xref: /qemu/net/tap-win32.c (revision b49f4755)
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 
29 #include "qemu/osdep.h"
30 #include "tap_int.h"
31 
32 #include "clients.h"            /* net_init_tap */
33 #include "net/eth.h"
34 #include "net/net.h"
35 #include "net/tap.h"            /* tap_has_ufo, ... */
36 #include "qemu/error-report.h"
37 #include "qemu/main-loop.h"
38 #include <windows.h>
39 #include <winioctl.h>
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 /* FIXME: The asynch write path appears to be broken at
81  * present. WriteFile() ignores the lpNumberOfBytesWritten parameter
82  * for overlapped writes, with the result we return zero bytes sent,
83  * and after handling a single packet, receive is disabled for this
84  * interface. */
85 /* #define TUN_ASYNCHRONOUS_WRITES 1 */
86 
87 #define TUN_BUFFER_SIZE 1560
88 #define TUN_MAX_BUFFER_COUNT 32
89 
90 /*
91  * The data member "buffer" must be the first element in the tun_buffer
92  * structure. See the function, tap_win32_free_buffer.
93  */
94 typedef struct tun_buffer_s {
95     unsigned char buffer [TUN_BUFFER_SIZE];
96     unsigned long read_size;
97     struct tun_buffer_s* next;
98 } tun_buffer_t;
99 
100 typedef struct tap_win32_overlapped {
101     HANDLE handle;
102     HANDLE read_event;
103     HANDLE write_event;
104     HANDLE output_queue_semaphore;
105     HANDLE free_list_semaphore;
106     HANDLE tap_semaphore;
107     CRITICAL_SECTION output_queue_cs;
108     CRITICAL_SECTION free_list_cs;
109     OVERLAPPED read_overlapped;
110     OVERLAPPED write_overlapped;
111     tun_buffer_t buffers[TUN_MAX_BUFFER_COUNT];
112     tun_buffer_t* free_list;
113     tun_buffer_t* output_queue_front;
114     tun_buffer_t* output_queue_back;
115 } tap_win32_overlapped_t;
116 
117 static tap_win32_overlapped_t tap_overlapped;
118 
119 static tun_buffer_t* get_buffer_from_free_list(tap_win32_overlapped_t* const overlapped)
120 {
121     tun_buffer_t* buffer = NULL;
122     WaitForSingleObject(overlapped->free_list_semaphore, INFINITE);
123     EnterCriticalSection(&overlapped->free_list_cs);
124     buffer = overlapped->free_list;
125 //    assert(buffer != NULL);
126     overlapped->free_list = buffer->next;
127     LeaveCriticalSection(&overlapped->free_list_cs);
128     buffer->next = NULL;
129     return buffer;
130 }
131 
132 static void put_buffer_on_free_list(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
133 {
134     EnterCriticalSection(&overlapped->free_list_cs);
135     buffer->next = overlapped->free_list;
136     overlapped->free_list = buffer;
137     LeaveCriticalSection(&overlapped->free_list_cs);
138     ReleaseSemaphore(overlapped->free_list_semaphore, 1, NULL);
139 }
140 
141 static tun_buffer_t* get_buffer_from_output_queue(tap_win32_overlapped_t* const overlapped, const int block)
142 {
143     tun_buffer_t* buffer = NULL;
144     DWORD result, timeout = block ? INFINITE : 0L;
145 
146     // Non-blocking call
147     result = WaitForSingleObject(overlapped->output_queue_semaphore, timeout);
148 
149     switch (result)
150     {
151         // The semaphore object was signaled.
152         case WAIT_OBJECT_0:
153             EnterCriticalSection(&overlapped->output_queue_cs);
154 
155             buffer = overlapped->output_queue_front;
156             overlapped->output_queue_front = buffer->next;
157 
158             if(overlapped->output_queue_front == NULL) {
159                 overlapped->output_queue_back = NULL;
160             }
161 
162             LeaveCriticalSection(&overlapped->output_queue_cs);
163             break;
164 
165         // Semaphore was nonsignaled, so a time-out occurred.
166         case WAIT_TIMEOUT:
167             // Cannot open another window.
