aboutsummaryrefslogtreecommitdiffstats
path: root/tap-win32.c
blob: ff1e1ed5f43c261b1cd99f2521daabff4f0620ee (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
/*
 *  TAP-Win32 -- A kernel driver to provide virtual tap device functionality
 *               on Windows.  Originally derived from the CIPE-Win32
 *               project by Damion K. Wilson, with extensive modifications by
 *               James Yonan.
 *
 *  All source code which derives from the CIPE-Win32 project is
 *  Copyright (C) Damion K. Wilson, 2003, and is released under the
 *  GPL version 2 (see below).
 *
 *  All other source code is Copyright (C) James Yonan, 2003-2004,
 *  and is released under the GPL version 2 (see below).
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program (see the file COPYING included with this
 *  distribution); if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#include "qemu-common.h"
#include "net.h"
#include "sysemu.h"
#include <stdio.h>
#include <windows.h>

/* NOTE: PCIBus is redefined in winddk.h */
#define PCIBus _PCIBus
#include <ddk/ntapi.h>
#include <ddk/winddk.h>
#include <ddk/ntddk.h>
#undef PCIBus

//=============
// TAP IOCTLs
//=============

#define TAP_CONTROL_CODE(request,method) \
  CTL_CODE (FILE_DEVICE_UNKNOWN, request, method, FILE_ANY_ACCESS)

#define TAP_IOCTL_GET_MAC               TAP_CONTROL_CODE (1, METHOD_BUFFERED)
#define TAP_IOCTL_GET_VERSION           TAP_CONTROL_CODE (2, METHOD_BUFFERED)
#define TAP_IOCTL_GET_MTU               TAP_CONTROL_CODE (3, METHOD_BUFFERED)
#define TAP_IOCTL_GET_INFO              TAP_CONTROL_CODE (4, METHOD_BUFFERED)
#define TAP_IOCTL_CONFIG_POINT_TO_POINT TAP_CONTROL_CODE (5, METHOD_BUFFERED)
#define TAP_IOCTL_SET_MEDIA_STATUS      TAP_CONTROL_CODE (6, METHOD_BUFFERED)
#define TAP_IOCTL_CONFIG_DHCP_MASQ      TAP_CONTROL_CODE (7, METHOD_BUFFERED)
#define TAP_IOCTL_GET_LOG_LINE          TAP_CONTROL_CODE (8, METHOD_BUFFERED)
#define TAP_IOCTL_CONFIG_DHCP_SET_OPT   TAP_CONTROL_CODE (9, METHOD_BUFFERED)

//=================
// Registry keys
//=================

#define ADAPTER_KEY "SYSTEM\\CurrentControlSet\\Control\\Class\\{4D36E972-E325-11CE-BFC1-08002BE10318}"

#define NETWORK_CONNECTIONS_KEY "SYSTEM\\CurrentControlSet\\Control\\Network\\{4D36E972-E325-11CE-BFC1-08002BE10318}"

//======================
// Filesystem prefixes
//======================

#define USERMODEDEVICEDIR "\\\\.\\Global\\"
#define TAPSUFFIX         ".tap"


//======================
// Compile time configuration
//======================

//#define DEBUG_TAP_WIN32

#define TUN_ASYNCHRONOUS_WRITES 1

#define TUN_BUFFER_SIZE 1560
#define TUN_MAX_BUFFER_COUNT 32

/*
 * The data member "buffer" must be the first element in the tun_buffer
 * structure. See the function, tap_win32_free_buffer.
 */
typedef struct tun_buffer_s {
    unsigned char buffer [TUN_BUFFER_SIZE];
    unsigned long read_size;
    struct tun_buffer_s* next;
} tun_buffer_t;

typedef struct tap_win32_overlapped {
    HANDLE handle;
    HANDLE read_event;
    HANDLE write_event;
    HANDLE output_queue_semaphore;
    HANDLE free_list_semaphore;
    HANDLE tap_semaphore;
    CRITICAL_SECTION output_queue_cs;
    CRITICAL_SECTION free_list_cs;
    OVERLAPPED read_overlapped;
    OVERLAPPED write_overlapped;
    tun_buffer_t buffers[TUN_MAX_BUFFER_COUNT];
    tun_buffer_t* free_list;
    tun_buffer_t* output_queue_front;
    tun_buffer_t* output_queue_back;
} tap_win32_overlapped_t;

