commit dd16182b4b3f107d5c26015622c1cb8c06619ad7
author Anders Fredlund <anders.fredlund@sonyericsson.com> Fri May 20 08:12:37 2011 +0200
committer Johan Redestig <johan.redestig@sonyericsson.com> Fri May 20 08:12:37 2011 +0200
tree f63aecec0f28085d3226e0b08e07934be9e12d74
parent a7a9dddb5dfe783d65fec4d3b0dee9f734345a29

Remove expired dns cache entries before removing oldest

A suggestion how to make a smarter delete function when the cache
is full. First look through the entire cache and remove all entries
which have expired. If none use the old solution and just remove
the last entry in the MRU list.

Change-Id: I5f997ab35290a55dc6e1ddf37d725759edf83d36

libc/netbsd/resolv/res_cache.c

diff --git a/libc/netbsd/resolv/res_cache.c b/libc/netbsd/resolv/res_cache.c
index e6302ed..58d60c9 100644
--- a/libc/netbsd/resolv/res_cache.c
+++ b/libc/netbsd/resolv/res_cache.c
@@ -1396,6 +1396,27 @@
     _cache_remove_p(cache, lookup);
 }
 
+/* Remove all expired entries from the hash table.
+ */
+static void _cache_remove_expired(Cache* cache) {
+    Entry* e;
+    time_t now = _time_now();
+
+    for (e = cache->mru_list.mru_next; e != &cache->mru_list;) {
+        // Entry is old, remove
+        if (now >= e->expires) {
+            Entry** lookup = _cache_lookup_p(cache, e);
+            if (*lookup == NULL) { /* should not happen */
+                XLOG("%s: ENTRY NOT IN HTABLE ?", __FUNCTION__);
+                return;
+            }
+            e = e->mru_next;
+            _cache_remove_p(cache, lookup);
+        } else {
+            e = e->mru_next;
+        }
+    }
+}
 
 ResolvCacheStatus
 _resolv_cache_lookup( struct resolv_cache*  cache,
@@ -1509,7 +1530,10 @@
     }
 
     if (cache->num_entries >= cache->max_entries) {
-        _cache_remove_oldest(cache);
+        _cache_remove_expired(cache);
+        if (cache->num_entries >= cache->max_entries) {
+            _cache_remove_oldest(cache);
+        }
         /* need to lookup again */
         lookup = _cache_lookup_p(cache, key);
         e      = *lookup;