/* SPDX-License-Identifier: GPL-2.0 */
// Copyright (c) 2018 Politecnico di Torino
#include <stddef.h>
#include <string.h>
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/ip.h>
#include <linux/pkt_cls.h>
#include <bpf/bpf_helpers.h>

struct {
        __uint(type, MAP_TYPE);
        __uint(max_entries, 32);
        __uint(map_flags, 0);
        __uint(key_size, 0);
        __uint(value_size, sizeof(__u32));
} map_in SEC(".maps");

struct {
        __uint(type, MAP_TYPE);
        __uint(max_entries, 32);
        __uint(map_flags, 0);
        __uint(key_size, 0);
        __uint(value_size, sizeof(__u32));
} map_out SEC(".maps");

SEC("tc")
int _test(struct __sk_buff *skb)
{
        void *data_end = (void *)(long)skb->data_end;
        void *data = (void *)(long)skb->data;
        struct ethhdr *eth = (struct ethhdr *)(data);
        __u32 value;
        int err;

        if (eth + 1 > data_end)
                return TC_ACT_SHOT;

        struct iphdr *iph = (struct iphdr *)(eth + 1);

        if (iph + 1 > data_end)
                return TC_ACT_SHOT;

        err = bpf_map_pop_elem(&map_in, &value);
        if (err)
                return TC_ACT_SHOT;

        iph->daddr = value;

        err = bpf_map_push_elem(&map_out, &iph->saddr, 0);
        if (err)
                return TC_ACT_SHOT;

        return TC_ACT_OK;
}

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