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