MINOR: dns: introduce roundrobin into the internal cache (WIP)

This patch introduces a bit of roundrobin in the records stored in our
local cache.
Purpose is to allow some kind of distribution of the IPs found in a
response.
Note that distribution properly applies only when the IP used by many
requesters disappear and is replaced by an other one.

diff --git a/src/dns.c b/src/dns.c
index 0193f7396f77ff8e657fc5d5326294d78dbdeb79..cab1ad30bbe3b9d983e841dab313394dfdafe753 100644 (file)
--- a/src/dns.c
+++ b/src/dns.c
@@ -895,14 +895,14 @@ int dns_get_ip_from_response(struct dns_response_packet *dns_p,
                        *newip_sin_family = AF_INET;
                        if (currentip_found == 1)
                                return DNS_UPD_NO;
-                       return DNS_UPD_SRVIP_NOT_FOUND;
+                       goto return_DNS_UPD_SRVIP_NOT_FOUND;
                }
                else if (newip6) {
                        *newip = newip6;
                        *newip_sin_family = AF_INET6;
                        if (currentip_found == 1)
                                return DNS_UPD_NO;
-                       return DNS_UPD_SRVIP_NOT_FOUND;
+                       goto return_DNS_UPD_SRVIP_NOT_FOUND;
                }
        }
        /* case when the caller looks first for an IPv6 address */
@@ -912,14 +912,14 @@ int dns_get_ip_from_response(struct dns_response_packet *dns_p,
                        *newip_sin_family = AF_INET6;
                        if (currentip_found == 1)
                                return DNS_UPD_NO;
-                       return DNS_UPD_SRVIP_NOT_FOUND;
+                       goto return_DNS_UPD_SRVIP_NOT_FOUND;
                }
                else if (newip4) {
                        *newip = newip4;
                        *newip_sin_family = AF_INET;
                        if (currentip_found == 1)
                                return DNS_UPD_NO;
-                       return DNS_UPD_SRVIP_NOT_FOUND;
+                       goto return_DNS_UPD_SRVIP_NOT_FOUND;
                }
        }
        /* case when the caller have no preference (we prefer IPv6) */
@@ -929,19 +929,30 @@ int dns_get_ip_from_response(struct dns_response_packet *dns_p,
                        *newip_sin_family = AF_INET6;
                        if (currentip_found == 1)
                                return DNS_UPD_NO;
-                       return DNS_UPD_SRVIP_NOT_FOUND;
+                       goto return_DNS_UPD_SRVIP_NOT_FOUND;
                }
                else if (newip4) {
                        *newip = newip4;
                        *newip_sin_family = AF_INET;
                        if (currentip_found == 1)
                                return DNS_UPD_NO;
-                       return DNS_UPD_SRVIP_NOT_FOUND;
+                       goto return_DNS_UPD_SRVIP_NOT_FOUND;
                }
        }
 
        /* no reason why we should change the server's IP address */
        return DNS_UPD_NO;
+
+ return_DNS_UPD_SRVIP_NOT_FOUND:
+       list_for_each_entry(record, &dns_p->answer_list, list) {
+               /* move the first record to the end of the list, for internal round robin */
+               if (record) {
+                       LIST_DEL(&record->list);
+                       LIST_ADDQ(&dns_p->answer_list, &record->list);
+                       break;
+               }
+       }
+       return DNS_UPD_SRVIP_NOT_FOUND;
 }
 
 /*