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, see <http://www.gnu.org/licenses/>.
  27  */
  28 #include "qemu-common.h"
  29 #include "net.h"
  30 #include "sysemu.h"
  31 #include <stdio.h>
  32 #include <windows.h>
  33
  34 /* NOTE: PCIBus is redefined in winddk.h */
  35 #define PCIBus _PCIBus
  36 #include <ddk/ntapi.h>
  37 #include <ddk/winddk.h>
  38 #include <ddk/ntddk.h>
  39 #undef PCIBus
  40
  41 //=============
  42 // TAP IOCTLs
  43 //=============
  44
  45 #define TAP_CONTROL_CODE(request,method) \
  46   CTL_CODE (FILE_DEVICE_UNKNOWN, request, method, FILE_ANY_ACCESS)
  47
  48 #define TAP_IOCTL_GET_MAC               TAP_CONTROL_CODE (1, METHOD_BUFFERED)
  49 #define TAP_IOCTL_GET_VERSION           TAP_CONTROL_CODE (2, METHOD_BUFFERED)
  50 #define TAP_IOCTL_GET_MTU               TAP_CONTROL_CODE (3, METHOD_BUFFERED)
  51 #define TAP_IOCTL_GET_INFO              TAP_CONTROL_CODE (4, METHOD_BUFFERED)
  52 #define TAP_IOCTL_CONFIG_POINT_TO_POINT TAP_CONTROL_CODE (5, METHOD_BUFFERED)
  53 #define TAP_IOCTL_SET_MEDIA_STATUS      TAP_CONTROL_CODE (6, METHOD_BUFFERED)
  54 #define TAP_IOCTL_CONFIG_DHCP_MASQ      TAP_CONTROL_CODE (7, METHOD_BUFFERED)
  55 #define TAP_IOCTL_GET_LOG_LINE          TAP_CONTROL_CODE (8, METHOD_BUFFERED)
  56 #define TAP_IOCTL_CONFIG_DHCP_SET_OPT   TAP_CONTROL_CODE (9, METHOD_BUFFERED)
  57
  58 //=================
  59 // Registry keys
  60 //=================
  61
  62 #define ADAPTER_KEY "SYSTEM\\CurrentControlSet\\Control\\Class\\{4D36E972-E325-11CE-BFC1-08002BE10318}"
  63
  64 #define NETWORK_CONNECTIONS_KEY "SYSTEM\\CurrentControlSet\\Control\\Network\\{4D36E972-E325-11CE-BFC1-08002BE10318}"
  65
  66 //======================
  67 // Filesystem prefixes
  68 //======================
  69
  70 #define USERMODEDEVICEDIR "\\\\.\\Global\\"
  71 #define TAPSUFFIX         ".tap"
  72
  73
  74 //======================
  75 // Compile time configuration
  76 //======================
  77
  78 //#define DEBUG_TAP_WIN32
  79
  80 #define TUN_ASYNCHRONOUS_WRITES 1
  81
  82 #define TUN_BUFFER_SIZE 1560
  83 #define TUN_MAX_BUFFER_COUNT 32
  84
  85 /*
  86  * The data member "buffer" must be the first element in the tun_buffer
  87  * structure. See the function, tap_win32_free_buffer.
