[2504] Add testcase that reproduces the problem

This test currently fails with an assertion.

src/lib/datasrc/tests/memory/testdata/2504-test.zone

@@ -0,0 +1,10 @@
+ok.ok.ok.ok.dnssec.tjeb.nl.	600	IN	SOA	ns2.tjeb.nl. tjeb.tjeb.nl. 2012120601 28800 7200 604800 18000
+ok.ok.ok.ok.dnssec.tjeb.nl.	600	IN	A	178.18.82.80
+ok.ok.ok.ok.dnssec.tjeb.nl.	3600	IN	DNSKEY	256 3 5 AwEAAag7J/qxkLI1keftNSKe0fqa2mU1GaeZGQoOSgVZvJAMh6LK9F1NMmWP2MeaeJvfTkmZs2UggGnFjkb7QQygrZnfxxCOVu5fG8x3Na5Z7jAdMgVfuJ1FTmsi2Bj4W/+b3fuvv/eVGqlEsFdth+sGA+BKH9mdBwmt+aXJf9gohXpx ;{id = 34791 (zsk), size = 1024b}
+ok.ok.ok.ok.dnssec.tjeb.nl.	600	IN	NS	ns2.tjeb.nl.
+ok.ok.ok.ok.dnssec.tjeb.nl.	18000	IN	NSEC	ok.ok.ok.ok.dnssec.tjeb.nl. A NS SOA RRSIG NSEC DNSKEY
+ok.ok.ok.ok.dnssec.tjeb.nl.	600	IN	RRSIG	SOA 5 7 600 20200101000000 20120627091929 34791 ok.ok.ok.ok.dnssec.tjeb.nl. Z+LjS0NtrUkOje1PZht8a3TylxEKabDltJSye3NO/n6tE9268S5EqQ6r0nZ0hO78c9r4lYxMlvnfyTAj/5rR/zdApCS0EnpQenVyvwagIAVdIcNqpZxr7i/tFmOvxyQK3NRhWqH83WhNwqRE1E4thUfNovtyscSLR+TOhuEBKlg=
+ok.ok.ok.ok.dnssec.tjeb.nl.	600	IN	RRSIG	A 5 7 600 20200101000000 20120627091929 34791 ok.ok.ok.ok.dnssec.tjeb.nl. oYbwX46pDyaTNIeZByyLnUVc4RNgFmGeUuJ4sn0aIqrX6UqfNJwJpZiCspcyBRBNIZye6ypVNFD9RUHesrELHjFOAustg86GFws1jeEoDbi4W6wmeNQqiUfnyaqME3rHD9WE7I99Nqiyp8ZEBseem/SIOCsEXxPLrhoAL+Fa1+s=
+ok.ok.ok.ok.dnssec.tjeb.nl.	600	IN	RRSIG	NS 5 7 600 20200101000000 20120627091929 34791 ok.ok.ok.ok.dnssec.tjeb.nl. KBRov1y79yN75feRo2Bv5B+UpmDAyEr/kTgWgL9dYtkuQXvT7Y1Lg5jhcFmyrAkpYud70i5Un2DEUtmnI2oUR7XUh1RDnMQZRgKkaDXNXj5D379hLxpD2jtN+A311ShReaM4laj44UiDzu0pjGtrDT7BY1c4Qb5XI0RLyI0VKSs=
+ok.ok.ok.ok.dnssec.tjeb.nl.	3600	IN	RRSIG	DNSKEY 5 7 3600 20200101000000 20120627091929 34791 ok.ok.ok.ok.dnssec.tjeb.nl. NriwgSl8QskWiQMlIPzn3WvWQwfQDy8pnJ4U2qlOjWFeJ4wH7DS/P5BDh9+JXjKamh5Bdy2umSf1uY1BeodSP+Ga4yKxNb1sigGbToYGDsbLP1NfPPq6uijl5nRhqBQAAzjCmyU9sm6GUr/CyOpSTTxtFjosXZQ1t1GFya6Tgho=
+ok.ok.ok.ok.dnssec.tjeb.nl.	18000	IN	RRSIG	NSEC 5 7 18000 20200101000000 20120627091929 34791 ok.ok.ok.ok.dnssec.tjeb.nl. ijT2etFxkmNLMdbugWsIrnPuJqxdPPO/ilWUb0ZapcuwtqV4mTZCalUlb3KSpcczHPfyClF7WvMEKdluLrX55TPKEBxx1AIdOduhwSTxCxgZpOp4LFIR3rg5hTH9bupEUvbFPWU8RX5oX0GLE0V/EpfNYpHOtvvG3rnegwynML4=

src/lib/datasrc/tests/memory/testdata/Makefile.am

@@ -29,3 +29,5 @@ EXTRA_DIST += example.org-rrsigs.zone
 EXTRA_DIST += example.org-wildcard-dname.zone
 EXTRA_DIST += example.org-wildcard-ns.zone
 EXTRA_DIST += example.org-wildcard-nsec3.zone
+
+EXTRA_DIST += 2504-test.zone

src/lib/datasrc/tests/memory/zone_finder_unittest.cc

@@ -13,6 +13,7 @@
 // PERFORMANCE OF THIS SOFTWARE.
 
 #include "memory_segment_test.h"
+#include "zone_table_segment_test.h"
 
 // NOTE: this faked_nsec3 inclusion (and all related code below)
 // was ported during #2109 for the convenience of implementing #2218
@@ -25,7 +26,10 @@
 #include <datasrc/memory/zone_finder.h>
 #include <datasrc/memory/zone_data_updater.h>
 #include <datasrc/memory/rdata_serialization.h>
+#include <datasrc/memory/zone_table_segment.h>
+#include <datasrc/memory/memory_client.h>
 #include <datasrc/data_source.h>
+#include <datasrc/client.h>
 #include <testutils/dnsmessage_test.h>
 
 #include <boost/foreach.hpp>
@@ -1426,6 +1430,24 @@ TEST_F(InMemoryZoneFinderTest, findOrphanRRSIG) {
              ZoneFinder::DELEGATION, true, ns_rrset);
 }
 
+// \brief testcase for #2504 (Problem in inmem NSEC denial of existence
+// handling)
+TEST_F(InMemoryZoneFinderTest, NSECNonExistentTest) {
+    shared_ptr<ZoneTableSegment> ztable_segment(
+         new ZoneTableSegmentTest(class_, mem_sgmt_));
+    InMemoryClient client(ztable_segment, class_);
+    Name name("ok.ok.ok.ok.dnssec.tjeb.nl.");
+
+    client.load(name, TEST_DATA_DIR "/2504-test.zone");
+    DataSourceClient::FindResult result(client.findZone(name));
+
+    // Check for a non-existing name
+    Name search_name("nonexist.ok.ok.ok.ok.dnssec.tjeb.nl.");
+    ZoneFinderContextPtr find_result(
+        result.zone_finder->find(search_name,
+                                 RRType::A(), ZoneFinder::FIND_DNSSEC));
+}
+
 /// \brief NSEC3 specific tests fixture for the InMemoryZoneFinder class
 class InMemoryZoneFinderNSEC3Test : public InMemoryZoneFinderTest {
 public: