xref: /openbmc/qemu/net/tap-win32.c (revision f6476697)
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 "qemu-common.h"
33 #include "clients.h"            /* net_init_tap */
34 #include "net/eth.h"
35 #include "net/net.h"
36 #include "net/tap.h"            /* tap_has_ufo, ... */
37 #include "qemu/error-report.h"
38 #include "qemu/main-loop.h"
39 #include <windows.h>
40 #include <winioctl.h>
41 
42 //=============
43 // TAP IOCTLs
44 //=============
45 
46 #define TAP_CONTROL_CODE(request,method) \
47   CTL_CODE (FILE_DEVICE_UNKNOWN, request, method, FILE_ANY_ACCESS)
48 
49 #define TAP_IOCTL_GET_MAC               TAP_CONTROL_CODE (1, METHOD_BUFFERED)
50 #define TAP_IOCTL_GET_VERSION           TAP_CONTROL_CODE (2, METHOD_BUFFERED)
51 #define TAP_IOCTL_GET_MTU               TAP_CONTROL_CODE (3, METHOD_BUFFERED)
52 #define TAP_IOCTL_GET_INFO              TAP_CONTROL_CODE (4, METHOD_BUFFERED)
53 #define TAP_IOCTL_CONFIG_POINT_TO_POINT TAP_CONTROL_CODE (5, METHOD_BUFFERED)
54 #define TAP_IOCTL_SET_MEDIA_STATUS      TAP_CONTROL_CODE (6, METHOD_BUFFERED)
55 #define TAP_IOCTL_CONFIG_DHCP_MASQ      TAP_CONTROL_CODE (7, METHOD_BUFFERED)
56 #define TAP_IOCTL_GET_LOG_LINE          TAP_CONTROL_CODE (8, METHOD_BUFFERED)
57 #define TAP_IOCTL_CONFIG_DHCP_SET_OPT   TAP_CONTROL_CODE (9, METHOD_BUFFERED)
58 
59 //=================
60 // Registry keys
61 //=================
62 
63 #define ADAPTER_KEY "SYSTEM\\CurrentControlSet\\Control\\Class\\{4D36E972-E325-11CE-BFC1-08002BE10318}"
64 
65 #define NETWORK_CONNECTIONS_KEY "SYSTEM\\CurrentControlSet\\Control\\Network\\{4D36E972-E325-11CE-BFC1-08002BE10318}"
66 
67 //======================
68 // Filesystem prefixes
69 //======================
70 
71 #define USERMODEDEVICEDIR "\\\\.\\Global\\"
72 #define TAPSUFFIX         ".tap"
73 
74 
75 //======================
76 // Compile time configuration
77 //======================
78 
79 //#define DEBUG_TAP_WIN32
80 
81 /* FIXME: The asynch write path appears to be broken at
82  * present. WriteFile() ignores the lpNumberOfBytesWritten parameter
83  * for overlapped writes, with the result we return zero bytes sent,
84  * and after handling a single packet, receive is disabled for this
85  * interface. */
86 /* #define TUN_ASYNCHRONOUS_WRITES 1 */
87 
88 #define TUN_BUFFER_SIZE 1560
89 #define TUN_MAX_BUFFER_COUNT 32
90 
91 /*
92  * The data member "buffer" must be the first element in the tun_buffer
93  * structure. See the function, tap_win32_free_buffer.
94  */
95 typedef struct tun_buffer_s {
96     unsigned char buffer [TUN_BUFFER_SIZE];
97     unsigned long read_size;
98     struct tun_buffer_s* next;
99 } tun_buffer_t;
100 
101 typedef struct tap_win32_overlapped {
102     HANDLE handle;
103     HANDLE read_event;
104     HANDLE write_event;
105     HANDLE output_queue_semaphore;
106     HANDLE free_list_semaphore;
107     HANDLE tap_semaphore;
108     CRITICAL_SECTION output_queue_cs;
109     CRITICAL_SECTION free_list_cs;
110     OVERLAPPED read_overlapped;
111     OVERLAPPED write_overlapped;
112     tun_buffer_t buffers[TUN_MAX_BUFFER_COUNT];
113     tun_buffer_t* free_list;
114     tun_buffer_t* output_queue_front;
115     tun_buffer_t* output_queue_back;
116 } tap_win32_overlapped_t;
117 
118 static tap_win32_overlapped_t tap_overlapped;
119 
120 static tun_buffer_t* get_buffer_from_free_list(tap_win32_overlapped_t* const overlapped)
121 {
122     tun_buffer_t* buffer = NULL;
123     WaitForSingleObject(overlapped->free_list_semaphore, INFINITE);
124     EnterCriticalSection(&overlapped->free_list_cs);
125     buffer = overlapped->free_list;
126 //    assert(buffer != NULL);
127     overlapped->free_list = buffer->next;
128     LeaveCriticalSection(&overlapped->free_list_cs);
129     buffer->next = NULL;
130     return buffer;
131 }
132 
133 static void put_buffer_on_free_list(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
134 {
135     EnterCriticalSection(&overlapped->free_list_cs);
136     buffer->next = overlapped->free_list;
137     overlapped->free_list = buffer;
138     LeaveCriticalSection(&overlapped->free_list_cs);
139     ReleaseSemaphore(overlapped->free_list_semaphore, 1, NULL);
140 }
141 
142 static tun_buffer_t* get_buffer_from_output_queue(tap_win32_overlapped_t* const overlapped, const int block)
143 {
144     tun_buffer_t* buffer = NULL;
145     DWORD result, timeout = block ? INFINITE : 0L;
146 
147     // Non-blocking call
148     result = WaitForSingleObject(overlapped->output_queue_semaphore, timeout);
149 
150     switch (result)
151     {
152         // The semaphore object was signaled.
153         case WAIT_OBJECT_0:
154             EnterCriticalSection(&overlapped->output_queue_cs);
155 
156             buffer = overlapped->output_queue_front;
157             overlapped->output_queue_front = buffer->next;
158 
159             if(overlapped->output_queue_front == NULL) {
160                 overlapped->output_queue_back = NULL;
161             }
162 
163             LeaveCriticalSection(&overlapped->output_queue_cs);
164             break;
165 
166         // Semaphore was nonsignaled, so a time-out occurred.
167         case WAIT_TIMEOUT:
168             // Cannot open another window.
169             break;
170     }
171 
172     return buffer;
173 }
174 
175 static tun_buffer_t* get_buffer_from_output_queue_immediate (tap_win32_overlapped_t* const overlapped)
176 {
177     return get_buffer_from_output_queue(overlapped, 0);
178 }
179 
180 static void put_buffer_on_output_queue(tap_win32_overlapped_t* const overlapped, tun_buffer_t* const buffer)
181 {
182     EnterCriticalSection(&overlapped->output_queue_cs);
183 
184     if(overlapped->output_queue_front == NULL && overlapped->output_queue_back == NULL) {
185         overlapped->output_queue_front = overlapped->output_queue_back = buffer;
186     } else {
187         buffer->next = NULL;
188         overlapped->output_queue_back->next = buffer;
189         overlapped->output_queue_back = buffer;
190     }
191 
192     LeaveCriticalSection(&overlapped->output_queue_cs);
193 
194     ReleaseSemaphore(overlapped->output_queue_semaphore, 1, NULL);
195 }
196 
197 
198 static int is_tap_win32_dev(const char *guid)
199 {
200     HKEY netcard_key;
201     LONG status;
202     DWORD len;
203     int i = 0;
204 
205     status = RegOpenKeyEx(
206         HKEY_LOCAL_MACHINE,
207         ADAPTER_KEY,
208         0,
209         KEY_READ,
210         &netcard_key);
211 
212     if (status != ERROR_SUCCESS) {
213         return FALSE;
214     }
215 
216     for (;;) {
217         char enum_name[256];
218         char unit_string[256];
219         HKEY unit_key;
220         char component_id_string[] = "ComponentId";
221         char component_id[256];
222         char net_cfg_instance_id_string[] = "NetCfgInstanceId";
223         char net_cfg_instance_id[256];
224         DWORD data_type;
225 
226         len = sizeof (enum_name);
