Support syscallReadWaiter and syscallPacketReadWaiter on windows

common/bufio/copy_direct_windows.go

@@ -2,16 +2,40 @@ package bufio
 
 import (
 	"io"
+	"net/netip"
 	"os"
 	"syscall"
+	"unsafe"
 
 	"github.com/sagernet/sing/common/buf"
 	E "github.com/sagernet/sing/common/exceptions"
+	M "github.com/sagernet/sing/common/metadata"
 	N "github.com/sagernet/sing/common/network"
 
 	"golang.org/x/sys/windows"
 )
 
+//go:linkname modws2_32 golang.org/x/sys/windows.modws2_32
+var modws2_32 *windows.LazyDLL
+
+var procrecv = modws2_32.NewProc("recv")
+
+//go:linkname errnoErr golang.org/x/sys/windows.errnoErr
+func errnoErr(e syscall.Errno) error
+
+func recv(s windows.Handle, buf []byte, flags int32) (n int32, err error) {
+	var _p0 *byte
+	if len(buf) > 0 {
+		_p0 = &buf[0]
+	}
+	r0, _, e1 := syscall.SyscallN(procrecv.Addr(), uintptr(s), uintptr(unsafe.Pointer(_p0)), uintptr(len(buf)), uintptr(flags))
+	n = int32(r0)
+	if n == -1 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 var _ N.ReadWaiter = (*syscallReadWaiter)(nil)
 
 type syscallReadWaiter struct {
@@ -38,15 +62,13 @@ func (w *syscallReadWaiter) InitializeReadWaiter(options N.ReadWaitOptions) (nee
 	w.readFunc = func(fd uintptr) (done bool) {
 		if !w.hasData {
 			w.hasData = true
+			// golang's internal/poll.FD.RawRead will Use a zero-byte read as a way to get notified when this
+			// socket is readable if we return false. So the `recv` syscall will not block the system thread.
 			return false
 		}
 		buffer := w.options.NewBuffer()
-		iovecList := []windows.WSABuf{windows.WSABuf{}}
-		iovecList[0].Buf = &buffer.FreeBytes()[0]
-		iovecList[0].Len = uint32(len(buffer.FreeBytes()))
-		var readN uint32
-		var flags uint32
-		w.readErr = windows.WSARecv(windows.Handle(fd), &iovecList[0], uint32(len(iovecList)), &readN, &flags, nil, nil)
+		var readN int32
+		readN, w.readErr = recv(windows.Handle(fd), buffer.FreeBytes(), 0)
 		if readN > 0 {
 			buffer.Truncate(int(readN))
 			w.options.PostReturn(buffer)
@@ -85,6 +107,79 @@ func (w *syscallReadWaiter) WaitReadBuffer() (buffer *buf.Buffer, err error) {
 	return
 }
 
-func createSyscallPacketReadWaiter(reader any) (N.PacketReadWaiter, bool) {
+var _ N.PacketReadWaiter = (*syscallPacketReadWaiter)(nil)
+
+type syscallPacketReadWaiter struct {
+	rawConn  syscall.RawConn
+	readErr  error
+	readFrom M.Socksaddr
+	readFunc func(fd uintptr) (done bool)
+	hasData  bool
+	buffer   *buf.Buffer
+	options  N.ReadWaitOptions
+}
+
+func createSyscallPacketReadWaiter(reader any) (*syscallPacketReadWaiter, bool) {
+	if syscallConn, isSyscallConn := reader.(syscall.Conn); isSyscallConn {
+		rawConn, err := syscallConn.SyscallConn()
+		if err == nil {
+			return &syscallPacketReadWaiter{rawConn: rawConn}, true
+		}
+	}
 	return nil, false
 }
+
+func (w *syscallPacketReadWaiter) InitializeReadWaiter(options N.ReadWaitOptions) (needCopy bool) {
+	w.options = options
+	w.readFunc = func(fd uintptr) (done bool) {
+		if !w.hasData {
+			w.hasData = true
+			// golang's internal/poll.FD.RawRead will Use a zero-byte read as a way to get notified when this
+			// socket is readable if we return false. So the `recvfrom` syscall will not block the system thread.
+			return false
+		}
+		buffer := w.options.NewPacketBuffer()
+		var readN int
+		var from windows.Sockaddr
+		readN, from, w.readErr = windows.Recvfrom(windows.Handle(fd), buffer.FreeBytes(), 0)
+		if readN > 0 {
+			buffer.Truncate(readN)
+			w.options.PostReturn(buffer)
+			w.buffer = buffer
+		} else {
+			buffer.Release()
+		}
+		if w.readErr == windows.WSAEWOULDBLOCK {
+			return false
+		}
+		if from != nil {
+			switch fromAddr := from.(type) {
+			case *windows.SockaddrInet4:
+				w.readFrom = M.SocksaddrFrom(netip.AddrFrom4(fromAddr.Addr), uint16(fromAddr.Port))
+			case *windows.SockaddrInet6:
+				w.readFrom = M.SocksaddrFrom(netip.AddrFrom16(fromAddr.Addr), uint16(fromAddr.Port)).Unwrap()
+			}
+		}
+		w.hasData = false
+		return true
+	}
+	return false
+}
+
+func (w *syscallPacketReadWaiter) WaitReadPacket() (buffer *buf.Buffer, destination M.Socksaddr, err error) {
+	if w.readFunc == nil {
+		return nil, M.Socksaddr{}, os.ErrInvalid
+	}
+	err = w.rawConn.Read(w.readFunc)
+	if err != nil {
+		return
+	}
+	if w.readErr != nil {
+		err = E.Cause(w.readErr, "raw read")
+		return
+	}
+	buffer = w.buffer
+	w.buffer = nil
+	destination = w.readFrom
+	return
+}