lib/config, lib/connections: Configurables for KCP, disable by default

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4030

lib/config/config.go

@@ -44,9 +44,12 @@ var (
 	// config.
 	DefaultListenAddresses = []string{
 		util.Address("tcp", net.JoinHostPort("0.0.0.0", strconv.Itoa(DefaultTCPPort))),
-		util.Address("kcp", net.JoinHostPort("0.0.0.0", strconv.Itoa(DefaultKCPPort))),
 		"dynamic+https://relays.syncthing.net/endpoint",
 	}
+	// DefaultKCPListenAddress gets added to the default listen address set
+	// when the appropriate feature flag is set. Feature flag stuff to be
+	// removed later.
+	DefaultKCPListenAddress = util.Address("kcp", net.JoinHostPort("0.0.0.0", strconv.Itoa(DefaultKCPPort)))
 	// DefaultDiscoveryServersV4 should be substituted when the configuration
 	// contains <globalAnnounceServer>default-v4</globalAnnounceServer>.
 	DefaultDiscoveryServersV4 = []string{

lib/config/config_test.go

@@ -67,6 +67,12 @@ func TestDefaultValues(t *testing.T) {
 		WeakHashSelectionMethod: WeakHashAuto,
 		StunKeepaliveS:          24,
 		StunServers:             []string{"default"},
+		DefaultKCPEnabled:       false,
+		KCPCongestionControl:    true,
+		KCPReceiveWindowSize:    128,
+		KCPSendWindowSize:       128,
+		KCPUpdateIntervalMs:     100,
+		KCPFastResend:           false,
 	}
 
 	cfg := New(device1)
@@ -207,6 +213,12 @@ func TestOverriddenValues(t *testing.T) {
 		WeakHashSelectionMethod: WeakHashNever,
 		StunKeepaliveS:          10,
 		StunServers:             []string{"a.stun.com", "b.stun.com"},
+		DefaultKCPEnabled:       true,
+		KCPCongestionControl:    false,
+		KCPReceiveWindowSize:    1280,
+		KCPSendWindowSize:       1280,
+		KCPUpdateIntervalMs:     1000,
+		KCPFastResend:           true,
 	}
 
 	os.Unsetenv("STNOUPGRADE")

lib/config/optionsconfiguration.go

@@ -133,6 +133,13 @@ type OptionsConfiguration struct {
 	WeakHashSelectionMethod WeakHashSelectionMethod `xml:"weakHashSelectionMethod" json:"weakHashSelectionMethod"`
 	StunServers             []string                `xml:"stunServer" json:"stunServers" default:"default"`
 	StunKeepaliveS          int                     `xml:"stunKeepaliveSeconds" json:"stunKeepaliveSeconds" default:"24"`
+	DefaultKCPEnabled       bool                    `xml:"defaultKCPEnabled" json:"defaultKCPEnabled" default:"false"`
+	KCPNoDelay              bool                    `xml:"kcpNoDelay" json:"kcpNoDelay" default:"false"`
+	KCPUpdateIntervalMs     int                     `xml:"kcpUpdateIntervalMs" json:"kcpUpdateIntervalMs" default:"100"`
+	KCPFastResend           bool                    `xml:"kcpFastResend" json:"kcpFastResend" default:"false"`
+	KCPCongestionControl    bool                    `xml:"kcpCongestionControl" json:"kcpCongestionControl" default:"true"`
+	KCPSendWindowSize       int                     `xml:"kcpSendWindowSize" json:"kcpSendWindowSize" default:"128"`
+	KCPReceiveWindowSize    int                     `xml:"kcpReceiveWindowSize" json:"kcpReceiveWindowSize" default:"128"`
 
