wintun: Use native Win32 API for I/O

Signed-off-by: Simon Rozman <simon@rozman.si>

tun/tun.go

@@ -6,7 +6,6 @@
 package tun
 
 import (
-	"fmt"
 	"os"
 )
 
@@ -27,15 +26,3 @@ type TUNDevice interface {
 	Events() chan TUNEvent          // returns a constant channel of events related to the device
 	Close() error                   // stops the device and closes the event channel
 }
-
-func (tun *NativeTun) operateOnFd(fn func(fd uintptr)) {
-	sysconn, err := tun.tunFile.SyscallConn()
-	if err != nil {
-		tun.errors <- fmt.Errorf("unable to find sysconn for tunfile: %s", err.Error())
-		return
-	}
-	err = sysconn.Control(fn)
-	if err != nil {
-		tun.errors <- fmt.Errorf("unable to control sysconn for tunfile: %s", err.Error())
-	}
-}