- Clean up iterator/iterator.c::error_response_cache() and allow for

  better interaction with serve-expired, prefetch and cached error
  responses.

diff --git a/iterator/iterator.c b/iterator/iterator.c
index 2d4c43f581ac5feef98cad23aa0bab4ad1a1815c..5f2703f3cbb99251d1cecd19a57cad0af7152f59 100644 (file)
--- a/iterator/iterator.c
+++ b/iterator/iterator.c
@@ -302,95 +302,65 @@ error_response(struct module_qstate* qstate, int id, int rcode)
 static int
 error_response_cache(struct module_qstate* qstate, int id, int rcode)
 {
-       if(!qstate->no_cache_store) {
-               /* store in cache */
-               struct reply_info err;
-               if(qstate->prefetch_leeway > NORR_TTL) {
-                       verbose(VERB_ALGO, "error response for prefetch in cache");
-                       /* attempt to adjust the cache entry prefetch */
-                       if(dns_cache_prefetch_adjust(qstate->env, &qstate->qinfo,
-                               NORR_TTL, qstate->query_flags))
-                               return error_response(qstate, id, rcode);
-                       /* if that fails (not in cache), fall through to store err */
+       struct reply_info err;
+       struct msgreply_entry* msg;
+       if(qstate->no_cache_store) {
+               return error_response(qstate, id, rcode);
+       }
+       if(qstate->prefetch_leeway > NORR_TTL) {
+               verbose(VERB_ALGO, "error response for prefetch in cache");
+               /* attempt to adjust the cache entry prefetch */
+               if(dns_cache_prefetch_adjust(qstate->env, &qstate->qinfo,
+                       NORR_TTL, qstate->query_flags))
+                       return error_response(qstate, id, rcode);
+               /* if that fails (not in cache), fall through to store err */
+       }
+       if((msg=msg_cache_lookup(qstate->env,
+               qstate->qinfo.qname, qstate->qinfo.qname_len,
+               qstate->qinfo.qtype, qstate->qinfo.qclass,
+               qstate->query_flags, 0,
+               qstate->env->cfg->serve_expired_ttl_reset)) != NULL) {
+               struct reply_info* rep = (struct reply_info*)msg->entry.data;
+               if(qstate->env->cfg->serve_expired &&
+                       qstate->env->cfg->serve_expired_ttl_reset && rep &&
+                       *qstate->env->now + qstate->env->cfg->serve_expired_ttl
+                       > rep->serve_expired_ttl) {
+                       verbose(VERB_ALGO, "reset serve-expired-ttl for "
+                               "response in cache");
+                       rep->serve_expired_ttl = *qstate->env->now +
+                               qstate->env->cfg->serve_expired_ttl;
                }
-               if(qstate->env->cfg->serve_expired) {
-                       /* if serving expired contents, and such content is
-                        * already available, don't overwrite this servfail */
-                       struct msgreply_entry* msg;
-                       if((msg=msg_cache_lookup(qstate->env,
-                               qstate->qinfo.qname, qstate->qinfo.qname_len,
-                               qstate->qinfo.qtype, qstate->qinfo.qclass,
-                               qstate->query_flags, 0, 1)) != NULL) {
-                               struct reply_info* rep =
-                                       (struct reply_info*)msg->entry.data;
-                               if(qstate->env->cfg->serve_expired_ttl_reset) {
-                                       if(rep && *qstate->env->now +
-                                               qstate->env->cfg->serve_expired_ttl  >
-                                               rep->serve_expired_ttl) {
-                                               verbose(VERB_ALGO, "reset "
-                                                       "serve-expired-ttl for "
-                                                       "response in cache");
-                                               rep->serve_expired_ttl =
-                                                       *qstate->env->now +
-                                                       qstate->env->cfg->serve_expired_ttl;
-                                       }
-                               }
-                               /* if the expired record is an error response
-                                * refresh for another NORR_TTL */
-                               if(rep && *qstate->env->now > rep->ttl &&
