From: kenny roytman <kenny.roytman@...>
Date: 2007-10-30T14:41:23+09:00
Subject: ruby libpcap fails when passing command-line argument

Hi,

Can someone please help me out here?   I'm trying to use Ruby/Libpcap
extension to write a rudimentary packet sniffer.

I downloaded ruby/libpcap 0.6 from http://www.goto.info.waseda.ac.jp/~fukusima/ruby/pcap-e.html.

The following code breaks when calling it from the command-line with a
parameter, such as:

$>ruby dumptraffic.rb en1
/usr/local/lib/ruby/site_ruby/1.8/universal-darwin8.0/pcap.bundle:
warning: do not use Fixnums as Symbols
/usr/local/lib/ruby/site_ruby/1.8/universal-darwin8.0/pcap.bundle:
warning: do not use Fixnums as Symbols
/usr/local/lib/ruby/site_ruby/1.8/universal-darwin8.0/pcap.bundle:
warning: do not use Fixnums as Symbols
setfilter: parse error
$>

The code:

------- start of code

require 'pcaplet'

include Pcap

class Sniffer
  def sniff(d)
    pcaplet = Pcaplet.new("-i " + d)
    c = pcaplet.capture
    d = Dumper.open(c,"dump.txt")

    c.each_packet(50) { |pkt|
        if pkt.ip?
            d.dump(pkt)
            puts "hello from #{pkt.src.to_num_s}"
        end
    }

    pcaplet.close
  end
end

if __FILE__ == $0
  d = ARGV[0]
  sniffit = Sniffer.new
  sniffit.sniff(d)
end


---- end of code

Any help would be greatly appreciated.  Thanks.

- kenny r.