Source file src/internal/poll/fd_windows.go

Documentation: internal/poll

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package poll
     6  
     7  import (
     8  	"errors"
     9  	"internal/race"
    10  	"internal/syscall/windows"
    11  	"io"
    12  	"sync"
    13  	"syscall"
    14  	"unicode/utf16"
    15  	"unicode/utf8"
    16  	"unsafe"
    17  )
    18  
    19  var (
    20  	initErr error
    21  	ioSync  uint64
    22  )
    23  
    24  // This package uses the SetFileCompletionNotificationModes Windows
    25  // API to skip calling GetQueuedCompletionStatus if an IO operation
    26  // completes synchronously. There is a known bug where
    27  // SetFileCompletionNotificationModes crashes on some systems (see
    28  // https://support.microsoft.com/kb/2568167 for details).
    29  
    30  var useSetFileCompletionNotificationModes bool // determines is SetFileCompletionNotificationModes is present and safe to use
    31  
    32  // checkSetFileCompletionNotificationModes verifies that
    33  // SetFileCompletionNotificationModes Windows API is present
    34  // on the system and is safe to use.
    35  // See https://support.microsoft.com/kb/2568167 for details.
    36  func checkSetFileCompletionNotificationModes() {
    37  	err := syscall.LoadSetFileCompletionNotificationModes()
    38  	if err != nil {
    39  		return
    40  	}
    41  	protos := [2]int32{syscall.IPPROTO_TCP, 0}
    42  	var buf [32]syscall.WSAProtocolInfo
    43  	len := uint32(unsafe.Sizeof(buf))
    44  	n, err := syscall.WSAEnumProtocols(&protos[0], &buf[0], &len)
    45  	if err != nil {
    46  		return
    47  	}
    48  	for i := int32(0); i < n; i++ {
    49  		if buf[i].ServiceFlags1&syscall.XP1_IFS_HANDLES == 0 {
    50  			return
    51  		}
    52  	}
    53  	useSetFileCompletionNotificationModes = true
    54  }
    55  
    56  // InitWSA initiates the use of the Winsock DLL by the current process.
    57  // It is called from the net package at init time to avoid
    58  // loading ws2_32.dll when net is not used.
    59  var InitWSA = sync.OnceFunc(func() {
    60  	var d syscall.WSAData
    61  	e := syscall.WSAStartup(uint32(0x202), &d)
    62  	if e != nil {
    63  		initErr = e
    64  	}
    65  	checkSetFileCompletionNotificationModes()
    66  })
    67  
    68  // operation contains superset of data necessary to perform all async IO.
    69  type operation struct {
    70  	// Used by IOCP interface, it must be first field
    71  	// of the struct, as our code rely on it.
    72  	o syscall.Overlapped
    73  
    74  	// fields used by runtime.netpoll
    75  	runtimeCtx uintptr
    76  	mode       int32
    77  
    78  	// fields used only by net package
    79  	fd     *FD
    80  	buf    syscall.WSABuf
    81  	msg    windows.WSAMsg
    82  	sa     syscall.Sockaddr
    83  	rsa    *syscall.RawSockaddrAny
    84  	rsan   int32
    85  	handle syscall.Handle
    86  	flags  uint32
    87  	qty    uint32
    88  	bufs   []syscall.WSABuf
    89  }
    90  
    91  func (o *operation) InitBuf(buf []byte) {
    92  	o.buf.Len = uint32(len(buf))
    93  	o.buf.Buf = nil
    94  	if len(buf) != 0 {
    95  		o.buf.Buf = &buf[0]
    96  	}
    97  }
    98  
    99  func (o *operation) InitBufs(buf *[][]byte) {
   100  	if o.bufs == nil {
   101  		o.bufs = make([]syscall.WSABuf, 0, len(*buf))
   102  	} else {
   103  		o.bufs = o.bufs[:0]
   104  	}
   105  	for _, b := range *buf {
   106  		if len(b) == 0 {
   107  			o.bufs = append(o.bufs, syscall.WSABuf{})
   108  			continue
   109  		}
   110  		for len(b) > maxRW {
   111  			o.bufs = append(o.bufs, syscall.WSABuf{Len: maxRW, Buf: &b[0]})
   112  			b = b[maxRW:]
   113  		}
   114  		if len(b) > 0 {
   115  			o.bufs = append(o.bufs, syscall.WSABuf{Len: uint32(len(b)), Buf: &b[0]})
   116  		}
   117  	}
   118  }
   119  
   120  // ClearBufs clears all pointers to Buffers parameter captured
   121  // by InitBufs, so it can be released by garbage collector.
   122  func (o *operation) ClearBufs() {
   123  	for i := range o.bufs {
   124  		o.bufs[i].Buf = nil
   125  	}
   126  	o.bufs = o.bufs[:0]
   127  }
   128  
   129  func (o *operation) InitMsg(p []byte, oob []byte) {
   130  	o.InitBuf(p)
   131  	o.msg.Buffers = &o.buf
   132  	o.msg.BufferCount = 1
   133  
   134  	o.msg.Name = nil
   135  	o.msg.Namelen = 0
   136  
   137  	o.msg.Flags = 0
   138  	o.msg.Control.Len = uint32(len(oob))
   139  	o.msg.Control.Buf = nil
   140  	if len(oob) != 0 {
   141  		o.msg.Control.Buf = &oob[0]
   142  	}
   143  }
   144  
   145  // execIO executes a single IO operation o. It submits and cancels
   146  // IO in the current thread for systems where Windows CancelIoEx API
   147  // is available. Alternatively, it passes the request onto
   148  // runtime netpoll and waits for completion or cancels request.
   149  func execIO(o *operation, submit func(o *operation) error) (int, error) {
   150  	if o.fd.pd.runtimeCtx == 0 {
   151  		return 0, errors.New("internal error: polling on unsupported descriptor type")
   152  	}
   153  
   154  	fd := o.fd
   155  	// Notify runtime netpoll about starting IO.
   156  	err := fd.pd.prepare(int(o.mode), fd.isFile)
   157  	if err != nil {
   158  		return 0, err
   159  	}
   160  	// Start IO.
   161  	err = submit(o)
   162  	switch err {
   163  	case nil:
   164  		// IO completed immediately
   165  		if o.fd.skipSyncNotif {
   166  			// No completion message will follow, so return immediately.
   167  			return int(o.qty), nil
   168  		}
   169  		// Need to get our completion message anyway.
   170  	case syscall.ERROR_IO_PENDING:
   171  		// IO started, and we have to wait for its completion.
   172  		err = nil
   173  	default:
   174  		return 0, err
   175  	}
   176  	// Wait for our request to complete.
   177  	err = fd.pd.wait(int(o.mode), fd.isFile)
   178  	if err == nil {
   179  		err = windows.WSAGetOverlappedResult(fd.Sysfd, &o.o, &o.qty, false, &o.flags)
   180  		// All is good. Extract our IO results and return.
