1 /* SPDX-License-Identifier: GPL-2.0
2  * Copyright (c) 2018 Facebook
3  *
4  * This program is free software; you can redistribute it and/or
5  * modify it under the terms of version 2 of the GNU General Public
6  * License as published by the Free Software Foundation.
7  */
8 #include <linux/bpf.h>
9 #include <linux/if_ether.h>
10 #include "bpf_helpers.h"
11 
12 int _version SEC("version") = 1;
13 
14 SEC("xdp_adjust_tail")
_xdp_adjust_tail(struct xdp_md * xdp)15 int _xdp_adjust_tail(struct xdp_md *xdp)
16 {
17 	void *data_end = (void *)(long)xdp->data_end;
18 	void *data = (void *)(long)xdp->data;
19 	int offset = 0;
20 
21 	if (data_end - data == 54)
22 		offset = 256;
23 	else
24 		offset = 20;
25 	if (bpf_xdp_adjust_tail(xdp, 0 - offset))
26 		return XDP_DROP;
27 	return XDP_TX;
28 }
29 
30 char _license[] SEC("license") = "GPL";
31