[dnsdist] Modify EDNS NSID response back to client

[Remi Gacogne]

Hi Rob,

On 10/21/21 18:13, Robert Schwartz via dnsdist wrote:
> I'm trying to find a way to add a suffix to an existing NSID string 
> response coming back from a backend server. My use-case is to be able to 
> know, not only which backend server responded to the query (that's in 
> the backend response), but to also know which DNSDist box handled the 
> proxy request. The DNSDist boxes are behind an anycast IP (aws global 
> accelerator) so it's not always clear which DNSDist box handled a given 
> request.
> 
> Is this possible and how would I go by implementing this?

I'm afraid dnsdist doesn't offer any way to do that easily, short of 
parsing and rewriting the whole DNS payload in Lua by yourself.
As a rule we tend to avoid adding code to alter responses, as we believe 
dnsdist is not really well-suited to that job.
In your case I see how it might be difficult to do that in the backend 
itself, of course :-/

Best,
-- 
Remi Gacogne
PowerDNS.COM BV - https://www.powerdns.com/
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