   181  		if err != nil {
   182  			// More data available. Return back the size of received data.
   183  			if err == syscall.ERROR_MORE_DATA || err == windows.WSAEMSGSIZE {
   184  				return int(o.qty), err
   185  			}
   186  			return 0, err
   187  		}
   188  		return int(o.qty), nil
   189  	}
   190  	// IO is interrupted by "close" or "timeout"
   191  	netpollErr := err
   192  	switch netpollErr {
   193  	case ErrNetClosing, ErrFileClosing, ErrDeadlineExceeded:
   194  		// will deal with those.
   195  	default:
   196  		panic("unexpected runtime.netpoll error: " + netpollErr.Error())
   197  	}
   198  	// Cancel our request.
   199  	err = syscall.CancelIoEx(fd.Sysfd, &o.o)
   200  	// Assuming ERROR_NOT_FOUND is returned, if IO is completed.
   201  	if err != nil && err != syscall.ERROR_NOT_FOUND {
   202  		// TODO(brainman): maybe do something else, but panic.
   203  		panic(err)
   204  	}
   205  	// Wait for cancellation to complete.
   206  	fd.pd.waitCanceled(int(o.mode))
   207  	err = windows.WSAGetOverlappedResult(fd.Sysfd, &o.o, &o.qty, false, &o.flags)
   208  	if err != nil {
   209  		if err == syscall.ERROR_OPERATION_ABORTED { // IO Canceled
   210  			err = netpollErr
   211  		}
   212  		return 0, err
   213  	}
   214  	// We issued a cancellation request. But, it seems, IO operation succeeded
   215  	// before the cancellation request run. We need to treat the IO operation as
   216  	// succeeded (the bytes are actually sent/recv from network).
   217  	return int(o.qty), nil
   218  }
   219  
   220  // FD is a file descriptor. The net and os packages embed this type in
   221  // a larger type representing a network connection or OS file.
   222  type FD struct {
   223  	// Lock sysfd and serialize access to Read and Write methods.
   224  	fdmu fdMutex
   225  
   226  	// System file descriptor. Immutable until Close.
   227  	Sysfd syscall.Handle
   228  
   229  	// Read operation.
   230  	rop operation
   231  	// Write operation.
   232  	wop operation
   233  
   234  	// I/O poller.
   235  	pd pollDesc
   236  
   237  	// Used to implement pread/pwrite.
   238  	l sync.Mutex
   239  
   240  	// For console I/O.
   241  	lastbits       []byte   // first few bytes of the last incomplete rune in last write
   242  	readuint16     []uint16 // buffer to hold uint16s obtained with ReadConsole
   243  	readbyte       []byte   // buffer to hold decoding of readuint16 from utf16 to utf8
   244  	readbyteOffset int      // readbyte[readOffset:] is yet to be consumed with file.Read
   245  
   246  	// Semaphore signaled when file is closed.
   247  	csema uint32
   248  
   249  	skipSyncNotif bool
   250  
   251  	// Whether this is a streaming descriptor, as opposed to a
   252  	// packet-based descriptor like a UDP socket.
   253  	IsStream bool
   254  
   255  	// Whether a zero byte read indicates EOF. This is false for a
   256  	// message based socket connection.
   257  	ZeroReadIsEOF bool
   258  
   259  	// Whether this is a file rather than a network socket.
   260  	isFile bool
   261  
   262  	// The kind of this file.
   263  	kind fileKind
   264  }
   265  
   266  // fileKind describes the kind of file.
   267  type fileKind byte
   268  
   269  const (
   270  	kindNet fileKind = iota
   271  	kindFile
   272  	kindConsole
   273  	kindPipe
   274  )
   275  
   276  // logInitFD is set by tests to enable file descriptor initialization logging.
   277  var logInitFD func(net string, fd *FD, err error)
   278  
   279  // Init initializes the FD. The Sysfd field should already be set.
   280  // This can be called multiple times on a single FD.
   281  // The net argument is a network name from the net package (e.g., "tcp"),
   282  // or "file" or "console" or "dir".
   283  // Set pollable to true if fd should be managed by runtime netpoll.
   284  func (fd *FD) Init(net string, pollable bool) (string, error) {
   285  	if initErr != nil {
   286  		return "", initErr
   287  	}
   288  
   289  	switch net {
   290  	case "file", "dir":
   291  		fd.kind = kindFile
   292  	case "console":
   293  		fd.kind = kindConsole
   294  	case "pipe":
   295  		fd.kind = kindPipe
   296  	case "tcp", "tcp4", "tcp6",
   297  		"udp", "udp4", "udp6",
   298  		"ip", "ip4", "ip6",
   299  		"unix", "unixgram", "unixpacket":
   300  		fd.kind = kindNet
   301  	default:
   302  		return "", errors.New("internal error: unknown network type " + net)
   303  	}
   304  	fd.isFile = fd.kind != kindNet
   305  
   306  	var err error
   307  	if pollable {
   308  		// Only call init for a network socket.
   309  		// This means that we don't add files to the runtime poller.
   310  		// Adding files to the runtime poller can confuse matters
   311  		// if the user is doing their own overlapped I/O.
   312  		// See issue #21172.
   313  		//
   314  		// In general the code below avoids calling the execIO
   315  		// function for non-network sockets. If some method does
   316  		// somehow call execIO, then execIO, and therefore the
   317  		// calling method, will return an error, because
   318  		// fd.pd.runtimeCtx will be 0.
   319  		err = fd.pd.init(fd)
   320  	}
   321  	if logInitFD != nil {
   322  		logInitFD(net, fd, err)
   323  	}
   324  	if err != nil {
   325  		return "", err
   326  	}
   327  	if pollable && useSetFileCompletionNotificationModes {
   328  		// We do not use events, so we can skip them always.
   329  		flags := uint8(syscall.FILE_SKIP_SET_EVENT_ON_HANDLE)
   330  		switch net {
   331  		case "tcp", "tcp4", "tcp6",
   332  			"udp", "udp4", "udp6":
   333  			flags |= syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS
   334  		}
   335  		err := syscall.SetFileCompletionNotificationModes(fd.Sysfd, flags)
   336  		if err == nil && flags&syscall.FILE_SKIP_COMPLETION_PORT_ON_SUCCESS != 0 {
   337  			fd.skipSyncNotif = true
   338  		}
   339  	}
   340  	// Disable SIO_UDP_CONNRESET behavior.
