dnsproxy: Delete expired cache entries when they expire

The DNS cache has logic to never replace cached data if it already exists.
However, this only works well if we actually delete the data parts
of the cache entries as they expire.

This patch creates a cache_enforce_validity() function, which will
delete the data portion of cache entries if they are expired.
With this in place, consecutive lookups of the same name can get
cached again.

diff --git a/src/dnsproxy.c b/src/dnsproxy.c
index cdc5b11..4810c6e 100644 (file)
--- a/src/dnsproxy.c
+++ b/src/dnsproxy.c
@@ -422,23 +422,50 @@ static gboolean cache_check_is_valid(struct cache_data *data,
        return TRUE;
 }
 
+/*
+ * remove stale cached entries so that they can be refreshed
+ */
+static void cache_enforce_validity(struct cache_entry *entry)
+{
+       time_t current_time = time(0);
+
+       if (cache_check_is_valid(entry->ipv4, current_time) == FALSE
+                                                       && entry->ipv4) {
+               DBG("cache timeout \"%s\" type A", entry->key);
+               g_free(entry->ipv4->data);
+               g_free(entry->ipv4);
+               entry->ipv4 = NULL;
+
+       }
+
+       if (cache_check_is_valid(entry->ipv6, current_time) == FALSE
+                                                       && entry->ipv6) {
+               DBG("cache timeout \"%s\" type AAAA", entry->key);
+               g_free(entry->ipv6->data);
+               g_free(entry->ipv6);
+               entry->ipv6 = NULL;
+       }
+}
+
+
 static uint16_t cache_check_validity(char *question, uint16_t type,
-                               struct cache_data *ipv4,
-                               struct cache_data *ipv6)
+                               struct cache_entry *entry)
 {
        time_t current_time = time(0);
 
+       cache_enforce_validity(entry);
+
        switch (type) {
        case 1:         /* IPv4 */
-               if (cache_check_is_valid(ipv4, current_time) == FALSE) {
-                       DBG("cache %s \"%s\" type A",
-                               ipv4 ? "timeout" : "entry missing", question);
+               if (cache_check_is_valid(entry->ipv4, current_time) == FALSE) {
+                       DBG("cache %s \"%s\" type A", entry->ipv4 ?
+                                       "timeout" : "entry missing", question);
 
                        /*
                         * We do not remove cache entry if there is still
                         * valid IPv6 entry found in the cache.
                         */
-                       if (cache_check_is_valid(ipv6, current_time) == FALSE)
+                       if (cache_check_is_valid(entry->ipv6, current_time) == FALSE)
                                g_hash_table_remove(cache, question);
 
                        type = 0;
@@ -446,11 +473,11 @@ static uint16_t cache_check_validity(char *question, uint16_t type,
                break;
 
        case 28:        /* IPv6 */
-               if (cache_check_is_valid(ipv6, current_time) == FALSE) {
-                       DBG("cache %s \"%s\" type AAAA",
-                               ipv6 ? "timeout" : "entry missing", question);
+               if (cache_check_is_valid(entry->ipv6, current_time) == FALSE) {
+                       DBG("cache %s \"%s\" type AAAA", entry->ipv6 ?
+                                       "timeout" : "entry missing", question);
 
-                       if (cache_check_is_valid(ipv4, current_time) == FALSE)
+                       if (cache_check_is_valid(entry->ipv4, current_time) == FALSE)
                                g_hash_table_remove(cache, question);
 
                        type = 0;
@@ -481,7 +508,7 @@ static struct cache_entry *cache_check(gpointer request, int *qtype)
        if (entry == NULL)
                return NULL;
 
-       type = cache_check_validity(question, type, entry->ipv4, entry->ipv6);
+       type = cache_check_validity(question, type, entry);
        if (type == 0)
                return NULL;