bpf_comp.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * Copyright 2013 Daniel Borkmann.
   4  * Subject to the GPL, version 2.
   5  */
   6
   7 #define NEED_TCPDUMP_LIKE_FILTER
   8
   9 #include <pcap.h>
  10 #include <linux/filter.h>
  11
  12 #include "xmalloc.h"
  13 #include "config.h"
  14 #include "bpf.h"
  15 #include "die.h"
  16
  17 void bpf_try_compile(const char *rulefile, struct sock_fprog *bpf, uint32_t link_type)
  18 {
  19         int i, ret;
  20         const struct bpf_insn *ins;
  21         struct sock_filter *out;
  22         struct bpf_program _bpf;
  23
  24         ret = pcap_compile_nopcap(65535, link_type, &_bpf, rulefile, 1, 0xffffffff);
  25         if (ret < 0)
  26                 panic("Cannot compile filter %s\n", rulefile);
  27
  28         bpf->len = _bpf.bf_len;
  29         bpf->filter = xrealloc(bpf->filter, 1, bpf->len * sizeof(*out));
  30
  31         for (i = 0, ins = _bpf.bf_insns, out = bpf->filter; i < bpf->len;
  32              ++i, ++ins, ++out) {
  33                 out->code = ins->code;
  34                 out->jt = ins->jt;
  35                 out->jf = ins->jf;
  36                 out->k = ins->k;
  37
  38                 if (out->code == 0x06 && out->k > 0)
  39                         out->k = 0xFFFFFFFF;
  40         }
  41
  42         pcap_freecode(&_bpf);
  43
  44         if (__bpf_validate(bpf) == 0)
  45                 panic("This is not a valid BPF program!\n");
  46 }