168             break;
169     }
170 
171     return buffer;
172 }
173 
174 static tun_buffer_t* get_buffer_from_output_queue_immediate (tap_win32_overlapped_t* const overlapped)
175 {
176     return get_buffer_from_output_queue(overlapped, 0);
177 }
178 
179 static void put_buffer_on_output_queue(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
180 {
181     EnterCriticalSection(&overlapped->output_queue_cs);
182 
183     if(overlapped->output_queue_front == NULL && overlapped->output_queue_back == NULL) {
184         overlapped->output_queue_front = overlapped->output_queue_back = buffer;
185     } else {
186         buffer->next = NULL;
187         overlapped->output_queue_back->next = buffer;
188         overlapped->output_queue_back = buffer;
189     }
190 
191     LeaveCriticalSection(&overlapped->output_queue_cs);
192 
193     ReleaseSemaphore(overlapped->output_queue_semaphore, 1, NULL);
194 }
195 
196 
197 static int is_tap_win32_dev(const char *guid)
198 {
199     HKEY netcard_key;
200     LONG status;
201     DWORD len;
202     int i = 0;
203 
204     status = RegOpenKeyEx(
205         HKEY_LOCAL_MACHINE,
206         ADAPTER_KEY,
207         0,
208         KEY_READ,
209         &netcard_key);
210 
211     if (status != ERROR_SUCCESS) {
212         return FALSE;
213     }
214 
215     for (;;) {
216         char enum_name[256];
217         char unit_string[256];
218         HKEY unit_key;
219         char component_id_string[] = "ComponentId";
220         char component_id[256];
221         char net_cfg_instance_id_string[] = "NetCfgInstanceId";
222         char net_cfg_instance_id[256];
223         DWORD data_type;
224 
225         len = sizeof (enum_name);
226         status = RegEnumKeyEx(
227             netcard_key,
228             i,
229             enum_name,
230             &len,
231             NULL,
232             NULL,
233             NULL,
234             NULL);
235 
236         if (status == ERROR_NO_MORE_ITEMS)
237             break;
238         else if (status != ERROR_SUCCESS) {
239             return FALSE;
240         }
241 
242         snprintf (unit_string, sizeof(unit_string), "%s\\%s",
243                   ADAPTER_KEY, enum_name);
244 
245         status = RegOpenKeyEx(
246             HKEY_LOCAL_MACHINE,
247             unit_string,
248             0,
249             KEY_READ,
250             &unit_key);
251 
252         if (status != ERROR_SUCCESS) {
253             return FALSE;
254         } else {
255             len = sizeof (component_id);
256             status = RegQueryValueEx(
257                 unit_key,
258                 component_id_string,
259                 NULL,
260                 &data_type,
261                 (LPBYTE)component_id,
262                 &len);
263 
264             if (!(status != ERROR_SUCCESS || data_type != REG_SZ)) {
265                 len = sizeof (net_cfg_instance_id);
266                 status = RegQueryValueEx(
267                     unit_key,
268                     net_cfg_instance_id_string,
269                     NULL,
270                     &data_type,
271                     (LPBYTE)net_cfg_instance_id,
272                     &len);
273 
274                 if (status == ERROR_SUCCESS && data_type == REG_SZ) {
275                     if (/* !strcmp (component_id, TAP_COMPONENT_ID) &&*/
276                         !strcmp (net_cfg_instance_id, guid)) {
277                         RegCloseKey (unit_key);
278                         RegCloseKey (netcard_key);
279                         return TRUE;
280                     }
281                 }
282             }
283             RegCloseKey (unit_key);
284         }
285         ++i;
286     }
287 
288     RegCloseKey (netcard_key);
289     return FALSE;
290 }
291 
292 static int get_device_guid(
293     char *name,
294     int name_size,
295     char *actual_name,
296     int actual_name_size)
297 {
298     LONG status;
299     HKEY control_net_key;
300     DWORD len;
301     int i = 0;
302     int stop = 0;
303 
304     status = RegOpenKeyEx(
305         HKEY_LOCAL_MACHINE,
306         NETWORK_CONNECTIONS_KEY,
307         0,
308         KEY_READ,
