- 1.2.1 feature: negative caching for failed queries.

Queries that failed are cached for 5 seconds (NORR_TTL).
	  If the failure is local, like out of memory, it is not cached.
	- the TTL comparison for the cache used different comparisons,
	  causing many cache responses that used the iterator and validator
	  state machines unnecessarily.



git-svn-id: file:///svn/unbound/trunk@1432 be551aaa-1e26-0410-a405-d3ace91eadb9

daemon/worker.c

@@ -537,7 +537,7 @@ answer_from_cache(struct worker* worker, struct query_info* qinfo,
 	int secure;
 	int must_validate = !(flags&BIT_CD) && worker->env.need_to_validate;
 	/* see if it is possible */
-	if(rep->ttl <= timenow) {
+	if(rep->ttl < timenow) {
 		/* the rrsets may have been updated in the meantime.
 		 * we will refetch the message format from the
 		 * authoritative server 

doc/Changelog

@@ -1,3 +1,11 @@
+14 January 2009: Wouter
+	- 1.2.1 feature: negative caching for failed queries.
+	  Queries that failed are cached for 5 seconds (NORR_TTL).
+	  If the failure is local, like out of memory, it is not cached.
+	- the TTL comparison for the cache used different comparisons,
+	  causing many cache responses that used the iterator and validator
+	  state machines unnecessarily.
+
 13 January 2009: Wouter
 	- fixed bug in lameness marking, removed printouts.
 	- find NS rrset more cleanly for qtype NS.

iterator/iterator.c

@@ -229,6 +229,34 @@ error_response(struct module_qstate* qstate, int id, int rcode)
 	return 0;
 }
 
+/**
+ * Return an error to the client and cache the error code in the
+ * message cache (so per qname, qtype, qclass).
+ * @param qstate: our query state
+ * @param id: module id
+ * @param rcode: error code (DNS errcode).
+ * @return: 0 for use by caller, to make notation easy, like:
+ * 	return error_response(..). 
+ */
+static int
+error_response_cache(struct module_qstate* qstate, int id, int rcode)
+{
+	/* store in cache */
+	struct reply_info err;
+	memset(&err, 0, sizeof(err));
+	err.flags = BIT_QR | BIT_RA;
+	FLAGS_SET_RCODE(err.flags, rcode);
+	err.qdcount = 1;
+	err.ttl = NORR_TTL;
+	/* do not waste time trying to validate this servfail */
+	err.security = sec_status_indeterminate;
+	verbose(VERB_ALGO, "store error response in message cache");
+	if(!iter_dns_store(qstate->env, &qstate->qinfo, &err, 0)) {
+		log_err("error_response_cache: could not store error (nomem)");
+	}
+	return error_response(qstate, id, rcode);
+}
+
 /** check if prepend item is duplicate item */
 static int
 prepend_is_duplicate(struct ub_packed_rrset_key** sets, size_t to,
@@ -1308,7 +1336,7 @@ processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
 					"returning SERVFAIL");
 				/* fail -- no more targets, no more hope 
 				 * of targets, no hope of a response. */
-				return error_response(qstate, id,
+				return error_response_cache(qstate, id,
 					LDNS_RCODE_SERVFAIL);
 			}
 		}