runtime,internal/poll: move websocket handling out of the runtime on Windows

On Windows, the netpoll is currently coupled with the websocket usage
in the internal/poll package.

This CL moves the websocket handling out of the runtime and puts it into
the internal/poll package, which already contains most of the async I/O
logic for websockets.

This is a good refactor per se, as the Go runtime shouldn't know about
websockets. In addition, it will make it easier (in a future CL) to only
load ws2_32.dll when the Go program actually uses websockets.

Change-Id: Ic820872cf9bdbbf092505ed7f7504edb6687735e
Reviewed-on: https://go-review.googlesource.com/c/go/+/556936
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/internal/poll/fd_windows.go

@@ -71,8 +71,6 @@ type operation struct {
 	// fields used by runtime.netpoll
 	runtimeCtx uintptr
 	mode       int32
-	errno      int32
-	qty        uint32
 
 	// fields used only by net package
 	fd     *FD
@@ -83,6 +81,7 @@ type operation struct {
 	rsan   int32
 	handle syscall.Handle
 	flags  uint32
+	qty    uint32
 	bufs   []syscall.WSABuf
 }
 
@@ -174,9 +173,9 @@ func execIO(o *operation, submit func(o *operation) error) (int, error) {
 	// Wait for our request to complete.
 	err = fd.pd.wait(int(o.mode), fd.isFile)
 	if err == nil {
+		err = windows.WSAGetOverlappedResult(fd.Sysfd, &o.o, &o.qty, false, &o.flags)
 		// All is good. Extract our IO results and return.
-		if o.errno != 0 {
-			err = syscall.Errno(o.errno)
+		if err != nil {
 			// More data available. Return back the size of received data.
 			if err == syscall.ERROR_MORE_DATA || err == windows.WSAEMSGSIZE {
 				return int(o.qty), err
@@ -202,8 +201,8 @@ func execIO(o *operation, submit func(o *operation) error) (int, error) {
 	}
 	// Wait for cancellation to complete.
 	fd.pd.waitCanceled(int(o.mode))
-	if o.errno != 0 {
-		err = syscall.Errno(o.errno)
+	err = windows.WSAGetOverlappedResult(fd.Sysfd, &o.o, &o.qty, false, &o.flags)
+	if err != nil {
 		if err == syscall.ERROR_OPERATION_ABORTED { // IO Canceled
 			err = netpollErr
 		}

src/internal/syscall/windows/syscall_windows.go

@@ -235,6 +235,7 @@ type WSAMsg struct {
 }
 
 //sys	WSASocket(af int32, typ int32, protocol int32, protinfo *syscall.WSAProtocolInfo, group uint32, flags uint32) (handle syscall.Handle, err error) [failretval==syscall.InvalidHandle] = ws2_32.WSASocketW
+//sys	WSAGetOverlappedResult(h syscall.Handle, o *syscall.Overlapped, bytes *uint32, wait bool, flags *uint32) (err error) = ws2_32.WSAGetOverlappedResult
 
 func loadWSASendRecvMsg() error {
 	sendRecvMsgFunc.once.Do(func() {

src/internal/syscall/windows/zsyscall_windows.go

@@ -86,6 +86,7 @@ var (
 	procCreateEnvironmentBlock            = moduserenv.NewProc("CreateEnvironmentBlock")
 	procDestroyEnvironmentBlock           = moduserenv.NewProc("DestroyEnvironmentBlock")
 	procGetProfilesDirectoryW             = moduserenv.NewProc("GetProfilesDirectoryW")
+	procWSAGetOverlappedResult            = modws2_32.NewProc("WSAGetOverlappedResult")
 	procWSASocketW                        = modws2_32.NewProc("WSASocketW")
 )
 
@@ -426,6 +427,18 @@ func GetProfilesDirectory(dir *uint16, dirLen *uint32) (err error) {
 	return
 }
 