227         status = RegEnumKeyEx(
228             netcard_key,
229             i,
230             enum_name,
231             &len,
232             NULL,
233             NULL,
234             NULL,
235             NULL);
236 
237         if (status == ERROR_NO_MORE_ITEMS)
238             break;
239         else if (status != ERROR_SUCCESS) {
240             return FALSE;
241         }
242 
243         snprintf (unit_string, sizeof(unit_string), "%s\\%s",
244                   ADAPTER_KEY, enum_name);
245 
246         status = RegOpenKeyEx(
247             HKEY_LOCAL_MACHINE,
248             unit_string,
249             0,
250             KEY_READ,
251             &unit_key);
252 
253         if (status != ERROR_SUCCESS) {
254             return FALSE;
255         } else {
256             len = sizeof (component_id);
257             status = RegQueryValueEx(
258                 unit_key,
259                 component_id_string,
260                 NULL,
261                 &data_type,
262                 (LPBYTE)component_id,
263                 &len);
264 
265             if (!(status != ERROR_SUCCESS || data_type != REG_SZ)) {
266                 len = sizeof (net_cfg_instance_id);
267                 status = RegQueryValueEx(
268                     unit_key,
269                     net_cfg_instance_id_string,
270                     NULL,
271                     &data_type,
272                     (LPBYTE)net_cfg_instance_id,
273                     &len);
274 
275                 if (status == ERROR_SUCCESS && data_type == REG_SZ) {
276                     if (/* !strcmp (component_id, TAP_COMPONENT_ID) &&*/
277                         !strcmp (net_cfg_instance_id, guid)) {
278                         RegCloseKey (unit_key);
279                         RegCloseKey (netcard_key);
280                         return TRUE;
281                     }
282                 }
283             }
284             RegCloseKey (unit_key);
285         }
286         ++i;
287     }
288 
289     RegCloseKey (netcard_key);
290     return FALSE;
291 }
292 
293 static int get_device_guid(
294     char *name,
295     int name_size,
296     char *actual_name,
297     int actual_name_size)
298 {
299     LONG status;
300     HKEY control_net_key;
301     DWORD len;
302     int i = 0;
303     int stop = 0;
304 
305     status = RegOpenKeyEx(
306         HKEY_LOCAL_MACHINE,
307         NETWORK_CONNECTIONS_KEY,
308         0,
309         KEY_READ,
310         &control_net_key);
311 
312     if (status != ERROR_SUCCESS) {
313         return -1;
314     }
315 
316     while (!stop)
317     {
318         char enum_name[256];
319         char connection_string[256];
320         HKEY connection_key;
321         char name_data[256];
322         DWORD name_type;
323         const char name_string[] = "Name";
324 
325         len = sizeof (enum_name);
326         status = RegEnumKeyEx(
327             control_net_key,
328             i,
329             enum_name,
330             &len,
331             NULL,
332             NULL,
333             NULL,
334             NULL);
335 
336         if (status == ERROR_NO_MORE_ITEMS)
337             break;
338         else if (status != ERROR_SUCCESS) {
339             return -1;
340         }
341 
342         snprintf(connection_string,
343              sizeof(connection_string),
344              "%s\\%s\\Connection",
345              NETWORK_CONNECTIONS_KEY, enum_name);
346 
347         status = RegOpenKeyEx(
348             HKEY_LOCAL_MACHINE,
349             connection_string,
350             0,
351             KEY_READ,
352             &connection_key);
353 
354         if (status == ERROR_SUCCESS) {
355             len = sizeof (name_data);
356             status = RegQueryValueEx(
357                 connection_key,
358                 name_string,
359                 NULL,
360                 &name_type,
361                 (LPBYTE)name_data,
362                 &len);
363 
364             if (status != ERROR_SUCCESS || name_type != REG_SZ) {
365                 ++i;
366                 continue;
367             }
368             else {
369                 if (is_tap_win32_dev(enum_name)) {
370                     snprintf(name, name_size, "%s", enum_name);
371                     if (actual_name) {
372                         if (strcmp(actual_name, "") != 0) {
373                             if (strcmp(name_data, actual_name) != 0) {
