// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <linux/version.h>

#include <bpf/bpf_helpers.h>
#include "netcnt_common.h"

#define MAX_BPS (3 * 1024 * 1024)

#define REFRESH_TIME_NS 100000000
#define NS_PER_SEC      1000000000

struct {
        __uint(type, BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE);
        __type(key, struct bpf_cgroup_storage_key);
        __type(value, union percpu_net_cnt);
} percpu_netcnt SEC(".maps");

struct {
        __uint(type, BPF_MAP_TYPE_CGROUP_STORAGE);
        __type(key, struct bpf_cgroup_storage_key);
        __type(value, union net_cnt);
} netcnt SEC(".maps");

SEC("cgroup/skb")
int bpf_nextcnt(struct __sk_buff *skb)
{
        union percpu_net_cnt *percpu_cnt;
        union net_cnt *cnt;
        __u64 ts, dt;
        int ret;

        cnt = bpf_get_local_storage(&netcnt, 0);
        percpu_cnt = bpf_get_local_storage(&percpu_netcnt, 0);

        percpu_cnt->packets++;
        percpu_cnt->bytes += skb->len;

        if (percpu_cnt->packets > MAX_PERCPU_PACKETS) {
                __sync_fetch_and_add(&cnt->packets,
                                     percpu_cnt->packets);
                percpu_cnt->packets = 0;

                __sync_fetch_and_add(&cnt->bytes,
                                     percpu_cnt->bytes);
                percpu_cnt->bytes = 0;
        }

        ts = bpf_ktime_get_ns();
        dt = ts - percpu_cnt->prev_ts;

        dt *= MAX_BPS;
        dt /= NS_PER_SEC;

        if (cnt->bytes + percpu_cnt->bytes - percpu_cnt->prev_bytes < dt)
                ret = 1;
        else
                ret = 0;

        if (dt > REFRESH_TIME_NS) {
                percpu_cnt->prev_ts = ts;
                percpu_cnt->prev_packets = cnt->packets;
                percpu_cnt->prev_bytes = cnt->bytes;
        }

        return !!ret;
}

char _license[] SEC("license") = "GPL";