   341  	// http://support.microsoft.com/kb/263823
   342  	switch net {
   343  	case "udp", "udp4", "udp6":
   344  		ret := uint32(0)
   345  		flag := uint32(0)
   346  		size := uint32(unsafe.Sizeof(flag))
   347  		err := syscall.WSAIoctl(fd.Sysfd, syscall.SIO_UDP_CONNRESET, (*byte)(unsafe.Pointer(&flag)), size, nil, 0, &ret, nil, 0)
   348  		if err != nil {
   349  			return "wsaioctl", err
   350  		}
   351  	}
   352  	fd.rop.mode = 'r'
   353  	fd.wop.mode = 'w'
   354  	fd.rop.fd = fd
   355  	fd.wop.fd = fd
   356  	fd.rop.runtimeCtx = fd.pd.runtimeCtx
   357  	fd.wop.runtimeCtx = fd.pd.runtimeCtx
   358  	return "", nil
   359  }
   360  
   361  func (fd *FD) destroy() error {
   362  	if fd.Sysfd == syscall.InvalidHandle {
   363  		return syscall.EINVAL
   364  	}
   365  	// Poller may want to unregister fd in readiness notification mechanism,
   366  	// so this must be executed before fd.CloseFunc.
   367  	fd.pd.close()
   368  	var err error
   369  	switch fd.kind {
   370  	case kindNet:
   371  		// The net package uses the CloseFunc variable for testing.
   372  		err = CloseFunc(fd.Sysfd)
   373  	default:
   374  		err = syscall.CloseHandle(fd.Sysfd)
   375  	}
   376  	fd.Sysfd = syscall.InvalidHandle
   377  	runtime_Semrelease(&fd.csema)
   378  	return err
   379  }
   380  
   381  // Close closes the FD. The underlying file descriptor is closed by
   382  // the destroy method when there are no remaining references.
   383  func (fd *FD) Close() error {
   384  	if !fd.fdmu.increfAndClose() {
   385  		return errClosing(fd.isFile)
   386  	}
   387  	if fd.kind == kindPipe {
   388  		syscall.CancelIoEx(fd.Sysfd, nil)
   389  	}
   390  	// unblock pending reader and writer
   391  	fd.pd.evict()
   392  	err := fd.decref()
   393  	// Wait until the descriptor is closed. If this was the only
   394  	// reference, it is already closed.
   395  	runtime_Semacquire(&fd.csema)
   396  	return err
   397  }
   398  
   399  // Windows ReadFile and WSARecv use DWORD (uint32) parameter to pass buffer length.
   400  // This prevents us reading blocks larger than 4GB.
   401  // See golang.org/issue/26923.
   402  const maxRW = 1 << 30 // 1GB is large enough and keeps subsequent reads aligned
   403  
   404  // Read implements io.Reader.
   405  func (fd *FD) Read(buf []byte) (int, error) {
   406  	if err := fd.readLock(); err != nil {
   407  		return 0, err
   408  	}
   409  	defer fd.readUnlock()
   410  
   411  	if len(buf) > maxRW {
   412  		buf = buf[:maxRW]
   413  	}
   414  
   415  	var n int
   416  	var err error
   417  	if fd.isFile {
   418  		fd.l.Lock()
   419  		defer fd.l.Unlock()
   420  		switch fd.kind {
   421  		case kindConsole:
   422  			n, err = fd.readConsole(buf)
   423  		default:
   424  			n, err = syscall.Read(fd.Sysfd, buf)
   425  			if fd.kind == kindPipe && err == syscall.ERROR_OPERATION_ABORTED {
   426  				// Close uses CancelIoEx to interrupt concurrent I/O for pipes.
   427  				// If the fd is a pipe and the Read was interrupted by CancelIoEx,
   428  				// we assume it is interrupted by Close.
   429  				err = ErrFileClosing
   430  			}
   431  		}
   432  		if err != nil {
   433  			n = 0
   434  		}
   435  	} else {
   436  		o := &fd.rop
   437  		o.InitBuf(buf)
   438  		n, err = execIO(o, func(o *operation) error {
   439  			return syscall.WSARecv(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
   440  		})
   441  		if race.Enabled {
   442  			race.Acquire(unsafe.Pointer(&ioSync))
   443  		}
   444  	}
   445  	if len(buf) != 0 {
   446  		err = fd.eofError(n, err)
   447  	}
   448  	return n, err
   449  }
   450  
   451  var ReadConsole = syscall.ReadConsole // changed for testing
   452  
   453  // readConsole reads utf16 characters from console File,
   454  // encodes them into utf8 and stores them in buffer b.
   455  // It returns the number of utf8 bytes read and an error, if any.
   456  func (fd *FD) readConsole(b []byte) (int, error) {
   457  	if len(b) == 0 {
   458  		return 0, nil
   459  	}
   460  
   461  	if fd.readuint16 == nil {
   462  		// Note: syscall.ReadConsole fails for very large buffers.
   463  		// The limit is somewhere around (but not exactly) 16384.
   464  		// Stay well below.
   465  		fd.readuint16 = make([]uint16, 0, 10000)
   466  		fd.readbyte = make([]byte, 0, 4*cap(fd.readuint16))
   467  	}
   468  
   469  	for fd.readbyteOffset >= len(fd.readbyte) {
   470  		n := cap(fd.readuint16) - len(fd.readuint16)
   471  		if n > len(b) {
   472  			n = len(b)
   473  		}
   474  		var nw uint32
   475  		err := ReadConsole(fd.Sysfd, &fd.readuint16[:len(fd.readuint16)+1][len(fd.readuint16)], uint32(n), &nw, nil)
   476  		if err != nil {
   477  			return 0, err
   478  		}
   479  		uint16s := fd.readuint16[:len(fd.readuint16)+int(nw)]
   480  		fd.readuint16 = fd.readuint16[:0]
   481  		buf := fd.readbyte[:0]
   482  		for i := 0; i < len(uint16s); i++ {
   483  			r := rune(uint16s[i])
   484  			if utf16.IsSurrogate(r) {
   485  				if i+1 == len(uint16s) {
   486  					if nw > 0 {
   487  						// Save half surrogate pair for next time.
   488  						fd.readuint16 = fd.readuint16[:1]
   489  						fd.readuint16[0] = uint16(r)
   490  						break
   491  					}
   492  					r = utf8.RuneError
   493  				} else {
   494  					r = utf16.DecodeRune(r, rune(uint16s[i+1]))
   495  					if r != utf8.RuneError {
   496  						i++
   497  					}
   498  				}
   499  			}
   500  			buf = utf8.AppendRune(buf, r)
   501  		}
   502  		fd.readbyte = buf
   503  		fd.readbyteOffset = 0
   504  		if nw == 0 {
   505  			break
   506  		}
   507  	}
   508  
   509  	src := fd.readbyte[fd.readbyteOffset:]
   510  	var i int
   511  	for i = 0; i < len(src) && i < len(b); i++ {
   512  		x := src[i]
   513  		if x == 0x1A { // Ctrl-Z
   514  			if i == 0 {
   515  				fd.readbyteOffset++
   516  			}
   517  			break
   518  		}
   519  		b[i] = x
   520  	}
   521  	fd.readbyteOffset += i
   522  	return i, nil
   523  }
   524  
   525  // Pread emulates the Unix pread system call.
