samples/bpf/test_cgrp2_attach.c

   1 /* eBPF example program:
   2  *
   3  * - Creates arraymap in kernel with 4 bytes keys and 8 byte values
   4  *
   5  * - Loads eBPF program
   6  *
   7  *   The eBPF program accesses the map passed in to store two pieces of
   8  *   information. The number of invocations of the program, which maps
   9  *   to the number of packets received, is stored to key 0. Key 1 is
  10  *   incremented on each iteration by the number of bytes stored in
  11  *   the skb.
  12  *
  13  * - Attaches the new program to a cgroup using BPF_PROG_ATTACH
  14  *
  15  * - Every second, reads map[0] and map[1] to see how many bytes and
  16  *   packets were seen on any socket of tasks in the given cgroup.
  17  */
  18
  19 #define _GNU_SOURCE
  20
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <stddef.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26 #include <assert.h>
  27 #include <errno.h>
  28 #include <fcntl.h>
  29
  30 #include <linux/bpf.h>
  31
  32 #include "libbpf.h"
  33
  34 enum {
  35         MAP_KEY_PACKETS,
  36         MAP_KEY_BYTES,
  37 };
  38
  39 char bpf_log_buf[BPF_LOG_BUF_SIZE];
  40
  41 static int prog_load(int map_fd, int verdict)
  42 {
  43         struct bpf_insn prog[] = {
  44                 BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */
  45
  46                 /* Count packets */
  47                 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */
  48                 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
  49                 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
  50                 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
  51                 BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */
  52                 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
  53                 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
  54                 BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
  55                 BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
  56
  57                 /* Count bytes */
  58                 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */
  59                 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
  60                 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
  61                 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
  62                 BPF_LD_MAP_FD(BPF_REG_1, map_fd),
  63                 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
  64                 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
  65                 BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */
  66                 BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
  67
  68                 BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
  69                 BPF_EXIT_INSN(),
  70         };
  71         size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
  72
  73         return bpf_load_program(BPF_PROG_TYPE_CGROUP_SKB,
  74                                 prog, insns_cnt, "GPL", 0,
  75                                 bpf_log_buf, BPF_LOG_BUF_SIZE);
  76 }
  77
  78 static int usage(const char *argv0)
  79 {
  80         printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0);
  81         printf("        -d      Drop Traffic\n");
  82         printf("        -D      Detach filter, and exit\n");
  83         return EXIT_FAILURE;
  84 }
  85
  86 static int attach_filter(int cg_fd, int type, int verdict)
  87 {
  88         int prog_fd, map_fd, ret, key;
  89         long long pkt_cnt, byte_cnt;
  90
  91         map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY,
  92                                 sizeof(key), sizeof(byte_cnt),
  93                                 256, 0);
  94         if (map_fd < 0) {
  95                 printf("Failed to create map: '%s'\n", strerror(errno));
  96                 return EXIT_FAILURE;
  97         }
  98
  99         prog_fd = prog_load(map_fd, verdict);
 100         printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
 101
 102         if (prog_fd < 0) {
 103                 printf("Failed to load prog: '%s'\n", strerror(errno));
 104                 return EXIT_FAILURE;
 105         }
 106
 107         ret = bpf_prog_attach(prog_fd, cg_fd, type, 0);
 108         if (ret < 0) {
 109                 printf("Failed to attach prog to cgroup: '%s'\n",
 110                        strerror(errno));
 111                 return EXIT_FAILURE;
 112         }
 113         while (1) {
 114                 key = MAP_KEY_PACKETS;
 115                 assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0);
 116
 117                 key = MAP_KEY_BYTES;
 118                 assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0);
 119
 120                 printf("cgroup received %lld packets, %lld bytes\n",
 121                        pkt_cnt, byte_cnt);
 122                 sleep(1);
 123         }
 124
 125         return EXIT_SUCCESS;
 126 }
 127
 128 int main(int argc, char **argv)
 129 {
 130         int detach_only = 0, verdict = 1;
 131         enum bpf_attach_type type;
 132         int opt, cg_fd, ret;
 133
 134         while ((opt = getopt(argc, argv, "Dd")) != -1) {
 135                 switch (opt) {
 136                 case 'd':
 137                         verdict = 0;
 138                         break;
 139                 case 'D':
 140                         detach_only = 1;
 141                         break;
 142                 default:
 143                         return usage(argv[0]);
 144                 }
 145         }
 146
 147         if (argc - optind < 2)
 148                 return usage(argv[0]);
 149
 150         if (strcmp(argv[optind + 1], "ingress") == 0)
 151                 type = BPF_CGROUP_INET_INGRESS;
 152         else if (strcmp(argv[optind + 1], "egress") == 0)
 153                 type = BPF_CGROUP_INET_EGRESS;
 154         else
 155                 return usage(argv[0]);
 156
 157         cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY);
 158         if (cg_fd < 0) {
 159                 printf("Failed to open cgroup path: '%s'\n", strerror(errno));
 160                 return EXIT_FAILURE;
 161         }
 162
 163         if (detach_only) {
 164                 ret = bpf_prog_detach(cg_fd, type);
 165                 printf("bpf_prog_detach() returned '%s' (%d)\n",
 166                        strerror(errno), errno);
 167         } else
 168                 ret = attach_filter(cg_fd, type, verdict);
 169
 170         return ret;
 171 }