bpfgen

#!/usr/bin/env python

import argparse
import os
import stat
import string
import sys

import bpftools


def main():
    parser = argparse.ArgumentParser(
        formatter_class=argparse.RawDescriptionHelpFormatter,
        description=r'''

This tool creates a Berkeley Packet Filter (BPF) bytecode that will
match packets based on given criteria. Right now we support the
following generators:

 dns          - matches dns queries for given domains
 dns_validate - matches dns malformed requests
 suffix       - matches packets with given suffix

Generators can take arbitrary parameters and command line options. To
read more on their usage pass '--help' option to the genrator (not to
this wrapper), for example:

    %(prog)s dns -- --help

Example of use:

    %(prog)s dns -- -i *.example.com
    %(prog)s dns -- -i example.com *.example.com *.*.example.com
    %(prog)s dns_validate
    %(prog)s dns_validate -- --strict
    %(prog)s suffix -- 010203

Note that some common options are accepted by this wrapper, not by the
BPF generators, for example:

    %(prog)s -s suffix -- 010203
    %(prog)s -s -n suffix -- 010203
    %(prog)s -s -n -o 14 suffix -- 010203
    %(prog)s -s -n -o 14 -6 suffix -- 010203
    ''')

    parser.add_argument('-6', '--inet6', action='store_true',
                        help='generate script for IPv6')
    parser.add_argument('-n', '--negate', action='store_true',
                        help='negate the logic')
    parser.add_argument('-o', '--offset', type=int, default=0,
                        help='offset of an L3 header')
    parser.add_argument('-s', '--assembly', action='store_true',
                        help='print readable assembly, not numeric bytecode')
    parser.add_argument('type', nargs=1, choices=bpftools.generator_names,
                        help='BPF generator type')
    parser.add_argument('parameters', nargs='*',
                        help='parameters passed to the BPF generator')

    args = parser.parse_args()

    if len(args.type) != 1:
        parser.print_help()
        sys.exit(-1)

    name, ret = bpftools.gen(args.type[0],
                             args.parameters,
                             assembly=args.assembly,
                             l3_off=args.offset,
                             ipversion=4 if not args.inet6 else 6,
                             negate=args.negate,
                             )
    print ret


if __name__ == "__main__":
    main()