bpf_shared.c revision 92a36995b3ceb4de4ebd43d9358e0edebce67615 
1#include "../../include/bpf_api.h"
2
3/* Minimal, stand-alone toy map pinning example:
4 *
5 * clang -target bpf -O2 [...] -o bpf_shared.o -c bpf_shared.c
6 * tc filter add dev foo parent 1: bpf obj bpf_shared.o sec egress
7 * tc filter add dev foo parent ffff: bpf obj bpf_shared.o sec ingress
8 *
9 * Both classifier will share the very same map instance in this example,
10 * so map content can be accessed from ingress *and* egress side!
11 *
12 * This example has a pinning of PIN_OBJECT_NS, so it's private and
13 * thus shared among various program sections within the object.
14 *
15 * A setting of PIN_GLOBAL_NS would place it into a global namespace,
16 * so that it can be shared among different object files. A setting
17 * of PIN_NONE (= 0) means no sharing, so each tc invocation a new map
18 * instance is being created.
19 */
20
21BPF_ARRAY4(map_sh, 0, PIN_OBJECT_NS, 1); /* or PIN_GLOBAL_NS, or PIN_NONE */
22
23__section("egress")
24int emain(struct __sk_buff *skb)
25{
26	int key = 0, *val;
27
28	val = map_lookup_elem(&map_sh, &key);
29	if (val)
30		lock_xadd(val, 1);
31
32	return BPF_H_DEFAULT;
33}
34
35__section("ingress")
36int imain(struct __sk_buff *skb)
37{
38	int key = 0, *val;
39
40	val = map_lookup_elem(&map_sh, &key);
41	if (val)
42		printt("map val: %d\n", *val);
43
44	return BPF_H_DEFAULT;
45}
46
47BPF_LICENSE("GPL");
48