dns: add null mx record (rfc7505)

Author: abh

lib/NP/Model/DnsRoot.pm

@@ -55,6 +55,9 @@ sub data {
             {txt => "_globalsign-domain-verification=mVYWxIl-2ab_B1yPPFxEmDCLrBcl6ucouXJOU_P0_C"},
         ];
 
+        # null MX records by default, rfc7505
+        $data->{""}->{mx} = [{mx => ".", preference => 0},];
+
         if ($self->origin eq "pool.ntp.org") {
 
             # google domain verification
@@ -126,6 +129,7 @@ sub populate_country_zones {
             if ($ttl) {
                 $data->{$pgeodns_group}->{ttl} = $ttl;
             }
+            $data->{$pgeodns_group}->{mx} = [{mx => ".", preference => 0}];
 
             $min_non_duplicate_size = int(@$entries / $zone_count)
               if (@$entries / $zone_count > $min_non_duplicate_size);
@@ -143,6 +147,8 @@ sub populate_country_zones {
                         next;
                     }
 
+                    $data->{$pgeodns_group}->{mx} = [{mx => ".", preference => 0}];
+
                     $data->{$pgeodns_group}->{a} = [];
                     if ($ttl) {
                         $data->{$pgeodns_group}->{ttl} = $ttl;