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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2018 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*/
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <bpf/bpf_helpers.h>
SEC("xdp")
int _xdp_adjust_tail_shrink(struct xdp_md *xdp)
{
__u8 *data_end = (void *)(long)xdp->data_end;
__u8 *data = (void *)(long)xdp->data;
int offset = 0;
switch (bpf_xdp_get_buff_len(xdp)) {
case 54:
/* sizeof(pkt_v4) */
offset = 256; /* shrink too much */
break;
case 9000:
/* non-linear buff test cases */
if (data + 1 > data_end)
return XDP_DROP;
switch (data[0]) {
case 0:
offset = 10;
break;
case 1:
offset = 4100;
break;
case 2:
offset = 8200;
break;
default:
return XDP_DROP;
}
break;
default:
offset = 20;
break;
}
if (bpf_xdp_adjust_tail(xdp, 0 - offset))
return XDP_DROP;
return XDP_TX;
}
char _license[] SEC("license") = "GPL";
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