optimize fakeip cache

common/dns/fakedns/middleware.go

@@ -17,9 +17,7 @@ func withFakeIP(cache *cache.Cache, pool *fakeip.Pool) handler {
 	return func(w D.ResponseWriter, r *D.Msg) {
 		q := r.Question[0]
 
-		cacheItem := cache.Get("fakeip:" + q.String())
-		if cacheItem != nil {
-			msg := cacheItem.(*D.Msg).Copy()
+		if msg := getMsgFromCache(cache, "fakeip:"+q.String()); msg != nil {
 			setMsgTTL(msg, dnsFakeTTL)
 			msg.SetReply(r)
 			_ = w.WriteMsg(msg)

common/dns/fakedns/server.go

@@ -58,11 +58,11 @@ func (s *Server) StartServer(addr string) error {
 }
 
 func (s *Server) IPToHost(ip net.IP) (string, bool) {
-	c := s.c.Get(ip.String())
-	if c == nil {
+	msg := getMsgFromCache(s.c, ip.String())
+	if msg == nil {
 		return "", false
 	}
-	fqdn := c.(*D.Msg).Question[0].Name
+	fqdn := msg.Question[0].Name
 	return strings.TrimRight(fqdn, "."), true
 }
 
@@ -76,8 +76,8 @@ func NewServer(fakeIPRange, hostsLine string) (*Server, error) {
 		return nil, err
 	}
 
-	cacheItem := cache.New(cacheDuration)
 	hosts := lineToHosts(hostsLine)
+	cacheItem := cache.New(cacheDuration)
 	handler := newHandler(hosts, cacheItem, pool)
 
 	return &Server{

common/dns/fakedns/utils.go

@@ -13,11 +13,21 @@ func putMsgToCache(c *cache.Cache, key string, msg *D.Msg) {
 	if strings.HasPrefix(key, "fakeip:") {
 		ttl = time.Duration(dnsDefaultTTL) * time.Second
 	} else {
-		ttl = 6 * time.Duration(dnsDefaultTTL) * time.Second
+		ttl = 3 * time.Duration(dnsDefaultTTL) * time.Second
 	}
 	c.Put(key, msg.Copy(), ttl)
 }
 
+func getMsgFromCache(c *cache.Cache, key string) (msg *D.Msg) {
+	item := c.Get(key)
+	if item == nil {
+		return
+	}
+	msg = item.(*D.Msg).Copy()
+	putMsgToCache(c, key, msg)
+	return
+}
+
 func setMsgTTL(msg *D.Msg, ttl uint32) {
 	for _, answer := range msg.Answer {
 		answer.Header().Ttl = ttl