1// SPDX-License-Identifier: GPL-2.0-only
2
3/*
4 * Copyright 2020 Google LLC.
5 */
6
7#include <errno.h>
8#include <linux/bpf.h>
9#include <linux/if_ether.h>
10#include <linux/ip.h>
11#include <bpf/bpf_helpers.h>
12
13struct {
14 __uint(type, BPF_MAP_TYPE_ARRAY);
15 __uint(max_entries, 1);
16 __type(key, __u32);
17 __type(value, __u32);
18} test_result SEC(".maps");
19
20SEC("cgroup_skb/egress")
21int load_bytes_relative(struct __sk_buff *skb)
22{
23 struct ethhdr eth;
24 struct iphdr iph;
25
26 __u32 map_key = 0;
27 __u32 test_passed = 0;
28
29 /* MAC header is not set by the time cgroup_skb/egress triggers */
30 if (bpf_skb_load_bytes_relative(skb, 0, &eth, sizeof(eth),
31 BPF_HDR_START_MAC) != -EFAULT)
32 goto fail;
33
34 if (bpf_skb_load_bytes_relative(skb, 0, &iph, sizeof(iph),
35 BPF_HDR_START_NET))
36 goto fail;
37
38 if (bpf_skb_load_bytes_relative(skb, 0xffff, &iph, sizeof(iph),
39 BPF_HDR_START_NET) != -EFAULT)
40 goto fail;
41
42 test_passed = 1;
43
44fail:
45 bpf_map_update_elem(&test_result, &map_key, &test_passed, BPF_ANY);
46
47 return 1;
48}
49

source code of linux/tools/testing/selftests/bpf/progs/load_bytes_relative.c