samples/bpf/test_cgrp2_sock.c

   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
  26 char bpf_log_buf[BPF_LOG_BUF_SIZE];
  27
  28 static 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
  44 static int usage(const char *argv0)
  45 {
  46         printf("Usage: %s cg-path device-index\n", argv0);
  47         return EXIT_FAILURE;
  48 }
  49
  50 int 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 }