  88  */
  89 typedef struct tun_buffer_s {
  90     unsigned char buffer [TUN_BUFFER_SIZE];
  91     unsigned long read_size;
  92     struct tun_buffer_s* next;
  93 } tun_buffer_t;
  94
  95 typedef struct tap_win32_overlapped {
  96     HANDLE handle;
  97     HANDLE read_event;
  98     HANDLE write_event;
  99     HANDLE output_queue_semaphore;
 100     HANDLE free_list_semaphore;
 101     HANDLE tap_semaphore;
 102     CRITICAL_SECTION output_queue_cs;
 103     CRITICAL_SECTION free_list_cs;
 104     OVERLAPPED read_overlapped;
 105     OVERLAPPED write_overlapped;
 106     tun_buffer_t buffers[TUN_MAX_BUFFER_COUNT];
 107     tun_buffer_t* free_list;
 108     tun_buffer_t* output_queue_front;
 109     tun_buffer_t* output_queue_back;
 110 } tap_win32_overlapped_t;
 111
 112 static tap_win32_overlapped_t tap_overlapped;
 113
 114 static tun_buffer_t* get_buffer_from_free_list(tap_win32_overlapped_t* const overlapped)
 115 {
 116     tun_buffer_t* buffer = NULL;
 117     WaitForSingleObject(overlapped->free_list_semaphore, INFINITE);
 118     EnterCriticalSection(&overlapped->free_list_cs);
 119     buffer = overlapped->free_list;
 120 //    assert(buffer != NULL);
 121     overlapped->free_list = buffer->next;
 122     LeaveCriticalSection(&overlapped->free_list_cs);
 123     buffer->next = NULL;
 124     return buffer;
 125 }
 126
 127 static void put_buffer_on_free_list(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
 128 {
 129     EnterCriticalSection(&overlapped->free_list_cs);
 130     buffer->next = overlapped->free_list;
 131     overlapped->free_list = buffer;
 132     LeaveCriticalSection(&overlapped->free_list_cs);
 133     ReleaseSemaphore(overlapped->free_list_semaphore, 1, NULL);
 134 }
 135
 136 static tun_buffer_t* get_buffer_from_output_queue(tap_win32_overlapped_t* const overlapped, const int block)
 137 {
 138     tun_buffer_t* buffer = NULL;
 139     DWORD result, timeout = block ? INFINITE : 0L;
 140
 141     // Non-blocking call
 142     result = WaitForSingleObject(overlapped->output_queue_semaphore, timeout);
 143
 144     switch (result)
 145     {
 146         // The semaphore object was signaled.
 147         case WAIT_OBJECT_0:
 148             EnterCriticalSection(&overlapped->output_queue_cs);
 149
 150             buffer = overlapped->output_queue_front;
 151             overlapped->output_queue_front = buffer->next;
 152
 153             if(overlapped->output_queue_front == NULL) {
 154                 overlapped->output_queue_back = NULL;
 155             }
 156
 157             LeaveCriticalSection(&overlapped->output_queue_cs);
 158             break;
 159
 160         // Semaphore was nonsignaled, so a time-out occurred.
 161         case WAIT_TIMEOUT:
 162             // Cannot open another window.
 163             break;
 164     }
 165
 166     return buffer;
 167 }
 168
 169 static tun_buffer_t* get_buffer_from_output_queue_immediate (tap_win32_overlapped_t* const overlapped)
 170 {
 171     return get_buffer_from_output_queue(overlapped, 0);
 172 }
 173
 174 static void put_buffer_on_output_queue(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
 175 {
 176     EnterCriticalSection(&overlapped->output_queue_cs);
 177
 178     if(overlapped->output_queue_front == NULL && overlapped->output_queue_back == NULL) {
 179         overlapped->output_queue_front = overlapped->output_queue_back = buffer;
 180     } else {
 181         buffer->next = NULL;
 182         overlapped->output_queue_back->next = buffer;
 183         overlapped->output_queue_back = buffer;
 184     }
 185
 186     LeaveCriticalSection(&overlapped->output_queue_cs);
 187
 188     ReleaseSemaphore(overlapped->output_queue_semaphore, 1, NULL);
 189 }
 190
 191
 192 static int is_tap_win32_dev(const char *guid)
 193 {
 194     HKEY netcard_key;
 195     LONG status;
 196     DWORD len;
 197     int i = 0;
 198
 199     status = RegOpenKeyEx(
 200         HKEY_LOCAL_MACHINE,
 201         ADAPTER_KEY,
 202         0,
 203         KEY_READ,
 204         &netcard_key);
 205
