25 lines · c
1// SPDX-License-Identifier: GPL-2.02 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";25