git.maemo.org Git - qemu/blob - tap-win32.c

   1 /*
   2  *  TAP-Win32 -- A kernel driver to provide virtual tap device functionality
   3  *               on Windows.  Originally derived from the CIPE-Win32
   4  *               project by Damion K. Wilson, with extensive modifications by
   5  *               James Yonan.
   6  *
   7  *  All source code which derives from the CIPE-Win32 project is
   8  *  Copyright (C) Damion K. Wilson, 2003, and is released under the
   9  *  GPL version 2 (see below).
  10  *
  11  *  All other source code is Copyright (C) James Yonan, 2003-2004,
  12  *  and is released under the GPL version 2 (see below).
  13  *
  14  *  This program is free software; you can redistribute it and/or modify
  15  *  it under the terms of the GNU General Public License as published by
  16  *  the Free Software Foundation; either version 2 of the License, or
  17  *  (at your option) any later version.
  18  *
  19  *  This program is distributed in the hope that it will be useful,
  20  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  *  GNU General Public License for more details.
  23  *
  24  *  You should have received a copy of the GNU General Public License
  25  *  along with this program (see the file COPYING included with this
  26  *  distribution); if not, write to the Free Software Foundation, Inc.,
  27  *  59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  28  */
  29 #include "vl.h"
  30 #include <stdio.h>
  31 #include <windows.h>
  32
  33 /* NOTE: PCIBus is redefined in winddk.h */
  34 #define PCIBus _PCIBus
  35 #include <ddk/ntapi.h>
  36 #include <ddk/winddk.h>
  37 #include <ddk/ntddk.h>
  38 #undef PCIBus
  39
  40 //=============
  41 // TAP IOCTLs
  42 //=============
  43
  44 #define TAP_CONTROL_CODE(request,method) \
  45   CTL_CODE (FILE_DEVICE_UNKNOWN, request, method, FILE_ANY_ACCESS)
  46
  47 #define TAP_IOCTL_GET_MAC               TAP_CONTROL_CODE (1, METHOD_BUFFERED)
  48 #define TAP_IOCTL_GET_VERSION           TAP_CONTROL_CODE (2, METHOD_BUFFERED)
  49 #define TAP_IOCTL_GET_MTU               TAP_CONTROL_CODE (3, METHOD_BUFFERED)
  50 #define TAP_IOCTL_GET_INFO              TAP_CONTROL_CODE (4, METHOD_BUFFERED)
  51 #define TAP_IOCTL_CONFIG_POINT_TO_POINT TAP_CONTROL_CODE (5, METHOD_BUFFERED)
  52 #define TAP_IOCTL_SET_MEDIA_STATUS      TAP_CONTROL_CODE (6, METHOD_BUFFERED)
  53 #define TAP_IOCTL_CONFIG_DHCP_MASQ      TAP_CONTROL_CODE (7, METHOD_BUFFERED)
  54 #define TAP_IOCTL_GET_LOG_LINE          TAP_CONTROL_CODE (8, METHOD_BUFFERED)
  55 #define TAP_IOCTL_CONFIG_DHCP_SET_OPT   TAP_CONTROL_CODE (9, METHOD_BUFFERED)
  56
  57 //=================
  58 // Registry keys
  59 //=================
  60
  61 #define ADAPTER_KEY "SYSTEM\\CurrentControlSet\\Control\\Class\\{4D36E972-E325-11CE-BFC1-08002BE10318}"
  62
  63 #define NETWORK_CONNECTIONS_KEY "SYSTEM\\CurrentControlSet\\Control\\Network\\{4D36E972-E325-11CE-BFC1-08002BE10318}"
  64
  65 //======================
  66 // Filesystem prefixes
  67 //======================
  68
  69 #define USERMODEDEVICEDIR "\\\\.\\Global\\"
  70 #define TAPSUFFIX         ".tap"
  71
  72
  73 //======================
  74 // Compile time configuration
  75 //======================
  76
  77 //#define DEBUG_TAP_WIN32 1
  78
  79 #define TUN_ASYNCHRONOUS_WRITES 1
  80
  81 #define TUN_BUFFER_SIZE 1560
  82 #define TUN_MAX_BUFFER_COUNT 32
  83
  84 /*
  85  * The data member "buffer" must be the first element in the tun_buffer
  86  * structure. See the function, tap_win32_free_buffer.
