// 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> int _version SEC("version") = 1; SEC("xdp_adjust_tail_shrink") int _xdp_adjust_tail_shrink(struct xdp_md *xdp) { void *data_end = (void *)(long)xdp->data_end; void *data = (void *)(long)xdp->data; int offset = 0; if (data_end - data == 54) /* sizeof(pkt_v4) */ offset = 256; /* shrink too much */ else offset = 20; if (bpf_xdp_adjust_tail(xdp, 0 - offset)) return XDP_DROP; return XDP_TX; } char _license[] SEC("license") = "GPL";