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Commit | Line | Data |
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41d6e33f | 1 | #include "../../include/bpf_api.h" |
0b7e3fc8 DB |
2 | |
3 | #define ENTRY_INIT 3 | |
4 | #define ENTRY_0 0 | |
5 | #define ENTRY_1 1 | |
6 | #define MAX_JMP_SIZE 2 | |
7 | ||
8 | #define FOO 42 | |
9 | #define BAR 43 | |
10 | ||
11 | /* This example doesn't really do anything useful, but it's purpose is to | |
12 | * demonstrate eBPF tail calls on a very simple example. | |
13 | * | |
14 | * cls_entry() is our classifier entry point, from there we jump based on | |
15 | * skb->hash into cls_case1() or cls_case2(). They are both part of the | |
16 | * program array jmp_tc. Indicated via __section_tail(), the tc loader | |
17 | * populates the program arrays with the loaded file descriptors already. | |
18 | * | |
19 | * To demonstrate nested jumps, cls_case2() jumps within the same jmp_tc | |
20 | * array to cls_case1(). And whenever we arrive at cls_case1(), we jump | |
21 | * into cls_exit(), part of the jump array jmp_ex. | |
22 | * | |
23 | * Also, to show it's possible, all programs share map_sh and dump the value | |
24 | * that the entry point incremented. The sections that are loaded into a | |
25 | * program array can be atomically replaced during run-time, e.g. to change | |
26 | * classifier behaviour. | |
27 | */ | |
41d6e33f DB |
28 | |
29 | BPF_PROG_ARRAY(jmp_tc, FOO, PIN_OBJECT_NS, MAX_JMP_SIZE); | |
30 | BPF_PROG_ARRAY(jmp_ex, BAR, PIN_OBJECT_NS, 1); | |
31 | ||
32 | BPF_ARRAY4(map_sh, 0, PIN_OBJECT_NS, 1); | |
33 | ||
34 | __section_tail(FOO, ENTRY_0) | |
35 | int cls_case1(struct __sk_buff *skb) | |
0b7e3fc8 DB |
36 | { |
37 | char fmt[] = "case1: map-val: %d from:%u\n"; | |
38 | int key = 0, *val; | |
39 | ||
41d6e33f | 40 | val = map_lookup_elem(&map_sh, &key); |
0b7e3fc8 | 41 | if (val) |
41d6e33f | 42 | trace_printk(fmt, sizeof(fmt), *val, skb->cb[0]); |
0b7e3fc8 DB |
43 | |
44 | skb->cb[0] = ENTRY_0; | |
41d6e33f DB |
45 | tail_call(skb, &jmp_ex, ENTRY_0); |
46 | ||
47 | return BPF_H_DEFAULT; | |
0b7e3fc8 DB |
48 | } |
49 | ||
41d6e33f DB |
50 | __section_tail(FOO, ENTRY_1) |
51 | int cls_case2(struct __sk_buff *skb) | |
0b7e3fc8 DB |
52 | { |
53 | char fmt[] = "case2: map-val: %d from:%u\n"; | |
54 | int key = 0, *val; | |
55 | ||
41d6e33f | 56 | val = map_lookup_elem(&map_sh, &key); |
0b7e3fc8 | 57 | if (val) |
41d6e33f | 58 | trace_printk(fmt, sizeof(fmt), *val, skb->cb[0]); |
0b7e3fc8 DB |
59 | |
60 | skb->cb[0] = ENTRY_1; | |
41d6e33f DB |
61 | tail_call(skb, &jmp_tc, ENTRY_0); |
62 | ||
63 | return BPF_H_DEFAULT; | |
0b7e3fc8 DB |
64 | } |
65 | ||
41d6e33f DB |
66 | __section_tail(BAR, ENTRY_0) |
67 | int cls_exit(struct __sk_buff *skb) | |
0b7e3fc8 DB |
68 | { |
69 | char fmt[] = "exit: map-val: %d from:%u\n"; | |
70 | int key = 0, *val; | |
71 | ||
41d6e33f | 72 | val = map_lookup_elem(&map_sh, &key); |
0b7e3fc8 | 73 | if (val) |
41d6e33f | 74 | trace_printk(fmt, sizeof(fmt), *val, skb->cb[0]); |
0b7e3fc8 DB |
75 | |
76 | /* Termination point. */ | |
41d6e33f | 77 | return BPF_H_DEFAULT; |
0b7e3fc8 DB |
78 | } |
79 | ||
41d6e33f DB |
80 | __section_cls_entry |
81 | int cls_entry(struct __sk_buff *skb) | |
0b7e3fc8 DB |
82 | { |
83 | char fmt[] = "fallthrough\n"; | |
84 | int key = 0, *val; | |
85 | ||
86 | /* For transferring state, we can use skb->cb[0] ... skb->cb[4]. */ | |
41d6e33f | 87 | val = map_lookup_elem(&map_sh, &key); |
0b7e3fc8 | 88 | if (val) { |
41d6e33f | 89 | lock_xadd(val, 1); |
0b7e3fc8 DB |
90 | |
91 | skb->cb[0] = ENTRY_INIT; | |
41d6e33f | 92 | tail_call(skb, &jmp_tc, skb->hash & (MAX_JMP_SIZE - 1)); |
0b7e3fc8 DB |
93 | } |
94 | ||
41d6e33f DB |
95 | trace_printk(fmt, sizeof(fmt)); |
96 | return BPF_H_DEFAULT; | |
0b7e3fc8 DB |
97 | } |
98 | ||
41d6e33f | 99 | BPF_LICENSE("GPL"); |