  87  */
  88 typedef struct tun_buffer_s {
  89     unsigned char buffer [TUN_BUFFER_SIZE];
  90     unsigned long read_size;
  91     struct tun_buffer_s* next;
  92 } tun_buffer_t;
  93
  94 typedef struct tap_win32_overlapped {
  95     HANDLE handle;
  96     HANDLE read_event;
  97     HANDLE write_event;
  98     HANDLE output_queue_semaphore;
  99     HANDLE free_list_semaphore;
 100     CRITICAL_SECTION output_queue_cs;
 101     CRITICAL_SECTION free_list_cs;
 102     OVERLAPPED read_overlapped;
 103     OVERLAPPED write_overlapped;
 104     tun_buffer_t buffers[TUN_MAX_BUFFER_COUNT];
 105     tun_buffer_t* free_list;
 106     tun_buffer_t* output_queue_front;
 107     tun_buffer_t* output_queue_back;
 108 } tap_win32_overlapped_t;
 109
 110 static tap_win32_overlapped_t tap_overlapped;
 111
 112 static tun_buffer_t* get_buffer_from_free_list(tap_win32_overlapped_t* const overlapped)
 113 {
 114     tun_buffer_t* buffer = NULL;
 115     WaitForSingleObject(overlapped->free_list_semaphore, INFINITE);
 116     EnterCriticalSection(&overlapped->free_list_cs);
 117     buffer = overlapped->free_list;
 118 //    assert(buffer != NULL);
 119     overlapped->free_list = buffer->next;
 120     LeaveCriticalSection(&overlapped->free_list_cs);
 121     buffer->next = NULL;
 122     return buffer;
 123 }
 124
 125 static void put_buffer_on_free_list(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
 126 {
 127     EnterCriticalSection(&overlapped->free_list_cs);
 128     buffer->next = overlapped->free_list;
 129     overlapped->free_list = buffer;
 130     LeaveCriticalSection(&overlapped->free_list_cs);
 131     ReleaseSemaphore(overlapped->free_list_semaphore, 1, NULL);
 132 }
 133
 134 static tun_buffer_t* get_buffer_from_output_queue(tap_win32_overlapped_t* const overlapped, const int block)
 135 {
 136     tun_buffer_t* buffer = NULL;
 137     DWORD result, timeout = block ? INFINITE : 0L;
 138
 139     // Non-blocking call
 140     result = WaitForSingleObject(overlapped->output_queue_semaphore, timeout);
 141
 142     switch (result)
 143     {
 144         // The semaphore object was signaled.
 145         case WAIT_OBJECT_0:
 146             EnterCriticalSection(&overlapped->output_queue_cs);
 147
 148             buffer = overlapped->output_queue_front;
 149             overlapped->output_queue_front = buffer->next;
 150
 151             if(overlapped->output_queue_front == NULL) {
 152                 overlapped->output_queue_back = NULL;
 153             }
 154
 155             LeaveCriticalSection(&overlapped->output_queue_cs);
 156             break;
 157
 158         // Semaphore was nonsignaled, so a time-out occurred.
 159         case WAIT_TIMEOUT:
 160             // Cannot open another window.
