From: Todd Benson <caduceass@...>
Date: 2008-01-17T08:59:16+09:00
Subject: Re: Problem with IPAddr

On Jan 16, 2008 6:52 AM, fw <fwmailinglists@gmail.com> wrote:
> On Wed, 2008-01-16 at 14:53 +0900, Bryan Richardson wrote:
> > Gary,
> >
> > Thanks for the reply.  Here's what I get when I try something else:
> >
> > irb(main):001:0> require 'ipaddr'
> > => true
> > irb(main):002:0> net_1 = IPAddr.new("192.168.0.0/16")
> > => #<IPAddr: IPv4:192.168.0.0/255.255.0.0>
> > irb(main):003:0> net_2 = IPAddr.new("192.168.101.0/24")
> > => #<IPAddr: IPv4:192.168.101.0/255.255.255.0>
> > irb(main):004:0> net_1.include?(net_2)
> > => true
> > irb(main):005:0> net_2.include?(net_1)
> > => false
> > irb(main):006:0>
> >
> > Makes sense I guess.  Is there any way to tell IPAddr to look at it as a
> > network instead of as an address?  I have a situation where I may come
> > across an address (ending in .0, so defining a network) where the netmask
> > isn't given, so I assign it as a small network (say /29).  Later on I may
> > come across it again, this time with the netmask defined (say /16), and I
> > want to merge the first one into the second one.  Therefore, each time I add
> > a new network to my database, I compare it to the existing ones to see if
> > any should be merged.  Any suggestions?  Thanks!! -- BTR
>
> First I'd like to add that the last octet being 0 does not mean that the
> IP address is a network address: In the network 10.0.0.0/25, 10.0.1.0 is
> a host address.
>
> IPAddr doesn't seem to have this functionality, but you can add it like
> this:
>
> $ irb
> irb(main):001:0> require 'ipaddr'
> => true
> irb(main):002:0> class IPAddr
> irb(main):003:1>   def broadcast_addr
> irb(main):004:2>     _to_string(@addr | (2**32 - 1) - (@mask_addr))
> irb(main):005:2>   end
> irb(main):006:1>   def network_in_network?(network)
> irb(main):007:2>     return false unless self.include?(network)
> irb(main):008:2>     return false unless
> self.include?(IPAddr.new(network.broadcast_addr))
> irb(main):009:2>     return true
> irb(main):010:2>   end
> irb(main):011:1> end
> => nil
> irb(main):012:0> a = IPAddr.new('192.168.0.128/25')
> => #<IPAddr: IPv4:192.168.0.128/255.255.255.128>
> irb(main):013:0> b = IPAddr.new('192.168.0.0/24')
> => #<IPAddr: IPv4:192.168.0.0/255.255.255.0>
> irb(main):014:0> a.network_in_network?(b)
> => false
> irb(main):015:0> b.network_in_network?(a)
> => true
> irb(main):016:0>
>
>
> This works by determining the broadcast address of the network (by ORing
> the network address with the reverse netmask) and then checking if both
> network and broadcast address are included in the range you're checking
> against.

This might work too...

class IPAddr
  attr_accessor :mask_addr
  def network_in_network? ipaddr
    @mask_addr > ipaddr.mask_addr
  end
end

Todd