спасибо, разобрались
На сайте developers.google.com
In addition, Google Public DNS engineers have proposed a technical solution to the issue in an IETF draft, Client subnet information in DNS requests. This proposal defines an EDNS0 extension which allows resolvers to pass in part of the client's IP address as the source IP in the DNS message, so that nameservers can return optimized results based on the user's location rather than that of the resolver.
всё передается в расшренном заголовке ДНС-запроса. Вот как!
всем спасибо, вопрос закрыт