wintun: move ring constants into module

3 files changed, 133 insertions, 96 deletions

diff --git a/tun/tun_windows.go b/tun/tun_windows.go
index 1891d21..9c635b5 100644
--- a/tun/tun_windows.go
+++ b/tun/tun_windows.go
@@ -19,40 +19,11 @@ import (
 )
 
 const (
-	packetAlignment            = 4        // Number of bytes packets are aligned to in rings
-	packetSizeMax              = 0xffff   // Maximum packet size
-	packetCapacity             = 0x800000 // Ring capacity, 8MiB
-	packetTrailingSize         = uint32(unsafe.Sizeof(packetHeader{})) + ((packetSizeMax + (packetAlignment - 1)) &^ (packetAlignment - 1)) - packetAlignment
-	ioctlRegisterRings         = (51820 << 16) | (0x970 << 2) | 0 /*METHOD_BUFFERED*/ | (0x3 /*FILE_READ_DATA | FILE_WRITE_DATA*/ << 14)
 	rateMeasurementGranularity = uint64((time.Second / 2) / time.Nanosecond)
 	spinloopRateThreshold      = 800000000 / 8                                   // 800mbps
 	spinloopDuration           = uint64(time.Millisecond / 80 / time.Nanosecond) // ~1gbit/s
 )
 
-type packetHeader struct {
-	size uint32
-}
-
-type packet struct {
-	packetHeader
-	data [packetSizeMax]byte
-}
-
-type ring struct {
-	head      uint32
-	tail      uint32
-	alertable int32
-	data      [packetCapacity + packetTrailingSize]byte
-}
-
-type ringDescriptor struct {
-	send, receive struct {
-		size      uint32
-		ring      *ring
-		tailMoved windows.Handle
-	}
-}
-
 type rateJuggler struct {
 	current       uint64
 	nextByteCount uint64
@@ -64,7 +35,7 @@ type NativeTun struct {
 	wt        *wintun.Interface
 	handle    windows.Handle
 	close     bool
-	rings     ringDescriptor
+	rings     wintun.RingDescriptor
 	events    chan Event
 	errors    chan error
 	forcedMTU int
@@ -79,10 +50,6 @@ func procyield(cycles uint32)
 //go:linkname nanotime runtime.nanotime
 func nanotime() int64
 
-func packetAlign(size uint32) uint32 {
-	return (size + (packetAlignment - 1)) &^ (packetAlignment - 1)
-}
-
 //
 // CreateTUN creates a Wintun interface with the given name. Should a Wintun
 // interface with the same name exist, it is reused.
@@ -127,30 +94,13 @@ func CreateTUNWithRequestedGUID(ifname string, requestedGUID *windows.GUID) (Dev
 		forcedMTU: 1500,
 	}
 
-	tun.rings.send.size = uint32(unsafe.Sizeof(ring{}))
-	tun.rings.send.ring = &ring{}
-	tun.rings.send.tailMoved, err = windows.CreateEvent(nil, 0, 0, nil)
+	err = tun.rings.Init()
 	if err != nil {
 		tun.Close()
-		return nil, fmt.Errorf("Error creating event: %v", err)
+		return nil, fmt.Errorf("Error creating events: %v", err)
 	}
 
-	tun.rings.receive.size = uint32(unsafe.Sizeof(ring{}))
-	tun.rings.receive.ring = &ring{}
-	tun.rings.receive.tailMoved, err = windows.CreateEvent(nil, 0, 0, nil)
-	if err != nil {
-		tun.Close()
-		return nil, fmt.Errorf("Error creating event: %v", err)
-	}
-
-	tun.handle, err = tun.wt.Handle()
-	if err != nil {
-		tun.Close()
-		return nil, err
-	}
-
-	var bytesReturned uint32
-	err = windows.DeviceIoControl(tun.handle, ioctlRegisterRings, (*byte)(unsafe.Pointer(&tun.rings)), uint32(unsafe.Sizeof(tun.rings)), nil, 0, &bytesReturned, nil)
+	tun.handle, err = tun.wt.Register(&tun.rings)
 	if err != nil {
 		tun.Close()
 		return nil, fmt.Errorf("Error registering rings: %v", err)
@@ -172,18 +122,13 @@ func (tun *NativeTun) Events() chan Event {
 
 func (tun *NativeTun) Close() error {
 	tun.close = true
-	if tun.rings.send.tailMoved != 0 {
-		windows.SetEvent(tun.rings.send.tailMoved) // wake the reader if it's sleeping
+	if tun.rings.Send.TailMoved != 0 {
+		windows.SetEvent(tun.rings.Send.TailMoved) // wake the reader if it's sleeping
 	}
 	if tun.handle != windows.InvalidHandle {
 		windows.CloseHandle(tun.handle)
 	}
-	if tun.rings.send.tailMoved != 0 {
-		windows.CloseHandle(tun.rings.send.tailMoved)
-	}
-	if tun.rings.send.tailMoved != 0 {
-		windows.CloseHandle(tun.rings.receive.tailMoved)
-	}
+	tun.rings.Close()
 	var err error
 	if tun.wt != nil {
 		_, err = tun.wt.DeleteInterface()
@@ -214,8 +159,8 @@ retry:
 		return 0, os.ErrClosed
 	}
 
-	buffHead := atomic.LoadUint32(&tun.rings.send.ring.head)
-	if buffHead >= packetCapacity {
+	buffHead := atomic.LoadUint32(&tun.rings.Send.Ring.Head)
+	if buffHead >= wintun.PacketCapacity {
 		return 0, os.ErrClosed
 	}
 
@@ -223,7 +168,7 @@ retry:
 	shouldSpin := atomic.LoadUint64(&tun.rate.current) >= spinloopRateThreshold && uint64(start-atomic.LoadInt64(&tun.rate.nextStartTime)) <= rateMeasurementGranularity*2
 	var buffTail uint32
 	for {
-		buffTail = atomic.LoadUint32(&tun.rings.send.ring.tail)
+		buffTail = atomic.LoadUint32(&tun.rings.Send.Ring.Tail)
 		if buffHead != buffTail {
 			break
 		}
@@ -231,35 +176,35 @@ retry:
 			return 0, os.ErrClosed
 		}
 		if !shouldSpin || uint64(nanotime()-start) >= spinloopDuration {
-			windows.WaitForSingleObject(tun.rings.send.tailMoved, windows.INFINITE)
+			windows.WaitForSingleObject(tun.rings.Send.TailMoved, windows.INFINITE)
 			goto retry
 		}
 		procyield(1)
 	}
-	if buffTail >= packetCapacity {
+	if buffTail >= wintun.PacketCapacity {
 		return 0, os.ErrClosed
 	}
 
-	buffContent := tun.rings.send.ring.wrap(buffTail - buffHead)
-	if buffContent < uint32(unsafe.Sizeof(packetHeader{})) {
+	buffContent := tun.rings.Send.Ring.Wrap(buffTail - buffHead)
+	if buffContent < uint32(unsafe.Sizeof(wintun.PacketHeader{})) {
 		return 0, errors.New("incomplete packet header in send ring")
 	}
 
-	packet := (*packet)(unsafe.Pointer(&tun.rings.send.ring.data[buffHead]))
-	if packet.size > packetSizeMax {
+	packet := (*wintun.Packet)(unsafe.Pointer(&tun.rings.Send.Ring.Data[buffHead]))
+	if packet.Size > wintun.PacketSizeMax {
 		return 0, errors.New("packet too big in send ring")
 	}
 
-	alignedPacketSize := packetAlign(uint32(unsafe.Sizeof(packetHeader{})) + packet.size)
+	alignedPacketSize := wintun.PacketAlign(uint32(unsafe.Sizeof(wintun.PacketHeader{})) + packet.Size)
 	if alignedPacketSize > buffContent {
 		return 0, errors.New("incomplete packet in send ring")
 	}
 
-	copy(buff[offset:], packet.data[:packet.size])
-	buffHead = tun.rings.send.ring.wrap(buffHead + alignedPacketSize)
-	atomic.StoreUint32(&tun.rings.send.ring.head, buffHead)
-	tun.rate.update(uint64(packet.size))
-	return int(packet.size), nil
+	copy(buff[offset:], packet.Data[:packet.Size])
+	buffHead = tun.rings.Send.Ring.Wrap(buffHead + alignedPacketSize)
+	atomic.StoreUint32(&tun.rings.Send.Ring.Head, buffHead)
+	tun.rate.update(uint64(packet.Size))
+	return int(packet.Size), nil
 }
 
 func (tun *NativeTun) Flush() error {
@@ -273,29 +218,29 @@ func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
 
 	packetSize := uint32(len(buff) - offset)
 	tun.rate.update(uint64(packetSize))
-	alignedPacketSize := packetAlign(uint32(unsafe.Sizeof(packetHeader{})) + packetSize)
+	alignedPacketSize := wintun.PacketAlign(uint32(unsafe.Sizeof(wintun.PacketHeader{})) + packetSize)
 
-	buffHead := atomic.LoadUint32(&tun.rings.receive.ring.head)
-	if buffHead >= packetCapacity {
+	buffHead := atomic.LoadUint32(&tun.rings.Receive.Ring.Head)
+	if buffHead >= wintun.PacketCapacity {
 		return 0, os.ErrClosed
 	}
 
-	buffTail := atomic.LoadUint32(&tun.rings.receive.ring.tail)
-	if buffTail >= packetCapacity {
+	buffTail := atomic.LoadUint32(&tun.rings.Receive.Ring.Tail)
+	if buffTail >= wintun.PacketCapacity {
 		return 0, os.ErrClosed
 	}
 
-	buffSpace := tun.rings.receive.ring.wrap(buffHead - buffTail - packetAlignment)
+	buffSpace := tun.rings.Receive.Ring.Wrap(buffHead - buffTail - wintun.PacketAlignment)
 	if alignedPacketSize > buffSpace {
 		return 0, nil // Dropping when ring is full.
 	}
 
-	packet := (*packet)(unsafe.Pointer(&tun.rings.receive.ring.data[buffTail]))
-	packet.size = packetSize
-	copy(packet.data[:packetSize], buff[offset:])
-	atomic.StoreUint32(&tun.rings.receive.ring.tail, tun.rings.receive.ring.wrap(buffTail+alignedPacketSize))
-	if atomic.LoadInt32(&tun.rings.receive.ring.alertable) != 0 {
-		windows.SetEvent(tun.rings.receive.tailMoved)
+	packet := (*wintun.Packet)(unsafe.Pointer(&tun.rings.Receive.Ring.Data[buffTail]))
+	packet.Size = packetSize
+	copy(packet.Data[:packetSize], buff[offset:])
+	atomic.StoreUint32(&tun.rings.Receive.Ring.Tail, tun.rings.Receive.Ring.Wrap(buffTail+alignedPacketSize))
+	if atomic.LoadInt32(&tun.rings.Receive.Ring.Alertable) != 0 {
+		windows.SetEvent(tun.rings.Receive.TailMoved)
 	}
 	return int(packetSize), nil
 }
@@ -305,11 +250,6 @@ func (tun *NativeTun) LUID() uint64 {
 	return tun.wt.LUID()
 }
 
