calculate_ip

# File actionpack/lib/action_dispatch/middleware/remote_ip.rb, line 47
      def calculate_ip
        client_ip     = @env['HTTP_CLIENT_IP']
        forwarded_ips = ips_from('HTTP_X_FORWARDED_FOR')
        remote_addrs  = ips_from('REMOTE_ADDR')

        check_ip = client_ip && @middleware.check_ip
        if check_ip && !forwarded_ips.include?(client_ip)
          # We don't know which came from the proxy, and which from the user
          raise IpSpoofAttackError, "IP spoofing attack?!"              "HTTP_CLIENT_IP=#{@env['HTTP_CLIENT_IP'].inspect}"              "HTTP_X_FORWARDED_FOR=#{@env['HTTP_X_FORWARDED_FOR'].inspect}"
        end

        not_proxy = client_ip || forwarded_ips.last || remote_addrs.first

        # Return first REMOTE_ADDR if there are no other options
        not_proxy || ips_from('REMOTE_ADDR', :allow_proxies).first
      end