examples/bpf/bpf_shared.c

   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
  21 BPF_ARRAY4(map_sh, 0, PIN_OBJECT_NS, 1); /* or PIN_GLOBAL_NS, or PIN_NONE */
  22
  23 __section("egress")
  24 int 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")
  36 int imain(struct __sk_buff *skb)
  37 {
  38         char fmt[] = "map val: %d\n";
  39         int key = 0, *val;
  40
  41         val = map_lookup_elem(&map_sh, &key);
  42         if (val)
  43                 trace_printk(fmt, sizeof(fmt), *val);
  44
  45         return BPF_H_DEFAULT;
  46 }
  47
  48 BPF_LICENSE("GPL");