[1608] handle additional names at or below a DNAME delegation point.

src/lib/datasrc/memory_datasrc.cc

@@ -1273,7 +1273,11 @@ checkZoneCut(const DomainNode& node, pair<bool, bool>* arg) {
     if (arg->first) {
         return (false);
     }
-    if (node.getData()->find(RRType::NS()) != node.getData()->end()) {
+    // Once we encounter a delegation point due to a DNAME, anything under it
+    // should be hidden.
+    if (node.getData()->find(RRType::DNAME()) != node.getData()->end()) {
+        return (true);
+    } else if (node.getData()->find(RRType::NS()) != node.getData()->end()) {
         arg->first = true;
         arg->second = true;
         return (false);

src/lib/datasrc/tests/testdata/contexttest.zone

@@ -1,7 +1,7 @@
 ;; test zone file used for ZoneFinderContext tests.
 ;; RRSIGs are (obviouslly) faked ones for testing.
 
-example.org. 3600 IN SOA	ns1.example.org. bugs.x.w.example.org. 29 3600 300 3600000 3600
+example.org. 3600 IN SOA	ns1.example.org. bugs.x.w.example.org. 41 3600 300 3600000 3600
 example.org.			      3600 IN NS	ns1.example.org.
 example.org.			      3600 IN NS	ns2.example.org.
 example.org.			      3600 IN MX	1 mx1.example.org.
@@ -39,8 +39,21 @@ ns.b.example.org.		      3600 IN A		192.0.2.9
 ;; additional section.
 mxatcut.example.org.		      3600 IN MX	1 b.example.org.
 
+;; delegation, one of its NS names is under a DNAME delegation point;
+;; another is at that point; and yet another is under DNAME below a
+;; zone cut.
+c.example.org. 	      	      3600 IN NS	ns.dname.example.org.
+c.example.org. 	      	      3600 IN NS	dname.example.org.
+c.example.org.      	      3600 IN NS	ns.deepdname.example.org.
+ns.dname.example.org.		      3600 IN A		192.0.2.11
+dname.example.org.		      3600 IN A		192.0.2.12
+ns.deepdname.example.org.	      3600 IN AAAA	2001:db8::9
+
 ;; CNAME
 alias.example.org. 3600 IN CNAME cname.example.org.
 
 ;; DNAME
 dname.example.org. 3600 IN DNAME dname.example.com.
+
+;; DNAME under a NS (strange one)
+deepdname.c.example.org. 3600 IN DNAME deepdname.example.com.

src/lib/datasrc/tests/zone_finder_context_unittest.cc

@@ -234,6 +234,20 @@ TEST_P(ZoneFinderContextTest, getAdditionalDelegationAtZoneCut) {
                 result_sets_.begin(), result_sets_.end());
 }
 
+TEST_P(ZoneFinderContextTest, getAdditionalDelegationWithDname) {
+    // Delegation: One of the NS names under a DNAME delegation; another
+    // is at the delegation point; yet another is under DNAME below a zone cut.
+    // The first should be hidden.
+    ZoneFinderContextPtr ctx = finder_->find(Name("www.c.example.org"),
+                                             RRType::TXT());
+    EXPECT_EQ(ZoneFinder::DELEGATION, ctx->code);
+
+    ctx->getAdditional(REQUESTED_BOTH, result_sets_);
+    rrsetsCheck("dname.example.org. 3600 IN A 192.0.2.12\n"
+                "ns.deepdname.example.org. 3600 IN AAAA 2001:db8::9\n",
+                result_sets_.begin(), result_sets_.end());
+}
+
 TEST_P(ZoneFinderContextTest, getAdditionalMX) {
     // Similar to the previous cases, but for MX addresses.  The test zone
     // contains MX name under a zone cut.  Its address shouldn't be returned.