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 #include <bpf/bpf.h>
23 #include <bpf/libbpf.h>
24 
25 #include "bpf_insn.h"
26 
usage(const char * argv0)27 static int usage(const char *argv0)
28 {
29 	printf("Usage: %s cg-path filter-path [filter-id]\n", argv0);
30 	return EXIT_FAILURE;
31 }
32 
main(int argc,char ** argv)33 int main(int argc, char **argv)
34 {
35 	int cg_fd, err, ret = EXIT_FAILURE, filter_id = 0, prog_cnt = 0;
36 	const char *link_pin_path = "/sys/fs/bpf/test_cgrp2_sock2";
37 	struct bpf_link *link = NULL;
38 	struct bpf_program *progs[2];
39 	struct bpf_program *prog;
40 	struct bpf_object *obj;
41 
42 	if (argc < 3)
43 		return usage(argv[0]);
44 
45 	if (argc > 3)
46 		filter_id = atoi(argv[3]);
47 
48 	cg_fd = open(argv[1], O_DIRECTORY | O_RDONLY);
49 	if (cg_fd < 0) {
50 		printf("Failed to open cgroup path: '%s'\n", strerror(errno));
51 		return ret;
52 	}
53 
54 	obj = bpf_object__open_file(argv[2], NULL);
55 	if (libbpf_get_error(obj)) {
56 		printf("ERROR: opening BPF object file failed\n");
57 		return ret;
58 	}
59 
60 	bpf_object__for_each_program(prog, obj) {
61 		progs[prog_cnt] = prog;
62 		prog_cnt++;
63 	}
64 
65 	if (filter_id >= prog_cnt) {
66 		printf("Invalid program id; program not found in file\n");
67 		goto cleanup;
68 	}
69 
70 	/* load BPF program */
71 	if (bpf_object__load(obj)) {
72 		printf("ERROR: loading BPF object file failed\n");
73 		goto cleanup;
74 	}
75 
76 	link = bpf_program__attach_cgroup(progs[filter_id], cg_fd);
77 	if (libbpf_get_error(link)) {
78 		printf("ERROR: bpf_program__attach failed\n");
79 		link = NULL;
80 		goto cleanup;
81 	}
82 
83 	err = bpf_link__pin(link, link_pin_path);
84 	if (err < 0) {
85 		printf("ERROR: bpf_link__pin failed: %d\n", err);
86 		goto cleanup;
87 	}
88 
89 	ret = EXIT_SUCCESS;
90 
91 cleanup:
92 	bpf_link__destroy(link);
93 	bpf_object__close(obj);
94 	return ret;
95 }
96