374                                 RegCloseKey (connection_key);
375                                 ++i;
376                                 continue;
377                             }
378                         }
379                         else {
380                             snprintf(actual_name, actual_name_size, "%s", name_data);
381                         }
382                     }
383                     stop = 1;
384                 }
385             }
386 
387             RegCloseKey (connection_key);
388         }
389         ++i;
390     }
391 
392     RegCloseKey (control_net_key);
393 
394     if (stop == 0)
395         return -1;
396 
397     return 0;
398 }
399 
400 static int tap_win32_set_status(HANDLE handle, int status)
401 {
402     unsigned long len = 0;
403 
404     return DeviceIoControl(handle, TAP_IOCTL_SET_MEDIA_STATUS,
405                 &status, sizeof (status),
406                 &status, sizeof (status), &len, NULL);
407 }
408 
409 static void tap_win32_overlapped_init(tap_win32_overlapped_t* const overlapped, const HANDLE handle)
410 {
411     overlapped->handle = handle;
412 
413     overlapped->read_event = CreateEvent(NULL, FALSE, FALSE, NULL);
414     overlapped->write_event = CreateEvent(NULL, FALSE, FALSE, NULL);
415 
416     overlapped->read_overlapped.Offset = 0;
417     overlapped->read_overlapped.OffsetHigh = 0;
418     overlapped->read_overlapped.hEvent = overlapped->read_event;
419 
420     overlapped->write_overlapped.Offset = 0;
421     overlapped->write_overlapped.OffsetHigh = 0;
422     overlapped->write_overlapped.hEvent = overlapped->write_event;
423 
424     InitializeCriticalSection(&overlapped->output_queue_cs);
425     InitializeCriticalSection(&overlapped->free_list_cs);
426 
427     overlapped->output_queue_semaphore = CreateSemaphore(
428         NULL,   // default security attributes
429         0,   // initial count
430         TUN_MAX_BUFFER_COUNT,   // maximum count
431         NULL);  // unnamed semaphore
432 
433     if(!overlapped->output_queue_semaphore)  {
434         fprintf(stderr, "error creating output queue semaphore!\n");
435     }
436 
437     overlapped->free_list_semaphore = CreateSemaphore(
438         NULL,   // default security attributes
439         TUN_MAX_BUFFER_COUNT,   // initial count
440         TUN_MAX_BUFFER_COUNT,   // maximum count
441         NULL);  // unnamed semaphore
442 
443     if(!overlapped->free_list_semaphore)  {
444         fprintf(stderr, "error creating free list semaphore!\n");
445     }
446 
447     overlapped->free_list = overlapped->output_queue_front = overlapped->output_queue_back = NULL;
448 
449     {
450         unsigned index;
451         for(index = 0; index < TUN_MAX_BUFFER_COUNT; index++) {
452             tun_buffer_t* element = &overlapped->buffers[index];
453             element->next = overlapped->free_list;
454             overlapped->free_list = element;
455         }
456     }
457     /* To count buffers, initially no-signal. */
458     overlapped->tap_semaphore = CreateSemaphore(NULL, 0, TUN_MAX_BUFFER_COUNT, NULL);
459     if(!overlapped->tap_semaphore)
460         fprintf(stderr, "error creating tap_semaphore.\n");
461 }
462 
463 static int tap_win32_write(tap_win32_overlapped_t *overlapped,
464                            const void *buffer, unsigned long size)
465 {
466     unsigned long write_size;
467     BOOL result;
468     DWORD error;
469 
470 #ifdef TUN_ASYNCHRONOUS_WRITES
471     result = GetOverlappedResult( overlapped->handle, &overlapped->write_overlapped,
472                                   &write_size, FALSE);
473 
474     if (!result && GetLastError() == ERROR_IO_INCOMPLETE)
475         WaitForSingleObject(overlapped->write_event, INFINITE);
476 #endif
477 
478     result = WriteFile(overlapped->handle, buffer, size,
479                        &write_size, &overlapped->write_overlapped);
480 
481 #ifdef TUN_ASYNCHRONOUS_WRITES
482     /* FIXME: we can't sensibly set write_size here, without waiting
483      * for the IO to complete! Moreover, we can't return zero,
484      * because that will disable receive on this interface, and we
485      * also can't assume it will succeed and return the full size,
486      * because that will result in the buffer being reclaimed while
487      * the IO is in progress. */
488 #error Async writes are broken. Please disable TUN_ASYNCHRONOUS_WRITES.
