tun/tap 디바이스 생성 코드인데요..디바이스 생성이 안되네요;

string dev_name;
int fd = tap_open( dev_name );
cout << fd << ", " << dev_name.c_str() << endl;

string dev_name( "tap0" );
int fd = tap_open( dev_name );
cout << fd << ", " << dev_name.c_str() << endl;

#include <string>
#include <cstdlib>
#include <cstring>
#include <cerrno>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <linux/if.h>
#include <linux/if_tun.h>
#include <loki/ScopeGuard.h>
 
using namespace std;
 
#ifndef OTUNSETNOCSUM
/* pre 2.4.6 compatibility */
#define OTUNSETNOCSUM  (('T'<< 8) | 200)
#define OTUNSETDEBUG   (('T'<< 8) | 201)
#define OTUNSETIFF     (('T'<< 8) | 202)
#define OTUNSETPERSIST (('T'<< 8) | 203)
#define OTUNSETOWNER   (('T'<< 8) | 204)
#endif
 
static int tuntap_open( string& dev_name, bool istun )
{
        int fd = open( "/dev/net/tun", O_RDWR );
        Loki::ScopeGuard auto_close = Loki::MakeGuard( close, fd );
        if( fd < 0 )
                return -1;
 
        ifreq ifr;
        memset( &ifr, 0, sizeof ifr );
        ifr.ifr_flags = ( istun ? IFF_TUN : IFF_TAP ) | IFF_NO_PI;
        if( !dev_name.empty() )
                strncpy( ifr.ifr_name, dev_name.c_str(), IFNAMSIZ );
 
        if( ioctl( fd, TUNSETIFF, &ifr ) < 0 ) {
                if( EBADFD == errno ) {
                        if( ioctl( fd, OTUNSETIFF, &ifr) < 0 )
                                return -1;
                }
                else {
                        return -1;
                }
        }
 
        dev_name = ifr.ifr_name;
 
        auto_close.Dismiss();
        return fd;
}
 
int tun_open( string& tun_name )
{
        return tuntap_open( tun_name, true );
}
 
int tap_open( string& tap_name )
{
        return tuntap_open( tap_name, false );
}