1// SPDX-License-Identifier: GPL-2.0
2#include <linux/bpf.h>
3#include <bpf/bpf_helpers.h>
4
5struct {
6	__uint(type, BPF_MAP_TYPE_ARRAY);
7	__uint(max_entries, 1);
8	__uint(key_size, sizeof(__u32));
9	__uint(value_size, sizeof(__u32));
10} nop_table SEC(".maps");
11
12struct {
13	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
14	__uint(max_entries, 3);
15	__uint(key_size, sizeof(__u32));
16	__uint(value_size, sizeof(__u32));
17} jmp_table SEC(".maps");
18
19int count = 0;
20int noise = 0;
21
22static __always_inline int subprog_noise(void)
23{
24	__u32 key = 0;
25
26	bpf_map_lookup_elem(&nop_table, &key);
27	return 0;
28}
29
30__noinline
31int subprog_tail_2(struct __sk_buff *skb)
32{
33	if (noise)
34		subprog_noise();
35	bpf_tail_call_static(skb, &jmp_table, 2);
36	return skb->len * 3;
37}
38
39__noinline
40int subprog_tail_1(struct __sk_buff *skb)
41{
42	bpf_tail_call_static(skb, &jmp_table, 1);
43	return skb->len * 2;
44}
45
46__noinline
47int subprog_tail(struct __sk_buff *skb)
48{
49	bpf_tail_call_static(skb, &jmp_table, 0);
50	return skb->len;
51}
52
53SEC("tc")
54int classifier_1(struct __sk_buff *skb)
55{
56	return subprog_tail_2(skb);
57}
58
59SEC("tc")
60int classifier_2(struct __sk_buff *skb)
61{
62	count++;
63	return subprog_tail_2(skb);
64}
65
66SEC("tc")
67int classifier_0(struct __sk_buff *skb)
68{
69	return subprog_tail_1(skb);
70}
71
72SEC("tc")
73int entry(struct __sk_buff *skb)
74{
75	return subprog_tail(skb);
76}
77
78char __license[] SEC("license") = "GPL";
79