dns: more tweaking for ddos handling

Increase the window so we keep track of more queries
Set the max number of nxdomains to try and drop those.

Signed-off-by: Kevin Fenzi <kevin@scrye.com>

roles/dns/files/named.conf

@@ -54,10 +54,11 @@ options {
         max-cache-size  1024M;
         rate-limit {
                 responses-per-second 50;
-                window 5;
+                window 60;
                 max-table-size  2000000;
                 min-table-size  500000;
                 ipv4-prefix-length 32;
+                nxdomains-per-second 25;
         };
 };
 //