 206     if (status != ERROR_SUCCESS) {
 207         return FALSE;
 208     }
 209
 210     for (;;) {
 211         char enum_name[256];
 212         char unit_string[256];
 213         HKEY unit_key;
 214         char component_id_string[] = "ComponentId";
 215         char component_id[256];
 216         char net_cfg_instance_id_string[] = "NetCfgInstanceId";
 217         char net_cfg_instance_id[256];
 218         DWORD data_type;
 219
 220         len = sizeof (enum_name);
 221         status = RegEnumKeyEx(
 222             netcard_key,
 223             i,
 224             enum_name,
 225             &len,
 226             NULL,
 227             NULL,
 228             NULL,
 229             NULL);
 230
 231         if (status == ERROR_NO_MORE_ITEMS)
 232             break;
 233         else if (status != ERROR_SUCCESS) {
 234             return FALSE;
 235         }
 236
 237         snprintf (unit_string, sizeof(unit_string), "%s\\%s",
 238                   ADAPTER_KEY, enum_name);
 239
 240         status = RegOpenKeyEx(
 241             HKEY_LOCAL_MACHINE,
 242             unit_string,
 243             0,
 244             KEY_READ,
 245             &unit_key);
 246
 247         if (status != ERROR_SUCCESS) {
 248             return FALSE;
 249         } else {
 250             len = sizeof (component_id);
 251             status = RegQueryValueEx(
 252                 unit_key,
 253                 component_id_string,
 254                 NULL,
 255                 &data_type,
 256                 (LPBYTE)component_id,
 257                 &len);
 258
 259             if (!(status != ERROR_SUCCESS || data_type != REG_SZ)) {
 260                 len = sizeof (net_cfg_instance_id);
 261                 status = RegQueryValueEx(
 262                     unit_key,
 263                     net_cfg_instance_id_string,
 264                     NULL,
 265                     &data_type,
 266                     (LPBYTE)net_cfg_instance_id,
 267                     &len);
 268
 269                 if (status == ERROR_SUCCESS && data_type == REG_SZ) {
 270                     if (/* !strcmp (component_id, TAP_COMPONENT_ID) &&*/
 271                         !strcmp (net_cfg_instance_id, guid)) {
 272                         RegCloseKey (unit_key);
 273                         RegCloseKey (netcard_key);
 274                         return TRUE;
 275                     }
 276                 }
 277             }
 278             RegCloseKey (unit_key);
 279         }
 280         ++i;
 281     }
 282
 283     RegCloseKey (netcard_key);
 284     return FALSE;
 285 }
 286
 287 static int get_device_guid(
 288     char *name,
 289     int name_size,
 290     char *actual_name,
 291     int actual_name_size)
 292 {
 293     LONG status;
 294     HKEY control_net_key;
 295     DWORD len;
 296     int i = 0;
 297     int stop = 0;
 298
 299     status = RegOpenKeyEx(
 300         HKEY_LOCAL_MACHINE,
 301         NETWORK_CONNECTIONS_KEY,
 302         0,
 303         KEY_READ,
 304         &control_net_key);
 305
 306     if (status != ERROR_SUCCESS) {
 307         return -1;
 308     }
 309
 310     while (!stop)
 311     {
 312         char enum_name[256];
 313         char connection_string[256];
 314         HKEY connection_key;
 315         char name_data[256];
 316         DWORD name_type;
 317         const char name_string[] = "Name";
 318
 319         len = sizeof (enum_name);
 320         status = RegEnumKeyEx(
 321             control_net_key,
 322             i,
 323             enum_name,
 324             &len,
 325             NULL,
 326             NULL,
 327             NULL,
 328             NULL);
 329
 330         if (status == ERROR_NO_MORE_ITEMS)
 331             break;
 332         else if (status != ERROR_SUCCESS) {
 333             return -1;
 334         }
 335
 336         snprintf(connection_string,
 337              sizeof(connection_string),
 338              "%s\\%s\\Connection",
 339              NETWORK_CONNECTIONS_KEY, enum_name);
 340
 341         status = RegOpenKeyEx(
