[1608] handle the case where additional refers to an empty non-terminal node.

src/lib/datasrc/memory_datasrc.cc

@@ -309,6 +309,9 @@ insertRRsets(const AdditionalNodeInfo& additional,
              vector<ConstRRsetPtr>* result, bool glue_ok)
 {
     assert(additional.node_ != NULL);
+    if (additional.node_->isEmpty()) {
+        return;
+    }
     if (!glue_ok && additional.node_->getFlag(DOMAINFLAG_GLUE)) {
         return;
     }
@@ -1295,7 +1298,7 @@ addAdditional(RBNodeRRset* rrset, ZoneData* zone_data) {
         // child zone), mark the node as "GLUE", so we can selectively
         // include/exclude them when we use it.
 
-        // TODO: zone cut consideration (DNAME), empty node case, wildcard
+        // TODO: wildcard
         RBTreeNodeChain<Domain> node_path;
         DomainNode* node = NULL;
         // The callback argument is a pair of bools: the first is a flag to
@@ -1316,6 +1319,9 @@ addAdditional(RBNodeRRset* rrset, ZoneData* zone_data) {
                 // The node is under or at a zone cut; mark it as a glue.
                 node->setFlag(DOMAINFLAG_GLUE);
             }
+            // Note that node may be empty.  We should keep it in the list
+            // in case we dynamically update the tree and it becomes non empty
+            // (which is not supported yet)
             rrset->addAdditionalNode(node);
         }
     }

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. 41 3600 300 3600000 3600
+example.org. 3600 IN SOA	ns1.example.org. bugs.x.w.example.org. 52 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.
@@ -49,6 +49,14 @@ 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
 
+;; delegation, one of its NS name is at an empty non terminal.
+d.example.org. 	      	      3600 IN NS	ns.empty.example.org.
+d.example.org. 	      	      3600 IN NS	ns1.example.org.
+;; by adding these two we can create an empty RB node for
+;; ns.empty.example.org in the in-memory zone
+foo.ns.empty.example.org.     3600 IN A		192.0.2.13
+bar.ns.empty.example.org.     3600 IN A		192.0.2.14
+
 ;; CNAME
 alias.example.org. 3600 IN CNAME cname.example.org.
 

src/lib/datasrc/tests/zone_finder_context_unittest.cc

@@ -248,6 +248,19 @@ TEST_P(ZoneFinderContextTest, getAdditionalDelegationWithDname) {
                 result_sets_.begin(), result_sets_.end());
 }
 
+TEST_P(ZoneFinderContextTest, getAdditionalDelegationWithEmptyName) {
+    // One of NS names is at an empty non terminal node.  It shouldn't cause
+    // any disruption.
+    ZoneFinderContextPtr ctx = finder_->find(Name("www.d.example.org"),
+                                             RRType::A());
+    EXPECT_EQ(ZoneFinder::DELEGATION, ctx->code);
+
+    ctx->getAdditional(REQUESTED_BOTH, result_sets_);
+    rrsetsCheck("ns1.example.org. 3600 IN A 192.0.2.1\n"
+                "ns1.example.org. 3600 IN AAAA 2001:db8::1\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.