 161             break;
 162     }
 163
 164     return buffer;
 165 }
 166
 167 static tun_buffer_t* get_buffer_from_output_queue_immediate (tap_win32_overlapped_t* const overlapped)
 168 {
 169     return get_buffer_from_output_queue(overlapped, 0);
 170 }
 171
 172 static void put_buffer_on_output_queue(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
 173 {
 174     EnterCriticalSection(&overlapped->output_queue_cs);
 175
 176     if(overlapped->output_queue_front == NULL && overlapped->output_queue_back == NULL) {
 177         overlapped->output_queue_front = overlapped->output_queue_back = buffer;
 178     } else {
 179         buffer->next = NULL;
 180         overlapped->output_queue_back->next = buffer;
 181         overlapped->output_queue_back = buffer;
 182     }
 183
 184     LeaveCriticalSection(&overlapped->output_queue_cs);
 185
 186     ReleaseSemaphore(overlapped->output_queue_semaphore, 1, NULL);
 187 }
 188
 189
 190 static int is_tap_win32_dev(const char *guid)
 191 {
 192     HKEY netcard_key;
 193     LONG status;
 194     DWORD len;
 195     int i = 0;
 196
 197     status = RegOpenKeyEx(
 198         HKEY_LOCAL_MACHINE,
 199         ADAPTER_KEY,
 200         0,
 201         KEY_READ,
 202         &netcard_key);
 203
 204     if (status != ERROR_SUCCESS) {
 205         return FALSE;
 206     }
 207
 208     for (;;) {
 209         char enum_name[256];
 210         char unit_string[256];
 211         HKEY unit_key;
 212         char component_id_string[] = "ComponentId";
 213         char component_id[256];
 214         char net_cfg_instance_id_string[] = "NetCfgInstanceId";
 215         char net_cfg_instance_id[256];
 216         DWORD data_type;
 217
 218         len = sizeof (enum_name);
 219         status = RegEnumKeyEx(
 220             netcard_key,
 221             i,
 222             enum_name,
 223             &len,
 224             NULL,
 225             NULL,
 226             NULL,
 227             NULL);
 228
 229         if (status == ERROR_NO_MORE_ITEMS)
 230             break;
 231         else if (status != ERROR_SUCCESS) {
 232             return FALSE;
 233         }
 234
 235         snprintf (unit_string, sizeof(unit_string), "%s\\%s",
 236                   ADAPTER_KEY, enum_name);
 237
 238         status = RegOpenKeyEx(
 239             HKEY_LOCAL_MACHINE,
 240             unit_string,
 241             0,
 242             KEY_READ,
 243             &unit_key);
 244
 245         if (status != ERROR_SUCCESS) {
 246             return FALSE;
 247         } else {
 248             len = sizeof (component_id);
 249             status = RegQueryValueEx(
 250                 unit_key,
 251                 component_id_string,
 252                 NULL,
 253                 &data_type,
 254                 component_id,
 255                 &len);
 256
 257             if (!(status != ERROR_SUCCESS || data_type != REG_SZ)) {
 258                 len = sizeof (net_cfg_instance_id);
 259                 status = RegQueryValueEx(
 260                     unit_key,
 261                     net_cfg_instance_id_string,
 262                     NULL,
 263                     &data_type,
 264                     net_cfg_instance_id,
 265                     &len);
 266
 267                 if (status == ERROR_SUCCESS && data_type == REG_SZ) {
 268                     if (/* !strcmp (component_id, TAP_COMPONENT_ID) &&*/
 269                         !strcmp (net_cfg_instance_id, guid)) {
 270                         RegCloseKey (unit_key);
 271                         RegCloseKey (netcard_key);
 272                         return TRUE;
 273                     }
 274                 }
 275             }
 276             RegCloseKey (unit_key);
 277         }
 278         ++i;
 279     }
 280
 281     RegCloseKey (netcard_key);
 282     return FALSE;
 283 }
 284
 285 static int get_device_guid(
 286     char *name,
 287     int name_size,
 288     char *actual_name,
 289     int actual_name_size)
 290 {
 291     LONG status;
 292     HKEY control_net_key;
 293     DWORD len;
 294     int i = 0;
 295     int stop = 0;
 296
 297     status = RegOpenKeyEx(
 298         HKEY_LOCAL_MACHINE,
 299         NETWORK_CONNECTIONS_KEY,
 300         0,
 301         KEY_READ,
 302         &control_net_key);