489 #else /* !TUN_ASYNCHRONOUS_WRITES */
490     if (!result) {
491         error = GetLastError();
492         if (error == ERROR_IO_PENDING) {
493             result = GetOverlappedResult(overlapped->handle,
494                                          &overlapped->write_overlapped,
495                                          &write_size, TRUE);
496         }
497     }
498 #endif
499 
500     if (!result) {
501 #ifdef DEBUG_TAP_WIN32
502         LPTSTR msgbuf;
503         error = GetLastError();
504         FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM,
505                       NULL, error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
506                       &msgbuf, 0, NULL);
507         fprintf(stderr, "Tap-Win32: Error WriteFile %d - %s\n", error, msgbuf);
508         LocalFree(msgbuf);
509 #endif
510         return 0;
511     }
512 
513     return write_size;
514 }
515 
516 static DWORD WINAPI tap_win32_thread_entry(LPVOID param)
517 {
518     tap_win32_overlapped_t *overlapped = (tap_win32_overlapped_t*)param;
519     unsigned long read_size;
520     BOOL result;
521     DWORD dwError;
522     tun_buffer_t* buffer = get_buffer_from_free_list(overlapped);
523 
524 
525     for (;;) {
526         result = ReadFile(overlapped->handle,
527                           buffer->buffer,
528                           sizeof(buffer->buffer),
529                           &read_size,
530                           &overlapped->read_overlapped);
531         if (!result) {
532             dwError = GetLastError();
533             if (dwError == ERROR_IO_PENDING) {
534                 WaitForSingleObject(overlapped->read_event, INFINITE);
535                 result = GetOverlappedResult( overlapped->handle, &overlapped->read_overlapped,
536                                               &read_size, FALSE);
537                 if (!result) {
538 #ifdef DEBUG_TAP_WIN32
539                     LPVOID lpBuffer;
540                     dwError = GetLastError();
541                     FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
542                                    NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
543                                    (LPTSTR) & lpBuffer, 0, NULL );
544                     fprintf(stderr, "Tap-Win32: Error GetOverlappedResult %d - %s\n", dwError, lpBuffer);
545                     LocalFree( lpBuffer );
546 #endif
547                 }
548             } else {
549 #ifdef DEBUG_TAP_WIN32
550                 LPVOID lpBuffer;
551                 FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM,
552                                NULL, dwError, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
553                                (LPTSTR) & lpBuffer, 0, NULL );
554                 fprintf(stderr, "Tap-Win32: Error ReadFile %d - %s\n", dwError, lpBuffer);
555                 LocalFree( lpBuffer );
556 #endif
557             }
558         }
559 
560         if(read_size > 0) {
561             buffer->read_size = read_size;
562             put_buffer_on_output_queue(overlapped, buffer);
563             ReleaseSemaphore(overlapped->tap_semaphore, 1, NULL);
564             buffer = get_buffer_from_free_list(overlapped);
565         }
566     }
567 
568     return 0;
569 }
570 
571 static int tap_win32_read(tap_win32_overlapped_t *overlapped,
572                           uint8_t **pbuf, int max_size)
573 {
