From: Baptiste Assmann <bedis9@gmail.com>
Date: Wed, 6 Jan 2016 01:01:59 +0000 (+0100)
Subject: BUG/MINOR: dns: trigger a DNS query type change on resolution timeout
X-Git-Tag: v1.7-dev3~51
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=060e57301db98853eef91b344b6ace187b657190;p=thirdparty%2Fhaproxy.git

BUG/MINOR: dns: trigger a DNS query type change on resolution timeout

After Cedric Jeanneret reported an issue with HAProxy and DNS resolution
when multiple servers are in use, I saw that the implementation of DNS
query type update on resolution timeout was not implemented, even if it
is documented.

backport: 1.6 and above
---

diff --git a/src/dns.c b/src/dns.c
index 97f9f0ac0d..4603e21f70 100644
--- a/src/dns.c
+++ b/src/dns.c
@@ -1164,6 +1164,7 @@ struct task *dns_process_resolve(struct task *t)
 {
 	struct dns_resolvers *resolvers = t->context;
 	struct dns_resolution *resolution, *res_back;
+	int res_preferred_afinet, res_preferred_afinet6;
 
 	/* timeout occurs inevitably for the first element of the FIFO queue */
 	if (LIST_ISEMPTY(&resolvers->curr_resolution)) {
@@ -1193,6 +1194,19 @@ struct task *dns_process_resolve(struct task *t)
 
 		resolution->try -= 1;
 
+		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;
+
+		/* let's change the query type if needed */
+		if (res_preferred_afinet6) {
+			/* fallback from AAAA to A */
+			resolution->query_type = DNS_RTYPE_A;
+		}
+		else if (res_preferred_afinet) {
+			/* fallback from A to AAAA */
+			resolution->query_type = DNS_RTYPE_AAAA;
+		}
+
 		/* resend the DNS query */
 		dns_send_query(resolution);