309         &control_net_key);
310 
311     if (status != ERROR_SUCCESS) {
312         return -1;
313     }
314 
315     while (!stop)
316     {
317         char enum_name[256];
318         char connection_string[256];
319         HKEY connection_key;
320         char name_data[256];
321         DWORD name_type;
322         const char name_string[] = "Name";
323 
324         len = sizeof (enum_name);
325         status = RegEnumKeyEx(
326             control_net_key,
327             i,
328             enum_name,
329             &len,
330             NULL,
331             NULL,
332             NULL,
333             NULL);
334 
335         if (status == ERROR_NO_MORE_ITEMS)
336             break;
337         else if (status != ERROR_SUCCESS) {
338             return -1;
339         }
340 
341         snprintf(connection_string,
342              sizeof(connection_string),
343              "%s\\%s\\Connection",
344              NETWORK_CONNECTIONS_KEY, enum_name);
345 
346         status = RegOpenKeyEx(
347             HKEY_LOCAL_MACHINE,
348             connection_string,
349             0,
350             KEY_READ,
351             &connection_key);
352 
353         if (status == ERROR_SUCCESS) {
354             len = sizeof (name_data);
355             status = RegQueryValueEx(
356                 connection_key,
357                 name_string,
358                 NULL,
359                 &name_type,
360                 (LPBYTE)name_data,
361                 &len);
362 
363             if (status != ERROR_SUCCESS || name_type != REG_SZ) {
364                 ++i;
365                 continue;
366             }
367             else {
368                 if (is_tap_win32_dev(enum_name)) {
369                     snprintf(name, name_size, "%s", enum_name);
370                     if (actual_name) {
371                         if (strcmp(actual_name, "") != 0) {
372                             if (strcmp(name_data, actual_name) != 0) {
373                                 RegCloseKey (connection_key);
374                                 ++i;
375                                 continue;
376                             }
377                         }
378                         else {
379                             snprintf(actual_name, actual_name_size, "%s", name_data);
380                         }
381                     }
382                     stop = 1;
383                 }
384             }
385 
386             RegCloseKey (connection_key);
387         }
388         ++i;
389     }
390 
391     RegCloseKey (control_net_key);
392 
393     if (stop == 0)
394         return -1;
395 
396     return 0;
397 }
398 
399 static int tap_win32_set_status(HANDLE handle, int status)
400 {
401     unsigned long len = 0;
402 
403     return DeviceIoControl(handle, TAP_IOCTL_SET_MEDIA_STATUS,
404                 &status, sizeof (status),
405                 &status, sizeof (status), &len, NULL);
406 }
407 
408 static void tap_win32_overlapped_init(tap_win32_overlapped_t* const overlapped, const HANDLE handle)
409 {
410     overlapped->handle = handle;
411 
412     overlapped->read_event = CreateEvent(NULL, FALSE, FALSE, NULL);
413     overlapped->write_event = CreateEvent(NULL, FALSE, FALSE, NULL);
414 
415     overlapped->read_overlapped.Offset = 0;
416     overlapped->read_overlapped.OffsetHigh = 0;
417     overlapped->read_overlapped.hEvent = overlapped->read_event;
418 
419     overlapped->write_overlapped.Offset = 0;
420     overlapped->write_overlapped.OffsetHigh = 0;
421     overlapped->write_overlapped.hEvent = overlapped->write_event;
422 
423     InitializeCriticalSection(&overlapped->output_queue_cs);
424     InitializeCriticalSection(&overlapped->free_list_cs);
425 
426     overlapped->output_queue_semaphore = CreateSemaphore(
427         NULL,   // default security attributes
428         0,   // initial count
429         TUN_MAX_BUFFER_COUNT,   // maximum count
430         NULL);  // unnamed semaphore
431 
432     if(!overlapped->output_queue_semaphore)  {
433         fprintf(stderr, "error creating output queue semaphore!\n");
434     }
435 