574     int size = 0;
575 
576     tun_buffer_t* buffer = get_buffer_from_output_queue_immediate(overlapped);
577 
578     if(buffer != NULL) {
579         *pbuf = buffer->buffer;
580         size = (int)buffer->read_size;
581         if(size > max_size) {
582             size = max_size;
583         }
584     }
585 
586     return size;
587 }
588 
589 static void tap_win32_free_buffer(tap_win32_overlapped_t *overlapped,
590                                   uint8_t *pbuf)
591 {
592     tun_buffer_t* buffer = (tun_buffer_t*)pbuf;
593     put_buffer_on_free_list(overlapped, buffer);
594 }
595 
596 static int tap_win32_open(tap_win32_overlapped_t **phandle,
597                           const char *preferred_name)
598 {
599     char device_path[256];
600     char device_guid[0x100];
601     int rc;
602     HANDLE handle;
603     BOOL bret;
604     char name_buffer[0x100] = {0, };
605     struct {
606         unsigned long major;
607         unsigned long minor;
608         unsigned long debug;
609     } version;
610     DWORD version_len;
611     DWORD idThread;
612 
613     if (preferred_name != NULL) {
614         snprintf(name_buffer, sizeof(name_buffer), "%s", preferred_name);
615     }
616 
617     rc = get_device_guid(device_guid, sizeof(device_guid), name_buffer, sizeof(name_buffer));
618     if (rc)
619         return -1;
620 
621     snprintf (device_path, sizeof(device_path), "%s%s%s",
622               USERMODEDEVICEDIR,
623               device_guid,
624               TAPSUFFIX);
625 
626     handle = CreateFile (
627         device_path,
628         GENERIC_READ | GENERIC_WRITE,
629         0,
630         0,
631         OPEN_EXISTING,
632         FILE_ATTRIBUTE_SYSTEM | FILE_FLAG_OVERLAPPED,
633         0 );
634 
635     if (handle == INVALID_HANDLE_VALUE) {
636         return -1;
637     }
638 
639     bret = DeviceIoControl(handle, TAP_IOCTL_GET_VERSION,
640                            &version, sizeof (version),
641                            &version, sizeof (version), &version_len, NULL);
642 
643     if (bret == FALSE) {
644         CloseHandle(handle);
645         return -1;
646     }
647 
648     if (!tap_win32_set_status(handle, TRUE)) {
649         return -1;
650     }
651 
652     tap_win32_overlapped_init(&tap_overlapped, handle);
653 
654     *phandle = &tap_overlapped;
655 
656     CreateThread(NULL, 0, tap_win32_thread_entry,
657                  (LPVOID)&tap_overlapped, 0, &idThread);
658     return 0;
659 }
660 
661 /********************************************/
662 
663  typedef struct TAPState {
664      NetClientState nc;
665      tap_win32_overlapped_t *handle;
666  } TAPState;
667 
668 static void tap_cleanup(NetClientState *nc)
669 {
670     TAPState *s = DO_UPCAST(TAPState, nc, nc);
671 
672     qemu_del_wait_object(s->handle->tap_semaphore, NULL, NULL);
673 
674     /* FIXME: need to kill thread and close file handle:
675        tap_win32_close(s);
676     */
677 }
678 
679 static ssize_t tap_receive(NetClientState *nc, const uint8_t *buf, size_t size)
680 {
681     TAPState *s = DO_UPCAST(TAPState, nc, nc);
682 
683     return tap_win32_write(s->handle, buf, size);
684 }
685 
686 static void tap_win32_send(void *opaque)
687 {
688     TAPState *s = opaque;
689     uint8_t *buf, *orig_buf;
690     int max_size = 4096;
691     int size;
692     uint8_t min_pkt[ETH_ZLEN];
693     size_t min_pktsz = sizeof(min_pkt);
694 
