Consider non-stale data when in serve-stale mode

With 'stale-answer-enable yes;' and 'stale-answer-client-timeout off;',
consider the following situation:

A CNAME record and its target record are in the cache, then the CNAME
record expires, but the target record is still valid.

When a new query for the CNAME record arrives, and the query fails,
the stale record is used, and then the query "restarts" to follow
the CNAME target. The problem is that the query's multiple stale
options (like DNS_DBFIND_STALEOK) are not reset, so 'query_lookup()'
treats the restarted query as a lookup following a failed lookup,
and returns a SERVFAIL answer when there is no stale data found in the
cache, even if there is valid non-stale data there available.

With this change, query_lookup() now considers non-stale data in the
cache in the first place, and returns it if it is available.

diff --git a/lib/ns/query.c b/lib/ns/query.c
index ee89b62a17be8fb1b12958e33dbfab3de5ebaa41..0c3ee43e1a016b1188548ab0cd2db47dab4bc84f 100644 (file)
--- a/lib/ns/query.c
+++ b/lib/ns/query.c
@@ -5960,6 +5960,13 @@ query_lookup(query_ctx_t *qctx) {
                dns_cache_updatestats(qctx->view->cache, result);
        }
 
+       if (dns_rdataset_isassociated(qctx->rdataset) &&
+           dns_rdataset_count(qctx->rdataset) > 0 && !STALE(qctx->rdataset))
+       {
+               /* Found non-stale usable rdataset. */
+               goto gotanswer;
+       }
+
        /*
         * If DNS_DBFIND_STALEOK is set this means we are dealing with a
         * lookup following a failed lookup and it is okay to serve a stale
@@ -6131,6 +6138,7 @@ query_lookup(query_ctx_t *qctx) {
                qctx->rdataset->attributes |= DNS_RDATASETATTR_STALE_ADDED;
        }
 
+gotanswer:
        result = query_gotanswer(qctx, result);
 
 cleanup: