tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1/* eBPF example program:
2 *
3 * - Loads eBPF program
4 *
5 * The eBPF program sets the sk_bound_dev_if index in new AF_INET{6}
6 * sockets opened by processes in the cgroup.
7 *
8 * - Attaches the new program to a cgroup using BPF_PROG_ATTACH
9 */
10
11#define _GNU_SOURCE
12
13#include <stdio.h>
14#include <stdlib.h>
15#include <stddef.h>
16#include <string.h>
17#include <unistd.h>
18#include <assert.h>
19#include <errno.h>
20#include <fcntl.h>
21#include <net/if.h>
22#include <linux/bpf.h>
23
24#include "libbpf.h"
25
26char bpf_log_buf[BPF_LOG_BUF_SIZE];
27
28static int prog_load(int idx)
29{
30 struct bpf_insn prog[] = {
31 BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
32 BPF_MOV64_IMM(BPF_REG_3, idx),
33 BPF_MOV64_IMM(BPF_REG_2, offsetof(struct bpf_sock, bound_dev_if)),
34 BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_3, offsetof(struct bpf_sock, bound_dev_if)),
35 BPF_MOV64_IMM(BPF_REG_0, 1), /* r0 = verdict */
36 BPF_EXIT_INSN(),
37 };
38 size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
39
40 return bpf_load_program(BPF_PROG_TYPE_CGROUP_SOCK, prog, insns_cnt,
41 "GPL", 0, bpf_log_buf, BPF_LOG_BUF_SIZE);
42}
43
44static int usage(const char *argv0)
45{
46 printf("Usage: %s cg-path device-index\n", argv0);
47 return EXIT_FAILURE;
48}
49
50int main(int argc, char **argv)
51{
52 int cg_fd, prog_fd, ret;
53 unsigned int idx;
54
55 if (argc < 2)
56 return usage(argv[0]);
57
58 idx = if_nametoindex(argv[2]);
59 if (!idx) {
60 printf("Invalid device name\n");
61 return EXIT_FAILURE;
62 }
63
64 cg_fd = open(argv[1], O_DIRECTORY | O_RDONLY);
65 if (cg_fd < 0) {
66 printf("Failed to open cgroup path: '%s'\n", strerror(errno));
67 return EXIT_FAILURE;
68 }
69
70 prog_fd = prog_load(idx);
71 printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
72
73 if (prog_fd < 0) {
74 printf("Failed to load prog: '%s'\n", strerror(errno));
75 return EXIT_FAILURE;
76 }
77
78 ret = bpf_prog_attach(prog_fd, cg_fd, BPF_CGROUP_INET_SOCK_CREATE, 0);
79 if (ret < 0) {
80 printf("Failed to attach prog to cgroup: '%s'\n",
81 strerror(errno));
82 return EXIT_FAILURE;
83 }
84
85 return EXIT_SUCCESS;
86}