436     overlapped->free_list_semaphore = CreateSemaphore(
437         NULL,   // default security attributes
438         TUN_MAX_BUFFER_COUNT,   // initial count
439         TUN_MAX_BUFFER_COUNT,   // maximum count
440         NULL);  // unnamed semaphore
441 
442     if(!overlapped->free_list_semaphore)  {
443         fprintf(stderr, "error creating free list semaphore!\n");
444     }
445 
446     overlapped->free_list = overlapped->output_queue_front = overlapped->output_queue_back = NULL;
447 
448     {
449         unsigned index;
450         for(index = 0; index < TUN_MAX_BUFFER_COUNT; index++) {
451             tun_buffer_t* element = &overlapped->buffers[index];
452             element->next = overlapped->free_list;
453             overlapped->free_list = element;
454         }
455     }
456     /* To count buffers, initially no-signal. */
457     overlapped->tap_semaphore = CreateSemaphore(NULL, 0, TUN_MAX_BUFFER_COUNT, NULL);
458     if(!overlapped->tap_semaphore)
459         fprintf(stderr, "error creating tap_semaphore.\n");
460 }
461 
462 static int tap_win32_write(tap_win32_overlapped_t *overlapped,
463                            const void *buffer, unsigned long size)
464 {
465     unsigned long write_size;
466     BOOL result;
467     DWORD error;
468 
469 #ifdef TUN_ASYNCHRONOUS_WRITES
470     result = GetOverlappedResult( overlapped->handle, &overlapped->write_overlapped,
471                                   &write_size, FALSE);
472 
473     if (!result && GetLastError() == ERROR_IO_INCOMPLETE)
474         WaitForSingleObject(overlapped->write_event, INFINITE);
475 #endif
476 
477     result = WriteFile(overlapped->handle, buffer, size,
478                        &write_size, &overlapped->write_overlapped);
479 
480 #ifdef TUN_ASYNCHRONOUS_WRITES
481     /* FIXME: we can't sensibly set write_size here, without waiting
482      * for the IO to complete! Moreover, we can't return zero,
483      * because that will disable receive on this interface, and we
484      * also can't assume it will succeed and return the full size,
485      * because that will result in the buffer being reclaimed while
486      * the IO is in progress. */
487 #error Async writes are broken. Please disable TUN_ASYNCHRONOUS_WRITES.
488 #else /* !TUN_ASYNCHRONOUS_WRITES */
489     if (!result) {
490         error = GetLastError();
491         if (error == ERROR_IO_PENDING) {
492             result = GetOverlappedResult(overlapped->handle,
493                                          &overlapped->write_overlapped,
494                                          &write_size, TRUE);
495         }
496     }
497 #endif
498 
499     if (!result) {
500 #ifdef DEBUG_TAP_WIN32
501         LPTSTR msgbuf;
502         error = GetLastError();
503         FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM,
504                       NULL, error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
505                       &msgbuf, 0, NULL);
506         fprintf(stderr, "Tap-Win32: Error WriteFile %d - %s\n", error, msgbuf);
507         LocalFree(msgbuf);
508 #endif
509         return 0;
510     }
511 
512     return write_size;
513 }
514 
515 static DWORD WINAPI tap_win32_thread_entry(LPVOID param)
516 {
517     tap_win32_overlapped_t *overlapped = (tap_win32_overlapped_t*)param;
518     unsigned long read_size;
519     BOOL result;
520     DWORD dwError;
521     tun_buffer_t* buffer = get_buffer_from_free_list(overlapped);
522 
523 
524     for (;;) {
525         result = ReadFile(overlapped->handle,
526                           buffer->buffer,
527                           sizeof(buffer->buffer),
528                           &read_size,
529                           &overlapped->read_overlapped);
530         if (!result) {
531             dwError = GetLastError();
532             if (dwError == ERROR_IO_PENDING) {
533                 WaitForSingleObject(overlapped->read_event, INFINITE);
534                 result = GetOverlappedResult( overlapped->handle, &overlapped->read_overlapped,
535                                               &read_size, FALSE);
536                 if (!result) {
537 #ifdef DEBUG_TAP_WIN32