695     size = tap_win32_read(s->handle, &buf, max_size);
696     if (size > 0) {
697         orig_buf = buf;
698 
699         if (net_peer_needs_padding(&s->nc)) {
700             if (eth_pad_short_frame(min_pkt, &min_pktsz, buf, size)) {
701                 buf = min_pkt;
702                 size = min_pktsz;
703             }
704         }
705 
706         qemu_send_packet(&s->nc, buf, size);
707         tap_win32_free_buffer(s->handle, orig_buf);
708     }
709 }
710 
711 static bool tap_has_ufo(NetClientState *nc)
712 {
713     return false;
714 }
715 
716 static bool tap_has_vnet_hdr(NetClientState *nc)
717 {
718     return false;
719 }
720 
721 int tap_probe_vnet_hdr_len(int fd, int len)
722 {
723     return 0;
724 }
725 
726 void tap_fd_set_vnet_hdr_len(int fd, int len)
727 {
728 }
729 
730 int tap_fd_set_vnet_le(int fd, int is_le)
731 {
732     return -EINVAL;
733 }
734 
735 int tap_fd_set_vnet_be(int fd, int is_be)
736 {
737     return -EINVAL;
738 }
739 
740 static void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr)
741 {
742 }
743 
744 static void tap_set_offload(NetClientState *nc, int csum, int tso4,
745                      int tso6, int ecn, int ufo)
746 {
747 }
748 
749 struct vhost_net *tap_get_vhost_net(NetClientState *nc)
750 {
751     return NULL;
752 }
753 
754 static bool tap_has_vnet_hdr_len(NetClientState *nc, int len)
755 {
756     return false;
757 }
758 
759 static void tap_set_vnet_hdr_len(NetClientState *nc, int len)
760 {
761     abort();
762 }
763 
764 static NetClientInfo net_tap_win32_info = {
765     .type = NET_CLIENT_DRIVER_TAP,
766     .size = sizeof(TAPState),
767     .receive = tap_receive,
768     .cleanup = tap_cleanup,
769     .has_ufo = tap_has_ufo,
770     .has_vnet_hdr = tap_has_vnet_hdr,
771     .has_vnet_hdr_len = tap_has_vnet_hdr_len,
772     .using_vnet_hdr = tap_using_vnet_hdr,
773     .set_offload = tap_set_offload,
774     .set_vnet_hdr_len = tap_set_vnet_hdr_len,
775 };
776 
777 static int tap_win32_init(NetClientState *peer, const char *model,
778                           const char *name, const char *ifname)
779 {
780     NetClientState *nc;
781     TAPState *s;
782     tap_win32_overlapped_t *handle;
783 
784     if (tap_win32_open(&handle, ifname) < 0) {
785         printf("tap: Could not open '%s'\n", ifname);
786         return -1;
787     }
788 
789     nc = qemu_new_net_client(&net_tap_win32_info, peer, model, name);
790 
791     s = DO_UPCAST(TAPState, nc, nc);
792 
793     snprintf(s->nc.info_str, sizeof(s->nc.info_str),
794              "tap: ifname=%s", ifname);
795 
796     s->handle = handle;
797 
798     qemu_add_wait_object(s->handle->tap_semaphore, tap_win32_send, s);
799 
800     return 0;
801 }
802 
803 int net_init_tap(const Netdev *netdev, const char *name,
804                  NetClientState *peer, Error **errp)
805 {
806     /* FIXME error_setg(errp, ...) on failure */
807     const NetdevTapOptions *tap;
808 
809     assert(netdev->type == NET_CLIENT_DRIVER_TAP);
810     tap = &netdev->u.tap;
811 
812     if (!tap->has_ifname) {
813         error_report("tap: no interface name");
814         return -1;
815     }
816 
817     if (tap_win32_init(peer, "tap", name, tap->ifname) == -1) {
818         return -1;
819     }
820 
821     return 0;
822 }
823 
824 int tap_enable(NetClientState *nc)
825 {
826     abort();
827 }
828 
829 int tap_disable(NetClientState *nc)
830 {
831     abort();
832 }
833