/* * 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; }