[1580] Add new comments to NSEC3 proves for NXDOMAIN,and fix the

construction of wildcard domain name.

src/bin/auth/query.cc

@@ -171,48 +171,52 @@ Query::addNXDOMAINProof(ZoneFinder& finder, ConstRRsetPtr nsec) {
 // is broken, 'nsec3' should be a valid NSEC3 RR.  Likewise, the call to
 // findNSEC3() in this method should result an FindNSEC3Result that proves
 // the Closest Encloser Proof and non existent of matching wildcard.
-// If these assumptions aren't met due to a buggy data source implementation
-// or a broken zone, we'll let underlying libdns++ modules throw an exception,
-// which would result in either an SERVFAIL response or just ignoring the
-// query.  We at least prevent a complete crash due to such broken behavior.
+// Firstly, the call to findNSEC3() set the recursive to true in order to
+// get the an NSEC3 RR that matches the closest (provable) encloser and 
+// an NSEC3 RR that covers the "next closer" name to the closest encloser.
+// This corresponds to Section 7.2.1 of RFC 5155.
+// Then,construct the wildcard domain, call to findNSEC3() set the recursive
+// to false to get the prove that the wildcard that could have matched QNAME
+// also does not exist.
 void
 Query::addNSEC3NXDOMAINProof(ZoneFinder& finder) {
     // Firstly get the NSEC3 proves for Closest Encloser Proof
+    // See section 7.2.1 of RFC 5155.
     const ZoneFinder::FindNSEC3Result fresult1 = finder.findNSEC3(qname_,
                                                                   true);
-    if (fresult1.closest_proof->getRdataCount() == 0) {
-        isc_throw(BadNSEC3,  "NSEC3 for NXDOMAIN proving that matches the "
+    if (!fresult1.closest_proof) {
+        isc_throw(BadNSEC3,  "NSEC3 RR for NXDOMAIN proving that matches the "
                   "closest encloser is empty.");
     }
     // Add the NSEC3 proving that matches the closest (provable) encloser.
     response_.addRRset(Message::SECTION_AUTHORITY,
                        boost::const_pointer_cast<AbstractRRset>(
-                           fresult1.closest_proof),
+                       fresult1.closest_proof),
                        dnssec_);
-    // Add the NSEC3 RR that covers the "next closer" name to the closest
-    // encloser
-    if (fresult1.next_proof) {
-        response_.addRRset(Message::SECTION_AUTHORITY,
-                           boost::const_pointer_cast<AbstractRRset>(
-                               fresult1.next_proof),
-                           dnssec_);
+    if (!fresult1.next_proof) {
+        isc_throw(BadNSEC3,  "NSEC3 RR for NXDOMAIN proving that covers the "
+                  "next closer to the closest encloser is empty.");
     }
+    // Add the NSEC3 RR that covers the "next closer" name to the closest
+    // encloser.
+    response_.addRRset(Message::SECTION_AUTHORITY,
+                       boost::const_pointer_cast<AbstractRRset>(
+                       fresult1.next_proof),
+                       dnssec_);
     // Next, identify the best possible wildcard name that would match
     // the query name.  It's the longer common suffix with the qname
-    // between the owner or the next domain of the NSEC that proves NXDOMAIN,
-    // prefixed by the wildcard label, "*".
-    const Name wildname(Name("*").concatenate(qname_.split(1)));
+    // between the owner and the 'matched' domain of the NSEC3 that
+    // proves NXDOMAIN,prefixed by the wildcard label, "*".
+    const Name wildname(Name("*").concatenate(
+               qname_.split(qname_.getLabelCount() - fresult1.closest_labels)));
     const ZoneFinder::FindNSEC3Result fresult2 =
         finder.findNSEC3(wildname, false);
-    if (fresult2.closest_proof->getRdataCount() == 0) {
+    if (!fresult2.closest_proof) {
             isc_throw(BadNSEC3, "NSEC3 for NXDOMAIN covering the wildcard "
                       "RR at the closest encloser is empty.");
     }
-    // Add the (no-) wildcard proof only when it's different from the NSEC
-    // that proves NXDOMAIN; sometimes they can be the same.
-    // Note: name comparison is relatively expensive.  When we are at the
-    // stage of performance optimization, we should consider optimizing this
-    // for some optimized data source implementations.
+    // Add the wildcard proof only when it's different from the NSEC3 RR
+    // that covers the "next closer" name to the closest encloser.
     if (fresult1.next_proof->getName() != fresult2.closest_proof->getName()) {
         response_.addRRset(Message::SECTION_AUTHORITY,
                            boost::const_pointer_cast<AbstractRRset>(