| 1 | // SPDX-License-Identifier: GPL-2.0 |
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| 2 | /* Copyright (c) 2018 Facebook |
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| 3 | * |
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| 4 | * This program is free software; you can redistribute it and/or |
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| 5 | * modify it under the terms of version 2 of the GNU General Public |
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| 6 | * License as published by the Free Software Foundation. |
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| 7 | */ |
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| 8 | #include <linux/bpf.h> |
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| 9 | #include <linux/if_ether.h> |
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| 10 | #include <bpf/bpf_helpers.h> |
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| 11 | |
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| 12 | SEC("xdp" ) |
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| 13 | int _xdp_adjust_tail_shrink(struct xdp_md *xdp) |
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| 14 | { |
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| 15 | __u8 *data_end = (void *)(long)xdp->data_end; |
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| 16 | __u8 *data = (void *)(long)xdp->data; |
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| 17 | int offset = 0; |
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| 18 | |
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| 19 | switch (bpf_xdp_get_buff_len(xdp)) { |
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| 20 | case 54: |
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| 21 | /* sizeof(pkt_v4) */ |
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| 22 | offset = 256; /* shrink too much */ |
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| 23 | break; |
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| 24 | case 9000: |
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| 25 | /* non-linear buff test cases */ |
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| 26 | if (data + 1 > data_end) |
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| 27 | return XDP_DROP; |
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| 28 | |
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| 29 | switch (data[0]) { |
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| 30 | case 0: |
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| 31 | offset = 10; |
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| 32 | break; |
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| 33 | case 1: |
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| 34 | offset = 4100; |
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| 35 | break; |
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| 36 | case 2: |
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| 37 | offset = 8200; |
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| 38 | break; |
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| 39 | default: |
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| 40 | return XDP_DROP; |
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| 41 | } |
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| 42 | break; |
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| 43 | default: |
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| 44 | offset = 20; |
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| 45 | break; |
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| 46 | } |
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| 47 | if (bpf_xdp_adjust_tail(xdp, 0 - offset)) |
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| 48 | return XDP_DROP; |
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| 49 | return XDP_TX; |
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| 50 | } |
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| 51 | |
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| 52 | char _license[] SEC("license" ) = "GPL" ; |
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| 53 | |
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