-// wrap returns value modulo ring capacity
-func (rb *ring) wrap(value uint32) uint32 {
-	return value & (packetCapacity - 1)
-}
-
 func (rate *rateJuggler) update(packetLen uint64) {
 	now := nanotime()
 	total := atomic.AddUint64(&rate.nextByteCount, packetLen)
diff --git a/tun/wintun/ring.go b/tun/wintun/ring.go
new file mode 100644
index 0000000..8f46bc9
--- /dev/null
+++ b/tun/wintun/ring.go
@@ -0,0 +1,97 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2019 WireGuard LLC. All Rights Reserved.
+ */
+
+package wintun
+
+import (
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+const (
+	PacketAlignment    = 4        // Number of bytes packets are aligned to in rings
+	PacketSizeMax      = 0xffff   // Maximum packet size
+	PacketCapacity     = 0x800000 // Ring capacity, 8MiB
+	PacketTrailingSize = uint32(unsafe.Sizeof(PacketHeader{})) + ((PacketSizeMax + (PacketAlignment - 1)) &^ (PacketAlignment - 1)) - PacketAlignment
+	ioctlRegisterRings = (51820 << 16) | (0x970 << 2) | 0 /*METHOD_BUFFERED*/ | (0x3 /*FILE_READ_DATA | FILE_WRITE_DATA*/ << 14)
+)
+
+type PacketHeader struct {
+	Size uint32
+}
+
+type Packet struct {
+	PacketHeader
+	Data [PacketSizeMax]byte
+}
+
+type Ring struct {
+	Head      uint32
+	Tail      uint32
+	Alertable int32
+	Data      [PacketCapacity + PacketTrailingSize]byte
+}
+
+type RingDescriptor struct {
+	Send, Receive struct {
+		Size      uint32
+		Ring      *Ring
+		TailMoved windows.Handle
+	}
+}
+
+// Wrap returns value modulo ring capacity
+func (rb *Ring) Wrap(value uint32) uint32 {
+	return value & (PacketCapacity - 1)
+}
+
+// Aligns a packet size to PacketAlignment
+func PacketAlign(size uint32) uint32 {
+	return (size + (PacketAlignment - 1)) &^ (PacketAlignment - 1)
+}
+
+func (descriptor *RingDescriptor) Init() (err error) {
+	descriptor.Send.Size = uint32(unsafe.Sizeof(Ring{}))
+	descriptor.Send.Ring = &Ring{}
+	descriptor.Send.TailMoved, err = windows.CreateEvent(nil, 0, 0, nil)
+	if err != nil {
+		return
+	}
+
+	descriptor.Receive.Size = uint32(unsafe.Sizeof(Ring{}))
+	descriptor.Receive.Ring = &Ring{}
+	descriptor.Receive.TailMoved, err = windows.CreateEvent(nil, 0, 0, nil)
+	if err != nil {
+		windows.CloseHandle(descriptor.Send.TailMoved)
+		return
+	}
+
+	return
+}
+
+func (descriptor *RingDescriptor) Close() {
+	if descriptor.Send.TailMoved != 0 {
+		windows.CloseHandle(descriptor.Send.TailMoved)
+		descriptor.Send.TailMoved = 0
+	}
+	if descriptor.Send.TailMoved != 0 {
+		windows.CloseHandle(descriptor.Receive.TailMoved)
+		descriptor.Receive.TailMoved = 0
+	}
+}
+
+func (wintun *Interface) Register(descriptor *RingDescriptor) (windows.Handle, error) {
+	handle, err := wintun.handle()
+	if err != nil {
+		return 0, err
+	}
+	var bytesReturned uint32
+	err = windows.DeviceIoControl(handle, ioctlRegisterRings, (*byte)(unsafe.Pointer(descriptor)), uint32(unsafe.Sizeof(*descriptor)), nil, 0, &bytesReturned, nil)
+	if err != nil {
+		return 0, err
+	}
+	return handle, nil
+}
diff --git a/tun/wintun/wintun_windows.go b/tun/wintun/wintun_windows.go
index fb8b908..e726748 100644
--- a/tun/wintun/wintun_windows.go
+++ b/tun/wintun/wintun_windows.go
@@ -698,8 +698,8 @@ func (wintun *Interface) deviceData() (setupapi.DevInfo, *setupapi.DevInfoData,
 	return 0, nil, windows.ERROR_OBJECT_NOT_FOUND
 }
 
-// Handle returns a handle to the interface device object.
-func (wintun *Interface) Handle() (windows.Handle, error) {
+// handle returns a handle to the interface device object.
+func (wintun *Interface) handle() (windows.Handle, error) {
 	interfaces, err := setupapi.CM_Get_Device_Interface_List(wintun.devInstanceID, &deviceInterfaceNetGUID, setupapi.CM_GET_DEVICE_INTERFACE_LIST_PRESENT)
 	if err != nil {
 		return windows.InvalidHandle, fmt.Errorf("Error listing NDIS interfaces: %v", err)