+func WSAGetOverlappedResult(h syscall.Handle, o *syscall.Overlapped, bytes *uint32, wait bool, flags *uint32) (err error) {
+	var _p0 uint32
+	if wait {
+		_p0 = 1
+	}
+	r1, _, e1 := syscall.Syscall6(procWSAGetOverlappedResult.Addr(), 5, uintptr(h), uintptr(unsafe.Pointer(o)), uintptr(unsafe.Pointer(bytes)), uintptr(_p0), uintptr(unsafe.Pointer(flags)), 0)
+	if r1 == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 func WSASocket(af int32, typ int32, protocol int32, protinfo *syscall.WSAProtocolInfo, group uint32, flags uint32) (handle syscall.Handle, err error) {
 	r0, _, e1 := syscall.Syscall6(procWSASocketW.Addr(), 6, uintptr(af), uintptr(typ), uintptr(protocol), uintptr(unsafe.Pointer(protinfo)), uintptr(group), uintptr(flags))
 	handle = syscall.Handle(r0)

src/runtime/netpoll_windows.go

@@ -19,10 +19,8 @@ type net_op struct {
 	// used by windows
 	o overlapped
 	// used by netpoll
-	pd    *pollDesc
-	mode  int32
-	errno int32
-	qty   uint32
+	pd   *pollDesc
+	mode int32
 }
 
 type overlappedEntry struct {
@@ -86,7 +84,7 @@ func netpollBreak() {
 // delay > 0: block for up to that many nanoseconds
 func netpoll(delay int64) (gList, int32) {
 	var entries [64]overlappedEntry
-	var wait, qty, flags, n, i uint32
+	var wait, n, i uint32
 	var errno int32
 	var op *net_op
 	var toRun gList
@@ -131,12 +129,12 @@ func netpoll(delay int64) (gList, int32) {
 	for i = 0; i < n; i++ {
 		op = entries[i].op
 		if op != nil && op.pd == entries[i].key {
-			errno = 0
-			qty = 0
-			if stdcall5(_WSAGetOverlappedResult, op.pd.fd, uintptr(unsafe.Pointer(op)), uintptr(unsafe.Pointer(&qty)), 0, uintptr(unsafe.Pointer(&flags))) == 0 {
-				errno = int32(getlasterror())
+			mode := op.mode
+			if mode != 'r' && mode != 'w' {
+				println("runtime: GetQueuedCompletionStatusEx returned net_op with invalid mode=", mode)
+				throw("runtime: netpoll failed")
 			}
-			delta += handlecompletion(&toRun, op, errno, qty)
+			delta += netpollready(&toRun, op.pd, mode)
 		} else {
 			netpollWakeSig.Store(0)
 			if delay == 0 {
@@ -148,14 +146,3 @@ func netpoll(delay int64) (gList, int32) {
 	}
 	return toRun, delta
 }
-
-func handlecompletion(toRun *gList, op *net_op, errno int32, qty uint32) int32 {
-	mode := op.mode
-	if mode != 'r' && mode != 'w' {
-		println("runtime: GetQueuedCompletionStatusEx returned invalid mode=", mode)
-		throw("runtime: netpoll failed")
-	}
-	op.errno = errno
-	op.qty = qty
-	return netpollready(toRun, op.pd, mode)
-}

src/runtime/os_windows.go

@@ -139,7 +139,6 @@ var (
 	// These are from non-kernel32.dll, so we prefer to LoadLibraryEx them.
 	_timeBeginPeriod,
 	_timeEndPeriod,
-	_WSAGetOverlappedResult,
 	_ stdFunction
 )
 
@@ -148,7 +147,6 @@ var (
 	ntdlldll            = [...]uint16{'n', 't', 'd', 'l', 'l', '.', 'd', 'l', 'l', 0}
 	powrprofdll         = [...]uint16{'p', 'o', 'w', 'r', 'p', 'r', 'o', 'f', '.', 'd', 'l', 'l', 0}
 	winmmdll            = [...]uint16{'w', 'i', 'n', 'm', 'm', '.', 'd', 'l', 'l', 0}
-	ws2_32dll           = [...]uint16{'w', 's', '2', '_', '3', '2', '.', 'd', 'l', 'l', 0}
 )
 
 // Function to be called by windows CreateThread
@@ -256,15 +254,6 @@ func loadOptionalSyscalls() {
 	}
 	_RtlGetCurrentPeb = windowsFindfunc(n32, []byte("RtlGetCurrentPeb\000"))
 	_RtlGetNtVersionNumbers = windowsFindfunc(n32, []byte("RtlGetNtVersionNumbers\000"))
-
-	ws232 := windowsLoadSystemLib(ws2_32dll[:])
-	if ws232 == 0 {
-		throw("ws2_32.dll not found")
-	}
-	_WSAGetOverlappedResult = windowsFindfunc(ws232, []byte("WSAGetOverlappedResult\000"))
-	if _WSAGetOverlappedResult == nil {
-		throw("WSAGetOverlappedResult not found")
-	}
 }
 
 func monitorSuspendResume() {