cgroup_storage.c

 1// SPDX-License-Identifier: GPL-2.0
 2
 3#include <linux/bpf.h>
 4#include <bpf/bpf_helpers.h>
 5
 6struct {
 7	__uint(type, BPF_MAP_TYPE_CGROUP_STORAGE);
 8	__type(key, struct bpf_cgroup_storage_key);
 9	__type(value, __u64);
10} cgroup_storage SEC(".maps");
11
12SEC("cgroup_skb/egress")
13int bpf_prog(struct __sk_buff *skb)
14{
15	__u64 *counter;
16
17	counter = bpf_get_local_storage(&cgroup_storage, 0);
18	__sync_fetch_and_add(counter, 1);
19
20	/* Drop one out of every two packets */
21	return (*counter & 1);
22}
23
24char _license[] SEC("license") = "GPL";