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.

(cherry picked from commit 86a80e723fc7b6bdd87174f4a48aa702dbe17c5a)

diff --git a/lib/ns/query.c b/lib/ns/query.c
index 643debb7a25525d0cc760026423461932bc7674e..43638a35eb8034e1511acb772e3c988019c43f31 100644 (file)
--- a/lib/ns/query.c
+++ b/lib/ns/query.c
@@ -5837,6 +5837,13 @@ 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
@@ -5983,6 +5990,7 @@ query_lookup(query_ctx_t *qctx) {
                qctx->rdataset->attributes |= DNS_RDATASETATTR_STALE_ADDED;
        }
 
+gotanswer:
        result = query_gotanswer(qctx, result);
 
 cleanup: