net/tap.c

   1 /*
   2  * QEMU System Emulator
   3  *
   4  * Copyright (c) 2003-2008 Fabrice Bellard
   5  * Copyright (c) 2009 Red Hat, Inc.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  23  * THE SOFTWARE.
  24  */
  25
  26 #include "tap_int.h"
  27
  28 #include "config-host.h"
  29
  30 #include <sys/ioctl.h>
  31 #include <sys/stat.h>
  32 #include <sys/wait.h>
  33 #include <sys/socket.h>
  34 #include <net/if.h>
  35
  36 #include "net/net.h"
  37 #include "clients.h"
  38 #include "monitor/monitor.h"
  39 #include "sysemu/sysemu.h"
  40 #include "qemu-common.h"
  41 #include "qemu/error-report.h"
  42
  43 #include "net/tap.h"
  44
  45 #include "hw/vhost_net.h"
  46
  47 /* Maximum GSO packet size (64k) plus plenty of room for
  48  * the ethernet and virtio_net headers
  49  */
  50 #define TAP_BUFSIZE (4096 + 65536)
  51
  52 typedef struct TAPState {
  53     NetClientState nc;
  54     int fd;
  55     char down_script[1024];
  56     char down_script_arg[128];
  57     uint8_t buf[TAP_BUFSIZE];
  58     bool read_poll;
  59     bool write_poll;
  60     bool using_vnet_hdr;
  61     bool has_ufo;
  62     VHostNetState *vhost_net;
  63     unsigned host_vnet_hdr_len;
  64 } TAPState;
  65
  66 static int launch_script(const char *setup_script, const char *ifname, int fd);
  67
  68 static int tap_can_send(void *opaque);
  69 static void tap_send(void *opaque);
  70 static void tap_writable(void *opaque);
  71
  72 static void tap_update_fd_handler(TAPState *s)
  73 {
  74     qemu_set_fd_handler2(s->fd,
  75                          s->read_poll  ? tap_can_send : NULL,
  76                          s->read_poll  ? tap_send     : NULL,
  77                          s->write_poll ? tap_writable : NULL,
  78                          s);
  79 }
  80
  81 static void tap_read_poll(TAPState *s, bool enable)
  82 {
  83     s->read_poll = enable;
  84     tap_update_fd_handler(s);
  85 }
  86
  87 static void tap_write_poll(TAPState *s, bool enable)
  88 {
  89     s->write_poll = enable;
  90     tap_update_fd_handler(s);
  91 }
  92
  93 static void tap_writable(void *opaque)
  94 {
  95     TAPState *s = opaque;
  96
  97     tap_write_poll(s, false);
  98
  99     qemu_flush_queued_packets(&s->nc);
 100 }
 101
 102 static ssize_t tap_write_packet(TAPState *s, const struct iovec *iov, int iovcnt)
 103 {
 104     ssize_t len;
 105
 106     do {
 107         len = writev(s->fd, iov, iovcnt);
 108     } while (len == -1 && errno == EINTR);
 109
 110     if (len == -1 && errno == EAGAIN) {
 111         tap_write_poll(s, true);
 112         return 0;
 113     }
 114
 115     return len;
 116 }
 117
 118 static ssize_t tap_receive_iov(NetClientState *nc, const struct iovec *iov,
 119                                int iovcnt)
 120 {
 121     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 122     const struct iovec *iovp = iov;
 123     struct iovec iov_copy[iovcnt + 1];
 124     struct virtio_net_hdr_mrg_rxbuf hdr = { };
 125
 126     if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
 127         iov_copy[0].iov_base = &hdr;
 128         iov_copy[0].iov_len =  s->host_vnet_hdr_len;
 129         memcpy(&iov_copy[1], iov, iovcnt * sizeof(*iov));
 130         iovp = iov_copy;
 131         iovcnt++;
 132     }
 133
 134     return tap_write_packet(s, iovp, iovcnt);
 135 }
 136
 137 static ssize_t tap_receive_raw(NetClientState *nc, const uint8_t *buf, size_t size)
 138 {
 139     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 140     struct iovec iov[2];
 141     int iovcnt = 0;
 142     struct virtio_net_hdr_mrg_rxbuf hdr = { };
 143
 144     if (s->host_vnet_hdr_len) {
 145         iov[iovcnt].iov_base = &hdr;
 146         iov[iovcnt].iov_len  = s->host_vnet_hdr_len;
 147         iovcnt++;
 148     }
 149
 150     iov[iovcnt].iov_base = (char *)buf;
 151     iov[iovcnt].iov_len  = size;
 152     iovcnt++;
 153
 154     return tap_write_packet(s, iov, iovcnt);
 155 }
 156
 157 static ssize_t tap_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 158 {
 159     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 160     struct iovec iov[1];
 161
 162     if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
 163         return tap_receive_raw(nc, buf, size);
 164     }
 165
 166     iov[0].iov_base = (char *)buf;
 167     iov[0].iov_len  = size;
 168
 169     return tap_write_packet(s, iov, 1);
 170 }
 171
 172 static int tap_can_send(void *opaque)
 173 {
 174     TAPState *s = opaque;
 175
 176     return qemu_can_send_packet(&s->nc);
 177 }
 178
 179 #ifndef __sun__
 180 ssize_t tap_read_packet(int tapfd, uint8_t *buf, int maxlen)
 181 {
 182     return read(tapfd, buf, maxlen);
 183 }
 184 #endif
 185
 186 static void tap_send_completed(NetClientState *nc, ssize_t len)
 187 {
 188     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 189     tap_read_poll(s, true);
 190 }
 191
 192 static void tap_send(void *opaque)
 193 {
 194     TAPState *s = opaque;
 195     int size;
 196
 197     do {
 198         uint8_t *buf = s->buf;
 199
 200         size = tap_read_packet(s->fd, s->buf, sizeof(s->buf));
 201         if (size <= 0) {
 202             break;
 203         }
 204
 205         if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
 206             buf  += s->host_vnet_hdr_len;
 207             size -= s->host_vnet_hdr_len;
 208         }
 209
 210         size = qemu_send_packet_async(&s->nc, buf, size, tap_send_completed);
 211         if (size == 0) {
 212             tap_read_poll(s, false);
 213         }
 214     } while (size > 0 && qemu_can_send_packet(&s->nc));
 215 }
 216
 217 bool tap_has_ufo(NetClientState *nc)
 218 {
 219     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 220
 221     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 222
 223     return s->has_ufo;
 224 }
 225
 226 int tap_has_vnet_hdr(NetClientState *nc)
 227 {
 228     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 229
 230     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 231
 232     return !!s->host_vnet_hdr_len;
 233 }
 234
 235 int tap_has_vnet_hdr_len(NetClientState *nc, int len)
 236 {
 237     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 238
 239     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 240
 241     return tap_probe_vnet_hdr_len(s->fd, len);
 242 }
 243
 244 void tap_set_vnet_hdr_len(NetClientState *nc, int len)
 245 {
 246     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 247
 248     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 249     assert(len == sizeof(struct virtio_net_hdr_mrg_rxbuf) ||
 250            len == sizeof(struct virtio_net_hdr));
 251
 252     tap_fd_set_vnet_hdr_len(s->fd, len);
 253     s->host_vnet_hdr_len = len;
 254 }
 255
 256 void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr)
 257 {
 258     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 259
 260     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 261     assert(!!s->host_vnet_hdr_len == using_vnet_hdr);
 262
 263     s->using_vnet_hdr = using_vnet_hdr;
 264 }
 265
 266 void tap_set_offload(NetClientState *nc, int csum, int tso4,
 267                      int tso6, int ecn, int ufo)
 268 {
 269     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 270     if (s->fd < 0) {
 271         return;
 272     }
 273
 274     tap_fd_set_offload(s->fd, csum, tso4, tso6, ecn, ufo);
 275 }
 276
 277 static void tap_cleanup(NetClientState *nc)
 278 {
 279     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 280
 281     if (s->vhost_net) {
 282         vhost_net_cleanup(s->vhost_net);
 283         s->vhost_net = NULL;
 284     }
 285
 286     qemu_purge_queued_packets(nc);
 287
 288     if (s->down_script[0])
 289         launch_script(s->down_script, s->down_script_arg, s->fd);
 290
 291     tap_read_poll(s, false);
 292     tap_write_poll(s, false);
 293     close(s->fd);
 294     s->fd = -1;
 295 }
 296
 297 static void tap_poll(NetClientState *nc, bool enable)
 298 {
 299     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 300     tap_read_poll(s, enable);
 301     tap_write_poll(s, enable);
 302 }
 303
 304 int tap_get_fd(NetClientState *nc)
 305 {
 306     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 307     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 308     return s->fd;
 309 }
 310
 311 /* fd support */
 312
 313 static NetClientInfo net_tap_info = {
 314     .type = NET_CLIENT_OPTIONS_KIND_TAP,
 315     .size = sizeof(TAPState),
 316     .receive = tap_receive,
 317     .receive_raw = tap_receive_raw,
 318     .receive_iov = tap_receive_iov,
 319     .poll = tap_poll,
 320     .cleanup = tap_cleanup,
 321 };
 322
 323 static TAPState *net_tap_fd_init(NetClientState *peer,
 324                                  const char *model,
 325                                  const char *name,
 326                                  int fd,
 327                                  int vnet_hdr)
 328 {
 329     NetClientState *nc;
 330     TAPState *s;
 331
 332     nc = qemu_new_net_client(&net_tap_info, peer, model, name);
 333
 334     s = DO_UPCAST(TAPState, nc, nc);
 335
 336     s->fd = fd;
 337     s->host_vnet_hdr_len = vnet_hdr ? sizeof(struct virtio_net_hdr) : 0;
 338     s->using_vnet_hdr = false;
 339     s->has_ufo = tap_probe_has_ufo(s->fd);
 340     tap_set_offload(&s->nc, 0, 0, 0, 0, 0);
 341     /*
 342      * Make sure host header length is set correctly in tap:
 343      * it might have been modified by another instance of qemu.
 344      */
 345     if (tap_probe_vnet_hdr_len(s->fd, s->host_vnet_hdr_len)) {
 346         tap_fd_set_vnet_hdr_len(s->fd, s->host_vnet_hdr_len);
 347     }
 348     tap_read_poll(s, true);
 349     s->vhost_net = NULL;
 350     return s;
 351 }
 352
 353 static int launch_script(const char *setup_script, const char *ifname, int fd)
 354 {
 355     int pid, status;
 356     char *args[3];
 357     char **parg;
 358
 359     /* try to launch network script */
 360     pid = fork();
 361     if (pid == 0) {
 362         int open_max = sysconf(_SC_OPEN_MAX), i;
 363
 364         for (i = 0; i < open_max; i++) {
 365             if (i != STDIN_FILENO &&
 366                 i != STDOUT_FILENO &&
 367                 i != STDERR_FILENO &&
 368                 i != fd) {
 369                 close(i);
 370             }
 371         }
 372         parg = args;
 373         *parg++ = (char *)setup_script;
 374         *parg++ = (char *)ifname;
 375         *parg = NULL;
 376         execv(setup_script, args);
 377         _exit(1);
 378     } else if (pid > 0) {
 379         while (waitpid(pid, &status, 0) != pid) {
 380             /* loop */
 381         }
 382
 383         if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
 384             return 0;
 385         }
 386     }
 387     fprintf(stderr, "%s: could not launch network script\n", setup_script);
 388     return -1;
 389 }
 390
 391 static int recv_fd(int c)
 392 {
 393     int fd;
 394     uint8_t msgbuf[CMSG_SPACE(sizeof(fd))];
 395     struct msghdr msg = {
 396         .msg_control = msgbuf,
 397         .msg_controllen = sizeof(msgbuf),
 398     };
 399     struct cmsghdr *cmsg;
 400     struct iovec iov;
 401     uint8_t req[1];
 402     ssize_t len;
 403
 404     cmsg = CMSG_FIRSTHDR(&msg);
 405     cmsg->cmsg_level = SOL_SOCKET;
 406     cmsg->cmsg_type = SCM_RIGHTS;
 407     cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
 408     msg.msg_controllen = cmsg->cmsg_len;
 409
 410     iov.iov_base = req;
 411     iov.iov_len = sizeof(req);
 412
 413     msg.msg_iov = &iov;
 414     msg.msg_iovlen = 1;
 415
 416     len = recvmsg(c, &msg, 0);
 417     if (len > 0) {
 418         memcpy(&fd, CMSG_DATA(cmsg), sizeof(fd));
 419         return fd;
 420     }
 421
 422     return len;
 423 }
 424
 425 static int net_bridge_run_helper(const char *helper, const char *bridge)
 426 {
 427     sigset_t oldmask, mask;
 428     int pid, status;
 429     char *args[5];
 430     char **parg;
 431     int sv[2];
 432
 433     sigemptyset(&mask);
 434     sigaddset(&mask, SIGCHLD);
 435     sigprocmask(SIG_BLOCK, &mask, &oldmask);
 436
 437     if (socketpair(PF_UNIX, SOCK_STREAM, 0, sv) == -1) {
 438         return -1;
 439     }
 440
 441     /* try to launch bridge helper */
 442     pid = fork();
 443     if (pid == 0) {
 444         int open_max = sysconf(_SC_OPEN_MAX), i;
 445         char fd_buf[6+10];
 446         char br_buf[6+IFNAMSIZ] = {0};
 447         char helper_cmd[PATH_MAX + sizeof(fd_buf) + sizeof(br_buf) + 15];
 448
 449         for (i = 0; i < open_max; i++) {
 450             if (i != STDIN_FILENO &&
 451                 i != STDOUT_FILENO &&
 452                 i != STDERR_FILENO &&
 453                 i != sv[1]) {
 454                 close(i);
 455             }
 456         }
 457
 458         snprintf(fd_buf, sizeof(fd_buf), "%s%d", "--fd=", sv[1]);
 459
 460         if (strrchr(helper, ' ') || strrchr(helper, '\t')) {
 461             /* assume helper is a command */
 462
 463             if (strstr(helper, "--br=") == NULL) {
 464                 snprintf(br_buf, sizeof(br_buf), "%s%s", "--br=", bridge);
 465             }
 466
 467             snprintf(helper_cmd, sizeof(helper_cmd), "%s %s %s %s",
 468                      helper, "--use-vnet", fd_buf, br_buf);
 469
 470             parg = args;
 471             *parg++ = (char *)"sh";
 472             *parg++ = (char *)"-c";
 473             *parg++ = helper_cmd;
 474             *parg++ = NULL;
 475
 476             execv("/bin/sh", args);
 477         } else {
 478             /* assume helper is just the executable path name */
 479
 480             snprintf(br_buf, sizeof(br_buf), "%s%s", "--br=", bridge);
 481
 482             parg = args;
 483             *parg++ = (char *)helper;
 484             *parg++ = (char *)"--use-vnet";
 485             *parg++ = fd_buf;
 486             *parg++ = br_buf;
 487             *parg++ = NULL;
 488
 489             execv(helper, args);
 490         }
 491         _exit(1);
 492
 493     } else if (pid > 0) {
 494         int fd;
 495
 496         close(sv[1]);
 497
 498         do {
 499             fd = recv_fd(sv[0]);
 500         } while (fd == -1 && errno == EINTR);
 501
 502         close(sv[0]);
 503
 504         while (waitpid(pid, &status, 0) != pid) {
 505             /* loop */
 506         }
 507         sigprocmask(SIG_SETMASK, &oldmask, NULL);
 508         if (fd < 0) {
 509             fprintf(stderr, "failed to recv file descriptor\n");
 510             return -1;
 511         }
 512
 513         if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
 514             return fd;
 515         }
 516     }
 517     fprintf(stderr, "failed to launch bridge helper\n");
 518     return -1;
 519 }
 520
 521 int net_init_bridge(const NetClientOptions *opts, const char *name,
 522                     NetClientState *peer)
 523 {
 524     const NetdevBridgeOptions *bridge;
 525     const char *helper, *br;
 526
 527     TAPState *s;
 528     int fd, vnet_hdr;
 529
 530     assert(opts->kind == NET_CLIENT_OPTIONS_KIND_BRIDGE);
 531     bridge = opts->bridge;
 532
 533     helper = bridge->has_helper ? bridge->helper : DEFAULT_BRIDGE_HELPER;
 534     br     = bridge->has_br     ? bridge->br     : DEFAULT_BRIDGE_INTERFACE;
 535
 536     fd = net_bridge_run_helper(helper, br);
 537     if (fd == -1) {
 538         return -1;
 539     }
 540
 541     fcntl(fd, F_SETFL, O_NONBLOCK);
 542
 543     vnet_hdr = tap_probe_vnet_hdr(fd);
 544
 545     s = net_tap_fd_init(peer, "bridge", name, fd, vnet_hdr);
 546     if (!s) {
 547         close(fd);
 548         return -1;
 549     }
 550
 551     snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s,br=%s", helper,
 552              br);
 553
 554     return 0;
 555 }
 556
 557 static int net_tap_init(const NetdevTapOptions *tap, int *vnet_hdr,
 558                         const char *setup_script, char *ifname,
 559                         size_t ifname_sz)
 560 {
 561     int fd, vnet_hdr_required;
 562
 563     if (tap->has_ifname) {
 564         pstrcpy(ifname, ifname_sz, tap->ifname);
 565     } else {
 566         assert(ifname_sz > 0);
 567         ifname[0] = '\0';
 568     }
 569
 570     if (tap->has_vnet_hdr) {
 571         *vnet_hdr = tap->vnet_hdr;
 572         vnet_hdr_required = *vnet_hdr;
 573     } else {
 574         *vnet_hdr = 1;
 575         vnet_hdr_required = 0;
 576     }
 577
 578     TFR(fd = tap_open(ifname, ifname_sz, vnet_hdr, vnet_hdr_required));
 579     if (fd < 0) {
 580         return -1;
 581     }
 582
 583     if (setup_script &&
 584         setup_script[0] != '\0' &&
 585         strcmp(setup_script, "no") != 0 &&
 586         launch_script(setup_script, ifname, fd)) {
 587         close(fd);
 588         return -1;
 589     }
 590
 591     return fd;
 592 }
 593
 594 int net_init_tap(const NetClientOptions *opts, const char *name,
 595                  NetClientState *peer)
 596 {
 597     const NetdevTapOptions *tap;
 598
 599     int fd, vnet_hdr = 0;
 600     const char *model;
 601     TAPState *s;
 602
 603     /* for the no-fd, no-helper case */
 604     const char *script = NULL; /* suppress wrong "uninit'd use" gcc warning */
 605     char ifname[128];
 606
 607     assert(opts->kind == NET_CLIENT_OPTIONS_KIND_TAP);
 608     tap = opts->tap;
 609
 610     if (tap->has_fd) {
 611         if (tap->has_ifname || tap->has_script || tap->has_downscript ||
 612             tap->has_vnet_hdr || tap->has_helper) {
 613             error_report("ifname=, script=, downscript=, vnet_hdr=, "
 614                          "and helper= are invalid with fd=");
