| 1 | // SPDX-License-Identifier: GPL-2.0 |
|---|---|
| 2 | /* |
| 3 | * This program is free software; you can redistribute it and/or |
| 4 | * modify it under the terms of version 2 of the GNU General Public |
| 5 | * License as published by the Free Software Foundation. |
| 6 | */ |
| 7 | #include <linux/bpf.h> |
| 8 | #include <linux/if_ether.h> |
| 9 | #include <bpf/bpf_helpers.h> |
| 10 | |
| 11 | int _version SEC("version") = 1; |
| 12 | |
| 13 | SEC("xdp.frags") |
| 14 | int xdp_adjust_frags(struct xdp_md *xdp) |
| 15 | { |
| 16 | __u8 *data_end = (void *)(long)xdp->data_end; |
| 17 | __u8 *data = (void *)(long)xdp->data; |
| 18 | __u8 val[16] = {}; |
| 19 | __u32 offset; |
| 20 | int err; |
| 21 | |
| 22 | if (data + sizeof(__u32) > data_end) |
| 23 | return XDP_DROP; |
| 24 | |
| 25 | offset = *(__u32 *)data; |
| 26 | err = bpf_xdp_load_bytes(xdp, offset, val, sizeof(val)); |
| 27 | if (err < 0) |
| 28 | return XDP_DROP; |
| 29 | |
| 30 | if (val[0] != 0xaa || val[15] != 0xaa) /* marker */ |
| 31 | return XDP_DROP; |
| 32 | |
| 33 | val[0] = 0xbb; /* update the marker */ |
| 34 | val[15] = 0xbb; |
| 35 | err = bpf_xdp_store_bytes(xdp, offset, val, sizeof(val)); |
| 36 | if (err < 0) |
| 37 | return XDP_DROP; |
| 38 | |
| 39 | return XDP_PASS; |
| 40 | } |
| 41 | |
| 42 | char _license[] SEC("license") = "GPL"; |
| 43 |