 342             HKEY_LOCAL_MACHINE,
 343             connection_string,
 344             0,
 345             KEY_READ,
 346             &connection_key);
 347
 348         if (status == ERROR_SUCCESS) {
 349             len = sizeof (name_data);
 350             status = RegQueryValueEx(
 351                 connection_key,
 352                 name_string,
 353                 NULL,
 354                 &name_type,
 355                 (LPBYTE)name_data,
 356                 &len);
 357
 358             if (status != ERROR_SUCCESS || name_type != REG_SZ) {
 359                     return -1;
 360             }
 361             else {
 362                 if (is_tap_win32_dev(enum_name)) {
 363                     snprintf(name, name_size, "%s", enum_name);
 364                     if (actual_name) {
 365                         if (strcmp(actual_name, "") != 0) {
 366                             if (strcmp(name_data, actual_name) != 0) {
 367                                 RegCloseKey (connection_key);
 368                                 ++i;
 369                                 continue;
 370                             }
 371                         }
 372                         else {
 373                             snprintf(actual_name, actual_name_size, "%s", name_data);
 374                         }
 375                     }
 376                     stop = 1;
 377                 }
 378             }
 379
 380             RegCloseKey (connection_key);
 381         }
 382         ++i;
 383     }
 384
 385     RegCloseKey (control_net_key);
 386
 387     if (stop == 0)
 388         return -1;
 389
 390     return 0;
 391 }
 392
 393 static int tap_win32_set_status(HANDLE handle, int status)
 394 {
 395     unsigned long len = 0;
 396
 397     return DeviceIoControl(handle, TAP_IOCTL_SET_MEDIA_STATUS,
 398                 &status, sizeof (status),
 399                 &status, sizeof (status), &len, NULL);
 400 }
 401
 402 static void tap_win32_overlapped_init(tap_win32_overlapped_t* const overlapped, const HANDLE handle)
 403 {
 404     overlapped->handle = handle;
 405
 406     overlapped->read_event = CreateEvent(NULL, FALSE, FALSE, NULL);
 407     overlapped->write_event = CreateEvent(NULL, FALSE, FALSE, NULL);
 408
 409     overlapped->read_overlapped.Offset = 0;
 410     overlapped->read_overlapped.OffsetHigh = 0;
 411     overlapped->read_overlapped.hEvent = overlapped->read_event;
 412
 413     overlapped->write_overlapped.Offset = 0;
 414     overlapped->write_overlapped.OffsetHigh = 0;
 415     overlapped->write_overlapped.hEvent = overlapped->write_event;
 416
 417     InitializeCriticalSection(&overlapped->output_queue_cs);
 418     InitializeCriticalSection(&overlapped->free_list_cs);
 419
 420     overlapped->output_queue_semaphore = CreateSemaphore(
 421         NULL,   // default security attributes
 422         0,   // initial count
 423         TUN_MAX_BUFFER_COUNT,   // maximum count
 424         NULL);  // unnamed semaphore
 425
 426     if(!overlapped->output_queue_semaphore)  {
 427         fprintf(stderr, "error creating output queue semaphore!\n");
 428     }
 429
 430     overlapped->free_list_semaphore = CreateSemaphore(
 431         NULL,   // default security attributes
 432         TUN_MAX_BUFFER_COUNT,   // initial count
 433         TUN_MAX_BUFFER_COUNT,   // maximum count
 434         NULL);  // unnamed semaphore
 435
 436     if(!overlapped->free_list_semaphore)  {
 437         fprintf(stderr, "error creating free list semaphore!\n");
 438     }
 439
 440     overlapped->free_list = overlapped->output_queue_front = overlapped->output_queue_back = NULL;
 441
 442     {
 443         unsigned index;
 444         for(index = 0; index < TUN_MAX_BUFFER_COUNT; index++) {
 445             tun_buffer_t* element = &overlapped->buffers[index];
 446             element->next = overlapped->free_list;
 447             overlapped->free_list = element;
 448         }
 449     }
 450     /* To count buffers, initially no-signal. */
 451     overlapped->tap_semaphore = CreateSemaphore(NULL, 0, TUN_MAX_BUFFER_COUNT, NULL);
