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53 lines
1.2 KiB
C
53 lines
1.2 KiB
C
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/*
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* Minimal BPF assembler
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*
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* Instead of libpcap high-level filter expressions, it can be quite
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* useful to define filters in low-level BPF assembler (that is kept
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* close to Steven McCanne and Van Jacobson's original BPF paper).
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* In particular for BPF JIT implementors, JIT security auditors, or
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* just for defining BPF expressions that contain extensions which are
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* not supported by compilers.
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*
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* How to get into it:
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*
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* 1) read Documentation/networking/filter.txt
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* 2) Run `bpf_asm [-c] <filter-prog file>` to translate into binary
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* blob that is loadable with xt_bpf, cls_bpf et al. Note: -c will
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* pretty print a C-like construct.
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*
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* Copyright 2013 Daniel Borkmann <borkmann@redhat.com>
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* Licensed under the GNU General Public License, version 2.0 (GPLv2)
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*/
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#include <stdbool.h>
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#include <stdio.h>
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#include <string.h>
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extern void bpf_asm_compile(FILE *fp, bool cstyle);
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int main(int argc, char **argv)
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{
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FILE *fp = stdin;
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bool cstyle = false;
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int i;
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for (i = 1; i < argc; i++) {
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if (!strncmp("-c", argv[i], 2)) {
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cstyle = true;
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continue;
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}
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fp = fopen(argv[i], "r");
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if (!fp) {
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fp = stdin;
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continue;
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}
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break;
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}
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bpf_asm_compile(fp, cstyle);
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return 0;
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}
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