 615             return -1;
 616         }
 617
 618         fd = monitor_handle_fd_param(cur_mon, tap->fd);
 619         if (fd == -1) {
 620             return -1;
 621         }
 622
 623         fcntl(fd, F_SETFL, O_NONBLOCK);
 624
 625         vnet_hdr = tap_probe_vnet_hdr(fd);
 626
 627         model = "tap";
 628
 629     } else if (tap->has_helper) {
 630         if (tap->has_ifname || tap->has_script || tap->has_downscript ||
 631             tap->has_vnet_hdr) {
 632             error_report("ifname=, script=, downscript=, and vnet_hdr= "
 633                          "are invalid with helper=");
 634             return -1;
 635         }
 636
 637         fd = net_bridge_run_helper(tap->helper, DEFAULT_BRIDGE_INTERFACE);
 638         if (fd == -1) {
 639             return -1;
 640         }
 641
 642         fcntl(fd, F_SETFL, O_NONBLOCK);
 643
 644         vnet_hdr = tap_probe_vnet_hdr(fd);
 645
 646         model = "bridge";
 647
 648     } else {
 649         script = tap->has_script ? tap->script : DEFAULT_NETWORK_SCRIPT;
 650         fd = net_tap_init(tap, &vnet_hdr, script, ifname, sizeof ifname);
 651         if (fd == -1) {
 652             return -1;
 653         }
 654
 655         model = "tap";
 656     }
 657
 658     s = net_tap_fd_init(peer, model, name, fd, vnet_hdr);
 659     if (!s) {
 660         close(fd);
 661         return -1;
 662     }
 663
 664     if (tap_set_sndbuf(s->fd, tap) < 0) {
 665         return -1;
 666     }
 667
 668     if (tap->has_fd) {
 669         snprintf(s->nc.info_str, sizeof(s->nc.info_str), "fd=%d", fd);
 670     } else if (tap->has_helper) {
 671         snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s",
 672                  tap->helper);
 673     } else {
 674         const char *downscript;
 675
 676         downscript = tap->has_downscript ? tap->downscript :
 677                                            DEFAULT_NETWORK_DOWN_SCRIPT;
 678
 679         snprintf(s->nc.info_str, sizeof(s->nc.info_str),
 680                  "ifname=%s,script=%s,downscript=%s", ifname, script,
 681                  downscript);
 682
 683         if (strcmp(downscript, "no") != 0) {
 684             snprintf(s->down_script, sizeof(s->down_script), "%s", downscript);
 685             snprintf(s->down_script_arg, sizeof(s->down_script_arg), "%s", ifname);
 686         }
 687     }
 688
 689     if (tap->has_vhost ? tap->vhost :
 690         tap->has_vhostfd || (tap->has_vhostforce && tap->vhostforce)) {
 691         int vhostfd;
 692
 693         if (tap->has_vhostfd) {
 694             vhostfd = monitor_handle_fd_param(cur_mon, tap->vhostfd);
 695             if (vhostfd == -1) {
 696                 return -1;
 697             }
 698         } else {
 699             vhostfd = -1;
 700         }
 701
 702         s->vhost_net = vhost_net_init(&s->nc, vhostfd,
 703                                       tap->has_vhostforce && tap->vhostforce);
 704         if (!s->vhost_net) {
 705             error_report("vhost-net requested but could not be initialized");
 706             return -1;
 707         }
 708     } else if (tap->has_vhostfd) {
 709         error_report("vhostfd= is not valid without vhost");
 710         return -1;
 711     }
 712
 713     return 0;
 714 }
 715
 716 VHostNetState *tap_get_vhost_net(NetClientState *nc)
 717 {
 718     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 719     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 720     return s->vhost_net;
 721 }