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     bool enabled;
  63     VHostNetState *vhost_net;
  64     unsigned host_vnet_hdr_len;
  65 } TAPState;
  66
  67 static int launch_script(const char *setup_script, const char *ifname, int fd);
  68
  69 static int tap_can_send(void *opaque);
  70 static void tap_send(void *opaque);
  71 static void tap_writable(void *opaque);
  72
  73 static void tap_update_fd_handler(TAPState *s)
  74 {
  75     qemu_set_fd_handler2(s->fd,
  76                          s->read_poll && s->enabled ? tap_can_send : NULL,
  77                          s->read_poll && s->enabled ? tap_send     : NULL,
  78                          s->write_poll && s->enabled ? tap_writable : NULL,
  79                          s);
  80 }
  81
  82 static void tap_read_poll(TAPState *s, bool enable)
  83 {
  84     s->read_poll = enable;
  85     tap_update_fd_handler(s);
  86 }
  87
  88 static void tap_write_poll(TAPState *s, bool enable)
  89 {
  90     s->write_poll = enable;
  91     tap_update_fd_handler(s);
  92 }
  93
  94 static void tap_writable(void *opaque)
  95 {
  96     TAPState *s = opaque;
  97
  98     tap_write_poll(s, false);
  99
 100     qemu_flush_queued_packets(&s->nc);
 101 }
 102
 103 static ssize_t tap_write_packet(TAPState *s, const struct iovec *iov, int iovcnt)
 104 {
 105     ssize_t len;
 106
 107     do {
 108         len = writev(s->fd, iov, iovcnt);
 109     } while (len == -1 && errno == EINTR);
 110
 111     if (len == -1 && errno == EAGAIN) {
 112         tap_write_poll(s, true);
 113         return 0;
 114     }
 115
 116     return len;
 117 }
 118
 119 static ssize_t tap_receive_iov(NetClientState *nc, const struct iovec *iov,
 120                                int iovcnt)
 121 {
 122     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 123     const struct iovec *iovp = iov;
 124     struct iovec iov_copy[iovcnt + 1];
 125     struct virtio_net_hdr_mrg_rxbuf hdr = { };
 126
 127     if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
 128         iov_copy[0].iov_base = &hdr;
 129         iov_copy[0].iov_len =  s->host_vnet_hdr_len;
 130         memcpy(&iov_copy[1], iov, iovcnt * sizeof(*iov));
 131         iovp = iov_copy;
 132         iovcnt++;
 133     }
 134
 135     return tap_write_packet(s, iovp, iovcnt);
 136 }
 137
 138 static ssize_t tap_receive_raw(NetClientState *nc, const uint8_t *buf, size_t size)
 139 {
 140     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 141     struct iovec iov[2];
 142     int iovcnt = 0;
 143     struct virtio_net_hdr_mrg_rxbuf hdr = { };
 144
 145     if (s->host_vnet_hdr_len) {
 146         iov[iovcnt].iov_base = &hdr;
 147         iov[iovcnt].iov_len  = s->host_vnet_hdr_len;
 148         iovcnt++;
 149     }
 150
 151     iov[iovcnt].iov_base = (char *)buf;
 152     iov[iovcnt].iov_len  = size;
 153     iovcnt++;
 154
 155     return tap_write_packet(s, iov, iovcnt);
 156 }
 157
 158 static ssize_t tap_receive(NetClientState *nc, const uint8_t *buf, size_t size)
 159 {
 160     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 161     struct iovec iov[1];
 162
 163     if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
 164         return tap_receive_raw(nc, buf, size);
 165     }
 166
 167     iov[0].iov_base = (char *)buf;
 168     iov[0].iov_len  = size;
 169
 170     return tap_write_packet(s, iov, 1);
 171 }
 172
 173 static int tap_can_send(void *opaque)
 174 {
 175     TAPState *s = opaque;
 176
 177     return qemu_can_send_packet(&s->nc);
 178 }
 179
 180 #ifndef __sun__
 181 ssize_t tap_read_packet(int tapfd, uint8_t *buf, int maxlen)
 182 {
 183     return read(tapfd, buf, maxlen);
 184 }
 185 #endif
 186
 187 static void tap_send_completed(NetClientState *nc, ssize_t len)
 188 {
 189     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 190     tap_read_poll(s, true);
 191 }
 192
 193 static void tap_send(void *opaque)
 194 {
 195     TAPState *s = opaque;
 196     int size;
 197
 198     do {
 199         uint8_t *buf = s->buf;
 200
 201         size = tap_read_packet(s->fd, s->buf, sizeof(s->buf));
 202         if (size <= 0) {
 203             break;
 204         }
 205
 206         if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
 207             buf  += s->host_vnet_hdr_len;
 208             size -= s->host_vnet_hdr_len;
 209         }
 210
