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
11 int _version SEC("version") = 1;
12
13 struct bpf_map_def __attribute__ ((section("maps"), used)) map_in = {
14 .type = MAP_TYPE,
15 .key_size = 0,
16 .value_size = sizeof(__u32),
17 .max_entries = 32,
18 .map_flags = 0,
19 };
20
21 struct bpf_map_def __attribute__ ((section("maps"), used)) map_out = {
22 .type = MAP_TYPE,
23 .key_size = 0,
24 .value_size = sizeof(__u32),
25 .max_entries = 32,
26 .map_flags = 0,
27 };
28
29 SEC("test")
_test(struct __sk_buff * skb)30 int _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
59 char _license[] SEC("license") = "GPL";
60