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") _xdp_adjust_tail_shrink(struct xdp_md * xdp)13int _xdp_adjust_tail_shrink(struct xdp_md *xdp) 14 { 15 void *data_end = (void *)(long)xdp->data_end; 16 void *data = (void *)(long)xdp->data; 17 int offset = 0; 18 19 if (data_end - data == 54) /* sizeof(pkt_v4) */ 20 offset = 256; /* shrink too much */ 21 else 22 offset = 20; 23 if (bpf_xdp_adjust_tail(xdp, 0 - offset)) 24 return XDP_DROP; 25 return XDP_TX; 26 } 27 28 char _license[] SEC("license") = "GPL"; 29