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| 3 | * Minimal BPF assembler
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| 4 | *
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| 5 | * Instead of libpcap high-level filter expressions, it can be quite
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| 6 | * useful to define filters in low-level BPF assembler (that is kept
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| 7 | * close to Steven McCanne and Van Jacobson's original BPF paper).
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| 8 | * In particular for BPF JIT implementors, JIT security auditors, or
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| 9 | * just for defining BPF expressions that contain extensions which are
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| 10 | * not supported by compilers.
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| 11 | *
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| 12 | * How to get into it:
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| 13 | *
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| 14 | * 1) read Documentation/networking/filter.rst
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| 15 | * 2) Run `bpf_asm [-c] <filter-prog file>` to translate into binary
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| 16 | * blob that is loadable with xt_bpf, cls_bpf et al. Note: -c will
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| 17 | * pretty print a C-like construct.
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| 18 | *
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| 19 | * Copyright 2013 Daniel Borkmann <[email protected]>
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| 20 |
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| 21 |
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| 22 | #include <stdbool.h>
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| 23 | #include <stdio.h>
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| 24 | #include <string.h>
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| 25 |
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| 26 | extern void bpf_asm_compile(FILE *fp, bool cstyle);
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| 27 |
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| 28 | int main(int argc, char **argv)
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| 29 | {
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| 30 | FILE *fp = stdin;
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| 31 | bool cstyle = false;
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| 32 | int i;
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| 33 |
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| 34 | for (i = 1; i < argc; i++) {
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| 35 | if (!strncmp("-c", argv[i], 2)) {
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| 36 | cstyle = true;
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| 37 | continue;
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| 38 | }
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| 39 |
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| 40 | fp = fopen(argv[i], "r");
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| 41 | if (!fp) {
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| 42 | fp = stdin;
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| 43 | continue;
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| 44 | }
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| 45 |
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| 46 | break;
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| 47 | }
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| 48 |
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| 49 | bpf_asm_compile(fp, cstyle);
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| 50 |
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| 51 | return 0;
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| 52 | }
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