   526  func (fd *FD) Pread(b []byte, off int64) (int, error) {
   527  	if fd.kind == kindPipe {
   528  		// Pread does not work with pipes
   529  		return 0, syscall.ESPIPE
   530  	}
   531  	// Call incref, not readLock, because since pread specifies the
   532  	// offset it is independent from other reads.
   533  	if err := fd.incref(); err != nil {
   534  		return 0, err
   535  	}
   536  	defer fd.decref()
   537  
   538  	if len(b) > maxRW {
   539  		b = b[:maxRW]
   540  	}
   541  
   542  	fd.l.Lock()
   543  	defer fd.l.Unlock()
   544  	curoffset, e := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent)
   545  	if e != nil {
   546  		return 0, e
   547  	}
   548  	defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart)
   549  	o := syscall.Overlapped{
   550  		OffsetHigh: uint32(off >> 32),
   551  		Offset:     uint32(off),
   552  	}
   553  	var done uint32
   554  	e = syscall.ReadFile(fd.Sysfd, b, &done, &o)
   555  	if e != nil {
   556  		done = 0
   557  		if e == syscall.ERROR_HANDLE_EOF {
   558  			e = io.EOF
   559  		}
   560  	}
   561  	if len(b) != 0 {
   562  		e = fd.eofError(int(done), e)
   563  	}
   564  	return int(done), e
   565  }
   566  
   567  // ReadFrom wraps the recvfrom network call.
   568  func (fd *FD) ReadFrom(buf []byte) (int, syscall.Sockaddr, error) {
   569  	if len(buf) == 0 {
   570  		return 0, nil, nil
   571  	}
   572  	if len(buf) > maxRW {
   573  		buf = buf[:maxRW]
   574  	}
   575  	if err := fd.readLock(); err != nil {
   576  		return 0, nil, err
   577  	}
   578  	defer fd.readUnlock()
   579  	o := &fd.rop
   580  	o.InitBuf(buf)
   581  	n, err := execIO(o, func(o *operation) error {
   582  		if o.rsa == nil {
   583  			o.rsa = new(syscall.RawSockaddrAny)
   584  		}
   585  		o.rsan = int32(unsafe.Sizeof(*o.rsa))
   586  		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
   587  	})
   588  	err = fd.eofError(n, err)
   589  	if err != nil {
   590  		return n, nil, err
   591  	}
   592  	sa, _ := o.rsa.Sockaddr()
   593  	return n, sa, nil
   594  }
   595  
   596  // ReadFromInet4 wraps the recvfrom network call for IPv4.
   597  func (fd *FD) ReadFromInet4(buf []byte, sa4 *syscall.SockaddrInet4) (int, error) {
   598  	if len(buf) == 0 {
   599  		return 0, nil
   600  	}
   601  	if len(buf) > maxRW {
   602  		buf = buf[:maxRW]
   603  	}
   604  	if err := fd.readLock(); err != nil {
   605  		return 0, err
   606  	}
   607  	defer fd.readUnlock()
   608  	o := &fd.rop
   609  	o.InitBuf(buf)
   610  	n, err := execIO(o, func(o *operation) error {
   611  		if o.rsa == nil {
   612  			o.rsa = new(syscall.RawSockaddrAny)
   613  		}
   614  		o.rsan = int32(unsafe.Sizeof(*o.rsa))
   615  		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
   616  	})
   617  	err = fd.eofError(n, err)
   618  	if err != nil {
   619  		return n, err
   620  	}
   621  	rawToSockaddrInet4(o.rsa, sa4)
   622  	return n, err
   623  }
   624  
   625  // ReadFromInet6 wraps the recvfrom network call for IPv6.
   626  func (fd *FD) ReadFromInet6(buf []byte, sa6 *syscall.SockaddrInet6) (int, error) {
   627  	if len(buf) == 0 {
   628  		return 0, nil
   629  	}
   630  	if len(buf) > maxRW {
   631  		buf = buf[:maxRW]
   632  	}
   633  	if err := fd.readLock(); err != nil {
   634  		return 0, err
   635  	}
   636  	defer fd.readUnlock()
   637  	o := &fd.rop
   638  	o.InitBuf(buf)
   639  	n, err := execIO(o, func(o *operation) error {
   640  		if o.rsa == nil {
   641  			o.rsa = new(syscall.RawSockaddrAny)
   642  		}
   643  		o.rsan = int32(unsafe.Sizeof(*o.rsa))
   644  		return syscall.WSARecvFrom(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, o.rsa, &o.rsan, &o.o, nil)
   645  	})
   646  	err = fd.eofError(n, err)
   647  	if err != nil {
   648  		return n, err
   649  	}
   650  	rawToSockaddrInet6(o.rsa, sa6)
   651  	return n, err
   652  }
   653  
   654  // Write implements io.Writer.
   655  func (fd *FD) Write(buf []byte) (int, error) {
   656  	if err := fd.writeLock(); err != nil {
   657  		return 0, err
   658  	}
   659  	defer fd.writeUnlock()
   660  	if fd.isFile {
   661  		fd.l.Lock()
   662  		defer fd.l.Unlock()
   663  	}
   664  
   665  	ntotal := 0
   666  	for len(buf) > 0 {
   667  		b := buf
   668  		if len(b) > maxRW {
   669  			b = b[:maxRW]
   670  		}
   671  		var n int
   672  		var err error
   673  		if fd.isFile {
   674  			switch fd.kind {
   675  			case kindConsole:
   676  				n, err = fd.writeConsole(b)
   677  			default:
   678  				n, err = syscall.Write(fd.Sysfd, b)
   679  				if fd.kind == kindPipe && err == syscall.ERROR_OPERATION_ABORTED {
   680  					// Close uses CancelIoEx to interrupt concurrent I/O for pipes.
   681  					// If the fd is a pipe and the Write was interrupted by CancelIoEx,
   682  					// we assume it is interrupted by Close.
   683  					err = ErrFileClosing
   684  				}
   685  			}
   686  			if err != nil {
   687  				n = 0
   688  			}
   689  		} else {
   690  			if race.Enabled {
   691  				race.ReleaseMerge(unsafe.Pointer(&ioSync))
   692  			}
   693  			o := &fd.wop
   694  			o.InitBuf(b)
   695  			n, err = execIO(o, func(o *operation) error {
   696  				return syscall.WSASend(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, &o.o, nil)
   697  			})
   698  		}
   699  		ntotal += n
   700  		if err != nil {
   701  			return ntotal, err
   702  		}
   703  		buf = buf[n:]
   704  	}
   705  	return ntotal, nil
   706  }
   707  
   708  // writeConsole writes len(b) bytes to the console File.
