tools/testing/selftests/bpf/progs/test_xdp_adjust_tail_shrink.c

   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/bpf_helpers.h>
  11
  12 SEC("xdp")
  13 int _xdp_adjust_tail_shrink(struct xdp_md *xdp)
  14 {
  15         __u8 *data_end = (void *)(long)xdp->data_end;
  16         __u8 *data = (void *)(long)xdp->data;
  17         int offset = 0;
  18
  19         switch (bpf_xdp_get_buff_len(xdp)) {
  20         case 54:
  21                 /* sizeof(pkt_v4) */
  22                 offset = 256; /* shrink too much */
  23                 break;
  24         case 9000:
  25                 /* non-linear buff test cases */
  26                 if (data + 1 > data_end)
  27                         return XDP_DROP;
  28
  29                 switch (data[0]) {
  30                 case 0:
  31                         offset = 10;
  32                         break;
  33                 case 1:
  34                         offset = 4100;
  35                         break;
  36                 case 2:
  37                         offset = 8200;
  38                         break;
  39                 default:
  40                         return XDP_DROP;
  41                 }
  42                 break;
  43         default:
  44                 offset = 20;
  45                 break;
  46         }
  47         if (bpf_xdp_adjust_tail(xdp, 0 - offset))
  48                 return XDP_DROP;
  49         return XDP_TX;
  50 }
  51
  52 char _license[] SEC("license") = "GPL";