lib/connections: Add QUIC protocol support (fixes #5377) (#5737)

lib/connections/quic_dial.go

@@ -0,0 +1,128 @@
+// Copyright (C) 2019 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+// +build go1.12
+
+package connections
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+	"net/url"
+	"time"
+
+	"github.com/lucas-clemente/quic-go"
+
+	"github.com/syncthing/syncthing/lib/config"
+	"github.com/syncthing/syncthing/lib/connections/registry"
+	"github.com/syncthing/syncthing/lib/protocol"
+)
+
+const quicPriority = 100
+
+func init() {
+	factory := &quicDialerFactory{}
+	for _, scheme := range []string{"quic", "quic4", "quic6"} {
+		dialers[scheme] = factory
+	}
+}
+
+type quicDialer struct {
+	cfg    config.Wrapper
+	tlsCfg *tls.Config
+}
+
+func (d *quicDialer) Dial(id protocol.DeviceID, uri *url.URL) (internalConn, error) {
+	uri = fixupPort(uri, config.DefaultQUICPort)
+
+	addr, err := net.ResolveUDPAddr("udp", uri.Host)
+	if err != nil {
+		return internalConn{}, err
+	}
+
+	var conn net.PacketConn
+	closeConn := false
+	if listenConn := registry.Get(uri.Scheme, packetConnLess); listenConn != nil {
+		conn = listenConn.(net.PacketConn)
+	} else {
+		if packetConn, err := net.ListenPacket("udp", ":0"); err != nil {
+			return internalConn{}, err
+		} else {
+			closeConn = true
+			conn = packetConn
+		}
+	}
+
+	ctx, _ := context.WithTimeout(context.Background(), 10*time.Second)
+	session, err := quic.DialContext(ctx, conn, addr, uri.Host, d.tlsCfg, quicConfig)
+	if err != nil {
+		if closeConn {
+			_ = conn.Close()
+		}
+		return internalConn{}, err
+	}
+
+	// OpenStreamSync is blocks, but we want to make sure the connection is usable
+	// before we start killing off other connections, so do the dance.
+	ok := make(chan struct{})
+	go func() {
+		select {
+		case <-ok:
+			return
+		case <-time.After(10 * time.Second):
+			l.Debugln("timed out waiting for OpenStream on", session.RemoteAddr())
+			// This will unblock OpenStreamSync
+			_ = session.Close()
+		}
+	}()
+
+	stream, err := session.OpenStreamSync()
+	close(ok)
+	if err != nil {
+		// It's ok to close these, this does not close the underlying packetConn.
+		_ = session.Close()
+		if closeConn {
+			_ = conn.Close()
+		}
+		return internalConn{}, err
+	}
+
+	return internalConn{&quicTlsConn{session, stream}, connTypeQUICClient, quicPriority}, nil
+}
+
+func (d *quicDialer) RedialFrequency() time.Duration {
+	return time.Duration(d.cfg.Options().ReconnectIntervalS) * time.Second
+}
+
+type quicDialerFactory struct {
+	cfg    config.Wrapper
+	tlsCfg *tls.Config
+}
+
+func (quicDialerFactory) New(cfg config.Wrapper, tlsCfg *tls.Config) genericDialer {
+	return &quicDialer{
+		cfg:    cfg,
+		tlsCfg: tlsCfg,
+	}
+}
+
+func (quicDialerFactory) Priority() int {
+	return quicPriority
+}
+
+func (quicDialerFactory) AlwaysWAN() bool {
+	return false
+}
+
+func (quicDialerFactory) Valid(_ config.Configuration) error {
+	// Always valid
+	return nil
+}
+
+func (quicDialerFactory) String() string {
+	return "QUIC Dialer"
+}