   709  // It returns the number of bytes written and an error, if any.
   710  func (fd *FD) writeConsole(b []byte) (int, error) {
   711  	n := len(b)
   712  	runes := make([]rune, 0, 256)
   713  	if len(fd.lastbits) > 0 {
   714  		b = append(fd.lastbits, b...)
   715  		fd.lastbits = nil
   716  
   717  	}
   718  	for len(b) >= utf8.UTFMax || utf8.FullRune(b) {
   719  		r, l := utf8.DecodeRune(b)
   720  		runes = append(runes, r)
   721  		b = b[l:]
   722  	}
   723  	if len(b) > 0 {
   724  		fd.lastbits = make([]byte, len(b))
   725  		copy(fd.lastbits, b)
   726  	}
   727  	// syscall.WriteConsole seems to fail, if given large buffer.
   728  	// So limit the buffer to 16000 characters. This number was
   729  	// discovered by experimenting with syscall.WriteConsole.
   730  	const maxWrite = 16000
   731  	for len(runes) > 0 {
   732  		m := len(runes)
   733  		if m > maxWrite {
   734  			m = maxWrite
   735  		}
   736  		chunk := runes[:m]
   737  		runes = runes[m:]
   738  		uint16s := utf16.Encode(chunk)
   739  		for len(uint16s) > 0 {
   740  			var written uint32
   741  			err := syscall.WriteConsole(fd.Sysfd, &uint16s[0], uint32(len(uint16s)), &written, nil)
   742  			if err != nil {
   743  				return 0, err
   744  			}
   745  			uint16s = uint16s[written:]
   746  		}
   747  	}
   748  	return n, nil
   749  }
   750  
   751  // Pwrite emulates the Unix pwrite system call.
   752  func (fd *FD) Pwrite(buf []byte, off int64) (int, error) {
   753  	if fd.kind == kindPipe {
   754  		// Pwrite does not work with pipes
   755  		return 0, syscall.ESPIPE
   756  	}
   757  	// Call incref, not writeLock, because since pwrite specifies the
   758  	// offset it is independent from other writes.
   759  	if err := fd.incref(); err != nil {
   760  		return 0, err
   761  	}
   762  	defer fd.decref()
   763  
   764  	fd.l.Lock()
   765  	defer fd.l.Unlock()
   766  	curoffset, e := syscall.Seek(fd.Sysfd, 0, io.SeekCurrent)
   767  	if e != nil {
   768  		return 0, e
   769  	}
   770  	defer syscall.Seek(fd.Sysfd, curoffset, io.SeekStart)
   771  
   772  	ntotal := 0
   773  	for len(buf) > 0 {
   774  		b := buf
   775  		if len(b) > maxRW {
   776  			b = b[:maxRW]
   777  		}
   778  		var n uint32
   779  		o := syscall.Overlapped{
   780  			OffsetHigh: uint32(off >> 32),
   781  			Offset:     uint32(off),
   782  		}
   783  		e = syscall.WriteFile(fd.Sysfd, b, &n, &o)
   784  		ntotal += int(n)
   785  		if e != nil {
   786  			return ntotal, e
   787  		}
   788  		buf = buf[n:]
   789  		off += int64(n)
   790  	}
   791  	return ntotal, nil
   792  }
   793  
   794  // Writev emulates the Unix writev system call.
   795  func (fd *FD) Writev(buf *[][]byte) (int64, error) {
   796  	if len(*buf) == 0 {
   797  		return 0, nil
   798  	}
   799  	if err := fd.writeLock(); err != nil {
   800  		return 0, err
   801  	}
   802  	defer fd.writeUnlock()
   803  	if race.Enabled {
   804  		race.ReleaseMerge(unsafe.Pointer(&ioSync))
   805  	}
   806  	o := &fd.wop
   807  	o.InitBufs(buf)
   808  	n, err := execIO(o, func(o *operation) error {
   809  		return syscall.WSASend(o.fd.Sysfd, &o.bufs[0], uint32(len(o.bufs)), &o.qty, 0, &o.o, nil)
   810  	})
   811  	o.ClearBufs()
   812  	TestHookDidWritev(n)
   813  	consume(buf, int64(n))
   814  	return int64(n), err
   815  }
   816  
   817  // WriteTo wraps the sendto network call.
   818  func (fd *FD) WriteTo(buf []byte, sa syscall.Sockaddr) (int, error) {
   819  	if err := fd.writeLock(); err != nil {
   820  		return 0, err
   821  	}
   822  	defer fd.writeUnlock()
   823  
   824  	if len(buf) == 0 {
   825  		// handle zero-byte payload
   826  		o := &fd.wop
   827  		o.InitBuf(buf)
   828  		o.sa = sa
   829  		n, err := execIO(o, func(o *operation) error {
   830  			return syscall.WSASendto(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, o.sa, &o.o, nil)
   831  		})
   832  		return n, err
   833  	}
   834  
   835  	ntotal := 0
   836  	for len(buf) > 0 {
   837  		b := buf
   838  		if len(b) > maxRW {
   839  			b = b[:maxRW]
   840  		}
   841  		o := &fd.wop
   842  		o.InitBuf(b)
   843  		o.sa = sa
   844  		n, err := execIO(o, func(o *operation) error {
   845  			return syscall.WSASendto(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, o.sa, &o.o, nil)
   846  		})
   847  		ntotal += int(n)
   848  		if err != nil {
   849  			return ntotal, err
   850  		}
   851  		buf = buf[n:]
   852  	}
   853  	return ntotal, nil
   854  }
   855  
   856  // WriteToInet4 is WriteTo, specialized for syscall.SockaddrInet4.
   857  func (fd *FD) WriteToInet4(buf []byte, sa4 *syscall.SockaddrInet4) (int, error) {
   858  	if err := fd.writeLock(); err != nil {
   859  		return 0, err
   860  	}
   861  	defer fd.writeUnlock()
   862  
   863  	if len(buf) == 0 {
   864  		// handle zero-byte payload
   865  		o := &fd.wop
   866  		o.InitBuf(buf)
   867  		n, err := execIO(o, func(o *operation) error {
   868  			return windows.WSASendtoInet4(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa4, &o.o, nil)
   869  		})
   870  		return n, err
   871  	}
   872  
   873  	ntotal := 0
   874  	for len(buf) > 0 {
   875  		b := buf
   876  		if len(b) > maxRW {
   877  			b = b[:maxRW]
   878  		}
   879  		o := &fd.wop
   880  		o.InitBuf(b)
   881  		n, err := execIO(o, func(o *operation) error {
   882  			return windows.WSASendtoInet4(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa4, &o.o, nil)
   883  		})
   884  		ntotal += int(n)
   885  		if err != nil {
   886  			return ntotal, err
   887  		}
   888  		buf = buf[n:]
   889  	}
   890  	return ntotal, nil
   891  }
   892  
   893  // WriteToInet6 is WriteTo, specialized for syscall.SockaddrInet6.