static tap_win32_overlapped_t tap_overlapped;

static tun_buffer_t* get_buffer_from_free_list(tap_win32_overlapped_t* const overlapped)
{
    tun_buffer_t* buffer = NULL;
    WaitForSingleObject(overlapped->free_list_semaphore, INFINITE);
    EnterCriticalSection(&overlapped->free_list_cs);
    buffer = overlapped->free_list;
//    assert(buffer != NULL);
    overlapped->free_list = buffer->next;
    LeaveCriticalSection(&overlapped->free_list_cs);
    buffer->next = NULL;
    return buffer;
}

static void put_buffer_on_free_list(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
{
    EnterCriticalSection(&overlapped->free_list_cs);
    buffer->next = overlapped->free_list;
    overlapped->free_list = buffer;
    LeaveCriticalSection(&overlapped->free_list_cs);
    ReleaseSemaphore(overlapped->free_list_semaphore, 1, NULL);
}

static tun_buffer_t* get_buffer_from_output_queue(tap_win32_overlapped_t* const overlapped, const int block)
{
    tun_buffer_t* buffer = NULL;
    DWORD result, timeout = block ? INFINITE : 0L;

    // Non-blocking call
    result = WaitForSingleObject(overlapped->output_queue_semaphore, timeout);

    switch (result)
    {
        // The semaphore object was signaled.
        case WAIT_OBJECT_0:
            EnterCriticalSection(&overlapped->output_queue_cs);

            buffer = overlapped->output_queue_front;
            overlapped->output_queue_front = buffer->next;

            if(overlapped->output_queue_front == NULL) {
                overlapped->output_queue_back = NULL;
            }

            LeaveCriticalSection(&overlapped->output_queue_cs);
            break;

        // Semaphore was nonsignaled, so a time-out occurred.
        case WAIT_TIMEOUT:
            // Cannot open another window.
            break;
    }

    return buffer;
}

static tun_buffer_t* get_buffer_from_output_queue_immediate (tap_win32_overlapped_t* const overlapped)
{
    return get_buffer_from_output_queue(overlapped, 0);
}

static void put_buffer_on_output_queue(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
{
    EnterCriticalSection(&overlapped->output_queue_cs);

    if(overlapped->output_queue_front == NULL && overlapped->output_queue_back == NULL) {
        overlapped->output_queue_front = overlapped->output_queue_back = buffer;
    } else {
        buffer->next = NULL;
        overlapped->output_queue_back->next = buffer;
        overlapped->output_queue_back = buffer;
    }

    LeaveCriticalSection(&overlapped->output_queue_cs);

    ReleaseSemaphore(overlapped->output_queue_semaphore, 1, NULL);
}


static int is_tap_win32_dev(const char *guid)
{
    HKEY netcard_key;
    LONG status;
    DWORD len;
    int i = 0;

    status = RegOpenKeyEx(
        HKEY_LOCAL_MACHINE,
        ADAPTER_KEY,
        0,
        KEY_READ,
        &netcard_key);

    if (status != ERROR_SUCCESS) {
        return FALSE;
    }

    for (;;) {
        char enum_name[256];
        char unit_string[256];
        HKEY unit_key;
        char component_id_string[] = "ComponentId";
        char component_id[256];
        char net_cfg_instance_id_string[] = "NetCfgInstanceId";
        char net_cfg_instance_id[256];
        DWORD data_type;

        len = sizeof (enum_name);
        status = RegEnumKeyEx(
            netcard_key,
            i,
            enum_name,
            &len,
            NULL,
            NULL,
            NULL,
            NULL);

        if (status == ERROR_NO_MORE_ITEMS)
            break;
        else if (status != ERROR_SUCCESS) {
            return FALSE;
        }

        snprintf (unit_string, sizeof(unit_string), "%s\\%s",
                  ADAPTER_KEY, enum_name);

        status = RegOpenKeyEx(
            HKEY_LOCAL_MACHINE,
            unit_string,
            0,
            KEY_READ,
            &unit_key);

        if (status != ERROR_SUCCESS) {
            return FALSE;
        } else {
            len = sizeof (component_id);
            status = RegQueryValueEx(
                unit_key,
                component_id_string,
                NULL,
                &data_type,
                (LPBYTE)component_id,
                &len);

