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 #include <bpf/bpf.h>
  32
  33 #include "bpf_insn.h"
  34
  35 enum {
  36         MAP_KEY_PACKETS,
  37         MAP_KEY_BYTES,
  38 };
  39
  40 char bpf_log_buf[BPF_LOG_BUF_SIZE];
  41
  42 static int prog_load(int map_fd, int verdict)
  43 {
  44         struct bpf_insn prog[] = {
  45                 BPF_MOV64_REG(BPF_REG_6, BPF_REG_1), /* save r6 so it's not clobbered by BPF_CALL */
  46
  47                 /* Count packets */
  48                 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_PACKETS), /* r0 = 0 */
  49                 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
  50                 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
  51                 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
  52                 BPF_LD_MAP_FD(BPF_REG_1, map_fd), /* load map fd to r1 */
  53                 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
  54                 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
  55                 BPF_MOV64_IMM(BPF_REG_1, 1), /* r1 = 1 */
  56                 BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
  57
  58                 /* Count bytes */
  59                 BPF_MOV64_IMM(BPF_REG_0, MAP_KEY_BYTES), /* r0 = 1 */
  60                 BPF_STX_MEM(BPF_W, BPF_REG_10, BPF_REG_0, -4), /* *(u32 *)(fp - 4) = r0 */
  61                 BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),
  62                 BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), /* r2 = fp - 4 */
  63                 BPF_LD_MAP_FD(BPF_REG_1, map_fd),
  64                 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
  65                 BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 2),
  66                 BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_6, offsetof(struct __sk_buff, len)), /* r1 = skb->len */
  67
  68                 BPF_ATOMIC_OP(BPF_DW, BPF_ADD, BPF_REG_0, BPF_REG_1, 0),
  69
  70                 BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
  71                 BPF_EXIT_INSN(),
  72         };
  73         size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
  74
  75         return bpf_load_program(BPF_PROG_TYPE_CGROUP_SKB,
  76                                 prog, insns_cnt, "GPL", 0,
  77                                 bpf_log_buf, BPF_LOG_BUF_SIZE);
  78 }
  79
  80 static int usage(const char *argv0)
  81 {
  82         printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0);
  83         printf("        -d      Drop Traffic\n");
  84         printf("        -D      Detach filter, and exit\n");
  85         return EXIT_FAILURE;
  86 }
  87
  88 static int attach_filter(int cg_fd, int type, int verdict)
  89 {
  90         int prog_fd, map_fd, ret, key;
  91         long long pkt_cnt, byte_cnt;
  92
  93         map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY,
  94                                 sizeof(key), sizeof(byte_cnt),
  95                                 256, 0);
  96         if (map_fd < 0) {
  97                 printf("Failed to create map: '%s'\n", strerror(errno));
  98                 return EXIT_FAILURE;
  99         }
 100
 101         prog_fd = prog_load(map_fd, verdict);
 102         printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
 103
 104         if (prog_fd < 0) {
 105                 printf("Failed to load prog: '%s'\n", strerror(errno));
 106                 return EXIT_FAILURE;
 107         }
 108
 109         ret = bpf_prog_attach(prog_fd, cg_fd, type, 0);
 110         if (ret < 0) {
 111                 printf("Failed to attach prog to cgroup: '%s'\n",
 112                        strerror(errno));
 113                 return EXIT_FAILURE;
 114         }
 115         while (1) {
 116                 key = MAP_KEY_PACKETS;
 117                 assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0);
 118
 119                 key = MAP_KEY_BYTES;
 120                 assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0);
 121
 122                 printf("cgroup received %lld packets, %lld bytes\n",
 123                        pkt_cnt, byte_cnt);
 124                 sleep(1);
 125         }
 126
 127         return EXIT_SUCCESS;
 128 }
 129
 130 int main(int argc, char **argv)
 131 {
 132         int detach_only = 0, verdict = 1;
 133         enum bpf_attach_type type;
 134         int opt, cg_fd, ret;
 135
 136         while ((opt = getopt(argc, argv, "Dd")) != -1) {
 137                 switch (opt) {
 138                 case 'd':
 139                         verdict = 0;
 140                         break;
 141                 case 'D':
 142                         detach_only = 1;
 143                         break;
 144                 default:
 145                         return usage(argv[0]);
 146                 }
 147         }
 148
 149         if (argc - optind < 2)
 150                 return usage(argv[0]);
 151
 152         if (strcmp(argv[optind + 1], "ingress") == 0)
 153                 type = BPF_CGROUP_INET_INGRESS;
 154         else if (strcmp(argv[optind + 1], "egress") == 0)
 155                 type = BPF_CGROUP_INET_EGRESS;
 156         else
 157                 return usage(argv[0]);
 158
 159         cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY);
 160         if (cg_fd < 0) {
 161                 printf("Failed to open cgroup path: '%s'\n", strerror(errno));
 162                 return EXIT_FAILURE;
 163         }
 164
 165         if (detach_only) {
 166                 ret = bpf_prog_detach(cg_fd, type);
 167                 printf("bpf_prog_detach() returned '%s' (%d)\n",
 168                        strerror(errno), errno);
 169         } else
 170                 ret = attach_filter(cg_fd, type, verdict);
 171
 172         return ret;
 173 }