Unbound as sinkhole setup

[Daisuke HIGASHI]

Hi,

"inform_redirect" local-zone (Unbound 1.9.1 or later) with SOA record
local-data generates "NODATA" negative response which DNS clients may
(or may not) do negative caching:

    local-zone: "example.com" inform_redirect
    local-data: "example.com 10800 SOA localhost. nobody.invalid. 1
3600 1200 604800 10800"

example.com zone response:
===========
;; QUESTION SECTION:
;; www.example.com.             IN      A

;; AUTHORITY SECTION:
example.com.            10800   IN      SOA     localhost.
nobody.invalid. 1 3600 1200 604800 10800
============