refactor: move quicdialing base functionality to netxlite (#406)

Part of https://github.com/ooni/probe/issues/1505

internal/netxlite/quic.go

@@ -0,0 +1,81 @@
+package netxlite
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"net"
+	"strconv"
+
+	"github.com/lucas-clemente/quic-go"
+)
+
+// QUICDialerContext is a dialer for QUIC using Context.
+type QUICContextDialer interface {
+	// DialContext establishes a new QUIC session using the given
+	// network and address. The tlsConfig and the quicConfig arguments
+	// MUST NOT be nil. Returns either the session or an error.
+	DialContext(ctx context.Context, network, address string,
+		tlsConfig *tls.Config, quicConfig *quic.Config) (quic.EarlySession, error)
+}
+
+// QUICDialer dials QUIC connections.
+type QUICDialer interface {
+	// DialContext establishes a new QUIC session using the given
+	// network and address. The tlsConfig and the quicConfig arguments
+	// MUST NOT be nil. Returns either the session or an error.
+	Dial(network, address string, tlsConfig *tls.Config,
+		quicConfig *quic.Config) (quic.EarlySession, error)
+}
+
+// QUICListener listens for QUIC connections.
+type QUICListener interface {
+	// Listen creates a new listening net.PacketConn.
+	Listen(addr *net.UDPAddr) (net.PacketConn, error)
+}
+
+// QUICListenerStdlib is a QUICListener using the standard library.
+type QUICListenerStdlib struct{}
+
+var _ QUICListener = &QUICListenerStdlib{}
+
+// Listen implements QUICListener.Listen.
+func (qls *QUICListenerStdlib) Listen(addr *net.UDPAddr) (net.PacketConn, error) {
+	return net.ListenUDP("udp", addr)
+}
+
+// QUICDialerQUICGo dials using the lucas-clemente/quic-go library.
+type QUICDialerQUICGo struct {
+	// QUICListener is the underlying QUICListener to use.
+	QUICListener QUICListener
+}
+
+var _ QUICContextDialer = &QUICDialerQUICGo{}
+
+// errInvalidIP indicates that a string is not a valid IP.
+var errInvalidIP = errors.New("netxlite: invalid IP")
+
+// DialContext implements ContextDialer.DialContext
+func (d *QUICDialerQUICGo) DialContext(ctx context.Context, network string,
+	address string, tlsConfig *tls.Config, quicConfig *quic.Config) (
+	quic.EarlySession, error) {
+	onlyhost, onlyport, err := net.SplitHostPort(address)
+	if err != nil {
+		return nil, err
+	}
+	port, err := strconv.Atoi(onlyport)
+	if err != nil {
+		return nil, err
+	}
+	ip := net.ParseIP(onlyhost)
+	if ip == nil {
+		return nil, errInvalidIP
+	}
+	pconn, err := d.QUICListener.Listen(&net.UDPAddr{IP: net.IPv4zero, Port: 0})
+	if err != nil {
+		return nil, err
+	}
+	udpAddr := &net.UDPAddr{IP: ip, Port: port, Zone: ""}
+	return quic.DialEarlyContext(
+		ctx, pconn, udpAddr, address, tlsConfig, quicConfig)
+}