118 lines
3.1 KiB
Go
118 lines
3.1 KiB
Go
/* SPDX-License-Identifier: MIT
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*
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* Copyright (C) 2020 WireGuard LLC. All Rights Reserved.
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*/
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package wintun
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import (
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"runtime"
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"unsafe"
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"golang.org/x/sys/windows"
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)
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const (
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PacketAlignment = 4 // Number of bytes packets are aligned to in rings
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PacketSizeMax = 0xffff // Maximum packet size
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PacketCapacity = 0x800000 // Ring capacity, 8MiB
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PacketTrailingSize = uint32(unsafe.Sizeof(PacketHeader{})) + ((PacketSizeMax + (PacketAlignment - 1)) &^ (PacketAlignment - 1)) - PacketAlignment
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ioctlRegisterRings = (51820 << 16) | (0x970 << 2) | 0 /*METHOD_BUFFERED*/ | (0x3 /*FILE_READ_DATA | FILE_WRITE_DATA*/ << 14)
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)
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type PacketHeader struct {
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Size uint32
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}
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type Packet struct {
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PacketHeader
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Data [PacketSizeMax]byte
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}
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type Ring struct {
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Head uint32
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Tail uint32
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Alertable int32
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Data [PacketCapacity + PacketTrailingSize]byte
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}
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type RingDescriptor struct {
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Send, Receive struct {
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Size uint32
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Ring *Ring
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TailMoved windows.Handle
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}
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}
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// Wrap returns value modulo ring capacity
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func (rb *Ring) Wrap(value uint32) uint32 {
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return value & (PacketCapacity - 1)
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}
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// Aligns a packet size to PacketAlignment
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func PacketAlign(size uint32) uint32 {
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return (size + (PacketAlignment - 1)) &^ (PacketAlignment - 1)
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}
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func NewRingDescriptor() (descriptor *RingDescriptor, err error) {
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descriptor = new(RingDescriptor)
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allocatedRegion, err := windows.VirtualAlloc(0, unsafe.Sizeof(Ring{})*2, windows.MEM_COMMIT|windows.MEM_RESERVE, windows.PAGE_READWRITE)
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if err != nil {
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return
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}
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defer func() {
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if err != nil {
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descriptor.free()
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descriptor = nil
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}
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}()
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descriptor.Send.Size = uint32(unsafe.Sizeof(Ring{}))
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descriptor.Send.Ring = (*Ring)(unsafe.Pointer(allocatedRegion))
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descriptor.Send.TailMoved, err = windows.CreateEvent(nil, 0, 0, nil)
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if err != nil {
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return
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}
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descriptor.Receive.Size = uint32(unsafe.Sizeof(Ring{}))
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descriptor.Receive.Ring = (*Ring)(unsafe.Pointer(allocatedRegion + unsafe.Sizeof(Ring{})))
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descriptor.Receive.TailMoved, err = windows.CreateEvent(nil, 0, 0, nil)
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if err != nil {
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windows.CloseHandle(descriptor.Send.TailMoved)
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return
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}
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runtime.SetFinalizer(descriptor, func(d *RingDescriptor) { d.free() })
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return
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}
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func (descriptor *RingDescriptor) free() {
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if descriptor.Send.Ring != nil {
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windows.VirtualFree(uintptr(unsafe.Pointer(descriptor.Send.Ring)), 0, windows.MEM_RELEASE)
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descriptor.Send.Ring = nil
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descriptor.Receive.Ring = nil
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}
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}
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func (descriptor *RingDescriptor) Close() {
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if descriptor.Send.TailMoved != 0 {
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windows.CloseHandle(descriptor.Send.TailMoved)
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descriptor.Send.TailMoved = 0
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}
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if descriptor.Send.TailMoved != 0 {
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windows.CloseHandle(descriptor.Receive.TailMoved)
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descriptor.Receive.TailMoved = 0
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}
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}
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func (wintun *Interface) Register(descriptor *RingDescriptor) (windows.Handle, error) {
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handle, err := wintun.handle()
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if err != nil {
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return 0, err
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}
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var bytesReturned uint32
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err = windows.DeviceIoControl(handle, ioctlRegisterRings, (*byte)(unsafe.Pointer(descriptor)), uint32(unsafe.Sizeof(*descriptor)), nil, 0, &bytesReturned, nil)
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if err != nil {
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return 0, err
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}
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return handle, nil
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}
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