1 #include "../../include/bpf_api.h"
2
3 /* This example demonstrates how classifier run-time behaviour
4 * can be altered with tail calls. We start out with an empty
5 * jmp_tc array, then add section aaa to the array slot 0, and
6 * later on atomically replace it with section bbb. Note that
7 * as shown in other examples, the tc loader can prepopulate
8 * tail called sections, here we start out with an empty one
9 * on purpose to show it can also be done this way.
10 *
11 * tc filter add dev foo parent ffff: bpf obj graft.o
12 * tc exec bpf dbg
13 * [...]
14 * Socket Thread-20229 [001] ..s. 138993.003923: : fallthrough
15 * <idle>-0 [001] ..s. 138993.202265: : fallthrough
16 * Socket Thread-20229 [001] ..s. 138994.004149: : fallthrough
17 * [...]
18 *
19 * tc exec bpf graft m:globals/jmp_tc key 0 obj graft.o sec aaa
20 * tc exec bpf dbg
21 * [...]
22 * Socket Thread-19818 [002] ..s. 139012.053587: : aaa
23 * <idle>-0 [002] ..s. 139012.172359: : aaa
24 * Socket Thread-19818 [001] ..s. 139012.173556: : aaa
25 * [...]
26 *
27 * tc exec bpf graft m:globals/jmp_tc key 0 obj graft.o sec bbb
28 * tc exec bpf dbg
29 * [...]
30 * Socket Thread-19818 [002] ..s. 139022.102967: : bbb
31 * <idle>-0 [002] ..s. 139022.155640: : bbb
32 * Socket Thread-19818 [001] ..s. 139022.156730: : bbb
33 * [...]
34 */
35
36 BPF_PROG_ARRAY(jmp_tc, 0, PIN_GLOBAL_NS, 1);
37
38 __section("aaa")
cls_aaa(struct __sk_buff * skb)39 int cls_aaa(struct __sk_buff *skb)
40 {
41 char fmt[] = "aaa\n";
42
43 trace_printk(fmt, sizeof(fmt));
44 return TC_H_MAKE(1, 42);
45 }
46
47 __section("bbb")
cls_bbb(struct __sk_buff * skb)48 int cls_bbb(struct __sk_buff *skb)
49 {
50 char fmt[] = "bbb\n";
51
52 trace_printk(fmt, sizeof(fmt));
53 return TC_H_MAKE(1, 43);
54 }
55
56 __section_cls_entry
cls_entry(struct __sk_buff * skb)57 int cls_entry(struct __sk_buff *skb)
58 {
59 char fmt[] = "fallthrough\n";
60
61 tail_call(skb, &jmp_tc, 0);
62 trace_printk(fmt, sizeof(fmt));
63
64 return BPF_H_DEFAULT;
65 }
66
67 BPF_LICENSE("GPL");
68