1 // SPDX-License-Identifier: GPL-2.0
2 /* eBPF example program:
3  *
4  * - Loads eBPF program
5  *
6  *   The eBPF program loads a filter from file and attaches the
7  *   program to a cgroup using BPF_PROG_ATTACH
8  */
9 
10 #define _GNU_SOURCE
11 
12 #include <stdio.h>
13 #include <stdlib.h>
14 #include <stddef.h>
15 #include <string.h>
16 #include <unistd.h>
17 #include <assert.h>
18 #include <errno.h>
19 #include <fcntl.h>
20 #include <net/if.h>
21 #include <linux/bpf.h>
22 
23 #include "libbpf.h"
24 #include "bpf_load.h"
25 
26 static int usage(const char *argv0)
27 {
28 	printf("Usage: %s cg-path filter-path [filter-id]\n", argv0);
29 	return EXIT_FAILURE;
30 }
31 
32 int main(int argc, char **argv)
33 {
34 	int cg_fd, ret, filter_id = 0;
35 
36 	if (argc < 3)
37 		return usage(argv[0]);
38 
39 	cg_fd = open(argv[1], O_DIRECTORY | O_RDONLY);
40 	if (cg_fd < 0) {
41 		printf("Failed to open cgroup path: '%s'\n", strerror(errno));
42 		return EXIT_FAILURE;
43 	}
44 
45 	if (load_bpf_file(argv[2]))
46 		return EXIT_FAILURE;
47 
48 	printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
49 
50 	if (argc > 3)
51 		filter_id = atoi(argv[3]);
52 
53 	if (filter_id > prog_cnt) {
54 		printf("Invalid program id; program not found in file\n");
55 		return EXIT_FAILURE;
56 	}
57 
58 	ret = bpf_prog_attach(prog_fd[filter_id], cg_fd,
59 			      BPF_CGROUP_INET_SOCK_CREATE, 0);
60 	if (ret < 0) {
61 		printf("Failed to attach prog to cgroup: '%s'\n",
62 		       strerror(errno));
63 		return EXIT_FAILURE;
64 	}
65 
66 	return EXIT_SUCCESS;
67 }
68