dns: update accessed time when answer found on caches

Also, remove process of moving the answer to the back of LRU when doing
upsert on caches, since this is already handled by get().

2 files changed, 4 insertions, 7 deletions

diff --git a/lib/dns/caches.go b/lib/dns/caches.go
index 8aa5440d..14af58d6 100644
--- a/lib/dns/caches.go
+++ b/lib/dns/caches.go
@@ -66,7 +66,7 @@ func newCaches(pruneDelay, pruneThreshold time.Duration) (ca *caches) {
 // it will return list of answer and nil answer.
 //
 // If answer exist on cache, their accessed time will be updated to current
-// time.
+// time and moved to back of LRU to prevent being pruned later.
 //
 func (c *caches) get(qname string, qtype, qclass uint16) (ans *answers, an *answer) {
 	c.Lock()
@@ -78,9 +78,10 @@ func (c *caches) get(qname string, qtype, qclass uint16) (ans *answers, an *answ
 		an, _ = ans.get(qtype, qclass)
 		if an != nil {
 			// Move the answer to the back of LRU if its not
-			// local.
+			// local and update its accessed time.
 			if an.receivedAt > 0 {
 				c.lru.MoveToBack(an.el)
+				an.accessedAt = time.Now().Unix()
 			}
 		}
 	}
@@ -165,10 +166,6 @@ func (c *caches) upsert(nu *answer) (inserted bool) {
 				// not local and its inserted to list.
 				nu.el = c.lru.PushBack(nu)
 			}
-		} else {
-			if nu.receivedAt > 0 {
-				c.lru.MoveToBack(an.el)
-			}
 		}
 	}
 
diff --git a/lib/dns/caches_test.go b/lib/dns/caches_test.go
index c228f5fd..d25d235e 100644
--- a/lib/dns/caches_test.go
+++ b/lib/dns/caches_test.go
@@ -259,7 +259,7 @@ func TestCachesUpsert(t *testing.T) {
 		desc:    "With update on answer",
 		nu:      an1Update,
 		expLen:  2,
-		expList: []*answer{an2, an1},
+		expList: []*answer{an1, an2},
 	}, {
 		desc:    "With update on answer (2)",
 		nu:      an2Update,