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MINOR: DNS client query type failover management

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In the first version of the DNS resolver, HAProxy sends an ANY query
type and in case of issue fails over to the type pointed by the
directive in 'resolve-prefer'.
This patch allows the following new failover management:
1. default query type is still ANY
2. if response is truncated or in error because ANY is not supported by
   the server, then a fail over to a new query type is performed. The
   new query type is the one pointed by the directive 'resolve-prefer'.
3. if no response or still some errors occurs, then a query type fail over
   is performed to the remaining IP address family.
This commit is contained in:
Baptiste Assmann 2015-09-02 22:20:56 +02:00 committed by Willy Tarreau
parent 3440f0da2a
commit 90447582d7
1 changed files with 20 additions and 4 deletions
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24
src/server.c
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@ -2112,6 +2112,7 @@ int snr_resolution_error_cb(struct dns_resolution *resolution, int error_code)
{
struct server *s;
struct dns_resolvers *resolvers;
int qtype_any, res_preferred_afinet, res_preferred_afinet6;
/* shortcut to the server whose name is being resolved */
s = (struct server *)resolution->requester;
@ -2134,12 +2135,27 @@ int snr_resolution_error_cb(struct dns_resolution *resolution, int error_code)
case DNS_RESP_ANCOUNT_ZERO:
case DNS_RESP_TRUNCATED:
case DNS_RESP_ERROR:
if (resolution->query_type == DNS_RTYPE_ANY) {
qtype_any = resolution->query_type == DNS_RTYPE_ANY;
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) {
/* let's change the query type */
if (resolution->resolver_family_priority == AF_INET6)
resolution->query_type = DNS_RTYPE_AAAA;
else
if (qtype_any) {
/* fallback from ANY to resolution preference */
if (resolution->resolver_family_priority == AF_INET6)
resolution->query_type = DNS_RTYPE_AAAA;
else
resolution->query_type = DNS_RTYPE_A;
}
else 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;
}
dns_send_query(resolution);