1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (c) 2024 ByteDance */
 3#include <linux/bpf.h>
 4#include <bpf/bpf_helpers.h>
 5
 6struct {
 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
13long change_tail_ret = 1;
14
15SEC("sk_skb")
16int 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
40char _license[] SEC("license") = "GPL";