538                     LPVOID lpBuffer;
539                     dwError = GetLastError();
540                     FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
541                                    NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
542                                    (LPTSTR) & lpBuffer, 0, NULL );
543                     fprintf(stderr, "Tap-Win32: Error GetOverlappedResult %d - %s\n", dwError, lpBuffer);
544                     LocalFree( lpBuffer );
545 #endif
546                 }
547             } else {
548 #ifdef DEBUG_TAP_WIN32
549                 LPVOID lpBuffer;
550                 FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
551                                NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
552                                (LPTSTR) & lpBuffer, 0, NULL );
553                 fprintf(stderr, "Tap-Win32: Error ReadFile %d - %s\n", dwError, lpBuffer);
554                 LocalFree( lpBuffer );
555 #endif
556             }
557         }
558 
559         if(read_size > 0) {
560             buffer->read_size = read_size;
561             put_buffer_on_output_queue(overlapped, buffer);
562             ReleaseSemaphore(overlapped->tap_semaphore, 1, NULL);
563             buffer = get_buffer_from_free_list(overlapped);
564         }
565     }
566 
567     return 0;
568 }
569 
570 static int tap_win32_read(tap_win32_overlapped_t *overlapped,
571                           uint8_t **pbuf, int max_size)
572 {
573     int size = 0;
574 
575     tun_buffer_t* buffer = get_buffer_from_output_queue_immediate(overlapped);
576 
577     if(buffer != NULL) {
578         *pbuf = buffer->buffer;
579         size = (int)buffer->read_size;
580         if(size > max_size) {
581             size = max_size;
582         }
583     }
584 
585     return size;
586 }
587 
588 static void tap_win32_free_buffer(tap_win32_overlapped_t *overlapped,
589                                   uint8_t *pbuf)
590 {
591     tun_buffer_t* buffer = (tun_buffer_t*)pbuf;
592     put_buffer_on_free_list(overlapped, buffer);
593 }
594 
595 static int tap_win32_open(tap_win32_overlapped_t **phandle,
596                           const char *preferred_name)
597 {
598     char device_path[256];
599     char device_guid[0x100];
600     int rc;
601     HANDLE handle;
602     BOOL bret;
603     char name_buffer[0x100] = {0, };
604     struct {
605         unsigned long major;
606         unsigned long minor;
607         unsigned long debug;
608     } version;
609     DWORD version_len;
610     DWORD idThread;
611 
612     if (preferred_name != NULL) {
613         snprintf(name_buffer, sizeof(name_buffer), "%s", preferred_name);
614     }
615 
616     rc = get_device_guid(device_guid, sizeof(device_guid), name_buffer, sizeof(name_buffer));
617     if (rc)
618         return -1;
619 
620     snprintf (device_path, sizeof(device_path), "%s%s%s",
621               USERMODEDEVICEDIR,
622               device_guid,
623               TAPSUFFIX);
624 
625     handle = CreateFile (
626         device_path,
627         GENERIC_READ | GENERIC_WRITE,
628         0,
629         0,
630         OPEN_EXISTING,
631         FILE_ATTRIBUTE_SYSTEM | FILE_FLAG_OVERLAPPED,
632         0 );
633 
634     if (handle == INVALID_HANDLE_VALUE) {
635         return -1;
636     }
637 
638     bret = DeviceIoControl(handle, TAP_IOCTL_GET_VERSION,
639                            &version, sizeof (version),
640                            &version, sizeof (version), &version_len, NULL);
641 
642     if (bret == FALSE) {
643         CloseHandle(handle);
644         return -1;
645     }
646 
647     if (!tap_win32_set_status(handle, TRUE)) {
648         return -1;
649     }
650 
651     tap_win32_overlapped_init(&tap_overlapped, handle);
652 
653     *phandle = &tap_overlapped;
654 
655     CreateThread(NULL, 0, tap_win32_thread_entry,
656                  (LPVOID)&tap_overlapped, 0, &idThread);
657     return 0;
658 }
659 
660 /********************************************/
661 
662  typedef struct TAPState {
663      NetClientState nc;
664      tap_win32_overlapped_t *handle;
665  } TAPState;
666 
