Rails Ruby on Rails

actionpack-3.0.3/lib/action_dispatch/http/request.rb:

    LOCALHOST = [/^127\.0\.0\.\d{1,3}$/, "::1", /^0:0:0:0:0:0:0:1(%.*)?$/].freeze

All IPv4 127.x.x.x addresses are loopback/localhost addresses. 127.0.0.0 is a Class A /8 network.

This code should be:

    LOCALHOST = [/^127\.\d{1,3}\.\d{1,3}\.\d{1,3}$/, "::1", /^0:0:0:0:0:0:0:1(%.*)?$/].freeze

Not sure if this issue exists elsewhere in Rails 3.

Citations:

http://www.faqs.org/rfcs/rfc1700.html: "Special Addresses"

  (g)   {127, <any>}
     Internal host loopback address.  Should never appear outside
     a host.

http://www.faqs.org/rfcs/rfc3330.html

 127.0.0.0/8 - This block is assigned for use as the Internet host
   loopback address.  A datagram sent by a higher level protocol to an
   address anywhere within this block should loop back inside the host.
   This is ordinarily implemented using only 127.0.0.1/32 for loopback,
   but no addresses within this block should ever appear on any network
   anywhere [RFC1700, page 5].

ifconfig lo:

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host