Bug fix and refine

transport/internet/tls/ech.go

@@ -80,12 +80,17 @@ type ECHConfigCache struct {
 	echConfig atomic.Pointer[[]byte]
 	expire    atomic.Pointer[time.Time]
 	// updateLock is not for preventing concurrent read/write, but for preventing concurrent update
-	updateLock sync.Mutex
+	UpdateLock sync.Mutex
 }
 
-func (c *ECHConfigCache) update(domain string, server string) ([]byte, error) {
-	c.updateLock.Lock()
-	defer c.updateLock.Unlock()
+// Update updates the ECH config for given domain and server.
+// this method is concurrent safe, only one update request will be sent, others get the cache.
+// if isLockedUpdate is true, it means pass the lock to this function, it will release the lock after update.
+func (c *ECHConfigCache) Update(domain string, server string, isLockedUpdate bool) ([]byte, error) {
+	if !isLockedUpdate {
+	c.UpdateLock.Lock()
+	}
+	defer c.UpdateLock.Unlock()
 	// Double check cache after acquiring lock
 	if c.expire.Load().After(time.Now()) {
 		errors.LogDebug(context.Background(), "Cache hit for domain after double check: ", domain)
@@ -132,12 +137,13 @@ func QueryRecord(domain string, server string) ([]byte, error) {
 
 	// If expire is zero value, it means we are in initial state, wait for the query to finish
 	// otherwise return old value immediately and update in a goroutine
-	if *echConfigCache.expire.Load() == (time.Time{}) {
-		return echConfigCache.update(domain, server)
+	// but if the cache is too old, wait for update
+	if *echConfigCache.expire.Load() == (time.Time{}) || echConfigCache.expire.Load().Add(time.Hour*6).Before(time.Now()) {
+		return echConfigCache.Update(domain, server, false)
 	} else {
 		// If someone already acquired the lock, it means it is updating, do not start another update goroutine
-		if echConfigCache.updateLock.TryLock() {
-			go echConfigCache.update(domain, server)
+		if echConfigCache.UpdateLock.TryLock() {
+			go echConfigCache.Update(domain, server, true)
 		}
 		return *echConfigCache.echConfig.Load(), nil
 	}
@@ -210,7 +216,12 @@ func dnsQuery(server string, domain string) ([]byte, uint32, error) {
 		defer cancel()
 		// use xray's internet.DialSystem as mentioned above
 		conn, err := internet.DialSystem(dnsTimeoutCtx, dest, nil)
-		defer conn.Close()
+		defer func() {
+			err := conn.Close()
+			if err != nil {
+				errors.LogDebug(context.Background(), "Failed to close connection: ", err)
+			}
+		}()
 		if err != nil {
 			return []byte{}, 0, err
 		}