prevent close of closed

proxy/dns/dns.go

@@ -5,6 +5,7 @@ import (
 	go_errors "errors"
 	"io"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/xtls/xray-core/common"
@@ -369,6 +370,10 @@ type outboundConn struct {
 	access sync.Mutex
 	dialer func() (stat.Connection, error)
 
+	closeOnce sync.Once
+	dialOnce  sync.Once
+	closed    atomic.Bool
+
 	conn      net.Conn
 	connReady chan struct{}
 }
@@ -378,24 +383,28 @@ func (c *outboundConn) dial() error {
 	if err != nil {
 		return err
 	}
+	if c.closed.Load() {
+		return errors.New("connection closed during dial")
+	}
 	c.conn = conn
 	c.connReady <- struct{}{}
 	return nil
 }
 
 func (c *outboundConn) Write(b []byte) (int, error) {
+	c.dialOnce.Do(func() {
+		c.dial()
+	})
 	c.access.Lock()
-
-	if c.conn == nil {
-		if err := c.dial(); err != nil {
-			c.access.Unlock()
-			errors.LogWarningInner(context.Background(), err, "failed to dial outbound connection")
-			return len(b), nil
-		}
-	}
-
+	conn := c.conn
 	c.access.Unlock()
-
+	if conn == nil {
+		_, open := <-c.connReady
+		if !open {
+			return 0, io.EOF
+		}
+		conn = c.conn
+	}
 	return c.conn.Write(b)
 }
 
@@ -417,11 +426,14 @@ func (c *outboundConn) Read(b []byte) (int, error) {
 }
 
 func (c *outboundConn) Close() error {
-	c.access.Lock()
-	close(c.connReady)
-	if c.conn != nil {
-		c.conn.Close()
-	}
-	c.access.Unlock()
+	c.closeOnce.Do(func() {
+		c.access.Lock()
+		c.closed.Store(true)
+		close(c.connReady)
+		if c.conn != nil {
+			c.conn.Close()
+		}
+		c.access.Unlock()
+	})
 	return nil
 }