Fix native Windows TUN setup

core/sys_windows.go

@@ -29,10 +29,16 @@ func InitInterface(logger *slog.Logger, ifName string) error {
 }
 
 func ConfigureAlias(logger *slog.Logger, ifName string, addr netip.Addr) error {
+	if addr.Is6() {
+		return Exec(logger, "netsh", "interface", "ipv6", "add", "address", ifName, addr.String())
+	}
 	return Exec(logger, "netsh", "interface", "ip", "add", "address", ifName, addr.String())
 }
 
 func RemoveAlias(logger *slog.Logger, ifName string, addr netip.Addr) error {
+	if addr.Is6() {
+		return Exec(logger, "netsh", "interface", "ipv6", "delete", "address", ifName, addr.String())
+	}
 	return Exec(logger, "netsh", "interface", "ip", "delete", "address", ifName, addr.String())
 }
 

polyamide/device/send.go

@@ -249,6 +249,7 @@ func (device *Device) RoutineReadFromTUN() {
 			}
 			tce := device.GetTCElement()
 			tce.Buffer = bufs[i]
+			tce.Packet = bufs[i][offset : offset+sizes[i]]
 			tcBufs = append(tcBufs, tce)
 
 			bufs[i] = device.GetMessageBuffer()

polyamide/device/traffic_control.go

@@ -109,8 +109,7 @@ func (device *Device) TCBatch(batch []*TCElement, tcs *TCState) {
 	for i, elem := range batch {
 		// process TC Filters
 		act := TcPass
-		elem.ParsePacket()
-		if !elem.Validate() {
+		if !elem.ParsePacket() || !elem.Validate() {
 			device.Log.Errorf("Found malformed packet, dropping packet")
 			act = TcDrop
 		} else {

polyamide/device/traffic_manip.go

@@ -20,10 +20,25 @@ func (elem *TCElement) InitPacket(ver int, len uint16) {
 	elem.SetLength(len)
 }
 
-func (elem *TCElement) ParsePacket() {
-	elem.Packet = elem.Buffer[MessageTransportHeaderSize:]
+func (elem *TCElement) ParsePacket() bool {
+	if elem == nil {
+		return false
+	}
+	if len(elem.Packet) == 0 {
+		if elem.Buffer == nil {
+			return false
+		}
+		elem.Packet = elem.Buffer[MessageTransportHeaderSize:]
+	}
+	if !elem.hasPacketHeader() {
+		return false
+	}
 	l := elem.GetLength()
-	elem.Packet = elem.Buffer[MessageTransportHeaderSize : MessageTransportHeaderSize+l]
+	if int(l) > len(elem.Packet) {
+		return false
+	}
+	elem.Packet = elem.Packet[:l]
+	return true
 }
 
 func (elem *TCElement) Incoming() bool {
@@ -137,6 +152,9 @@ func (elem *TCElement) Validate() bool {
 	if elem == nil || len(elem.Packet) == 0 {
 		return false
 	}
+	if !elem.hasPacketHeader() {
+		return false
+	}
 	ver := elem.GetIPVersion()
 	if ver == 4 {
 		if elem.GetLength() < ipv4.HeaderLen {
@@ -154,6 +172,19 @@ func (elem *TCElement) Validate() bool {
 	return true
 }
 
+func (elem *TCElement) hasPacketHeader() bool {
+	if elem == nil || len(elem.Packet) < PolyHeaderSize {
+		return false
+	}
+	ver := elem.GetIPVersion()
+	if ver == 4 {
+		return len(elem.Packet) >= ipv4.HeaderLen
+	} else if ver == 6 {
+		return len(elem.Packet) >= ipv6.HeaderLen
+	}
+	return true
+}
+
 func (elem *TCElement) TTLBytes() []byte {
 	if elem.GetIPVersion() == 4 {
 		return elem.Packet[8:9]

