Can the DNS Server have source IP?

Question

Short Question :

Since DNS is anycast, is there any way for a DNS Server to know the "first" source DNS Query originated from?

Long Question : I've developed a custom DynDNS server using PowerDNS, I want to feed it information via web interface by users. I want the web interface to update records for each user "based on IP".

So when the DNS Server gets requests, If it could determine the source IP, it'd be easy to return records associated with that IP.

As long as I tested, the DNS Server can only know the "last" node IP on the DNS chain, not the source. Is there any way?

Regards

Answer 1

Google and Yahoo! submitted a draft (draft-vandergaast-edns-client-ip-01) to the IETF DNS Extensions Working Group that proposed a new EDNS0 option within DNS requests that recursive servers could use to indicate their own client's IP address to the upstream authoritative server.

The intent was to theoretically optimise the use of Content Delivery Networks by ensuring that the web server addresses returned were based on the end user's IP address, rather than on the address of the end user's DNS server.

The idea was not well received and wasn't accepted by the working group because it intentionally broke the caching layer of the DNS, and the draft has subsequently expired.

UPDATE - a variation on this has subsequently been published as RFC 7871.

Answer 2

Perhaps you have control of the software performing the lookup? If so, you could include the IP address as part of the request, e.g.

23-34-45-56.www.example.com

to which your custom-written server replies

23-34-45-56.www.example.com 1800 CNAME www-europe.example.com

or

23-34-45-56.www.example.com  300     A 34.45.56.67

etc.

If the client is a web browser, complications arise due to NAT, HTTP proxies, and the inability to query host interface addresses directly from Javascript. However, you might be able to do an AJAX-style lookup to a what's-my-ip service, which understands X-Forwarded-For.