[3362] Added additional commentary regarding use of NXRRSET in NameChangeRemove

src/bin/d2/nc_remove.cc

@@ -214,6 +214,8 @@ NameRemoveTransaction::removingFwdAddrsHandler() {
         switch (getDnsUpdateStatus()) {
         case DNSClient::SUCCESS: {
             // We successfully received a response packet from the server.
+            // The RCODE will be based on a value-dependent RRset search,
+            // see RFC 2136 section 3.2.3/3.2.4.
             const dns::Rcode& rcode = getDnsUpdateResponse()->getRcode();
             if ((rcode == dns::Rcode::NOERROR()) ||
                 (rcode == dns::Rcode::NXRRSET())) {
@@ -318,13 +320,14 @@ NameRemoveTransaction::removingFwdRRsHandler() {
         switch (getDnsUpdateStatus()) {
         case DNSClient::SUCCESS: {
             // We successfully received a response packet from the server.
+            // The RCODE will be based on a value-dependent RRset search,
+            // see RFC 2136 section 3.2.3/3.2.4.
             const dns::Rcode& rcode = getDnsUpdateResponse()->getRcode();
-            // A Rcode of NXRRSET means there are no RRs for the FQDN,
-            // which is fine.  We were asked to delete them, they are not there
-            // so all is well.
             if ((rcode == dns::Rcode::NOERROR()) ||
                 (rcode == dns::Rcode::NXRRSET())) {
-                // We were able to remove the forward mapping. Mark it as done.
+                // We were able to remove them or they were not there (
+                // Rcode of NXRRSET means there are no matching RRsets).
+                // In either case, we consider it success and mark it as done.
                 setForwardChangeCompleted(true);
 
                 // If request calls for reverse update then do that next,
@@ -470,11 +473,14 @@ NameRemoveTransaction::removingRevPtrsHandler() {
         switch (getDnsUpdateStatus()) {
         case DNSClient::SUCCESS: {
             // We successfully received a response packet from the server.
+            // The RCODE will be based on a value-dependent RRset search,
+            // see RFC 2136 section 3.2.3/3.2.4.
             const dns::Rcode& rcode = getDnsUpdateResponse()->getRcode();
             if ((rcode == dns::Rcode::NOERROR()) ||
                 (rcode == dns::Rcode::NXRRSET())) {
-                // We were able to update the reverse mapping. Mark it as done.
-                // We are also treating NXRRSET as success.
+                // We were able to remove the reverse mapping or they were
+                // not there (Rcode of NXRRSET means there are no matching
+                // RRsets). In either case, mark it as done.
                 setReverseChangeCompleted(true);
                 transition(PROCESS_TRANS_OK_ST, UPDATE_OK_EVT);
             } else {