 452     if(!overlapped->tap_semaphore)
 453         fprintf(stderr, "error creating tap_semaphore.\n");
 454 }
 455
 456 static int tap_win32_write(tap_win32_overlapped_t *overlapped,
 457                            const void *buffer, unsigned long size)
 458 {
 459     unsigned long write_size;
 460     BOOL result;
 461     DWORD error;
 462
 463     result = GetOverlappedResult( overlapped->handle, &overlapped->write_overlapped,
 464                                   &write_size, FALSE);
 465
 466     if (!result && GetLastError() == ERROR_IO_INCOMPLETE)
 467         WaitForSingleObject(overlapped->write_event, INFINITE);
 468
 469     result = WriteFile(overlapped->handle, buffer, size,
 470                        &write_size, &overlapped->write_overlapped);
 471
 472     if (!result) {
 473         switch (error = GetLastError())
 474         {
 475         case ERROR_IO_PENDING:
 476 #ifndef TUN_ASYNCHRONOUS_WRITES
 477             WaitForSingleObject(overlapped->write_event, INFINITE);
 478 #endif
 479             break;
 480         default:
 481             return -1;
 482         }
 483     }
 484
 485     return 0;
 486 }
 487
 488 static DWORD WINAPI tap_win32_thread_entry(LPVOID param)
 489 {
 490     tap_win32_overlapped_t *overlapped = (tap_win32_overlapped_t*)param;
 491     unsigned long read_size;
 492     BOOL result;
 493     DWORD dwError;
 494     tun_buffer_t* buffer = get_buffer_from_free_list(overlapped);
 495
 496
 497     for (;;) {
 498         result = ReadFile(overlapped->handle,
 499                           buffer->buffer,
 500                           sizeof(buffer->buffer),
 501                           &read_size,
 502                           &overlapped->read_overlapped);
 503         if (!result) {
 504             dwError = GetLastError();
 505             if (dwError == ERROR_IO_PENDING) {
 506                 WaitForSingleObject(overlapped->read_event, INFINITE);
 507                 result = GetOverlappedResult( overlapped->handle, &overlapped->read_overlapped,
 508                                               &read_size, FALSE);
 509                 if (!result) {
 510 #ifdef DEBUG_TAP_WIN32
 511                     LPVOID lpBuffer;
 512                     dwError = GetLastError();
 513                     FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
 514                                    NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
 515                                    (LPTSTR) & lpBuffer, 0, NULL );
 516                     fprintf(stderr, "Tap-Win32: Error GetOverlappedResult %d - %s\n", dwError, lpBuffer);
 517                     LocalFree( lpBuffer );
 518 #endif
 519                 }
 520             } else {
 521 #ifdef DEBUG_TAP_WIN32
 522                 LPVOID lpBuffer;
 523                 FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
 524                                NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
 525                                (LPTSTR) & lpBuffer, 0, NULL );
 526                 fprintf(stderr, "Tap-Win32: Error ReadFile %d - %s\n", dwError, lpBuffer);
 527                 LocalFree( lpBuffer );
 528 #endif
 529             }
 530         }
 531
 532         if(read_size > 0) {
 533             buffer->read_size = read_size;
 534             put_buffer_on_output_queue(overlapped, buffer);
 535             ReleaseSemaphore(overlapped->tap_semaphore, 1, NULL);
 536             buffer = get_buffer_from_free_list(overlapped);
 537         }
 538     }
 539
 540     return 0;
 541 }
 542
 543 static int tap_win32_read(tap_win32_overlapped_t *overlapped,
 544                           uint8_t **pbuf, int max_size)
 545 {
 546     int size = 0;
 547
 548     tun_buffer_t* buffer = get_buffer_from_output_queue_immediate(overlapped);
 549
 550     if(buffer != NULL) {
 551         *pbuf = buffer->buffer;
 552         size = (int)buffer->read_size;
 553         if(size > max_size) {
 554             size = max_size;
 555         }
 556     }
