From: Brian Candler <B.Candler@...>
Date: 2007-05-14T05:10:34+09:00
Subject: Re: No accept Ipv6 in IPAddr

On Mon, May 14, 2007 at 04:41:13AM +0900, Cyril Mougel wrote:
> I ask me a question since few day and I don't understand why this code
> doesn't run :
> 
>   require 'ipaddr'
>   IPAddr.new '2002:0000:1234:4561'
> 
> In fact this code raise an Exception :
> 
>   /usr/lib64/ruby/1.8/ipaddr.rb:422:in `initialize': invalid address
> (ArgumentError)

Correct - that's not a valid IPv6 address. IPv6 addresses have 128 bits;
your address has only 64 bits.

irb(main):001:0> require 'ipaddr'
=> true
irb(main):002:0> IPAddr.new '2002:0000:1234:4561'
ArgumentError: invalid address
        from /usr/lib/ruby/1.8/ipaddr.rb:423:in `initialize'
        from (irb):2
irb(main):003:0> IPAddr.new '2002:0000:1234:4561/64'
ArgumentError: invalid address
        from /usr/lib/ruby/1.8/ipaddr.rb:423:in `initialize'
        from (irb):3
irb(main):004:0> IPAddr.new '2002:0000:1234:4561::0/64'
=> #<IPAddr: IPv6:2002:0000:1234:4561:0000:0000:0000:0000/ffff:ffff:ffff:ffff:0000:0000:0000:0000>

The "::" means "add as many :0000:'s as necessary to make up to 128 bits".
But you could also use a valid 128 bit address explicitly:

irb(main):005:0> IPAddr.new '2002:0000:1234:4561:0000:0000:0000:0000'
=> #<IPAddr: IPv6:2002:0000:1234:4561:0000:0000:0000:0000/ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff>

> IPAddr think my IP like an invalid adress because it hadn't a name
> resolution. The line who raise the exception is :
> 
>   IPSocket.getaddress(prefix)
> 
> For me, the prefix is '2002:0000:1234:4561', because it's never modify
> before in intialize of IPAddr (Verify with the debuggeur). The command
> follow prouve it :
> 
>   hello% host 2002:0000:1234:4561
>   Host 2002:0000:1234:4561 not found: 3(NXDOMAIN)

If you give an address which is not syntactially valid as an IPv6 numeric
address, I guess it's reasonable for Ruby to try it as a hostname instead.

Brian.