From: fw <fwmailinglists@...>
Date: 2008-01-16T21:52:34+09:00
Subject: Re: Problem with IPAddr

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.

HTH,

Felix