   894  func (fd *FD) WriteToInet6(buf []byte, sa6 *syscall.SockaddrInet6) (int, error) {
   895  	if err := fd.writeLock(); err != nil {
   896  		return 0, err
   897  	}
   898  	defer fd.writeUnlock()
   899  
   900  	if len(buf) == 0 {
   901  		// handle zero-byte payload
   902  		o := &fd.wop
   903  		o.InitBuf(buf)
   904  		n, err := execIO(o, func(o *operation) error {
   905  			return windows.WSASendtoInet6(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa6, &o.o, nil)
   906  		})
   907  		return n, err
   908  	}
   909  
   910  	ntotal := 0
   911  	for len(buf) > 0 {
   912  		b := buf
   913  		if len(b) > maxRW {
   914  			b = b[:maxRW]
   915  		}
   916  		o := &fd.wop
   917  		o.InitBuf(b)
   918  		n, err := execIO(o, func(o *operation) error {
   919  			return windows.WSASendtoInet6(o.fd.Sysfd, &o.buf, 1, &o.qty, 0, sa6, &o.o, nil)
   920  		})
   921  		ntotal += int(n)
   922  		if err != nil {
   923  			return ntotal, err
   924  		}
   925  		buf = buf[n:]
   926  	}
   927  	return ntotal, nil
   928  }
   929  
   930  // Call ConnectEx. This doesn't need any locking, since it is only
   931  // called when the descriptor is first created. This is here rather
   932  // than in the net package so that it can use fd.wop.
   933  func (fd *FD) ConnectEx(ra syscall.Sockaddr) error {
   934  	o := &fd.wop
   935  	o.sa = ra
   936  	_, err := execIO(o, func(o *operation) error {
   937  		return ConnectExFunc(o.fd.Sysfd, o.sa, nil, 0, nil, &o.o)
   938  	})
   939  	return err
   940  }
   941  
   942  func (fd *FD) acceptOne(s syscall.Handle, rawsa []syscall.RawSockaddrAny, o *operation) (string, error) {
   943  	// Submit accept request.
   944  	o.handle = s
   945  	o.rsan = int32(unsafe.Sizeof(rawsa[0]))
   946  	_, err := execIO(o, func(o *operation) error {
   947  		return AcceptFunc(o.fd.Sysfd, o.handle, (*byte)(unsafe.Pointer(&rawsa[0])), 0, uint32(o.rsan), uint32(o.rsan), &o.qty, &o.o)
   948  	})
   949  	if err != nil {
   950  		CloseFunc(s)
   951  		return "acceptex", err
   952  	}
   953  
   954  	// Inherit properties of the listening socket.
   955  	err = syscall.Setsockopt(s, syscall.SOL_SOCKET, syscall.SO_UPDATE_ACCEPT_CONTEXT, (*byte)(unsafe.Pointer(&fd.Sysfd)), int32(unsafe.Sizeof(fd.Sysfd)))
   956  	if err != nil {
   957  		CloseFunc(s)
   958  		return "setsockopt", err
   959  	}
   960  
   961  	return "", nil
   962  }
   963  
   964  // Accept handles accepting a socket. The sysSocket parameter is used
   965  // to allocate the net socket.
   966  func (fd *FD) Accept(sysSocket func() (syscall.Handle, error)) (syscall.Handle, []syscall.RawSockaddrAny, uint32, string, error) {
   967  	if err := fd.readLock(); err != nil {
   968  		return syscall.InvalidHandle, nil, 0, "", err
   969  	}
   970  	defer fd.readUnlock()
   971  
   972  	o := &fd.rop
   973  	var rawsa [2]syscall.RawSockaddrAny
   974  	for {
   975  		s, err := sysSocket()
   976  		if err != nil {
   977  			return syscall.InvalidHandle, nil, 0, "", err
   978  		}
   979  
   980  		errcall, err := fd.acceptOne(s, rawsa[:], o)
   981  		if err == nil {
   982  			return s, rawsa[:], uint32(o.rsan), "", nil
   983  		}
   984  
   985  		// Sometimes we see WSAECONNRESET and ERROR_NETNAME_DELETED is
   986  		// returned here. These happen if connection reset is received
   987  		// before AcceptEx could complete. These errors relate to new
   988  		// connection, not to AcceptEx, so ignore broken connection and
   989  		// try AcceptEx again for more connections.
   990  		errno, ok := err.(syscall.Errno)
   991  		if !ok {
   992  			return syscall.InvalidHandle, nil, 0, errcall, err
   993  		}
   994  		switch errno {
   995  		case syscall.ERROR_NETNAME_DELETED, syscall.WSAECONNRESET:
   996  			// ignore these and try again
   997  		default:
   998  			return syscall.InvalidHandle, nil, 0, errcall, err
   999  		}
  1000  	}
  1001  }
  1002  
  1003  // Seek wraps syscall.Seek.
  1004  func (fd *FD) Seek(offset int64, whence int) (int64, error) {
  1005  	if fd.kind == kindPipe {
  1006  		return 0, syscall.ESPIPE
  1007  	}
  1008  	if err := fd.incref(); err != nil {
  1009  		return 0, err
  1010  	}
  1011  	defer fd.decref()
  1012  
  1013  	fd.l.Lock()
  1014  	defer fd.l.Unlock()
  1015  
  1016  	return syscall.Seek(fd.Sysfd, offset, whence)
  1017  }
  1018  
  1019  // Fchmod updates syscall.ByHandleFileInformation.Fileattributes when needed.
  1020  func (fd *FD) Fchmod(mode uint32) error {
  1021  	if err := fd.incref(); err != nil {
  1022  		return err
  1023  	}
  1024  	defer fd.decref()
  1025  
  1026  	var d syscall.ByHandleFileInformation
  1027  	if err := syscall.GetFileInformationByHandle(fd.Sysfd, &d); err != nil {
  1028  		return err
  1029  	}
  1030  	attrs := d.FileAttributes
  1031  	if mode&syscall.S_IWRITE != 0 {
  1032  		attrs &^= syscall.FILE_ATTRIBUTE_READONLY
  1033  	} else {
  1034  		attrs |= syscall.FILE_ATTRIBUTE_READONLY
  1035  	}
  1036  	if attrs == d.FileAttributes {
  1037  		return nil
  1038  	}
  1039  
  1040  	var du windows.FILE_BASIC_INFO
  1041  	du.FileAttributes = attrs
  1042  	return windows.SetFileInformationByHandle(fd.Sysfd, windows.FileBasicInfo, unsafe.Pointer(&du), uint32(unsafe.Sizeof(du)))
  1043  }
  1044  
  1045  // Fchdir wraps syscall.Fchdir.
