add negative caching result codes

lib/dns/include/dns/db.h

@@ -674,7 +674,7 @@ dns_db_find(dns_db_t *db, dns_name_t *name, dns_dbversion_t *version,
  *		DNS_R_NXDOMAIN			The desired name does not
  *						exist.
  *
- *		DNS_R_NXRDATASET		The desired name exists, but
+ *		DNS_R_NXRRSET			The desired name exists, but
  *						the desired type does not.
  *
  *		DNS_R_NXGLUE			The desired name exists, but
@@ -694,8 +694,17 @@ dns_db_find(dns_db_t *db, dns_name_t *name, dns_dbversion_t *version,
  *						use its nameserver(s) of last
  *						resort (e.g. root hints).
  *
- *		XXX There will be a result codes for negative cache entries
- *		    in the future.
+ *		DNS_R_NCACHENXDOMAIN		The desired name does not
+ *						exist.  'node' is bound to the
+ *						cache node with the desired
+ *						name, and 'rdataset' contains
+ *						the negative caching proof.
+ *
+ *		DNS_R_NCACHENXRRSET		The desired type does not
+ *						exist.  'node' is bound to the
+ *						cache node with the desired
+ *						name, and 'rdataset' contains
+ *						the negative caching proof.
  *
  *	Error results:
  *

lib/dns/include/dns/result.h

@@ -98,8 +98,10 @@ typedef isc_result_t dns_result_t;	/* XXXRTH for legacy use only */
 #define DNS_R_HINT			(ISC_RESULTCLASS_DNS + 48)
 #define DNS_R_DROP			(ISC_RESULTCLASS_DNS + 49)
 #define DNS_R_NOTLOADED			(ISC_RESULTCLASS_DNS + 50)
+#define DNS_R_NCACHENXDOMAIN		(ISC_RESULTCLASS_DNS + 51)
+#define DNS_R_NCACHENXRRSET		(ISC_RESULTCLASS_DNS + 52)
 
-#define DNS_R_NRESULTS			51	/* Number of results */
+#define DNS_R_NRESULTS			53	/* Number of results */
 
 /*
  * DNS wire format rcodes

lib/dns/result.c

@@ -78,6 +78,8 @@ static char *text[DNS_R_NRESULTS] = {
 	"hint",					/* 48 */
 	"drop",					/* 49 */
 	"zone not loaded",			/* 50 */
+	"ncache nxdomain",			/* 51 */
+	"ncache nxrrset",			/* 52 */
 };
 
 static char *rcode_text[DNS_R_NRCODERESULTS] = {