 303
 304     if (status != ERROR_SUCCESS) {
 305         return -1;
 306     }
 307
 308     while (!stop)
 309     {
 310         char enum_name[256];
 311         char connection_string[256];
 312         HKEY connection_key;
 313         char name_data[256];
 314         DWORD name_type;
 315         const char name_string[] = "Name";
 316
 317         len = sizeof (enum_name);
 318         status = RegEnumKeyEx(
 319             control_net_key,
 320             i,
 321             enum_name,
 322             &len,
 323             NULL,
 324             NULL,
 325             NULL,
 326             NULL);
 327
 328         if (status == ERROR_NO_MORE_ITEMS)
 329             break;
 330         else if (status != ERROR_SUCCESS) {
 331             return -1;
 332         }
 333
 334         snprintf(connection_string,
 335              sizeof(connection_string),
 336              "%s\\%s\\Connection",
 337              NETWORK_CONNECTIONS_KEY, enum_name);
 338
 339         status = RegOpenKeyEx(
 340             HKEY_LOCAL_MACHINE,
 341             connection_string,
 342             0,
 343             KEY_READ,
 344             &connection_key);
 345
 346         if (status == ERROR_SUCCESS) {
 347             len = sizeof (name_data);
 348             status = RegQueryValueEx(
 349                 connection_key,
 350                 name_string,
 351                 NULL,
 352                 &name_type,
 353                 name_data,
 354                 &len);
 355
 356             if (status != ERROR_SUCCESS || name_type != REG_SZ) {
 357                     return -1;
 358             }
 359             else {
 360                 if (is_tap_win32_dev(enum_name)) {
 361                     snprintf(name, name_size, "%s", enum_name);
 362                     if (actual_name) {
 363                         if (strcmp(actual_name, "") != 0) {
 364                             if (strcmp(name_data, actual_name) != 0) {
 365                                 RegCloseKey (connection_key);
 366                                 ++i;
 367                                 continue;
 368                             }
 369                         }
 370                         else {
 371                             snprintf(actual_name, actual_name_size, "%s", name_data);
 372                         }
 373                     }
 374                     stop = 1;
 375                 }
 376             }
 377
 378             RegCloseKey (connection_key);
 379         }
 380         ++i;
 381     }
 382
 383     RegCloseKey (control_net_key);
 384
 385     if (stop == 0)
 386         return -1;
 387
 388     return 0;
 389 }
 390
 391 static int tap_win32_set_status(HANDLE handle, int status)
 392 {
 393     unsigned long len = 0;
 394
 395     return DeviceIoControl(handle, TAP_IOCTL_SET_MEDIA_STATUS,
 396                 &status, sizeof (status),
 397                 &status, sizeof (status), &len, NULL);
 398 }
 399
 400 static void tap_win32_overlapped_init(tap_win32_overlapped_t* const overlapped, const HANDLE handle)
 401 {
 402     overlapped->handle = handle;
 403
 404     overlapped->read_event = CreateEvent(NULL, FALSE, FALSE, NULL);
 405     overlapped->write_event = CreateEvent(NULL, FALSE, FALSE, NULL);
 406
 407     overlapped->read_overlapped.Offset = 0;
 408     overlapped->read_overlapped.OffsetHigh = 0;
 409     overlapped->read_overlapped.hEvent = overlapped->read_event;
 410
 411     overlapped->write_overlapped.Offset = 0;
 412     overlapped->write_overlapped.OffsetHigh = 0;
 413     overlapped->write_overlapped.hEvent = overlapped->write_event;
 414
 415     InitializeCriticalSection(&overlapped->output_queue_cs);
 416     InitializeCriticalSection(&overlapped->free_list_cs);
 417
 418     overlapped->output_queue_semaphore = CreateSemaphore(
 419         NULL,   // default security attributes
 420         0,   // initial count
 421         TUN_MAX_BUFFER_COUNT,   // maximum count
 422         NULL);  // unnamed semaphore
 423
 424     if(!overlapped->output_queue_semaphore)  {
 425         fprintf(stderr, "error creating output queue semaphore!\n");
 426     }
 427
 428     overlapped->free_list_semaphore = CreateSemaphore(
 429         NULL,   // default security attributes
 430         TUN_MAX_BUFFER_COUNT,   // initial count
