upstream: use mutex. imp logging

upstream/quic.go

@@ -81,7 +81,7 @@ type dnsOverQUIC struct {
 	quicConfigMu sync.Mutex
 
 	// connMu protects conn.
-	connMu sync.RWMutex
+	connMu sync.Mutex
 
 	// bytesPoolGuard protects bytesPool.
 	bytesPoolMu sync.Mutex
@@ -214,7 +214,7 @@ func (p *dnsOverQUIC) exchangeQUIC(req *dns.Msg) (resp *dns.Msg, err error) {
 	var stream quic.Stream
 	stream, err = p.openStream(conn)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("opening stream: %w", err)
 	}
 
 	_, err = stream.Write(proxyutil.AddPrefix(buf))
@@ -226,7 +226,10 @@ func (p *dnsOverQUIC) exchangeQUIC(req *dns.Msg) (resp *dns.Msg, err error) {
 	// indicate through the STREAM FIN mechanism that no further data will
 	// be sent on that stream. Note, that stream.Close() closes the
 	// write-direction of the stream, but does not prevent reading from it.
-	_ = stream.Close()
+	err = stream.Close()
+	if err != nil {
+		log.Debug("closing quic stream: %s", err)
+	}
 
 	return p.readMsg(stream)
 }
@@ -259,29 +262,30 @@ func (p *dnsOverQUIC) getBytesPool() (pool *sync.Pool) {
 // argument controls whether we should try to use the existing cached
 // connection.  If it is false, we will forcibly create a new connection and
 // close the existing one if needed.
-func (p *dnsOverQUIC) getConnection(useCached bool) (quic.Connection, error) {
+func (p *dnsOverQUIC) getConnection(useCached bool) (c quic.Connection, err error) {
 	var conn quic.Connection
-	p.connMu.RLock()
-	conn = p.conn
-	if conn != nil && useCached {
-		p.connMu.RUnlock()
-
-		return conn, nil
-	}
-	if conn != nil {
-		// we're recreating the connection, let's create a new one.
-		_ = conn.CloseWithError(QUICCodeNoError, "")
-	}
-	p.connMu.RUnlock()
 
 	p.connMu.Lock()
 	defer p.connMu.Unlock()
 
-	var err error
+	conn = p.conn
+	if conn != nil {
+		if useCached {
+			return conn, nil
+		}
+
+		// We're recreating the connection, let's create a new one.
+		err = conn.CloseWithError(QUICCodeNoError, "")
+		if err != nil {
+			log.Debug("closing stale connection: %s", err)
+		}
+	}
+
 	conn, err = p.openConnection()
 	if err != nil {
 		return nil, err
 	}
+
 	p.conn = conn
 
 	return conn, nil
@@ -320,7 +324,9 @@ func (p *dnsOverQUIC) openStream(conn quic.Connection) (quic.Stream, error) {
 	defer cancel()
 
 	stream, err := conn.OpenStreamSync(ctx)
-	if err == nil {
+	if err != nil {
+		log.Debug("opening quic stream: %s", err)
+	} else {
 		return stream, nil
 	}
 
@@ -330,30 +336,35 @@ func (p *dnsOverQUIC) openStream(conn quic.Connection) (quic.Stream, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	// Open a new stream.
 	return newConn.OpenStreamSync(ctx)
 }
 
-// openConnection opens a new QUIC connection.
+// openConnection dials a new QUIC connection.
 func (p *dnsOverQUIC) openConnection() (conn quic.Connection, err error) {
 	dialContext, err := p.getDialer()
 	if err != nil {
-		return nil, fmt.Errorf("failed to bootstrap QUIC connection: %w", err)
+		return nil, fmt.Errorf("bootstrapping %s: %w", p.addr, err)
 	}
 
 	// we're using bootstrapped address instead of what's passed to the function
 	// it does not create an actual connection, but it helps us determine
 	// what IP is actually reachable (when there're v4/v6 addresses).
 	rawConn, err := dialContext(context.Background(), "udp", "")
 	if err != nil {
-		return nil, fmt.Errorf("failed to open a QUIC connection: %w", err)
+		return nil, fmt.Errorf("dialing raw connection to %s: %w", p.addr, err)
+	}
+
+	// It's never actually used.
+	err = rawConn.Close()
+	if err != nil {
+		log.Debug("closing raw connection for %s: %s", p.addr, err)
 	}
-	// It's never actually used
-	_ = rawConn.Close()
 
 	udpConn, ok := rawConn.(*net.UDPConn)
 	if !ok {
-		return nil, fmt.Errorf("failed to open connection to %s", p.addr)
+		return nil, fmt.Errorf("unexpected type %T of connection; should be %T", rawConn, udpConn)
 	}
 
 	addr := udpConn.RemoteAddr().String()
@@ -363,7 +374,7 @@ func (p *dnsOverQUIC) openConnection() (conn quic.Connection, err error) {
 
 	conn, err = quic.DialAddrEarly(ctx, addr, p.tlsConf.Clone(), p.getQUICConfig())
 	if err != nil {
-		return nil, fmt.Errorf("opening quic connection to %s: %w", p.addr, err)
+		return nil, fmt.Errorf("dialing quic connection to %s: %w", p.addr, err)
 	}
 
 	return conn, nil