stop the accept loop when listener is closed (#261)

* stop the loop when listener is closed

* simplify check

* set error after listener closed

* stop queuing new connections after listener closed

* simplify close condition check

layer4/listener.go

@@ -7,6 +7,7 @@ import (
 	"net"
 	"runtime"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"github.com/caddyserver/caddy/v2"
@@ -65,6 +66,7 @@ func (lw *ListenerWrapper) WrapListener(l net.Listener) net.Listener {
 		Listener:      l,
 		logger:        lw.logger,
 		compiledRoute: lw.compiledRoute,
+		done:          make(chan struct{}),
 		connChan:      connChan,
 		wg:            new(sync.WaitGroup),
 	}
@@ -114,25 +116,30 @@ type listener struct {
 	logger        *zap.Logger
 	compiledRoute Handler
 
+	closed atomic.Bool
+	done   chan struct{}
 	// closed when there is a non-recoverable error and all handle goroutines are done
 	connChan chan net.Conn
-	err      error
 
 	// count running handles
 	wg *sync.WaitGroup
 }
 
+func (l *listener) Close() error {
+	l.closed.Store(true)
+	return l.Listener.Close()
+}
+
 // loop accept connection from underlying listener and pipe the connection if there are any
 func (l *listener) loop() {
 	for {
 		conn, err := l.Listener.Accept()
 		var nerr net.Error
-		if errors.As(err, &nerr) && nerr.Temporary() {
+		if errors.As(err, &nerr) && nerr.Temporary() && !l.closed.Load() {
 			l.logger.Error("temporary error accepting connection", zap.Error(err))
 			continue
 		}
 		if err != nil {
-			l.err = err
 			break
 		}
 
@@ -145,6 +152,7 @@ func (l *listener) loop() {
 		l.wg.Wait()
 		close(l.connChan)
 	}()
+	close(l.done)
 	for conn := range l.connChan {
 		_ = conn.Close()
 	}
@@ -185,11 +193,15 @@ func (l *listener) handle(conn net.Conn) {
 }
 
 func (l *listener) Accept() (net.Conn, error) {
-	for conn := range l.connChan {
-		return conn, nil
+	select {
+	case conn, ok := <-l.connChan:
+		if ok {
+			return conn, nil
+		}
+		return nil, net.ErrClosed
+	case <-l.done:
+		return nil, net.ErrClosed
 	}
-	return nil, l.err
-
 }
 
 func (l *listener) pipeConnection(conn *Connection) error {