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