From: "James F.  Hranicky" <jfh@...>
Date: 2003-07-02T02:24:15+09:00
Subject: Re: IP arithmetic

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On Wed, 2 Jul 2003 01:12:15 +0900
Brian Candler <B.Candler@pobox.com> wrote:

> Are there any functions in the Ruby standard library which convert
> dotted-decimal IP addresses to numeric form, *without* doing any forward or
> reverse DNS lookups?
> 
> I want to do some address subnet matching: e.g.
> 
>     if ip_match("1.2.3.4", "1.2.3.0/24")
>       ... etc
>     end
> 
> and the efficient way of doing this would be to do bitwise operations on the
> numeric form.

Attached is something I've thrown together over the past year or so.

	ruby -I. -rnetaddr -e 'p IP4NetAddr.new("128.227.0.0/16").contains("128.127.215.35")'

More can be done I'm sure. Feel free to add.

Jim

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class IP4NetAddr
    
    attr_accessor        :network, :mask, :maskBits, :broadcast, :numIPs, :numHostIPs
    attr_accessor        :netn, :maskn, :wildcardn, :broadcastn

    def initialize(*argv)
        network, mask = argv
        network, mask = network.split("/") unless mask
        mask = mask.to_i

        raise "Invalid net or mask" unless 
            (network =~ /\d+\.\d+\.\d+\.\d+/ && (mask.to_s =~ /^\d{1,2}$/ || mask =~ /\d+\.\d+\.\d+\.\d+/))

        @network = network
        if (mask.to_s =~ /^\d{1,2}$/)
            @maskBits = mask
            @mask = bitsToMask(mask)
        else
            @mask = mask
            @maskBits = maskToBits(mask)
        end

        @numIPs = 2 ** (32 - maskBits)
        @numHostIPs = @numIPs - 2

        @netn = inet_aton(@network)
        @maskn = inet_aton(@mask)
        @wildcardn = @maskn ^ ((2 ** 32) - 1)
        @broadcastn = @netn ^ @wildcardn

        if (@netn & @wildcardn != 0)
            raise "Invalid netmask"
        end

    end

    def maskToBits(mask)
        bits = 0
        mask.scan(/\d+/) { |octet|
            7.downto(0) { |i|
                bits += 1 if (octet.to_i & ( 1 << i)) != 0
            }
        }
        bits
    end

    def bitsToMask(bits)
        octets = Array.new
        4.times { 
            if ( bits > 8 )
                octets << 255
            elsif ( bits <= 0 )
                octets << 0
            else
                octets << (((2 ** bits) - 1) << 8 - bits)
            end
            bits -= 8
        }
        octets.join(".")
    end

    def eachIPAddr
        @netn.upto(@broadcastn) { |ipn|
            yield inet_ntoa(ipn)
        }
    end
        
    def eachIPNumber
        @netn.upto(@broadcastn) { |ipn|
            yield ipn
        }
    end

    def eachHostIPAddr
        (@netn + 1).upto(@broadcastn - 1) { |ipn|
            yield inet_ntoa(ipn)
        }
    end

    def eachHostIPNumber
        (@netn + 1).upto(@broadcastn - 1) { |ipn|
            yield ipn
        }
    end

    def contains(ip)
        ipn = inet_aton(ip)
        return true if ipn >= @netn && ipn <= broadcastn
        return false
    end

    alias :all  :eachIPAddr 
    alias :each :eachHostIPAddr 

end

def inet_aton(ip)
    raise "Invalid ip: #{ip}" unless (ip =~ /\d+\.\d+\.\d+\.\d+/)
    n = 0
    shiftlen = 24
    ip.scan(/\d+/) { |octet|
        n += (octet.to_i << shiftlen)
        shiftlen -= 8
    }
    n
end

def inet_ntoa(n)
    raise "Invalid numeric IP value: #{n}" unless n >= 0 && n <= 2**32
    octets = Array.new
    shiftlen = 24
    4.times { 
        octets << ( (n & (255 << shiftlen)) >> shiftlen)
        shiftlen -= 8
    }
    octets.join(".")
end
        
if $0 == __FILE__
    n = IP4NetAddr.new("128.227.205.0", 29)
    puts "Net: #{n.network}"
    puts "Mask: #{n.mask}"
    puts "MaskBits: #{n.maskBits}"
    puts sprintf("netn: %x", n.netn)
    print "ntoa netn: ", inet_ntoa(n.netn), "\n"
    puts sprintf("nmaskn: %x", n.maskn)
    puts sprintf("nwildcardn: %08x", n.wildcardn)
    print "ntoa broadcastn: ", inet_ntoa(n.broadcastn), "\n"
    n.eachIPAddr { |ip|
        p ip
    }
    puts "Host IPS:"
    n.eachHostIPAddr { |ip|
        p ip
    }
end

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