From: Pieter Lexis <pieter.lexis@powerdns.com>
Date: Tue, 23 Mar 2021 15:29:05 +0000 (+0100)
Subject: Add a setting for autohints
X-Git-Tag: dnsdist-1.6.0-rc1~33^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0a21c8ea6f5395891240011bee68153c6259d92d;p=thirdparty%2Fpdns.git

Add a setting for autohints
---

diff --git a/docs/guides/svcb.rst b/docs/guides/svcb.rst
index 1daa1cf552..64749e39dc 100644
--- a/docs/guides/svcb.rst
+++ b/docs/guides/svcb.rst
@@ -4,9 +4,13 @@ The PowerDNS Authoritative Server has support for the SVCB record and derived re
 This support includes doing the standards recommended following of alias-form records in-zone and adding those to the additional section.
 Apart from that, there's the PowerDNS special for "autohints".
 
+.. _svc-autohints:
+
 Automatic hints
 ---------------
 PowerDNS can automatically fill in ``ipv4hint`` and ``ipv6hint`` parameters in SVCB records based on A and AAAA records already present in the zone.
+This can be enabled by setting :ref:`setting-svc-autohint` to 'yes'.
+
 Consider the following zone content::
 
   example.com      IN HTTPS 0 www.example.com
@@ -75,3 +79,7 @@ In this case, the ipv6hint parameter is dropped when answering the query (and on
 It will emit a warning when there are no hints to be found::
 
   [warning] HTTPS record for no-ipv6.example.org has automatic IPv6 hints, but no AAAA-record for the target at no-ipv6.example.org exists.
+
+When autohints exist but are disabled
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+When :ref:`setting-svc-autohint` is not enabled, the parameter is dropped when its value is ``auto``.
diff --git a/docs/settings.rst b/docs/settings.rst
index f45208dae9..deef616270 100644
--- a/docs/settings.rst
+++ b/docs/settings.rst
@@ -1517,6 +1517,16 @@ and :doc:`Virtual Hosting <guides/virtual-instances>` how this can differ.
 
 Turn on supermaster support. See :ref:`supermaster-operation`.
 
+.. _setting-svc-autohints:
+
+``svc-autohints``
+-----------------
+
+- Boolean
+- Default: no
+
+Whether or not to enable IPv4 and IPv6 :ref:`autohints <svc-autohints>`.
+
 .. _setting-tcp-control-address:
 
 ``tcp-control-address``
diff --git a/pdns/common_startup.cc b/pdns/common_startup.cc
index db4b4aa5dc..b5aab6b4d6 100644
--- a/pdns/common_startup.cc
+++ b/pdns/common_startup.cc
@@ -33,6 +33,7 @@
 #include "misc.hh"
 #include "query-local-address.hh"
 #include "trusted-notification-proxy.hh"
+#include "packethandler.hh"
 
 #include <thread>
 
@@ -240,6 +241,7 @@ void declareArguments()
 
   ::arg().set("max-generate-steps", "Maximum number of $GENERATE steps when loading a zone from a file")="0";
   ::arg().setSwitch("upgrade-unknown-types","Transparently upgrade known TYPExxx records. Recommended to keep off, except for PowerDNS upgrades until data sources are cleaned up")="no";
+  ::arg().setSwitch("svc-autohints", "Transparently fill ipv6hint=auto ipv4hint=auto SVC params with AAAA/A records for the target name of the record (if within the same zone)")="no";
 
   ::arg().setSwitch("consistent-backends", "Assume individual domains are not divided over backends. Send only ANY lookup operations to the backend to reduce the number of lookups")="no";
 
@@ -551,6 +553,7 @@ void mainthread()
 
    DNSPacket::s_udpTruncationThreshold = std::max(512, ::arg().asNum("udp-truncation-threshold"));
    DNSPacket::s_doEDNSSubnetProcessing = ::arg().mustDo("edns-subnet-processing");
+   PacketHandler::s_SVCAutohints = ::arg().mustDo("svc-autohints");
 
    PC.setTTL(::arg().asNum("cache-ttl"));
    PC.setMaxEntries(::arg().asNum("max-packet-cache-entries"));
diff --git a/pdns/packethandler.cc b/pdns/packethandler.cc
index 4ab8b8c0f2..2b897fb082 100644
--- a/pdns/packethandler.cc
+++ b/pdns/packethandler.cc
@@ -55,6 +55,7 @@
 AtomicCounter PacketHandler::s_count;
 NetmaskGroup PacketHandler::s_allowNotifyFrom;
 set<string> PacketHandler::s_forwardNotify;
+bool PacketHandler::s_SVCAutohints{false};
 
 extern string s_programname;
 
@@ -527,22 +528,26 @@ void PacketHandler::doAdditionalProcessing(DNSPacket& p, std::unique_ptr<DNSPack
     // Process auto hints
     auto rrc = getRR<SVCBBaseRecordContent>(rec->dr);
     DNSName target = rrc->getTarget().isRoot() ? rec->dr.d_name : rrc->getTarget();
-    if (rrc->autoHint(SvcParam::ipv4hint)) {
+    if (rrc->autoHint(SvcParam::ipv4hint) && s_SVCAutohints) {
       auto hints = getIPAddressFor(target, QType::A);
       if (hints.size() == 0) {
         rrc->removeParam(SvcParam::ipv4hint);
       } else {
         rrc->setHints(SvcParam::ipv4hint, hints);
       }
+    } else {
+      rrc->removeParam(SvcParam::ipv4hint);
     }
 
-    if (rrc->autoHint(SvcParam::ipv6hint)) {
+    if (rrc->autoHint(SvcParam::ipv6hint) && s_SVCAutohints) {
       auto hints = getIPAddressFor(target, QType::AAAA);
       if (hints.size() == 0) {
         rrc->removeParam(SvcParam::ipv6hint);
       } else {
         rrc->setHints(SvcParam::ipv6hint, hints);
       }
+    } else {
+      rrc->removeParam(SvcParam::ipv6hint);
     }
   }
 
diff --git a/pdns/packethandler.hh b/pdns/packethandler.hh
index 1df16962e0..ef18f7d602 100644
--- a/pdns/packethandler.hh
+++ b/pdns/packethandler.hh
@@ -63,6 +63,7 @@ public:
   int trySuperMasterSynchronous(const DNSPacket& p, const DNSName& tsigkeyname);
   static NetmaskGroup s_allowNotifyFrom;
   static set<string> s_forwardNotify;
+  static bool s_SVCAutohints;
   static const std::shared_ptr<CDNSKEYRecordContent> s_deleteCDNSKEYContent;
   static const std::shared_ptr<CDSRecordContent> s_deleteCDSContent;