max_entries != info->max_entries) {
		fprintf(stderr, "ERR: %s() "
			"Map max_entries(%d) mismatch expected size(%d)\n",
			__func__, info->max_entries, exp->max_entries);
		return EXIT_FAIL;
	}
	if (exp->type && exp->type  != info->type) {
		fprintf(stderr, "ERR: %s() "
			"Map type(%d) mismatch expected type(%d)\n",
			__func__, info->type, exp->type);
		return EXIT_FAIL;
	}

	return 0;
}

int open_bpf_map_file(const char *pin_dir,
		      const char *mapname,
		      struct bpf_map_info *info)
{
	char filename[PATH_MAX];
	int err, len, fd;
	__u32 info_len = sizeof(*info);

	len = snprintf(filename, PATH_MAX, "%s/%s", pin_dir, mapname);
	if (len < 0) {
		fprintf(stderr, "ERR: constructing full mapname path\n");
		return -1;
	}

	fd = bpf_obj_get(filename);
	if (fd < 0) {
		fprintf(stderr,
			"WARN: Failed to open bpf map file:%s err(%d):%s\n",
			filename, errno, strerror(errno));
		return fd;
	}

	if (info) {
		err = bpf_obj_get_info_by_fd(fd, info, &info_len);
		if (err) {
			fprintf(stderr, "ERR: %s() can't get info - %s\n",
				__func__,  strerror(errno));
			return EXIT_FAIL_BPF;
		}
	}

	return fd;
}