Crystal LibPcap

lib_pcap.cr

@[Link("pcap")]
lib LibPcap
  # Size to use when allocating the buffer that contains the libpcap errors.
  PCAP_ERRBUF_SIZE = UInt8.new(256)

  # Item in a list of interfaces.
  struct PcapIf
    next        : PcapIf*      # next interface in the list
    name        : LibC::Char*  # name to hand to pcap_open_live()
    description : LibC::Char*  # textual description of interface, or NULL
    addresses   : PcapAddr*    # here for structure, not for function
    flags       : LibC::UInt   # PCAP_IF_ interface flags
  end
  
  # Loose representation of an interface address. Not all that
  # useful at the moment!
  struct PcapAddr
    next      : PcapAddr*
    addr      : Void*
    netmask   : Void*
    broadaddr : Void*
    dstaddr   : Void*
  end

  # Find the default device on which to capture.
  # http://www.tcpdump.org/manpages/pcap_lookupdev.3pcap.html
  #fun pcap_lookupdev : LibC::Char*
  fun pcap_lookupdev(errbuf : LibC::Char* ) : LibC::Char*
  
  # Get a list of capture devices.
  # http://www.tcpdump.org/manpages/pcap_findalldevs.3pcap.html
  fun pcap_findalldevs(list : PcapIf**, errbuf : LibC::Char*) : LibC::Int
  
  # Free list of capture devices.
  # http://www.tcpdump.org/manpages/pcap_findalldevs.3pcap.html
  fun pcap_freealldevs(list : PcapIf*)
end


module Pcap
  def self.lookupdev
    err = LibPcap::PCAP_ERRBUF_SIZE.dup
    String.new(LibPcap.pcap_lookupdev(pointerof(err)))
  end
  
  def self.findalldevs
    err = LibPcap::PCAP_ERRBUF_SIZE.dup
    result = LibPcap.pcap_findalldevs(out iface_iterator, pointerof(err)) 
    if result == -1
      raise Exception.new "Unable to find devices! #{err}"
    end
    interfaces = [] of LibPcap::PcapIf
    orig = iface_iterator
    iface = iface_iterator
    until iface_iterator.null?
      iface = iface_iterator.value
      interfaces << iface
      iface_iterator = iface.next
    end
    LibPcap.pcap_freealldevs(orig)
    interfaces 
  end
end

interfaces = Pcap.findalldevs

puts String.new(interfaces.first.name) # no string, sometimes junk?!

#interfaces.each do |interface|
#  name = String.new(interface.name)
#  puts name
#end