1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2024 ByteDance */
3 #include <linux/bpf.h>
4 #include <bpf/bpf_helpers.h>
5
6 struct {
7 __uint(type, BPF_MAP_TYPE_SOCKMAP);
8 __uint(max_entries, 1);
9 __type(key, int);
10 __type(value, int);
11 } sock_map_rx SEC(".maps");
12
13 long change_tail_ret = 1;
14
15 SEC("sk_skb")
prog_skb_verdict(struct __sk_buff * skb)16 int prog_skb_verdict(struct __sk_buff *skb)
17 {
18 char *data, *data_end;
19
20 bpf_skb_pull_data(skb, 1);
21 data = (char *)(unsigned long)skb->data;
22 data_end = (char *)(unsigned long)skb->data_end;
23
24 if (data + 1 > data_end)
25 return SK_PASS;
26
27 if (data[0] == 'T') { /* Trim the packet */
28 change_tail_ret = bpf_skb_change_tail(skb, skb->len - 1, 0);
29 return SK_PASS;
30 } else if (data[0] == 'G') { /* Grow the packet */
31 change_tail_ret = bpf_skb_change_tail(skb, skb->len + 1, 0);
32 return SK_PASS;
33 } else if (data[0] == 'E') { /* Error */
34 change_tail_ret = bpf_skb_change_tail(skb, 65535, 0);
35 return SK_PASS;
36 }
37 return SK_PASS;
38 }
39
40 char _license[] SEC("license") = "GPL";
41