From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Tue, 10 Nov 2020 17:05:15 +0000 (+0100)
Subject: rec-4.3.x: Avoid a CNAME loop detection issue with DNS64
X-Git-Tag: rec-4.3.6~3^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F9702%2Fhead;p=thirdparty%2Fpdns.git

rec-4.3.x: Avoid a CNAME loop detection issue with DNS64

When the requested qname is a CNAME to a second CNAME, the CNAME
loop detection might get incorrectly triggered because the CNAMEs
were already present in the vector of result records.
---

diff --git a/pdns/lua-recursor4.cc b/pdns/lua-recursor4.cc
index 36239b0e14..f5f4351917 100644
--- a/pdns/lua-recursor4.cc
+++ b/pdns/lua-recursor4.cc
@@ -36,7 +36,16 @@ RecursorLua4::RecursorLua4() { prepareContext(); }
 
 static int getFakeAAAARecords(const DNSName& qname, const std::string& prefix, vector<DNSRecord>& ret)
 {
-  int rcode=directResolve(qname, QType(QType::A), 1, ret);
+  /* we pass a separate vector of records because we will be resolving the initial qname
+     again, possibly encountering the same CNAME(s), and we don't want to trigger the CNAME
+     loop detection. */
+  std::vector<DNSRecord> newRecords;
+  int rcode=directResolve(qname, QType(QType::A), 1, newRecords);
+
+  ret.reserve(ret.size() + newRecords.size());
+  for (auto& record : newRecords) {
+    ret.push_back(std::move(record));
+  }
 
   ComboAddress prefixAddress(prefix);