 431         TUN_MAX_BUFFER_COUNT,   // maximum count
 432         NULL);  // unnamed semaphore
 433
 434     if(!overlapped->free_list_semaphore)  {
 435         fprintf(stderr, "error creating free list semaphore!\n");
 436     }
 437
 438     overlapped->free_list = overlapped->output_queue_front = overlapped->output_queue_back = NULL;
 439
 440     {
 441         unsigned index;
 442         for(index = 0; index < TUN_MAX_BUFFER_COUNT; index++) {
 443             tun_buffer_t* element = &overlapped->buffers[index];
 444             element->next = overlapped->free_list;
 445             overlapped->free_list = element;
 446         }
 447     }
 448 }
 449
 450 static int tap_win32_write(tap_win32_overlapped_t *overlapped,
 451                            const void *buffer, unsigned long size)
 452 {
 453     unsigned long write_size;
 454     BOOL result;
 455     DWORD error;
 456
 457     result = GetOverlappedResult( overlapped->handle, &overlapped->write_overlapped,
 458                                   &write_size, FALSE);
 459
 460     if (!result && GetLastError() == ERROR_IO_INCOMPLETE)
 461         WaitForSingleObject(overlapped->write_event, INFINITE);
 462
 463     result = WriteFile(overlapped->handle, buffer, size,
 464                        &write_size, &overlapped->write_overlapped);
 465
 466     if (!result) {
 467         switch (error = GetLastError())
 468         {
 469         case ERROR_IO_PENDING:
 470 #ifndef TUN_ASYNCHRONOUS_WRITES
 471             WaitForSingleObject(overlapped->write_event, INFINITE);
 472 #endif
 473             break;
 474         default:
 475             return -1;
 476         }
 477     }
 478
 479     return 0;
 480 }
 481
 482 static DWORD WINAPI tap_win32_thread_entry(LPVOID param)
 483 {
 484     tap_win32_overlapped_t *overlapped = (tap_win32_overlapped_t*)param;
 485     unsigned long read_size;
 486     BOOL result;
 487     DWORD dwError;
 488     tun_buffer_t* buffer = get_buffer_from_free_list(overlapped);
 489
 490
 491     for (;;) {
 492         result = ReadFile(overlapped->handle,
 493                           buffer->buffer,
 494                           sizeof(buffer->buffer),
 495                           &read_size,
 496                           &overlapped->read_overlapped);
 497         if (!result) {
 498             dwError = GetLastError();
 499             if (dwError == ERROR_IO_PENDING) {
 500                 WaitForSingleObject(overlapped->read_event, INFINITE);
 501                 result = GetOverlappedResult( overlapped->handle, &overlapped->read_overlapped,
 502                                               &read_size, FALSE);
 503                 if (!result) {
 504 #if DEBUG_TAP_WIN32
 505                     LPVOID lpBuffer;
 506                     dwError = GetLastError();
 507                     FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
 508                                    NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
 509                                    (LPTSTR) & lpBuffer, 0, NULL );
 510                     fprintf(stderr, "Tap-Win32: Error GetOverlappedResult %d - %s\n", dwError, lpBuffer);
 511                     LocalFree( lpBuffer );
 512 #endif
 513                 }
 514             } else {
 515 #if DEBUG_TAP_WIN32
 516                 LPVOID lpBuffer;
 517                 FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
 518                                NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
 519                                (LPTSTR) & lpBuffer, 0, NULL );
 520                 fprintf(stderr, "Tap-Win32: Error ReadFile %d - %s\n", dwError, lpBuffer);
 521                 LocalFree( lpBuffer );
 522 #endif
 523             }
 524         }
 525
 526         if(read_size > 0) {
 527             buffer->read_size = read_size;
 528             put_buffer_on_output_queue(overlapped, buffer);
 529             buffer = get_buffer_from_free_list(overlapped);
 530         }
 531     }
 532
 533     return 0;
 534 }
 535
 536 static int tap_win32_read(tap_win32_overlapped_t *overlapped,
 537                           uint8_t **pbuf, int max_size)
 538 {
 539     int size = 0;
 540
 541     tun_buffer_t* buffer = get_buffer_from_output_queue_immediate(overlapped);