            if (!(status != ERROR_SUCCESS || data_type != REG_SZ)) {
                len = sizeof (net_cfg_instance_id);
                status = RegQueryValueEx(
                    unit_key,
                    net_cfg_instance_id_string,
                    NULL,
                    &data_type,
                    (LPBYTE)net_cfg_instance_id,
                    &len);

                if (status == ERROR_SUCCESS && data_type == REG_SZ) {
                    if (/* !strcmp (component_id, TAP_COMPONENT_ID) &&*/
                        !strcmp (net_cfg_instance_id, guid)) {
                        RegCloseKey (unit_key);
                        RegCloseKey (netcard_key);
                        return TRUE;
                    }
                }
            }
            RegCloseKey (unit_key);
        }
        ++i;
    }

    RegCloseKey (netcard_key);
    return FALSE;
}

static int get_device_guid(
    char *name,
    int name_size,
    char *actual_name,
    int actual_name_size)
{
    LONG status;
    HKEY control_net_key;
    DWORD len;
    int i = 0;
    int stop = 0;

    status = RegOpenKeyEx(
        HKEY_LOCAL_MACHINE,
        NETWORK_CONNECTIONS_KEY,
        0,
        KEY_READ,
        &control_net_key);

    if (status != ERROR_SUCCESS) {
        return -1;
    }

    while (!stop)
    {
        char enum_name[256];
        char connection_string[256];
        HKEY connection_key;
        char name_data[256];
        DWORD name_type;
        const char name_string[] = "Name";

        len = sizeof (enum_name);
        status = RegEnumKeyEx(
            control_net_key,
            i,
            enum_name,
            &len,
            NULL,
            NULL,
            NULL,
            NULL);

        if (status == ERROR_NO_MORE_ITEMS)
            break;
        else if (status != ERROR_SUCCESS) {
            return -1;
        }

        snprintf(connection_string,
             sizeof(connection_string),
             "%s\\%s\\Connection",
             NETWORK_CONNECTIONS_KEY, enum_name);

        status = RegOpenKeyEx(
            HKEY_LOCAL_MACHINE,
            connection_string,
            0,
            KEY_READ,
            &connection_key);

        if (status == ERROR_SUCCESS) {
            len = sizeof (name_data);
            status = RegQueryValueEx(
                connection_key,
                name_string,
                NULL,
                &name_type,
                (LPBYTE)name_data,
                &len);

            if (status != ERROR_SUCCESS || name_type != REG_SZ) {
                    return -1;
            }
            else {
                if (is_tap_win32_dev(enum_name)) {
                    snprintf(name, name_size, "%s", enum_name);
                    if (actual_name) {
                        if (strcmp(actual_name, "") != 0) {
                            if (strcmp(name_data, actual_name) != 0) {
                                RegCloseKey (connection_key);
                                ++i;
                                continue;
                            }
                        }
                        else {
                            snprintf(actual_name, actual_name_size, "%s", name_data);
                        }
                    }
                    stop = 1;
                }
            }

            RegCloseKey (connection_key);
        }
        ++i;
    }

    RegCloseKey (control_net_key);

    if (stop == 0)
        return -1;

    return 0;
}

static int tap_win32_set_status(HANDLE handle, int status)
{
    unsigned long len = 0;

    return DeviceIoControl(handle, TAP_IOCTL_SET_MEDIA_STATUS,
                &status, sizeof (status),
                &status, sizeof (status), &len, NULL);
}

static void tap_win32_overlapped_init(tap_win32_overlapped_t* const overlapped, const HANDLE handle)
{
    overlapped->handle = handle;

    overlapped->read_event = CreateEvent(NULL, FALSE, FALSE, NULL);
    overlapped->write_event = CreateEvent(NULL, FALSE, FALSE, NULL);

    overlapped->read_overlapped.Offset = 0;
    overlapped->read_overlapped.OffsetHigh = 0;
    overlapped->read_overlapped.hEvent = overlapped->read_event;

    overlapped->write_overlapped.Offset = 0;
    overlapped->write_overlapped.OffsetHigh = 0;
    overlapped->write_overlapped.hEvent = overlapped->write_event;

