From: Otto <otto.moerbeek@open-xchange.com>
Date: Tue, 5 Oct 2021 09:20:24 +0000 (+0200)
Subject: Use packetcache-servfail-ttl for all packet cache entries considered an error reply.
X-Git-Tag: dnsdist-1.7.0-alpha2~19^2~5
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9f3937016b719ed2441068679197ee34e6151a3d;p=thirdparty%2Fpdns.git

Use packetcache-servfail-ttl for all packet cache entries considered an error reply.

The "this is an error" test is: no answer records and rcode not equal to NoError. This needs to be validated.
Fixes #9135.
---

diff --git a/pdns/pdns_recursor.cc b/pdns/pdns_recursor.cc
index 280f936744..214a20d5d5 100644
--- a/pdns/pdns_recursor.cc
+++ b/pdns/pdns_recursor.cc
@@ -2299,8 +2299,11 @@ static void startDoResolve(void *p)
       g_stats.variableResponses++;
     }
     if (!SyncRes::s_nopacketcache && !variableAnswer && !sr.wasVariable()) {
-      minTTL = min(minTTL, pw.getHeader()->rcode == RCode::ServFail ? SyncRes::s_packetcacheservfailttl :
-                   SyncRes::s_packetcachettl);
+      const auto& hdr = pw.getHeader();
+      if (hdr->ancount == 0 && hdr->rcode != RCode::NoError) {
+        minTTL = min(minTTL, SyncRes::s_packetcacheservfailttl);
+      }
+      minTTL = min(minTTL, SyncRes::s_packetcachettl);
       t_packetCache->insertResponsePacket(dc->d_tag, dc->d_qhash, std::move(dc->d_query), dc->d_mdp.d_qname,
                                           dc->d_mdp.d_qtype, dc->d_mdp.d_qclass,
                                           string((const char*)&*packet.begin(), packet.size()),
diff --git a/pdns/recursordist/docs/settings.rst b/pdns/recursordist/docs/settings.rst
index eab06acac5..b7433d9dda 100644
--- a/pdns/recursordist/docs/settings.rst
+++ b/pdns/recursordist/docs/settings.rst
@@ -1413,7 +1413,7 @@ Maximum number of seconds to cache an item in the packet cache, no matter what t
 -  Integer
 -  Default: 60
 
-Maximum number of seconds to cache a 'server failure' answer in the packet cache.
+Maximum number of seconds to cache a 'server failure' and other answers signalling an error in the packet cache.
 
 .. versionchanged:: 4.0.0