667 static void tap_cleanup(NetClientState *nc)
668 {
669     TAPState *s = DO_UPCAST(TAPState, nc, nc);
670 
671     qemu_del_wait_object(s->handle->tap_semaphore, NULL, NULL);
672 
673     /* FIXME: need to kill thread and close file handle:
674        tap_win32_close(s);
675     */
676 }
677 
678 static ssize_t tap_receive(NetClientState *nc, const uint8_t *buf, size_t size)
679 {
680     TAPState *s = DO_UPCAST(TAPState, nc, nc);
681 
682     return tap_win32_write(s->handle, buf, size);
683 }
684 
685 static void tap_win32_send(void *opaque)
686 {
687     TAPState *s = opaque;
688     uint8_t *buf, *orig_buf;
689     int max_size = 4096;
690     int size;
691     uint8_t min_pkt[ETH_ZLEN];
692     size_t min_pktsz = sizeof(min_pkt);
693 
694     size = tap_win32_read(s->handle, &buf, max_size);
695     if (size > 0) {
696         orig_buf = buf;
697 
698         if (net_peer_needs_padding(&s->nc)) {
699             if (eth_pad_short_frame(min_pkt, &min_pktsz, buf, size)) {
700                 buf = min_pkt;
701                 size = min_pktsz;
702             }
703         }
704 
705         qemu_send_packet(&s->nc, buf, size);
706         tap_win32_free_buffer(s->handle, orig_buf);
707     }
708 }
709 
710 static bool tap_has_ufo(NetClientState *nc)
711 {
712     return false;
713 }
714 
715 static bool tap_has_vnet_hdr(NetClientState *nc)
716 {
717     return false;
718 }
719 
720 int tap_probe_vnet_hdr_len(int fd, int len)
721 {
722     return 0;
723 }
724 
725 void tap_fd_set_vnet_hdr_len(int fd, int len)
726 {
727 }
728 
729 int tap_fd_set_vnet_le(int fd, int is_le)
730 {
731     return -EINVAL;
732 }
733 
734 int tap_fd_set_vnet_be(int fd, int is_be)
735 {
736     return -EINVAL;
737 }
738 
739 static void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr)
740 {
741 }
742 
743 static void tap_set_offload(NetClientState *nc, int csum, int tso4,
744                      int tso6, int ecn, int ufo, int uso4, int uso6)
745 {
746 }
747 
748 struct vhost_net *tap_get_vhost_net(NetClientState *nc)
749 {
750     return NULL;
751 }
752 
753 static bool tap_has_vnet_hdr_len(NetClientState *nc, int len)
754 {
755     return false;
756 }
757 
758 static void tap_set_vnet_hdr_len(NetClientState *nc, int len)
759 {
760     abort();
761 }
762 
763 static NetClientInfo net_tap_win32_info = {
764     .type = NET_CLIENT_DRIVER_TAP,
765     .size = sizeof(TAPState),
766     .receive = tap_receive,
767     .cleanup = tap_cleanup,
768     .has_ufo = tap_has_ufo,
769     .has_vnet_hdr = tap_has_vnet_hdr,
770     .has_vnet_hdr_len = tap_has_vnet_hdr_len,
771     .using_vnet_hdr = tap_using_vnet_hdr,
772     .set_offload = tap_set_offload,
773     .set_vnet_hdr_len = tap_set_vnet_hdr_len,
774 };
775 
776 static int tap_win32_init(NetClientState *peer, const char *model,
777                           const char *name, const char *ifname)
778 {
779     NetClientState *nc;
780     TAPState *s;
781     tap_win32_overlapped_t *handle;
782 
783     if (tap_win32_open(&handle, ifname) < 0) {
784         printf("tap: Could not open '%s'\n", ifname);
785         return -1;
786     }
787 
788     nc = qemu_new_net_client(&net_tap_win32_info, peer, model, name);
789 
790     s = DO_UPCAST(TAPState, nc, nc);
791 
792     qemu_set_info_str(&s->nc, "tap: ifname=%s", ifname);
793 
794     s->handle = handle;
795 
796     qemu_add_wait_object(s->handle->tap_semaphore, tap_win32_send, s);
797 
798     return 0;
799 }
800 
801 int net_init_tap(const Netdev *netdev, const char *name,
802                  NetClientState *peer, Error **errp)
803 {
804     /* FIXME error_setg(errp, ...) on failure */
805     const NetdevTapOptions *tap;
806 
807     assert(netdev->type == NET_CLIENT_DRIVER_TAP);
808     tap = &netdev->u.tap;
809 
810     if (!tap->ifname) {
811         error_report("tap: no interface name");
812         return -1;
813     }
814 
815     if (tap_win32_init(peer, "tap", name, tap->ifname) == -1) {
816         return -1;
817     }
818 
819     return 0;
820 }
821 
822 int tap_enable(NetClientState *nc)
823 {
824     abort();
825 }
826 
827 int tap_disable(NetClientState *nc)
828 {
829     abort();
830 }
831