Refactor check_stale_header() function

The check_stale_header() function now updates header_prev directly
so it doesn't have to be handled in the outer loop; it's always
set to the correct value of the previous header in the chain.

lib/dns/qpcache.c

@@ -1196,9 +1196,12 @@ static bool
 check_stale_header(qpcnode_t *node, dns_slabheader_t *header,
 		   isc_rwlocktype_t *nlocktypep, isc_rwlock_t *nlock,
 		   qpc_search_t *search, dns_slabheader_t **header_prev) {
-	if (!ACTIVE(header, search->now)) {
+	if (ACTIVE(header, search->now)) {
-		dns_ttl_t stale = header->expire +
+		*header_prev = header;
-				  STALE_TTL(header, search->qpdb);
+		return false;
+	}
+
+	isc_stdtime_t stale = header->expire + STALE_TTL(header, search->qpdb);
 	/*
 	 * If this data is in the stale window keep it and if
 	 * DNS_DBFIND_STALEOK is not set we tell the caller to
@@ -1207,8 +1210,7 @@ check_stale_header(qpcnode_t *node, dns_slabheader_t *header,
 	 */
 
 	DNS_SLABHEADER_CLRATTR(header, DNS_SLABHEADERATTR_STALE_WINDOW);
-		if (!ZEROTTL(header) && KEEPSTALE(search->qpdb) &&
+	if (!ZEROTTL(header) && KEEPSTALE(search->qpdb) && stale > search->now)
-		    stale > search->now)
 	{
 		mark(header, DNS_SLABHEADERATTR_STALE);
 		*header_prev = header;
@@ -1219,11 +1221,9 @@ check_stale_header(qpcnode_t *node, dns_slabheader_t *header,
 		 * failed.
 		 */
 		if ((search->options & DNS_DBFIND_STALESTART) != 0) {
-				atomic_store_release(
+			atomic_store_release(&header->last_refresh_fail_ts,
-					&header->last_refresh_fail_ts,
 					     search->now);
-			} else if ((search->options &
+		} else if ((search->options & DNS_DBFIND_STALEENABLED) != 0 &&
-				    DNS_DBFIND_STALEENABLED) != 0 &&
 			   search->now <
 				   (atomic_load_acquire(
 					    &header->last_refresh_fail_ts) +
@@ -1235,13 +1235,10 @@ check_stale_header(qpcnode_t *node, dns_slabheader_t *header,
 			 * then don't skip this stale entry but use it
 			 * instead.
 			 */
-				DNS_SLABHEADER_SETATTR(
+			DNS_SLABHEADER_SETATTR(header,
-					header,
 					       DNS_SLABHEADERATTR_STALE_WINDOW);
 			return false;
-			} else if ((search->options &
+		} else if ((search->options & DNS_DBFIND_STALETIMEOUT) != 0) {
-				    DNS_DBFIND_STALETIMEOUT) != 0)
-			{
 			/*
 			 * We want stale RRset due to timeout, so we
 			 * don't skip it.
@@ -1285,8 +1282,6 @@ check_stale_header(qpcnode_t *node, dns_slabheader_t *header,
 		*header_prev = header;
 	}
 	return true;
-	}
-	return false;
 }
 
 static isc_result_t
@@ -1312,19 +1307,17 @@ check_zonecut(qpcnode_t *node, void *arg DNS__DB_FLARG) {
 		if (check_stale_header(node, header, &nlocktype, nlock, search,
 				       &header_prev))
 		{
-			/* Do nothing. */
+			continue;
-		} else if (header->type == dns_rdatatype_dname &&
+		}
-			   EXISTS(header) && !ANCIENT(header))
+
+		if (header->type == dns_rdatatype_dname && EXISTS(header) &&
+		    !ANCIENT(header))
 		{
 			dname_header = header;
-			header_prev = header;
 		} else if (header->type == DNS_SIGTYPE(dns_rdatatype_dname) &&
 			   EXISTS(header) && !ANCIENT(header))
 		{
 			sigdname_header = header;
-			header_prev = header;
-		} else {
-			header_prev = header;
 		}
 	}
 
@@ -1387,8 +1380,10 @@ find_deepest_zonecut(qpc_search_t *search, qpcnode_t *node,
 			if (check_stale_header(node, header, &nlocktype, nlock,
 					       search, &header_prev))
 			{
-				/* Do nothing. */
+				continue;
-			} else if (EXISTS(header) && !ANCIENT(header)) {
+			}
+
+			if (EXISTS(header) && !ANCIENT(header)) {
 				/*
 				 * We've found an extant rdataset.  See if
 				 * we're interested in it.
@@ -1406,9 +1401,6 @@ find_deepest_zonecut(qpc_search_t *search, qpcnode_t *node,
 						break;
 					}
 				}
-				header_prev = header;
-			} else {
-				header_prev = header;
 			}
 		}
 
@@ -1533,8 +1525,8 @@ find_coveringnsec(qpc_search_t *search, const dns_name_t *name,
 		{
 			continue;
 		}
+
 		if (!EXISTS(header) || DNS_TYPEPAIR_TYPE(header->type) == 0) {
-			header_prev = header;
 			continue;
 		}
 		if (header->type == matchtype) {
@@ -1548,7 +1540,6 @@ find_coveringnsec(qpc_search_t *search, const dns_name_t *name,
 				break;
 			}
 		}
-		header_prev = header;
 	}
 	if (found != NULL) {
 		bindrdataset(search->qpdb, node, found, search->now, nlocktype,
@@ -1724,8 +1715,10 @@ qpcache_find(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
 		if (check_stale_header(node, header, &nlocktype, nlock, &search,
 				       &header_prev))
 		{
-			/* Do nothing. */
+			continue;
-		} else if (EXISTS(header) && !ANCIENT(header)) {
+		}
+
+		if (EXISTS(header) && !ANCIENT(header)) {
 			/*
 			 * We now know that there is at least one active
 			 * non-stale rdataset at this node.
@@ -1811,9 +1804,6 @@ qpcache_find(dns_db_t *db, const dns_name_t *name, dns_dbversion_t *version,
 				 */
 				cnamesig = header;
 			}
-			header_prev = header;
-		} else {
-			header_prev = header;
 		}
 	}
 
@@ -2110,7 +2100,10 @@ qpcache_findzonecut(dns_db_t *db, const dns_name_t *name, unsigned int options,
 				 */
 				break;
 			}
-		} else if (EXISTS(header) && !ANCIENT(header)) {
+			continue;
+		}
+
+		if (EXISTS(header) && !ANCIENT(header)) {
 			if (header->type == dns_rdatatype_ns) {
 				found = header;
 				if (foundsig != NULL) {
@@ -2124,9 +2117,6 @@ qpcache_findzonecut(dns_db_t *db, const dns_name_t *name, unsigned int options,
 					break;
 				}
 			}
-			header_prev = header;
-		} else {
-			header_prev = header;
 		}
 	}