1/* SPDX-License-Identifier: GPL-2.0 */
 2// Copyright (c) 2018 Politecnico di Torino
 3#include <stddef.h>
 4#include <string.h>
 5#include <linux/bpf.h>
 6#include <linux/if_ether.h>
 7#include <linux/ip.h>
 8#include <linux/pkt_cls.h>
 9#include "bpf_helpers.h"
10
11int _version SEC("version") = 1;
12
13struct {
14	__uint(type, MAP_TYPE);
15	__uint(max_entries, 32);
16	__uint(map_flags, 0);
17	__uint(key_size, 0);
18	__uint(value_size, sizeof(__u32));
19} map_in SEC(".maps");
20
21struct {
22	__uint(type, MAP_TYPE);
23	__uint(max_entries, 32);
24	__uint(map_flags, 0);
25	__uint(key_size, 0);
26	__uint(value_size, sizeof(__u32));
27} map_out SEC(".maps");
28
29SEC("test")
30int _test(struct __sk_buff *skb)
31{
32	void *data_end = (void *)(long)skb->data_end;
33	void *data = (void *)(long)skb->data;
34	struct ethhdr *eth = (struct ethhdr *)(data);
35	__u32 value;
36	int err;
37
38	if (eth + 1 > data_end)
39		return TC_ACT_SHOT;
40
41	struct iphdr *iph = (struct iphdr *)(eth + 1);
42
43	if (iph + 1 > data_end)
44		return TC_ACT_SHOT;
45
46	err = bpf_map_pop_elem(&map_in, &value);
47	if (err)
48		return TC_ACT_SHOT;
49
50	iph->daddr = value;
51
52	err = bpf_map_push_elem(&map_out, &iph->saddr, 0);
53	if (err)
54		return TC_ACT_SHOT;
55
56	return TC_ACT_OK;
57}
58
59char _license[] SEC("license") = "GPL";