  1046  func (fd *FD) Fchdir() error {
  1047  	if err := fd.incref(); err != nil {
  1048  		return err
  1049  	}
  1050  	defer fd.decref()
  1051  	return syscall.Fchdir(fd.Sysfd)
  1052  }
  1053  
  1054  // GetFileType wraps syscall.GetFileType.
  1055  func (fd *FD) GetFileType() (uint32, error) {
  1056  	if err := fd.incref(); err != nil {
  1057  		return 0, err
  1058  	}
  1059  	defer fd.decref()
  1060  	return syscall.GetFileType(fd.Sysfd)
  1061  }
  1062  
  1063  // GetFileInformationByHandle wraps GetFileInformationByHandle.
  1064  func (fd *FD) GetFileInformationByHandle(data *syscall.ByHandleFileInformation) error {
  1065  	if err := fd.incref(); err != nil {
  1066  		return err
  1067  	}
  1068  	defer fd.decref()
  1069  	return syscall.GetFileInformationByHandle(fd.Sysfd, data)
  1070  }
  1071  
  1072  // RawRead invokes the user-defined function f for a read operation.
  1073  func (fd *FD) RawRead(f func(uintptr) bool) error {
  1074  	if err := fd.readLock(); err != nil {
  1075  		return err
  1076  	}
  1077  	defer fd.readUnlock()
  1078  	for {
  1079  		if f(uintptr(fd.Sysfd)) {
  1080  			return nil
  1081  		}
  1082  
  1083  		// Use a zero-byte read as a way to get notified when this
  1084  		// socket is readable. h/t https://stackoverflow.com/a/42019668/332798
  1085  		o := &fd.rop
  1086  		o.InitBuf(nil)
  1087  		if !fd.IsStream {
  1088  			o.flags |= windows.MSG_PEEK
  1089  		}
  1090  		_, err := execIO(o, func(o *operation) error {
  1091  			return syscall.WSARecv(o.fd.Sysfd, &o.buf, 1, &o.qty, &o.flags, &o.o, nil)
  1092  		})
  1093  		if err == windows.WSAEMSGSIZE {
  1094  			// expected with a 0-byte peek, ignore.
  1095  		} else if err != nil {
  1096  			return err
  1097  		}
  1098  	}
  1099  }
  1100  
  1101  // RawWrite invokes the user-defined function f for a write operation.
  1102  func (fd *FD) RawWrite(f func(uintptr) bool) error {
  1103  	if err := fd.writeLock(); err != nil {
  1104  		return err
  1105  	}
  1106  	defer fd.writeUnlock()
  1107  
  1108  	if f(uintptr(fd.Sysfd)) {
  1109  		return nil
  1110  	}
  1111  
  1112  	// TODO(tmm1): find a way to detect socket writability
  1113  	return syscall.EWINDOWS
  1114  }
  1115  
  1116  func sockaddrInet4ToRaw(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet4) int32 {
  1117  	*rsa = syscall.RawSockaddrAny{}
  1118  	raw := (*syscall.RawSockaddrInet4)(unsafe.Pointer(rsa))
  1119  	raw.Family = syscall.AF_INET
  1120  	p := (*[2]byte)(unsafe.Pointer(&raw.Port))
  1121  	p[0] = byte(sa.Port >> 8)
  1122  	p[1] = byte(sa.Port)
  1123  	raw.Addr = sa.Addr
  1124  	return int32(unsafe.Sizeof(*raw))
  1125  }
  1126  
  1127  func sockaddrInet6ToRaw(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet6) int32 {
  1128  	*rsa = syscall.RawSockaddrAny{}
  1129  	raw := (*syscall.RawSockaddrInet6)(unsafe.Pointer(rsa))
  1130  	raw.Family = syscall.AF_INET6
  1131  	p := (*[2]byte)(unsafe.Pointer(&raw.Port))
  1132  	p[0] = byte(sa.Port >> 8)
  1133  	p[1] = byte(sa.Port)
  1134  	raw.Scope_id = sa.ZoneId
  1135  	raw.Addr = sa.Addr
  1136  	return int32(unsafe.Sizeof(*raw))
  1137  }
  1138  
  1139  func rawToSockaddrInet4(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet4) {
  1140  	pp := (*syscall.RawSockaddrInet4)(unsafe.Pointer(rsa))
  1141  	p := (*[2]byte)(unsafe.Pointer(&pp.Port))
  1142  	sa.Port = int(p[0])<<8 + int(p[1])
  1143  	sa.Addr = pp.Addr
  1144  }
  1145  
  1146  func rawToSockaddrInet6(rsa *syscall.RawSockaddrAny, sa *syscall.SockaddrInet6) {
  1147  	pp := (*syscall.RawSockaddrInet6)(unsafe.Pointer(rsa))
  1148  	p := (*[2]byte)(unsafe.Pointer(&pp.Port))
  1149  	sa.Port = int(p[0])<<8 + int(p[1])
  1150  	sa.ZoneId = pp.Scope_id
  1151  	sa.Addr = pp.Addr
  1152  }
  1153  
  1154  func sockaddrToRaw(rsa *syscall.RawSockaddrAny, sa syscall.Sockaddr) (int32, error) {
  1155  	switch sa := sa.(type) {
  1156  	case *syscall.SockaddrInet4:
  1157  		sz := sockaddrInet4ToRaw(rsa, sa)
  1158  		return sz, nil
  1159  	case *syscall.SockaddrInet6:
  1160  		sz := sockaddrInet6ToRaw(rsa, sa)
  1161  		return sz, nil
  1162  	default:
  1163  		return 0, syscall.EWINDOWS
  1164  	}
  1165  }
  1166  
  1167  // ReadMsg wraps the WSARecvMsg network call.
  1168  func (fd *FD) ReadMsg(p []byte, oob []byte, flags int) (int, int, int, syscall.Sockaddr, error) {
  1169  	if err := fd.readLock(); err != nil {
  1170  		return 0, 0, 0, nil, err
  1171  	}
  1172  	defer fd.readUnlock()
  1173  
  1174  	if len(p) > maxRW {
  1175  		p = p[:maxRW]
  1176  	}
  1177  
  1178  	o := &fd.rop
  1179  	o.InitMsg(p, oob)
  1180  	if o.rsa == nil {
  1181  		o.rsa = new(syscall.RawSockaddrAny)
  1182  	}
  1183  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1184  	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
  1185  	o.msg.Flags = uint32(flags)
  1186  	n, err := execIO(o, func(o *operation) error {
  1187  		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
  1188  	})
  1189  	err = fd.eofError(n, err)
  1190  	var sa syscall.Sockaddr
  1191  	if err == nil {
  1192  		sa, err = o.rsa.Sockaddr()
  1193  	}
  1194  	return n, int(o.msg.Control.Len), int(o.msg.Flags), sa, err
  1195  }
  1196  
  1197  // ReadMsgInet4 is ReadMsg, but specialized to return a syscall.SockaddrInet4.
