PowerDNS recursor - on demand A record generator

pdns-resolver.lua

--
-- PowerDNS on demand A record generator
--
-- Resolves any record with format A-B-C-D.yourdomain.com to an A record with ip address A.B.C.D.
--

pdnslog("pdns-recursor - on demand A record generator script loaded", pdns.loglevels.Warning)

domain = newDN("yourdomain.com")

function preresolve(dq)
  if dq.qname:isPartOf(domain) then
    qname = dq.qname:toStringNoDot()
    pdnslog("Received query for '" .. qname .. "' from remote address " .. dq.remoteaddr:toString())
    -- Extract IP address using format: A-B-C-D.domain
    it = string.gmatch(qname, "(%d+).")
    ipAddress = ''
    for i = 0, 3 do
      octet = tonumber(it())
      -- Attempt 8-bit digit extraction
      if octet >= 0 and octet <= 255 then
        ipAddress = (i == 0) and (octet) or (ipAddress .. '.' .. octet)
      else
        -- Graceful failure
        return true
      end
    end
    -- Returns extracted IP address as A record
    dq:addAnswer(pdns.A, ipAddress)
  end
  return true
end