xdp_prog_user.c
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	/* SPDX-License-Identifier: GPL-2.0 */

	static const char *__doc__ = "XDP redirect helper\n"
	" - Allows to populate/query tx_port and redirect_params maps\n";

	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>
	#include <errno.h>
	#include <getopt.h>
	#include <stdbool.h>

	#include <locale.h>
	#include <unistd.h>
	#include <time.h>

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

	#include <net/if.h>
	#include <linux/if_ether.h>
	#include <linux/if_link.h> /* depend on kernel-headers installed */

	#include "common/common_params.h"
	#include "common/common_user_bpf_xdp.h"
	#include "common/common_libbpf.h"

	#include "common/xdp_stats_kern_user.h"

	static const struct option_wrapper long_options[] = {

	{{"help", no_argument, NULL, 'h' },
	"Show help", false},

	{{"dev", required_argument, NULL, 'd' },
	"Operate on device <ifname>", "<ifname>", true},

	{{"redirect-dev", required_argument, NULL, 'r' },
	"Redirect to device <ifname>", "<ifname>", true},

	{{"src-mac", required_argument, NULL, 'L' },
	"Source MAC address of <dev>", "<mac>", true },

	{{"dest-mac", required_argument, NULL, 'R' },
	"Destination MAC address of <redirect-dev>", "<mac>", true },

	{{"quiet", no_argument, NULL, 'q' },
	"Quiet mode (no output)"},

	{{0, 0, NULL, 0 }, NULL, false}
	};

	static int parse_u8(char str, unsigned char x)
	{
	unsigned long z;

	z = strtoul(str, 0, 16);
	if (z > 0xff)
	return -1;

	if (x)
	*x = z;

	return 0;
	}

	static int parse_mac(char *str, unsigned char mac[ETH_ALEN])
	{
	if (parse_u8(str, &mac[0]) < 0)
	return -1;
	if (parse_u8(str + 3, &mac[1]) < 0)
	return -1;
	if (parse_u8(str + 6, &mac[2]) < 0)
	return -1;
	if (parse_u8(str + 9, &mac[3]) < 0)
	return -1;
	if (parse_u8(str + 12, &mac[4]) < 0)
	return -1;
	if (parse_u8(str + 15, &mac[5]) < 0)
	return -1;

	return 0;
	}

	static int write_iface_params(int map_fd, unsigned char src, unsigned char dest)
	{
	if (bpf_map_update_elem(map_fd, src, dest, 0) < 0) {
	fprintf(stderr,
	"WARN: Failed to update bpf map file: err(%d):%s\n",
	errno, strerror(errno));
	return -1;
	}

	printf("forward: %02x:%02x:%02x:%02x:%02x:%02x -> %02x:%02x:%02x:%02x:%02x:%02x\n",
	src[0], src[1], src[2], src[3], src[4], src[5],
	dest[0], dest[1], dest[2], dest[3], dest[4], dest[5]
	);

	return 0;
	}

	#ifndef PATH_MAX
	#define PATH_MAX 4096
	#endif

	const char *pin_basedir = "/sys/fs/bpf";

	int main(int argc, char **argv)
	{
	int i;
	int len;
	int map_fd;
	bool redirect_map;
	char pin_dir[PATH_MAX];
	unsigned char src[ETH_ALEN];
	unsigned char dest[ETH_ALEN];

	struct config cfg = {
	.ifindex = -1,
	.redirect_ifindex = -1,
	};

	/* Cmdline options can change progsec */
	parse_cmdline_args(argc, argv, long_options, &cfg, __doc__);

	redirect_map = (cfg.ifindex > 0) && (cfg.redirect_ifindex > 0);

	if (cfg.redirect_ifindex > 0 && cfg.ifindex == -1) {
	fprintf(stderr, "ERR: required option --dev missing\n\n");
	usage(argv[0], __doc__, long_options, (argc == 1));
	return EXIT_FAIL_OPTION;
	}

	len = snprintf(pin_dir, PATH_MAX, "%s/%s", pin_basedir, cfg.ifname);
	if (len < 0) {
	fprintf(stderr, "ERR: creating pin dirname\n");
	return EXIT_FAIL_OPTION;
	}

	if (parse_mac(cfg.src_mac, src) < 0) {
	fprintf(stderr, "ERR: can't parse mac address %s\n", cfg.src_mac);
	return EXIT_FAIL_OPTION;
	}

	if (parse_mac(cfg.dest_mac, dest) < 0) {
	fprintf(stderr, "ERR: can't parse mac address %s\n", cfg.dest_mac);
	return EXIT_FAIL_OPTION;
	}

	/* Open the tx_port map corresponding to the cfg.ifname interface */
	map_fd = open_bpf_map_file(pin_dir, "tx_port", NULL);
	if (map_fd < 0) {
	return EXIT_FAIL_BPF;
	}

	printf("map dir: %s\n", pin_dir);

	if (redirect_map) {
	/* setup a virtual port for the static redirect */
	i = 0;
	bpf_map_update_elem(map_fd, &i, &cfg.redirect_ifindex, 0);
	printf("redirect from ifnum=%d to ifnum=%d\n", cfg.ifindex, cfg.redirect_ifindex);

	/* Open the redirect_params map */
	map_fd = open_bpf_map_file(pin_dir, "redirect_params", NULL);
	if (map_fd < 0) {
	return EXIT_FAIL_BPF;
	}

	/* Setup the mapping containing MAC addresses */
	if (write_iface_params(map_fd, src, dest) < 0) {
	fprintf(stderr, "can't write iface params\n");
	return 1;
	}
	} else {
	/* setup 1-1 mapping for the dynamic router */
	for (i = 1; i < 256; ++i)
	bpf_map_update_elem(map_fd, &i, &i, 0);
	}

	return EXIT_OK;
	}

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