1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/bpf.h>
3 
4 #include <bpf/bpf_helpers.h>
5 
6 struct {
7 	__uint(type, BPF_MAP_TYPE_PROG_ARRAY);
8 	__uint(max_entries, 3);
9 	__uint(key_size, sizeof(__u32));
10 	__uint(value_size, sizeof(__u32));
11 } jmp_table SEC(".maps");
12 
13 #define TAIL_FUNC(x) 				\
14 	SEC("tc")				\
15 	int classifier_##x(struct __sk_buff *skb)	\
16 	{					\
17 		return x;			\
18 	}
19 TAIL_FUNC(0)
20 TAIL_FUNC(1)
21 TAIL_FUNC(2)
22 
23 SEC("tc")
24 int entry(struct __sk_buff *skb)
25 {
26 	/* Multiple locations to make sure we patch
27 	 * all of them.
28 	 */
29 	bpf_tail_call_static(skb, &jmp_table, 0);
30 	bpf_tail_call_static(skb, &jmp_table, 0);
31 	bpf_tail_call_static(skb, &jmp_table, 0);
32 	bpf_tail_call_static(skb, &jmp_table, 0);
33 
34 	bpf_tail_call_static(skb, &jmp_table, 1);
35 	bpf_tail_call_static(skb, &jmp_table, 1);
36 	bpf_tail_call_static(skb, &jmp_table, 1);
37 	bpf_tail_call_static(skb, &jmp_table, 1);
38 
39 	bpf_tail_call_static(skb, &jmp_table, 2);
40 	bpf_tail_call_static(skb, &jmp_table, 2);
41 	bpf_tail_call_static(skb, &jmp_table, 2);
42 	bpf_tail_call_static(skb, &jmp_table, 2);
43 
44 	return 3;
45 }
46 
47 char __license[] SEC("license") = "GPL";
48