 557
 558     return size;
 559 }
 560
 561 static void tap_win32_free_buffer(tap_win32_overlapped_t *overlapped,
 562                                   uint8_t *pbuf)
 563 {
 564     tun_buffer_t* buffer = (tun_buffer_t*)pbuf;
 565     put_buffer_on_free_list(overlapped, buffer);
 566 }
 567
 568 static int tap_win32_open(tap_win32_overlapped_t **phandle,
 569                           const char *prefered_name)
 570 {
 571     char device_path[256];
 572     char device_guid[0x100];
 573     int rc;
 574     HANDLE handle;
 575     BOOL bret;
 576     char name_buffer[0x100] = {0, };
 577     struct {
 578         unsigned long major;
 579         unsigned long minor;
 580         unsigned long debug;
 581     } version;
 582     DWORD version_len;
 583     DWORD idThread;
 584     HANDLE hThread;
 585
 586     if (prefered_name != NULL)
 587         snprintf(name_buffer, sizeof(name_buffer), "%s", prefered_name);
 588
 589     rc = get_device_guid(device_guid, sizeof(device_guid), name_buffer, sizeof(name_buffer));
 590     if (rc)
 591         return -1;
 592
 593     snprintf (device_path, sizeof(device_path), "%s%s%s",
 594               USERMODEDEVICEDIR,
 595               device_guid,
 596               TAPSUFFIX);
 597
 598     handle = CreateFile (
 599         device_path,
 600         GENERIC_READ | GENERIC_WRITE,
 601         0,
 602         0,
 603         OPEN_EXISTING,
 604         FILE_ATTRIBUTE_SYSTEM | FILE_FLAG_OVERLAPPED,
 605         0 );
 606
 607     if (handle == INVALID_HANDLE_VALUE) {
 608         return -1;
 609     }
 610
 611     bret = DeviceIoControl(handle, TAP_IOCTL_GET_VERSION,
 612                            &version, sizeof (version),
 613                            &version, sizeof (version), &version_len, NULL);
 614
 615     if (bret == FALSE) {
 616         CloseHandle(handle);
 617         return -1;
 618     }
 619
 620     if (!tap_win32_set_status(handle, TRUE)) {
 621         return -1;
 622     }
 623
 624     tap_win32_overlapped_init(&tap_overlapped, handle);
 625
 626     *phandle = &tap_overlapped;
 627
 628     hThread = CreateThread(NULL, 0, tap_win32_thread_entry,
 629                            (LPVOID)&tap_overlapped, 0, &idThread);
 630     return 0;
 631 }
 632
 633 /********************************************/
 634
 635  typedef struct TAPState {
 636      VLANClientState *vc;
 637      tap_win32_overlapped_t *handle;
 638  } TAPState;
 639
 640 static void tap_cleanup(VLANClientState *vc)
 641 {
 642     TAPState *s = vc->opaque;
 643
 644     qemu_del_wait_object(s->handle->tap_semaphore, NULL, NULL);
 645
 646     /* FIXME: need to kill thread and close file handle:
 647        tap_win32_close(s);
 648     */
 649     qemu_free(s);
 650 }
 651
 652 static ssize_t tap_receive(VLANClientState *vc, const uint8_t *buf, size_t size)
 653 {
 654     TAPState *s = vc->opaque;
 655
 656     return tap_win32_write(s->handle, buf, size);
 657 }
 658
 659 static void tap_win32_send(void *opaque)
 660 {
 661     TAPState *s = opaque;
 662     uint8_t *buf;
 663     int max_size = 4096;
 664     int size;
 665
 666     size = tap_win32_read(s->handle, &buf, max_size);
 667     if (size > 0) {
 668         qemu_send_packet(s->vc, buf, size);
 669         tap_win32_free_buffer(s->handle, buf);
 670     }
 671 }
 672
 673 int tap_win32_init(VLANState *vlan, const char *model,
 674                    const char *name, const char *ifname)
 675 {
 676     TAPState *s;
 677
 678     s = qemu_mallocz(sizeof(TAPState));
 679     if (!s)
 680         return -1;
 681     if (tap_win32_open(&s->handle, ifname) < 0) {
 682         printf("tap: Could not open '%s'\n", ifname);
 683         return -1;
 684     }
 685
 686     s->vc = qemu_new_vlan_client(vlan, model, name, NULL, tap_receive,
 687                                  NULL, tap_cleanup, s);
 688
 689     snprintf(s->vc->info_str, sizeof(s->vc->info_str),
 690              "tap: ifname=%s", ifname);
 691
 692     qemu_add_wait_object(s->handle->tap_semaphore, tap_win32_send, s);
 693     return 0;
 694 }