Add TLS fragment support

common/tlsfragment/wait_windows.go

@@ -0,0 +1,28 @@
+package tf
+
+import (
+	"context"
+	"errors"
+	"net"
+	"time"
+
+	"github.com/sagernet/sing/common/winiphlpapi"
+
+	"golang.org/x/sys/windows"
+)
+
+func writeAndWaitAck(ctx context.Context, conn *net.TCPConn, payload []byte, fallbackDelay time.Duration) error {
+	start := time.Now()
+	err := winiphlpapi.WriteAndWaitAck(ctx, conn, payload)
+	if err != nil {
+		if errors.Is(err, windows.ERROR_ACCESS_DENIED) {
+			time.Sleep(fallbackDelay)
+			return nil
+		}
+		return err
+	}
+	if time.Since(start) <= 20*time.Millisecond {
+		time.Sleep(fallbackDelay)
+	}
+	return nil
+}