  1198  func (fd *FD) ReadMsgInet4(p []byte, oob []byte, flags int, sa4 *syscall.SockaddrInet4) (int, int, int, error) {
  1199  	if err := fd.readLock(); err != nil {
  1200  		return 0, 0, 0, err
  1201  	}
  1202  	defer fd.readUnlock()
  1203  
  1204  	if len(p) > maxRW {
  1205  		p = p[:maxRW]
  1206  	}
  1207  
  1208  	o := &fd.rop
  1209  	o.InitMsg(p, oob)
  1210  	if o.rsa == nil {
  1211  		o.rsa = new(syscall.RawSockaddrAny)
  1212  	}
  1213  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1214  	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
  1215  	o.msg.Flags = uint32(flags)
  1216  	n, err := execIO(o, func(o *operation) error {
  1217  		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
  1218  	})
  1219  	err = fd.eofError(n, err)
  1220  	if err == nil {
  1221  		rawToSockaddrInet4(o.rsa, sa4)
  1222  	}
  1223  	return n, int(o.msg.Control.Len), int(o.msg.Flags), err
  1224  }
  1225  
  1226  // ReadMsgInet6 is ReadMsg, but specialized to return a syscall.SockaddrInet6.
  1227  func (fd *FD) ReadMsgInet6(p []byte, oob []byte, flags int, sa6 *syscall.SockaddrInet6) (int, int, int, error) {
  1228  	if err := fd.readLock(); err != nil {
  1229  		return 0, 0, 0, err
  1230  	}
  1231  	defer fd.readUnlock()
  1232  
  1233  	if len(p) > maxRW {
  1234  		p = p[:maxRW]
  1235  	}
  1236  
  1237  	o := &fd.rop
  1238  	o.InitMsg(p, oob)
  1239  	if o.rsa == nil {
  1240  		o.rsa = new(syscall.RawSockaddrAny)
  1241  	}
  1242  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1243  	o.msg.Namelen = int32(unsafe.Sizeof(*o.rsa))
  1244  	o.msg.Flags = uint32(flags)
  1245  	n, err := execIO(o, func(o *operation) error {
  1246  		return windows.WSARecvMsg(o.fd.Sysfd, &o.msg, &o.qty, &o.o, nil)
  1247  	})
  1248  	err = fd.eofError(n, err)
  1249  	if err == nil {
  1250  		rawToSockaddrInet6(o.rsa, sa6)
  1251  	}
  1252  	return n, int(o.msg.Control.Len), int(o.msg.Flags), err
  1253  }
  1254  
  1255  // WriteMsg wraps the WSASendMsg network call.
  1256  func (fd *FD) WriteMsg(p []byte, oob []byte, sa syscall.Sockaddr) (int, int, error) {
  1257  	if len(p) > maxRW {
  1258  		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
  1259  	}
  1260  
  1261  	if err := fd.writeLock(); err != nil {
  1262  		return 0, 0, err
  1263  	}
  1264  	defer fd.writeUnlock()
  1265  
  1266  	o := &fd.wop
  1267  	o.InitMsg(p, oob)
  1268  	if sa != nil {
  1269  		if o.rsa == nil {
  1270  			o.rsa = new(syscall.RawSockaddrAny)
  1271  		}
  1272  		len, err := sockaddrToRaw(o.rsa, sa)
  1273  		if err != nil {
  1274  			return 0, 0, err
  1275  		}
  1276  		o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1277  		o.msg.Namelen = len
  1278  	}
  1279  	n, err := execIO(o, func(o *operation) error {
  1280  		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
  1281  	})
  1282  	return n, int(o.msg.Control.Len), err
  1283  }
  1284  
  1285  // WriteMsgInet4 is WriteMsg specialized for syscall.SockaddrInet4.
  1286  func (fd *FD) WriteMsgInet4(p []byte, oob []byte, sa *syscall.SockaddrInet4) (int, int, error) {
  1287  	if len(p) > maxRW {
  1288  		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
  1289  	}
  1290  
  1291  	if err := fd.writeLock(); err != nil {
  1292  		return 0, 0, err
  1293  	}
  1294  	defer fd.writeUnlock()
  1295  
  1296  	o := &fd.wop
  1297  	o.InitMsg(p, oob)
  1298  	if o.rsa == nil {
  1299  		o.rsa = new(syscall.RawSockaddrAny)
  1300  	}
  1301  	len := sockaddrInet4ToRaw(o.rsa, sa)
  1302  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1303  	o.msg.Namelen = len
  1304  	n, err := execIO(o, func(o *operation) error {
  1305  		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
  1306  	})
  1307  	return n, int(o.msg.Control.Len), err
  1308  }
  1309  
  1310  // WriteMsgInet6 is WriteMsg specialized for syscall.SockaddrInet6.
  1311  func (fd *FD) WriteMsgInet6(p []byte, oob []byte, sa *syscall.SockaddrInet6) (int, int, error) {
  1312  	if len(p) > maxRW {
  1313  		return 0, 0, errors.New("packet is too large (only 1GB is allowed)")
  1314  	}
  1315  
  1316  	if err := fd.writeLock(); err != nil {
  1317  		return 0, 0, err
  1318  	}
  1319  	defer fd.writeUnlock()
  1320  
  1321  	o := &fd.wop
  1322  	o.InitMsg(p, oob)
  1323  	if o.rsa == nil {
  1324  		o.rsa = new(syscall.RawSockaddrAny)
  1325  	}
  1326  	len := sockaddrInet6ToRaw(o.rsa, sa)
  1327  	o.msg.Name = (syscall.Pointer)(unsafe.Pointer(o.rsa))
  1328  	o.msg.Namelen = len
  1329  	n, err := execIO(o, func(o *operation) error {
  1330  		return windows.WSASendMsg(o.fd.Sysfd, &o.msg, 0, &o.qty, &o.o, nil)
  1331  	})
  1332  	return n, int(o.msg.Control.Len), err
  1333  }
  1334  
  1335  func DupCloseOnExec(fd int) (int, string, error) {
  1336  	proc, err := syscall.GetCurrentProcess()
  1337  	if err != nil {
  1338  		return 0, "GetCurrentProcess", err
  1339  	}
  1340  
  1341  	var nfd syscall.Handle
  1342  	const inherit = false // analogous to CLOEXEC
  1343  	if err := syscall.DuplicateHandle(proc, syscall.Handle(fd), proc, &nfd, 0, inherit, syscall.DUPLICATE_SAME_ACCESS); err != nil {
  1344  		return 0, "DuplicateHandle", err
  1345  	}
  1346  	return int(nfd), "", nil
  1347  }
  1348  

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