 542
 543     if(buffer != NULL) {
 544         *pbuf = buffer->buffer;
 545         size = (int)buffer->read_size;
 546         if(size > max_size) {
 547             size = max_size;
 548         }
 549     }
 550
 551     return size;
 552 }
 553
 554 static void tap_win32_free_buffer(tap_win32_overlapped_t *overlapped,
 555                                   char* pbuf)
 556 {
 557     tun_buffer_t* buffer = (tun_buffer_t*)pbuf;
 558     put_buffer_on_free_list(overlapped, buffer);
 559 }
 560
 561 static int tap_win32_open(tap_win32_overlapped_t **phandle,
 562                           const char *prefered_name)
 563 {
 564     char device_path[256];
 565     char device_guid[0x100];
 566     int rc;
 567     HANDLE handle;
 568     BOOL bret;
 569     char name_buffer[0x100] = {0, };
 570     struct {
 571         unsigned long major;
 572         unsigned long minor;
 573         unsigned long debug;
 574     } version;
 575     LONG version_len;
 576     DWORD idThread;
 577     HANDLE hThread;
 578
 579     if (prefered_name != NULL)
 580         snprintf(name_buffer, sizeof(name_buffer), "%s", prefered_name);
 581
 582     rc = get_device_guid(device_guid, sizeof(device_guid), name_buffer, sizeof(name_buffer));
 583     if (rc)
 584         return -1;
 585
 586     snprintf (device_path, sizeof(device_path), "%s%s%s",
 587               USERMODEDEVICEDIR,
 588               device_guid,
 589               TAPSUFFIX);
 590
 591     handle = CreateFile (
 592         device_path,
 593         GENERIC_READ | GENERIC_WRITE,
 594         0,
 595         0,
 596         OPEN_EXISTING,
 597         FILE_ATTRIBUTE_SYSTEM | FILE_FLAG_OVERLAPPED,
 598         0 );
 599
 600     if (handle == INVALID_HANDLE_VALUE) {
 601         return -1;
 602     }
 603
 604     bret = DeviceIoControl(handle, TAP_IOCTL_GET_VERSION,
 605                            &version, sizeof (version),
 606                            &version, sizeof (version), &version_len, NULL);
 607
 608     if (bret == FALSE) {
 609         CloseHandle(handle);
 610         return -1;
 611     }
 612
 613     if (!tap_win32_set_status(handle, TRUE)) {
 614         return -1;
 615     }
 616
 617     tap_win32_overlapped_init(&tap_overlapped, handle);
 618
 619     *phandle = &tap_overlapped;
 620
 621     hThread = CreateThread(NULL, 0, tap_win32_thread_entry,
 622                            (LPVOID)&tap_overlapped, 0, &idThread);
 623     SetThreadPriority(hThread,THREAD_PRIORITY_TIME_CRITICAL);
 624
 625     return 0;
 626 }
 627
 628 /********************************************/
 629
 630  typedef struct TAPState {
 631      VLANClientState *vc;
 632      tap_win32_overlapped_t *handle;
 633      HANDLE tap_event;
 634  } TAPState;
 635
 636 static TAPState *tap_win32_state = NULL;
 637
 638 static void tap_receive(void *opaque, const uint8_t *buf, int size)
 639 {
 640     TAPState *s = opaque;
 641
 642     tap_win32_write(s->handle, buf, size);
 643 }
 644
 645 /* XXX: horrible, suppress this by using proper thread signaling */
 646 void tap_win32_poll(void)
 647 {
 648     TAPState *s = tap_win32_state;
 649     uint8_t *buf;
 650     int max_size = 4096;
 651     int size;
 652
 653     if (!s)
 654         return;
 655
 656     size = tap_win32_read(s->handle, &buf, max_size);
 657     if (size > 0) {
 658         qemu_send_packet(s->vc, buf, size);
 659         tap_win32_free_buffer(s->handle, buf);
 660         SetEvent(s->tap_event);
 661     }
 662 }
 663
 664 int tap_win32_init(VLANState *vlan, const char *ifname)
 665 {
 666     TAPState *s;
 667
 668     s = qemu_mallocz(sizeof(TAPState));
 669     if (!s)
 670         return -1;
 671     if (tap_win32_open(&s->handle, ifname) < 0) {
 672         printf("tap: Could not open '%s'\n", ifname);
 673         return -1;
 674     }
 675
 676     s->vc = qemu_new_vlan_client(vlan, tap_receive, NULL, s);
 677
 678     snprintf(s->vc->info_str, sizeof(s->vc->info_str),
 679              "tap: ifname=%s", ifname);
 680     tap_win32_state = s;
 681
 682     s->tap_event = CreateEvent(NULL, FALSE, FALSE, NULL);
 683     if (!s->tap_event) {
 684         fprintf(stderr, "tap-win32: Failed CreateEvent\n");
 685     }
 686     qemu_add_wait_object(s->tap_event, NULL, NULL);
 687     return 0;
 688 }