-                                       (FLAGS_GET_RCODE(rep->flags) !=
-                                       LDNS_RCODE_NOERROR &&
-                                       FLAGS_GET_RCODE(rep->flags) !=
-                                       LDNS_RCODE_NXDOMAIN &&
-                                       FLAGS_GET_RCODE(rep->flags) !=
-                                       LDNS_RCODE_YXDOMAIN)) {
-                                       verbose(VERB_ALGO, "refresh TTL for "
-                                               "error response in cache");
-                                       rep->ttl = *qstate->env->now + NORR_TTL;
-                               }
-                               lock_rw_unlock(&msg->entry.lock);
-                               return error_response(qstate, id, rcode);
-                       }
-                       /* serving expired contents, but nothing is cached
-                        * at all, so the servfail cache entry is useful
-                        * (stops waste of time on this servfail NORR_TTL) */
-               } else {
-                       /* don't overwrite existing (non-expired) data in
-                        * cache with a servfail */
-                       struct msgreply_entry* msg;
-                       if((msg=msg_cache_lookup(qstate->env,
-                               qstate->qinfo.qname, qstate->qinfo.qname_len,
-                               qstate->qinfo.qtype, qstate->qinfo.qclass,
-                               qstate->query_flags, *qstate->env->now, 0))
-                               != NULL) {
-                               struct reply_info* rep = (struct reply_info*)
-                                       msg->entry.data;
-                               if(FLAGS_GET_RCODE(rep->flags) ==
-                                       LDNS_RCODE_NOERROR ||
-                                       FLAGS_GET_RCODE(rep->flags) ==
-                                       LDNS_RCODE_NXDOMAIN) {
-                                       /* we have a good entry,
-                                        * don't overwrite */
-                                       lock_rw_unlock(&msg->entry.lock);
-                                       return error_response(qstate, id, rcode);
-                               }
-                               lock_rw_unlock(&msg->entry.lock);
-                       }
-                       
+               if(rep && (FLAGS_GET_RCODE(rep->flags) ==
+                       LDNS_RCODE_NOERROR ||
+                       FLAGS_GET_RCODE(rep->flags) ==
+                       LDNS_RCODE_NXDOMAIN ||
+                       FLAGS_GET_RCODE(rep->flags) ==
+                       LDNS_RCODE_YXDOMAIN) &&
+                       (qstate->env->cfg->serve_expired ||
+                       *qstate->env->now <= rep->ttl)) {
+                       /* we have a good entry, don't overwrite */
+                       lock_rw_unlock(&msg->entry.lock);
+                       return error_response(qstate, id, rcode);
                }
-               memset(&err, 0, sizeof(err));
-               err.flags = (uint16_t)(BIT_QR | BIT_RA);
-               FLAGS_SET_RCODE(err.flags, rcode);
-               err.qdcount = 1;
-               err.ttl = NORR_TTL;
-               err.prefetch_ttl = PREFETCH_TTL_CALC(err.ttl);
-               err.serve_expired_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");
-               iter_dns_store(qstate->env, &qstate->qinfo, &err, 0, 0, 0, NULL,
-                       qstate->query_flags, qstate->qstarttime);
-       }
+               lock_rw_unlock(&msg->entry.lock);
+               /* nothing interesting is cached (already error response or
+                * expired good record when we don't serve expired), so this
+                * servfail cache entry is useful (stops waste of time on this
+                * servfail NORR_TTL) */
+       }
+       /* store in cache */
+       memset(&err, 0, sizeof(err));
+       err.flags = (uint16_t)(BIT_QR | BIT_RA);
+       FLAGS_SET_RCODE(err.flags, rcode);
+       err.qdcount = 1;
+       err.ttl = NORR_TTL;
+       err.prefetch_ttl = PREFETCH_TTL_CALC(err.ttl);
+       err.serve_expired_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");
+       iter_dns_store(qstate->env, &qstate->qinfo, &err, 0, 0, 0, NULL,
+               qstate->query_flags, qstate->qstarttime);
        return error_response(qstate, id, rcode);
 }