Split set route to Start()

tun.go

@@ -24,6 +24,7 @@ type Handler interface {
 type Tun interface {
 	io.ReadWriter
 	N.VectorisedWriter
+	Start() error
 	Close() error
 }
 
@@ -89,10 +90,10 @@ func (o *Options) Inet4GatewayAddr() netip.Addr {
 		return o.Inet4Gateway
 	}
 	if len(o.Inet4Address) > 0 {
-		if HasNextAddress(o.Inet4Address[0], 1) {
-			return o.Inet4Address[0].Addr().Next()
-		} else if runtime.GOOS != "linux" {
+		if runtime.GOOS == "darwin" {
 			return o.Inet4Address[0].Addr()
+		} else if HasNextAddress(o.Inet4Address[0], 1) {
+			return o.Inet4Address[0].Addr().Next()
 		}
 	}
 	return netip.IPv4Unspecified()
@@ -103,10 +104,10 @@ func (o *Options) Inet6GatewayAddr() netip.Addr {
 		return o.Inet6Gateway
 	}
 	if len(o.Inet6Address) > 0 {
-		if HasNextAddress(o.Inet6Address[0], 1) {
-			return o.Inet6Address[0].Addr().Next()
-		} else if runtime.GOOS != "linux" {
+		if runtime.GOOS == "darwin" {
 			return o.Inet6Address[0].Addr()
+		} else if HasNextAddress(o.Inet6Address[0], 1) {
+			return o.Inet6Address[0].Addr().Next()
 		}
 	}
 	return netip.IPv6Unspecified()

tun_darwin.go

@@ -1,6 +1,7 @@
 package tun
 
 import (
+	"errors"
 	"fmt"
 	"net"
 	"net/netip"
@@ -24,9 +25,10 @@ const PacketOffset = 4
 type NativeTun struct {
 	tunFile      *os.File
 	tunWriter    N.VectorisedWriter
-	mtu          uint32
+	options      Options
 	inet4Address [4]byte
 	inet6Address [16]byte
+	routerSet    bool
 }
 
 func New(options Options) (Tun, error) {
@@ -54,7 +56,7 @@ func New(options Options) (Tun, error) {
 
 	nativeTun := &NativeTun{
 		tunFile: os.NewFile(uintptr(tunFd), "utun"),
-		mtu:     options.MTU,
+		options: options,
 	}
 	if len(options.Inet4Address) > 0 {
 		nativeTun.inet4Address = options.Inet4Address[0].Addr().As4()
@@ -70,6 +72,15 @@ func New(options Options) (Tun, error) {
 	return nativeTun, nil
 }
 
+func (t *NativeTun) Start() error {
+	return t.setRoutes()
+}
+
+func (t *NativeTun) Close() error {
+	defer flushDNSCache()
+	return E.Errors(t.unsetRoutes(), t.tunFile.Close())
+}
+
 func (t *NativeTun) Read(p []byte) (n int, err error) {
 	return t.tunFile.Read(p)
 }
@@ -93,11 +104,6 @@ func (t *NativeTun) WriteVectorised(buffers []*buf.Buffer) error {
 	return t.tunWriter.WriteVectorised(append([]*buf.Buffer{buf.As(packetHeader)}, buffers...))
 }
 
-func (t *NativeTun) Close() error {
-	flushDNSCache()
-	return t.tunFile.Close()
-}
-
 const utunControlName = "com.apple.net.utun_control"
 
 const (
@@ -239,28 +245,68 @@ func configure(tunFd int, ifIndex int, name string, options Options) error {
 			}
 		}
 	}
-	if options.AutoRoute {
-		var routeRanges []netip.Prefix
-		routeRanges, err = options.BuildAutoRouteRanges(false)
+	return nil
+}
+
+func (t *NativeTun) setRoutes() error {
+	if t.options.AutoRoute {
+		routeRanges, err := t.options.BuildAutoRouteRanges(false)
 		if err != nil {
 			return err
 		}
-		gateway4, gateway6 := options.Inet4GatewayAddr(), options.Inet6GatewayAddr()
-		for _, routeRange := range routeRanges {
-			if routeRange.Addr().Is4() {
-				err = addRoute(routeRange, gateway4)
+		gateway4, gateway6 := t.options.Inet4GatewayAddr(), t.options.Inet6GatewayAddr()
+		for _, destination := range routeRanges {
+			var gateway netip.Addr
+			if destination.Addr().Is4() {
+				gateway = gateway4
 			} else {
-				err = addRoute(routeRange, gateway6)
+				gateway = gateway6
 			}
+			err = execRoute(unix.RTM_ADD, destination, gateway)
 			if err != nil {
-				return E.Cause(err, "add route: ", routeRange)
+				if errors.Is(err, unix.EEXIST) {
+					err = execRoute(unix.RTM_DELETE, destination, gateway)
+					if err != nil {
+						return E.Cause(err, "remove existing route: ", destination)
+					}
+					err = execRoute(unix.RTM_ADD, destination, gateway)
+					if err != nil {
+						return E.Cause(err, "re-add route: ", destination)
+					}
+				}
+				return E.Cause(err, "add route: ", destination)
 			}
 		}
 		flushDNSCache()
+		t.routerSet = true
 	}
 	return nil
 }
 
