From ff1537871d451dc7f36e539189107f4ee2d05379 Mon Sep 17 00:00:00 2001
From: Otto Moerbeek <otto.moerbeek@open-xchange.com>
Date: Mon, 2 Jan 2023 16:34:56 +0100
Subject: [PATCH] Backport to 4.8.x: Do *not* use QName Minimization for DS
 retrievals in QM fallback mode.

---
 pdns/recursordist/rec-main.cc |  2 +-
 pdns/syncres.cc               |  4 +++-
 pdns/syncres.hh               | 13 +++++++++++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/pdns/recursordist/rec-main.cc b/pdns/recursordist/rec-main.cc
index 415b7c8338..a29c87b825 100644
--- a/pdns/recursordist/rec-main.cc
+++ b/pdns/recursordist/rec-main.cc
@@ -2583,7 +2583,7 @@ int main(int argc, char** argv)
   try {
 #if HAVE_FIBER_SANITIZER
     // Asan needs more stack
-    ::arg().set("stack-size", "stack size per mthread") = "400000";
+    ::arg().set("stack-size", "stack size per mthread") = "600000";
 #else
     ::arg().set("stack-size", "stack size per mthread") = "200000";
 #endif
diff --git a/pdns/syncres.cc b/pdns/syncres.cc
index 88a55a3789..54602efabf 100644
--- a/pdns/syncres.cc
+++ b/pdns/syncres.cc
@@ -1753,6 +1753,8 @@ int SyncRes::doResolve(const DNSName &qname, const QType qtype, vector<DNSRecord
         // Case 5: unexpected answer
         QLOG("Step5: other rcode, last effort final resolve");
         setQNameMinimization(false);
+        setQMFallbackMode(true);
+
         // We might have hit a depth level check, but we still want to allow some recursion levels in the fallback
         // no-qname-minimization case. This has the effect that a qname minimization fallback case might reach 150% of
         // maxdepth.
@@ -3589,7 +3591,7 @@ vState SyncRes::getDSRecords(const DNSName& zone, dsmap_t& ds, bool taOnly, unsi
 
   vState state = vState::Indeterminate;
   const bool oldCacheOnly = setCacheOnly(false);
-  const bool oldQM = setQNameMinimization(true);
+  const bool oldQM = setQNameMinimization(!getQMFallbackMode());
   int rcode = doResolve(zone, QType::DS, dsrecords, depth + 1, beenthere, state);
   setCacheOnly(oldCacheOnly);
   setQNameMinimization(oldQM);
diff --git a/pdns/syncres.hh b/pdns/syncres.hh
index df26b9ac4f..1bdf1508b7 100644
--- a/pdns/syncres.hh
+++ b/pdns/syncres.hh
@@ -328,6 +328,18 @@ public:
     return old;
   }
 
+  bool setQMFallbackMode(bool state = true)
+  {
+    auto old = d_qNameMinimizationFallbackMode;
+    d_qNameMinimizationFallbackMode = state;
+    return old;
+  }
+
+  bool getQMFallbackMode() const
+  {
+    return d_qNameMinimizationFallbackMode;
+  }
+
   void setDoEDNS0(bool state=true)
   {
     d_doEDNS0=state;
@@ -664,6 +676,7 @@ private:
   bool d_wasOutOfBand{false};
   bool d_wasVariable{false};
   bool d_qNameMinimization{false};
+  bool d_qNameMinimizationFallbackMode{false};
   bool d_queryReceivedOverTCP{false};
   bool d_followCNAME{true};
   bool d_refresh{false};
-- 
2.47.2