backport r3782, fixing qname-minimisation with various broken DNS servers,

often found at CDNs.

- Use QTYPE=A for QNAME minimisation.
- Keep track of number of time-outs when performing QNAME minimisation.
  Stop minimising when number of time-outs for a QNAME/QTYPE pair is
  more than three.

1 files changed, 18 insertions, 8 deletions

diff --git a/usr.sbin/unbound/iterator/iterator.c b/usr.sbin/unbound/iterator/iterator.c
index 139cae4bae0..749fba6af63 100644
--- a/usr.sbin/unbound/iterator/iterator.c
+++ b/usr.sbin/unbound/iterator/iterator.c
@@ -148,6 +148,7 @@ iter_new(struct module_qstate* qstate, int id)
 	iq->qchase = qstate->qinfo;
 	outbound_list_init(&iq->outlist);
 	iq->minimise_count = 0;
+	iq->minimise_timeout_count = 0;
 	if (qstate->env->cfg->qname_minimisation)
 		iq->minimisation_state = INIT_MINIMISE_STATE;
 	else
@@ -2008,7 +2009,7 @@ processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
 				iq->dp->name))) {
 			iq->qinfo_out.qname = iq->dp->name;
 			iq->qinfo_out.qname_len = iq->dp->namelen;
-			iq->qinfo_out.qtype = LDNS_RR_TYPE_NS;
+			iq->qinfo_out.qtype = LDNS_RR_TYPE_A;
 			iq->qinfo_out.qclass = iq->qchase.qclass;
 			iq->minimise_count = 0;
 		}
@@ -2023,6 +2024,7 @@ processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
 		iq->qinfo_out.qname = iq->qchase.qname;
 		iq->qinfo_out.qname_len = iq->qchase.qname_len;
 		iq->minimise_count++;
+		iq->minimise_timeout_count = 0;
 
 		/* Limit number of iterations for QNAMEs with more
 		 * than MAX_MINIMISE_COUNT labels. Send first MINIMISE_ONE_LAB
@@ -2059,8 +2061,9 @@ processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
 				&iq->qinfo_out.qname_len, 
 				labdiff-1);
 		}
-		if(labdiff < 1 || 
-			(labdiff < 2 && iq->qchase.qtype == LDNS_RR_TYPE_DS))
+		if(labdiff < 1 || (labdiff < 2 
+			&& (iq->qchase.qtype == LDNS_RR_TYPE_DS
+			|| iq->qchase.qtype == LDNS_RR_TYPE_A)))
 			/* Stop minimising this query, resolve "as usual" */
 			iq->minimisation_state = DONOT_MINIMISE_STATE;
 		else {
@@ -2077,10 +2080,17 @@ processQueryTargets(struct module_qstate* qstate, struct iter_qstate* iq,
 				return 1;
 		}
 	}
-	if(iq->minimisation_state == SKIP_MINIMISE_STATE)
-		/* Do not increment qname, continue incrementing next 
-		 * iteration */
-		iq->minimisation_state = MINIMISE_STATE;
+	if(iq->minimisation_state == SKIP_MINIMISE_STATE) {
+		iq->minimise_timeout_count++;
+		if(iq->minimise_timeout_count < MAX_MINIMISE_TIMEOUT_COUNT)
+			/* Do not increment qname, continue incrementing next 
+			 * iteration */
+			iq->minimisation_state = MINIMISE_STATE;
+		else
+			/* Too many time-outs detected for this QNAME and QTYPE.
+			 * We give up, disable QNAME minimisation. */
+			iq->minimisation_state = DONOT_MINIMISE_STATE;
+	}
 	if(iq->minimisation_state == DONOT_MINIMISE_STATE)
 		iq->qinfo_out = iq->qchase;
 
@@ -2158,7 +2168,7 @@ processQueryResponse(struct module_qstate* qstate, struct iter_qstate* iq,
 	iq->num_current_queries--;
 	if(iq->response == NULL) {
 		/* Don't increment qname when QNAME minimisation is enabled */
-		if (qstate->env->cfg->qname_minimisation)
+		if(qstate->env->cfg->qname_minimisation)
 			iq->minimisation_state = SKIP_MINIMISE_STATE;
 		iq->chase_to_rd = 0;
 		iq->dnssec_lame_query = 0;