+func (t *NativeTun) unsetRoutes() error {
+	if !t.routerSet {
+		return nil
+	}
+	routeRanges, err := t.options.BuildAutoRouteRanges(false)
+	if err != nil {
+		return err
+	}
+	gateway4, gateway6 := t.options.Inet4GatewayAddr(), t.options.Inet6GatewayAddr()
+	for _, destination := range routeRanges {
+		var gateway netip.Addr
+		if destination.Addr().Is4() {
+			gateway = gateway4
+		} else {
+			gateway = gateway6
+		}
+		err = execRoute(unix.RTM_DELETE, destination, gateway)
+		if err != nil {
+			err = E.Errors(err, E.Cause(err, "delete route: ", destination))
+		}
+	}
+	return err
+}
+
 func useSocket(domain, typ, proto int, block func(socketFd int) error) error {
 	socketFd, err := unix.Socket(domain, typ, proto)
 	if err != nil {
@@ -270,13 +316,16 @@ func useSocket(domain, typ, proto int, block func(socketFd int) error) error {
 	return block(socketFd)
 }
 
-func addRoute(destination netip.Prefix, gateway netip.Addr) error {
+func execRoute(rtmType int, destination netip.Prefix, gateway netip.Addr) error {
 	routeMessage := route.RouteMessage{
-		Type:    unix.RTM_ADD,
-		Flags:   unix.RTF_UP | unix.RTF_STATIC | unix.RTF_GATEWAY,
+		Type:    rtmType,
 		Version: unix.RTM_VERSION,
+		Flags:   unix.RTF_STATIC | unix.RTF_GATEWAY,
 		Seq:     1,
 	}
+	if rtmType == unix.RTM_ADD {
+		routeMessage.Flags |= unix.RTF_UP
+	}
 	if gateway.Is4() {
 		routeMessage.Addrs = []route.Addr{
 			syscall.RTAX_DST:     &route.Inet4Addr{IP: destination.Addr().As4()},
@@ -300,5 +349,5 @@ func addRoute(destination netip.Prefix, gateway netip.Addr) error {
 }
 
 func flushDNSCache() {
-	shell.Exec("dscacheutil", "-flushcache").Start()
+	go shell.Exec("dscacheutil", "-flushcache").Run()
 }

tun_darwin_gvisor.go

@@ -24,7 +24,7 @@ type DarwinEndpoint struct {
 }
 
 func (e *DarwinEndpoint) MTU() uint32 {
-	return e.tun.mtu
+	return e.tun.options.MTU
 }
 
 func (e *DarwinEndpoint) SetMTU(mtu uint32) {
@@ -57,7 +57,7 @@ func (e *DarwinEndpoint) Attach(dispatcher stack.NetworkDispatcher) {
 }
 
 func (e *DarwinEndpoint) dispatchLoop() {
-	packetBuffer := make([]byte, e.tun.mtu+PacketOffset)
+	packetBuffer := make([]byte, e.tun.options.MTU+PacketOffset)
 	for {
 		n, err := e.tun.tunFile.Read(packetBuffer)
 		if err != nil {

tun_linux.go

@@ -288,6 +288,15 @@ func (t *NativeTun) configure(tunLink netlink.Link) error {
 		t.txChecksumOffload = true
 	}
 
+	return nil
+}
+
+func (t *NativeTun) Start() error {
+	tunLink, err := netlink.LinkByName(t.options.Name)
+	if err != nil {
+		return err
+	}
+
 	err = netlink.LinkSetUp(tunLink)
 	if err != nil {
 		return err

tun_windows.go

@@ -106,27 +106,6 @@ func (t *NativeTun) configure() error {
 	if len(t.options.Inet4Address) > 0 || len(t.options.Inet6Address) > 0 {
 		_ = luid.DisableDNSRegistration()
 	}
-	if t.options.AutoRoute {
-		gateway4, gateway6 := t.options.Inet4GatewayAddr(), t.options.Inet6GatewayAddr()
-		routeRanges, err := t.options.BuildAutoRouteRanges(false)
-		if err != nil {
-			return err
-		}
-		for _, routeRange := range routeRanges {
-			if routeRange.Addr().Is4() {
-				err = luid.AddRoute(routeRange, gateway4, 0)
-			} else {
-				err = luid.AddRoute(routeRange, gateway6, 0)
-			}
-		}
-		if err != nil {
-			return err
-		}
-		err = windnsapi.FlushResolverCache()
-		if err != nil {
-			return err
-		}
-	}
 	if len(t.options.Inet4Address) > 0 {
 		inetIf, err := luid.IPInterface(winipcfg.AddressFamily(windows.AF_INET))
 		if err != nil {
@@ -166,8 +145,34 @@ func (t *NativeTun) configure() error {
 			return E.Cause(err, "set ipv6 options")
 		}
 	}
+	return nil
+}
 
-	if t.options.AutoRoute && t.options.StrictRoute {
+func (t *NativeTun) Start() error {
+	if !t.options.AutoRoute {
+		return nil
+	}
+	luid := winipcfg.LUID(t.adapter.LUID())
+	gateway4, gateway6 := t.options.Inet4GatewayAddr(), t.options.Inet6GatewayAddr()
+	routeRanges, err := t.options.BuildAutoRouteRanges(false)
+	if err != nil {
+		return err
+	}
+	for _, routeRange := range routeRanges {
+		if routeRange.Addr().Is4() {
+			err = luid.AddRoute(routeRange, gateway4, 0)
+		} else {
+			err = luid.AddRoute(routeRange, gateway6, 0)
+		}
+	}
+	if err != nil {
+		return err
+	}
+	err = windnsapi.FlushResolverCache()
+	if err != nil {
+		return err
+	}
+	if t.options.StrictRoute {
 		var engine uintptr
 		session := &winsys.FWPM_SESSION0{Flags: winsys.FWPM_SESSION_FLAG_DYNAMIC}
 		err := winsys.FwpmEngineOpen0(nil, winsys.RPC_C_AUTHN_DEFAULT, nil, session, unsafe.Pointer(&engine))
@@ -340,7 +345,6 @@ func (t *NativeTun) configure() error {
 			}
 		}
 	}
-
 	return nil
 }