commit f778bb46d6488629d24829e6c99b4566c7e46ce9
author Baptiste Assmann <bedis9@gmail.com> Wed Sep 09 00:54:38 2015 +0200
committer Willy Tarreau <w@1wt.eu> Thu Sep 10 15:46:03 2015 +0200
tree 2a396b9134e6e509ea9e2aa8399cba4e1ad01922
parent 0453a1dd4533530b444255b0cdb96cd6b95aec67

BUG/MINOR: DNS request retry counter used for retry only

There are two types of retries when performing a DNS resolution:
1. retry because of a timeout
2. retry of the full sequence of requests (query types failover)

Before this patch, the 'resolution->try' counter was incremented
after each send of a DNS request, which does not cover the 2 cases
above.
This patch fix this behavior.

src/checks.c

diff --git a/src/checks.c b/src/checks.c
index 3fb166b..eeff4ea 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -2215,13 +2215,14 @@
 	resolution->qid.key = query_id;
 	resolution->step = RSLV_STEP_RUNNING;
 	resolution->query_type = DNS_RTYPE_ANY;
-	resolution->try = 0;
+	resolution->try = resolvers->resolve_retries;
 	resolution->try_cname = 0;
 	resolution->nb_responses = 0;
 	resolution->resolver_family_priority = s->resolver_family_priority;
 	eb32_insert(&resolvers->query_ids, &resolution->qid);
 
 	dns_send_query(resolution);
+	resolution->try -= 1;
 
 	/* update wakeup date if this resolution is the only one in the FIFO list */
 	if (dns_check_resolution_queue(resolvers) == 1) {

src/dns.c

diff --git a/src/dns.c b/src/dns.c
index d002f1b..3439f7e 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -305,7 +305,6 @@
 	}
 
 	/* update resolution */
-	resolution->try += 1;
 	resolution->nb_responses = 0;
 	resolution->last_sent_packet = now_ms;
 
@@ -1103,7 +1102,7 @@
 		 * if current resolution has been tried too many times and finishes in timeout
 		 * we update its status and remove it from the list
 		 */
-		if (resolution->try >= resolvers->resolve_retries) {
+		if (resolution->try <= 0) {
 			/* clean up resolution information and remove from the list */
 			dns_reset_resolution(resolution);
 
@@ -1111,6 +1110,8 @@
 			resolution->requester_error_cb(resolution, DNS_RESP_TIMEOUT);
 		}
 
+		resolution->try -= 1;
+
 		/* check current resolution status */
 		if (resolution->step == RSLV_STEP_RUNNING) {
 			/* resend the DNS query */

src/server.c

diff --git a/src/server.c b/src/server.c
index 8bc3165..49ab68b 100644
--- a/src/server.c
+++ b/src/server.c
@@ -2132,7 +2132,8 @@
 			res_preferred_afinet = resolution->resolver_family_priority == AF_INET && resolution->query_type == DNS_RTYPE_A;
 			res_preferred_afinet6 = resolution->resolver_family_priority == AF_INET6 && resolution->query_type == DNS_RTYPE_AAAA;
 
-			if (qtype_any || res_preferred_afinet || res_preferred_afinet6) {
+			if ((qtype_any || res_preferred_afinet || res_preferred_afinet6)
+				       || (resolution->try > 0)) {
 				/* let's change the query type */
 				if (qtype_any) {
 					/* fallback from ANY to resolution preference */
@@ -2149,6 +2150,10 @@
 					/* fallback from A to AAAA */
 					resolution->query_type = DNS_RTYPE_AAAA;
 				}
+				else {
+					resolution->try -= 1;
+					resolution->query_type = DNS_RTYPE_ANY;
+				}
 
 				dns_send_query(resolution);