 	DeprecatedUPnPEnabled  bool     `xml:"upnpEnabled,omitempty" json:"-"`
 	DeprecatedUPnPLeaseM   int      `xml:"upnpLeaseMinutes,omitempty" json:"-"`

lib/config/testdata/overridenvalues.xml

@@ -38,5 +38,11 @@
         <stunKeepaliveSeconds>10</stunKeepaliveSeconds>
         <stunServer>a.stun.com</stunServer>
         <stunServer>b.stun.com</stunServer>
+		<defaultKCPEnabled>true</defaultKCPEnabled>
+		<kcpCongestionControl>false</kcpCongestionControl>
+		<kcpReceiveWindowSize>1280</kcpReceiveWindowSize>
+		<kcpSendWindowSize>1280</kcpSendWindowSize>
+		<kcpUpdateIntervalMs>1000</kcpUpdateIntervalMs>
+		<kcpFastResend>true</kcpFastResend>
     </options>
 </configuration>

lib/config/wrapper.go

@@ -391,6 +391,9 @@ func (w *Wrapper) ListenAddresses() []string {
 		switch addr {
 		case "default":
 			addresses = append(addresses, DefaultListenAddresses...)
+			if w.cfg.Options.DefaultKCPEnabled { // temporary feature flag
+				addresses = append(addresses, DefaultKCPListenAddress)
+			}
 		default:
 			addresses = append(addresses, addr)
 		}

lib/connections/config.go

@@ -22,23 +22,6 @@ const (
 	kcpNoFilterPriority           = 100
 	kcpConversationFilterPriority = 20
 	kcpStunFilterPriority         = 10
-
-	// KCP SetNoDelay options
-
-	// 0 - disabled (default)
-	// 1 - enabled
-	kcpNoDelay        = 0
-	kcpUpdateInterval = 100 // ms (default)
-	// 0 - disable (default)
-	// 1 - enabled
-	kcpFastResend = 0
-	// 0 - enabled (default)
-	// 1 - disabled
-	kcpCongestionControl = 0
-
-	// KCP window sizes
-	kcpSendWindowSize    = 128
-	kcpReceiveWindowSize = 128
 )
 
 var (

lib/connections/kcp_dial.go

@@ -49,11 +49,13 @@ func (d *kcpDialer) Dial(id protocol.DeviceID, uri *url.URL) (internalConn, erro
 		return internalConn{}, err
 	}
 
+	opts := d.cfg.Options()
+
 	conn.SetKeepAlive(0) // yamux and stun service does keep-alives.
 	conn.SetStreamMode(true)
 	conn.SetACKNoDelay(false)
-	conn.SetWindowSize(kcpSendWindowSize, kcpReceiveWindowSize)
+	conn.SetWindowSize(opts.KCPSendWindowSize, opts.KCPReceiveWindowSize)
-	conn.SetNoDelay(kcpNoDelay, kcpUpdateInterval, kcpFastResend, kcpCongestionControl)
+	conn.SetNoDelay(boolInt(opts.KCPNoDelay), opts.KCPUpdateIntervalMs, boolInt(opts.KCPFastResend), boolInt(!opts.KCPCongestionControl))
 
 	ses, err := yamux.Client(conn, yamuxConfig)
 	if err != nil {

lib/connections/kcp_listen.go

@@ -107,12 +107,13 @@ func (t *kcpListener) Serve() {
 			continue
 		}
 
-		conn.SetStreamMode(true)
+		opts := t.cfg.Options()
-		conn.SetACKNoDelay(false)
-		conn.SetWindowSize(kcpSendWindowSize, kcpReceiveWindowSize)
-		conn.SetNoDelay(kcpNoDelay, kcpUpdateInterval, kcpFastResend, kcpCongestionControl)
 
 		conn.SetKeepAlive(0) // yamux and stun service does keep-alives.
+		conn.SetStreamMode(true)
+		conn.SetACKNoDelay(false)
+		conn.SetWindowSize(opts.KCPSendWindowSize, opts.KCPReceiveWindowSize)
+		conn.SetNoDelay(boolInt(opts.KCPNoDelay), opts.KCPUpdateIntervalMs, boolInt(opts.KCPFastResend), boolInt(!opts.KCPCongestionControl))
 
 		l.Debugln("connect from", conn.RemoteAddr())
 

lib/connections/kcp_misc.go

@@ -180,3 +180,10 @@ func (w *sessionClosingStream) Close() error {
 	}
 	return err2
 }
+
+func boolInt(b bool) int {
+	if b {
+		return 1
+	}
+	return 0
+}