polyamide/device/traffic_manip_test.go

@@ -0,0 +1,41 @@
+package device
+
+import (
+	"encoding/binary"
+	"testing"
+)
+
+func TestParsePacketRejectsLengthBeyondReadBuffer(t *testing.T) {
+	var buf [MaxMessageSize]byte
+	packet := buf[MessageTransportHeaderSize : MessageTransportHeaderSize+2016]
+	packet[0] = 6 << 4
+	binary.BigEndian.PutUint16(packet[IPv6offsetPayloadLength:IPv6offsetPayloadLength+2], 2010)
+
+	elem := &TCElement{
+		Buffer: &buf,
+		Packet: packet,
+	}
+
+	if elem.ParsePacket() {
+		t.Fatal("expected oversized packet to be rejected")
+	}
+}
+
+func TestParsePacketTrimsToAdvertisedLength(t *testing.T) {
+	var buf [MaxMessageSize]byte
+	packet := buf[MessageTransportHeaderSize : MessageTransportHeaderSize+128]
+	packet[0] = 6 << 4
+	binary.BigEndian.PutUint16(packet[IPv6offsetPayloadLength:IPv6offsetPayloadLength+2], 8)
+
+	elem := &TCElement{
+		Buffer: &buf,
+		Packet: packet,
+	}
+
+	if !elem.ParsePacket() {
+		t.Fatal("expected valid packet to parse")
+	}
+	if len(elem.Packet) != 48 {
+		t.Fatalf("expected packet length 48, got %d", len(elem.Packet))
+	}
+}

polyamide/tun/tun_windows.go

@@ -12,7 +12,7 @@ import (
 	"sync"
 	"sync/atomic"
 	"time"
-	_ "unsafe"
+	"unsafe"
 
 	"golang.org/x/sys/windows"
 	"golang.zx2c4.com/wintun"
@@ -49,6 +49,9 @@ type NativeTun struct {
 var (
 	WintunTunnelType          = "WireGuard"
 	WintunStaticRequestedGUID *windows.GUID
+	modiphlpapi               = windows.NewLazySystemDLL("iphlpapi.dll")
+	procGetIpInterfaceEntry   = modiphlpapi.NewProc("GetIpInterfaceEntry")
+	procSetIpInterfaceEntry   = modiphlpapi.NewProc("SetIpInterfaceEntry")
 )
 
 //go:linkname procyield runtime.procyield
@@ -75,6 +78,11 @@ func CreateTUNWithRequestedGUID(ifname string, requestedGUID *windows.GUID, mtu
 	if mtu > 0 {
 		forcedMTU = mtu
 	}
+	if err := setInterfaceMTU(wt.LUID(), windows.AF_INET6, forcedMTU); err != nil {
+		wt.Close()
+		return nil, fmt.Errorf("Error setting IPv6 interface MTU: %w", err)
+	}
+	_ = setInterfaceMTU(wt.LUID(), windows.AF_INET, forcedMTU)
 
 	tun := &NativeTun{
 		wt:        wt,
@@ -225,6 +233,24 @@ func (tun *NativeTun) RunningVersion() (version uint32, err error) {
 	return wintun.RunningVersion()
 }
 
+func setInterfaceMTU(luid uint64, family uint16, mtu int) error {
+	var row windows.MibIpInterfaceRow
+	row.Family = family
+	row.InterfaceLuid = luid
+
+	r1, _, _ := procGetIpInterfaceEntry.Call(uintptr(unsafe.Pointer(&row)))
+	if r1 != 0 {
+		return windows.Errno(r1)
+	}
+
+	row.NlMtu = uint32(mtu)
+	r1, _, _ = procSetIpInterfaceEntry.Call(uintptr(unsafe.Pointer(&row)))
+	if r1 != 0 {
+		return windows.Errno(r1)
+	}
+	return nil
+}
+
 func (rate *rateJuggler) update(packetLen uint64) {
 	now := nanotime()
 	total := rate.nextByteCount.Add(packetLen)