upstream: added ipv6 dns result priorization option

Signed-off-by: nvima <[email protected]>

src/flb_upstream.c

@@ -53,6 +53,12 @@ struct flb_config_map upstream_net[] = {
      "Prioritize IPv4 DNS results when trying to establish a connection"
     },
 
+    {
+     FLB_CONFIG_MAP_BOOL, "net.dns.prefer_ipv6", "false",
+     0, FLB_TRUE, offsetof(struct flb_net_setup, dns_prefer_ipv6),
+     "Prioritize IPv6 DNS results when trying to establish a connection"
+    },
+
     {
      FLB_CONFIG_MAP_BOOL, "net.keepalive", "true",
      0, FLB_TRUE, offsetof(struct flb_net_setup, keepalive),
@@ -165,6 +171,12 @@ struct mk_list *flb_upstream_get_config_map(struct flb_config *config)
                 upstream_net[config_index].def_value = "true";
             }
         }
+        if (config->dns_prefer_ipv6) {
+            if (strcmp(upstream_net[config_index].name,
+                       "net.dns.prefer_ipv6") == 0) {
+                upstream_net[config_index].def_value = "true";
+            }
+        }
     }
 
     config_map = flb_config_map_create(config, upstream_net);