optimize some code (#3801)

pkg/util/net/dns.go

@@ -0,0 +1,33 @@
+// Copyright 2023 The frp Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package net
+
+import (
+	"context"
+	"net"
+)
+
+func SetDefaultDNSAddress(dnsAddress string) {
+	if _, _, err := net.SplitHostPort(dnsAddress); err != nil {
+		dnsAddress = net.JoinHostPort(dnsAddress, "53")
+	}
+	// Change default dns server
+	net.DefaultResolver = &net.Resolver{
+		PreferGo: true,
+		Dial: func(ctx context.Context, network, address string) (net.Conn, error) {
+			return net.Dial("udp", dnsAddress)
+		},
+	}
+}

pkg/util/net/listener.go

@@ -52,7 +52,10 @@ func (l *InternalListener) PutConn(conn net.Conn) error {
 			conn.Close()
 		}
 	})
-	return err
+	if err != nil {
+		return fmt.Errorf("put conn error: listener is closed")
+	}
+	return nil
 }
 
 func (l *InternalListener) Close() error {