    InitializeCriticalSection(&overlapped->output_queue_cs);
    InitializeCriticalSection(&overlapped->free_list_cs);

    overlapped->output_queue_semaphore = CreateSemaphore(
        NULL,   // default security attributes
        0,   // initial count
        TUN_MAX_BUFFER_COUNT,   // maximum count
        NULL);  // unnamed semaphore

    if(!overlapped->output_queue_semaphore)  {
        fprintf(stderr, "error creating output queue semaphore!\n");
    }

    overlapped->free_list_semaphore = CreateSemaphore(
        NULL,   // default security attributes
        TUN_MAX_BUFFER_COUNT,   // initial count
        TUN_MAX_BUFFER_COUNT,   // maximum count
        NULL);  // unnamed semaphore

    if(!overlapped->free_list_semaphore)  {
        fprintf(stderr, "error creating free list semaphore!\n");
    }

    overlapped->free_list = overlapped->output_queue_front = overlapped->output_queue_back = NULL;

    {
        unsigned index;
        for(index = 0; index < TUN_MAX_BUFFER_COUNT; index++) {
            tun_buffer_t* element = &overlapped->buffers[index];
            element->next = overlapped->free_list;
            overlapped->free_list = element;
        }
    }
    /* To count buffers, initially no-signal. */
    overlapped->tap_semaphore = CreateSemaphore(NULL, 0, TUN_MAX_BUFFER_COUNT, NULL);
    if(!overlapped->tap_semaphore)
        fprintf(stderr, "error creating tap_semaphore.\n");
}

static int tap_win32_write(tap_win32_overlapped_t *overlapped,
                           const void *buffer, unsigned long size)
{
    unsigned long write_size;
    BOOL result;
    DWORD error;

    result = GetOverlappedResult( overlapped->handle, &overlapped->write_overlapped,
                                  &write_size, FALSE);

    if (!result && GetLastError() == ERROR_IO_INCOMPLETE)
        WaitForSingleObject(overlapped->write_event, INFINITE);

    result = WriteFile(overlapped->handle, buffer, size,
                       &write_size, &overlapped->write_overlapped);

    if (!result) {
        switch (error = GetLastError())
        {
        case ERROR_IO_PENDING:
#ifndef TUN_ASYNCHRONOUS_WRITES
            WaitForSingleObject(overlapped->write_event, INFINITE);
#endif
            break;
        default:
            return -1;
        }
    }

    return 0;
}

static DWORD WINAPI tap_win32_thread_entry(LPVOID param)
{
    tap_win32_overlapped_t *overlapped = (tap_win32_overlapped_t*)param;
    unsigned long read_size;
    BOOL result;
    DWORD dwError;
    tun_buffer_t* buffer = get_buffer_from_free_list(overlapped);


    for (;;) {
        result = ReadFile(overlapped->handle,
                          buffer->buffer,
                          sizeof(buffer->buffer),
                          &read_size,
                          &overlapped->read_overlapped);
        if (!result) {
            dwError = GetLastError();
            if (dwError == ERROR_IO_PENDING) {
                WaitForSingleObject(overlapped->read_event, INFINITE);
                result = GetOverlappedResult( overlapped->handle, &overlapped->read_overlapped,
                                              &read_size, FALSE);
                if (!result) {
#ifdef DEBUG_TAP_WIN32
                    LPVOID lpBuffer;
                    dwError = GetLastError();
                    FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
                                   NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                                   (LPTSTR) & lpBuffer, 0, NULL );
                    fprintf(stderr, "Tap-Win32: Error GetOverlappedResult %d - %s\n", dwError, lpBuffer);
                    LocalFree( lpBuffer );
#endif
                }
            } else {
#ifdef DEBUG_TAP_WIN32
                LPVOID lpBuffer;
                FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
                               NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                               (LPTSTR) & lpBuffer, 0, NULL );
                fprintf(stderr, "Tap-Win32: Error ReadFile %d - %s\n", dwError, lpBuffer);
                LocalFree( lpBuffer );
#endif
            }
        }

        if(read_size > 0) {
            buffer->read_size = read_size;
            put_buffer_on_output_queue(overlapped, buffer);
            ReleaseSemaphore(overlapped->tap_semaphore, 1, NULL);
            buffer = get_buffer_from_free_list(overlapped);
        }
    }

