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