bpf/progs/test_xdp_adjust_tail_shrink.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /* Copyright (c) 2018 Facebook
0003  *
0004  * This program is free software; you can redistribute it and/or
0005  * modify it under the terms of version 2 of the GNU General Public
0006  * License as published by the Free Software Foundation.
0007  */
0008 #include <linux/bpf.h>
0009 #include <linux/if_ether.h>
0010 #include <bpf/bpf_helpers.h>
0011
0012 SEC("xdp")
0013 int _xdp_adjust_tail_shrink(struct xdp_md *xdp)
0014 {
0015     __u8 *data_end = (void *)(long)xdp->data_end;
0016     __u8 *data = (void *)(long)xdp->data;
0017     int offset = 0;
0018
0019     switch (bpf_xdp_get_buff_len(xdp)) {
0020     case 54:
0021         /* sizeof(pkt_v4) */
0022         offset = 256; /* shrink too much */
0023         break;
0024     case 9000:
0025         /* non-linear buff test cases */
0026         if (data + 1 > data_end)
0027             return XDP_DROP;
0028
0029         switch (data[0]) {
0030         case 0:
0031             offset = 10;
0032             break;
0033         case 1:
0034             offset = 4100;
0035             break;
0036         case 2:
0037             offset = 8200;
0038             break;
0039         default:
0040             return XDP_DROP;
0041         }
0042         break;
0043     default:
0044         offset = 20;
0045         break;
0046     }
0047     if (bpf_xdp_adjust_tail(xdp, 0 - offset))
0048         return XDP_DROP;
0049     return XDP_TX;
0050 }
0051
0052 char _license[] SEC("license") = "GPL";