    return 0;
}

static int tap_win32_read(tap_win32_overlapped_t *overlapped,
                          uint8_t **pbuf, int max_size)
{
    int size = 0;

    tun_buffer_t* buffer = get_buffer_from_output_queue_immediate(overlapped);

    if(buffer != NULL) {
        *pbuf = buffer->buffer;
        size = (int)buffer->read_size;
        if(size > max_size) {
            size = max_size;
        }
    }

    return size;
}

static void tap_win32_free_buffer(tap_win32_overlapped_t *overlapped,
                                  uint8_t *pbuf)
{
    tun_buffer_t* buffer = (tun_buffer_t*)pbuf;
    put_buffer_on_free_list(overlapped, buffer);
}

static int tap_win32_open(tap_win32_overlapped_t **phandle,
                          const char *prefered_name)
{
    char device_path[256];
    char device_guid[0x100];
    int rc;
    HANDLE handle;
    BOOL bret;
    char name_buffer[0x100] = {0, };
    struct {
        unsigned long major;
        unsigned long minor;
        unsigned long debug;
    } version;
    DWORD version_len;
    DWORD idThread;
    HANDLE hThread;

    if (prefered_name != NULL)
        snprintf(name_buffer, sizeof(name_buffer), "%s", prefered_name);

    rc = get_device_guid(device_guid, sizeof(device_guid), name_buffer, sizeof(name_buffer));
    if (rc)
        return -1;

    snprintf (device_path, sizeof(device_path), "%s%s%s",
              USERMODEDEVICEDIR,
              device_guid,
              TAPSUFFIX);

    handle = CreateFile (
        device_path,
        GENERIC_READ | GENERIC_WRITE,
        0,
        0,
        OPEN_EXISTING,
        FILE_ATTRIBUTE_SYSTEM | FILE_FLAG_OVERLAPPED,
        0 );

    if (handle == INVALID_HANDLE_VALUE) {
        return -1;
    }

    bret = DeviceIoControl(handle, TAP_IOCTL_GET_VERSION,
                           &version, sizeof (version),
                           &version, sizeof (version), &version_len, NULL);

    if (bret == FALSE) {
        CloseHandle(handle);
        return -1;
    }

    if (!tap_win32_set_status(handle, TRUE)) {
        return -1;
    }

    tap_win32_overlapped_init(&tap_overlapped, handle);

    *phandle = &tap_overlapped;

    hThread = CreateThread(NULL, 0, tap_win32_thread_entry,
                           (LPVOID)&tap_overlapped, 0, &idThread);
    return 0;
}

/********************************************/

 typedef struct TAPState {
     VLANClientState *vc;
     tap_win32_overlapped_t *handle;
 } TAPState;

static void tap_cleanup(VLANClientState *vc)
{
    TAPState *s = vc->opaque;

    qemu_del_wait_object(s->handle->tap_semaphore, NULL, NULL);

    /* FIXME: need to kill thread and close file handle:
       tap_win32_close(s);
    */
    qemu_free(s);
}

static void tap_receive(VLANClientState *vc, const uint8_t *buf, size_t size)
{
    TAPState *s = opaque;

    tap_win32_write(s->handle, buf, size);
}

static void tap_win32_send(void *opaque)
{
    TAPState *s = opaque;
    uint8_t *buf;
    int max_size = 4096;
    int size;

    size = tap_win32_read(s->handle, &buf, max_size);
    if (size > 0) {
        qemu_send_packet(s->vc, buf, size);
        tap_win32_free_buffer(s->handle, buf);
    }
}

int tap_win32_init(VLANState *vlan, const char *model,
                   const char *name, const char *ifname)
{
    TAPState *s;

    s = qemu_mallocz(sizeof(TAPState));
    if (!s)
        return -1;
    if (tap_win32_open(&s->handle, ifname) < 0) {
        printf("tap: Could not open '%s'\n", ifname);
        return -1;
    }

    s->vc = qemu_new_vlan_client(vlan, model, name, NULL, tap_receive,
                                 NULL, tap_cleanup, s);

    snprintf(s->vc->info_str, sizeof(s->vc->info_str),
             "tap: ifname=%s", ifname);

    qemu_add_wait_object(s->handle->tap_semaphore, tap_win32_send, s);
    return 0;
}