root/samples/bpf/test_cgrp2_attach.c

DEFINITIONS

1. prog_load
2. usage
3. attach_filter
4. main

   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_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
  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                 BPF_RAW_INSN(BPF_STX | BPF_XADD | BPF_DW, BPF_REG_0, BPF_REG_1, 0, 0), /* xadd r0 += r1 */
  68 
  69                 BPF_MOV64_IMM(BPF_REG_0, verdict), /* r0 = verdict */
  70                 BPF_EXIT_INSN(),
  71         };
  72         size_t insns_cnt = sizeof(prog) / sizeof(struct bpf_insn);
  73 
  74         return bpf_load_program(BPF_PROG_TYPE_CGROUP_SKB,
  75                                 prog, insns_cnt, "GPL", 0,
  76                                 bpf_log_buf, BPF_LOG_BUF_SIZE);
  77 }
  78 
  79 static int usage(const char *argv0)
  80 {
  81         printf("Usage: %s [-d] [-D] <cg-path> <egress|ingress>\n", argv0);
  82         printf("        -d      Drop Traffic\n");
  83         printf("        -D      Detach filter, and exit\n");
  84         return EXIT_FAILURE;
  85 }
  86 
  87 static int attach_filter(int cg_fd, int type, int verdict)
  88 {
  89         int prog_fd, map_fd, ret, key;
  90         long long pkt_cnt, byte_cnt;
  91 
  92         map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY,
  93                                 sizeof(key), sizeof(byte_cnt),
  94                                 256, 0);
  95         if (map_fd < 0) {
  96                 printf("Failed to create map: '%s'\n", strerror(errno));
  97                 return EXIT_FAILURE;
  98         }
  99 
 100         prog_fd = prog_load(map_fd, verdict);
 101         printf("Output from kernel verifier:\n%s\n-------\n", bpf_log_buf);
 102 
 103         if (prog_fd < 0) {
 104                 printf("Failed to load prog: '%s'\n", strerror(errno));
 105                 return EXIT_FAILURE;
 106         }
 107 
 108         ret = bpf_prog_attach(prog_fd, cg_fd, type, 0);
 109         if (ret < 0) {
 110                 printf("Failed to attach prog to cgroup: '%s'\n",
 111                        strerror(errno));
 112                 return EXIT_FAILURE;
 113         }
 114         while (1) {
 115                 key = MAP_KEY_PACKETS;
 116                 assert(bpf_map_lookup_elem(map_fd, &key, &pkt_cnt) == 0);
 117 
 118                 key = MAP_KEY_BYTES;
 119                 assert(bpf_map_lookup_elem(map_fd, &key, &byte_cnt) == 0);
 120 
 121                 printf("cgroup received %lld packets, %lld bytes\n",
 122                        pkt_cnt, byte_cnt);
 123                 sleep(1);
 124         }
 125 
 126         return EXIT_SUCCESS;
 127 }
 128 
 129 int main(int argc, char **argv)
 130 {
 131         int detach_only = 0, verdict = 1;
 132         enum bpf_attach_type type;
 133         int opt, cg_fd, ret;
 134 
 135         while ((opt = getopt(argc, argv, "Dd")) != -1) {
 136                 switch (opt) {
 137                 case 'd':
 138                         verdict = 0;
 139                         break;
 140                 case 'D':
 141                         detach_only = 1;
 142                         break;
 143                 default:
 144                         return usage(argv[0]);
 145                 }
 146         }
 147 
 148         if (argc - optind < 2)
 149                 return usage(argv[0]);
 150 
 151         if (strcmp(argv[optind + 1], "ingress") == 0)
 152                 type = BPF_CGROUP_INET_INGRESS;
 153         else if (strcmp(argv[optind + 1], "egress") == 0)
 154                 type = BPF_CGROUP_INET_EGRESS;
 155         else
 156                 return usage(argv[0]);
 157 
 158         cg_fd = open(argv[optind], O_DIRECTORY | O_RDONLY);
 159         if (cg_fd < 0) {
 160                 printf("Failed to open cgroup path: '%s'\n", strerror(errno));
 161                 return EXIT_FAILURE;
 162         }
 163 
 164         if (detach_only) {
 165                 ret = bpf_prog_detach(cg_fd, type);
 166                 printf("bpf_prog_detach() returned '%s' (%d)\n",
 167                        strerror(errno), errno);
 168         } else
 169                 ret = attach_filter(cg_fd, type, verdict);
 170 
 171         return ret;
 172 }