tools/testing/selftests/bpf/prog_tests/flow_dissector_load_bytes.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <test_progs.h>
   3 #include <network_helpers.h>
   4
   5 void test_flow_dissector_load_bytes(void)
   6 {
   7         struct bpf_flow_keys flow_keys;
   8         __u32 duration = 0, retval, size;
   9         struct bpf_insn prog[] = {
  10                 // BPF_REG_1 - 1st argument: context
  11                 // BPF_REG_2 - 2nd argument: offset, start at first byte
  12                 BPF_MOV64_IMM(BPF_REG_2, 0),
  13                 // BPF_REG_3 - 3rd argument: destination, reserve byte on stack
  14                 BPF_ALU64_REG(BPF_MOV, BPF_REG_3, BPF_REG_10),
  15                 BPF_ALU64_IMM(BPF_ADD, BPF_REG_3, -1),
  16                 // BPF_REG_4 - 4th argument: copy one byte
  17                 BPF_MOV64_IMM(BPF_REG_4, 1),
  18                 // bpf_skb_load_bytes(ctx, sizeof(pkt_v4), ptr, 1)
  19                 BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0,
  20                              BPF_FUNC_skb_load_bytes),
  21                 BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 2),
  22                 // if (ret == 0) return BPF_DROP (2)
  23                 BPF_MOV64_IMM(BPF_REG_0, BPF_DROP),
  24                 BPF_EXIT_INSN(),
  25                 // if (ret != 0) return BPF_OK (0)
  26                 BPF_MOV64_IMM(BPF_REG_0, BPF_OK),
  27                 BPF_EXIT_INSN(),
  28         };
  29         int fd, err;
  30
  31         /* make sure bpf_skb_load_bytes is not allowed from skb-less context
  32          */
  33         fd = bpf_load_program(BPF_PROG_TYPE_FLOW_DISSECTOR, prog,
  34                               ARRAY_SIZE(prog), "GPL", 0, NULL, 0);
  35         CHECK(fd < 0,
  36               "flow_dissector-bpf_skb_load_bytes-load",
  37               "fd %d errno %d\n",
  38               fd, errno);
  39
  40         err = bpf_prog_test_run(fd, 1, &pkt_v4, sizeof(pkt_v4),
  41                                 &flow_keys, &size, &retval, &duration);
  42         CHECK(size != sizeof(flow_keys) || err || retval != 1,
  43               "flow_dissector-bpf_skb_load_bytes",
  44               "err %d errno %d retval %d duration %d size %u/%zu\n",
  45               err, errno, retval, duration, size, sizeof(flow_keys));
  46
  47         if (fd >= -1)
  48                 close(fd);
  49 }