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

lib/connections/quic_misc.go

@@ -0,0 +1,57 @@
+// 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 http://mozilla.org/MPL/2.0/.
+
+// +build go1.12
+
+package connections
+
+import (
+	"net"
+
+	"github.com/lucas-clemente/quic-go"
+)
+
+var (
+	quicConfig = &quic.Config{
+		ConnectionIDLength: 4,
+		KeepAlive:          true,
+	}
+)
+
+type quicTlsConn struct {
+	quic.Session
+	quic.Stream
+}
+
+func (q *quicTlsConn) Close() error {
+	sterr := q.Stream.Close()
+	seerr := q.Session.Close()
+	if sterr != nil {
+		return sterr
+	}
+	return seerr
+}
+
+// Sort available packet connections by ip address, preferring unspecified local address.
+func packetConnLess(i interface{}, j interface{}) bool {
+	iIsUnspecified := false
+	jIsUnspecified := false
+	iLocalAddr := i.(net.PacketConn).LocalAddr()
+	jLocalAddr := j.(net.PacketConn).LocalAddr()
+
+	if host, _, err := net.SplitHostPort(iLocalAddr.String()); err == nil {
+		iIsUnspecified = host == "" || net.ParseIP(host).IsUnspecified()
+	}
+	if host, _, err := net.SplitHostPort(jLocalAddr.String()); err == nil {
+		jIsUnspecified = host == "" || net.ParseIP(host).IsUnspecified()
+	}
+
+	if jIsUnspecified == iIsUnspecified {
+		return len(iLocalAddr.Network()) < len(jLocalAddr.Network())
+	}
+
+	return iIsUnspecified
+}