 211         size = qemu_send_packet_async(&s->nc, buf, size, tap_send_completed);
 212         if (size == 0) {
 213             tap_read_poll(s, false);
 214         }
 215     } while (size > 0 && qemu_can_send_packet(&s->nc));
 216 }
 217
 218 bool tap_has_ufo(NetClientState *nc)
 219 {
 220     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 221
 222     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 223
 224     return s->has_ufo;
 225 }
 226
 227 int tap_has_vnet_hdr(NetClientState *nc)
 228 {
 229     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 230
 231     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 232
 233     return !!s->host_vnet_hdr_len;
 234 }
 235
 236 int tap_has_vnet_hdr_len(NetClientState *nc, int len)
 237 {
 238     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 239
 240     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 241
 242     return tap_probe_vnet_hdr_len(s->fd, len);
 243 }
 244
 245 void tap_set_vnet_hdr_len(NetClientState *nc, int len)
 246 {
 247     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 248
 249     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 250     assert(len == sizeof(struct virtio_net_hdr_mrg_rxbuf) ||
 251            len == sizeof(struct virtio_net_hdr));
 252
 253     tap_fd_set_vnet_hdr_len(s->fd, len);
 254     s->host_vnet_hdr_len = len;
 255 }
 256
 257 void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr)
 258 {
 259     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 260
 261     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 262     assert(!!s->host_vnet_hdr_len == using_vnet_hdr);
 263
 264     s->using_vnet_hdr = using_vnet_hdr;
 265 }
 266
 267 void tap_set_offload(NetClientState *nc, int csum, int tso4,
 268                      int tso6, int ecn, int ufo)
 269 {
 270     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 271     if (s->fd < 0) {
 272         return;
 273     }
 274
 275     tap_fd_set_offload(s->fd, csum, tso4, tso6, ecn, ufo);
 276 }
 277
 278 static void tap_cleanup(NetClientState *nc)
 279 {
 280     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 281
 282     if (s->vhost_net) {
 283         vhost_net_cleanup(s->vhost_net);
 284         s->vhost_net = NULL;
 285     }
 286
 287     qemu_purge_queued_packets(nc);
 288
 289     if (s->down_script[0])
 290         launch_script(s->down_script, s->down_script_arg, s->fd);
 291
 292     tap_read_poll(s, false);
 293     tap_write_poll(s, false);
 294     close(s->fd);
 295     s->fd = -1;
 296 }
 297
 298 static void tap_poll(NetClientState *nc, bool enable)
 299 {
 300     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 301     tap_read_poll(s, enable);
 302     tap_write_poll(s, enable);
 303 }
 304
 305 int tap_get_fd(NetClientState *nc)
 306 {
 307     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 308     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 309     return s->fd;
 310 }
 311
 312 /* fd support */
 313
 314 static NetClientInfo net_tap_info = {
 315     .type = NET_CLIENT_OPTIONS_KIND_TAP,
 316     .size = sizeof(TAPState),
 317     .receive = tap_receive,
 318     .receive_raw = tap_receive_raw,
 319     .receive_iov = tap_receive_iov,
 320     .poll = tap_poll,
 321     .cleanup = tap_cleanup,
 322 };
 323
 324 static TAPState *net_tap_fd_init(NetClientState *peer,
 325                                  const char *model,
 326                                  const char *name,
 327                                  int fd,
 328                                  int vnet_hdr)
 329 {
 330     NetClientState *nc;
 331     TAPState *s;
 332
 333     nc = qemu_new_net_client(&net_tap_info, peer, model, name);
 334
 335     s = DO_UPCAST(TAPState, nc, nc);
 336
 337     s->fd = fd;
 338     s->host_vnet_hdr_len = vnet_hdr ? sizeof(struct virtio_net_hdr) : 0;
 339     s->using_vnet_hdr = false;
 340     s->has_ufo = tap_probe_has_ufo(s->fd);
 341     s->enabled = true;
 342     tap_set_offload(&s->nc, 0, 0, 0, 0, 0);
 343     /*
 344      * Make sure host header length is set correctly in tap:
 345      * it might have been modified by another instance of qemu.
 346      */
 347     if (tap_probe_vnet_hdr_len(s->fd, s->host_vnet_hdr_len)) {
 348         tap_fd_set_vnet_hdr_len(s->fd, s->host_vnet_hdr_len);
 349     }
 350     tap_read_poll(s, true);
 351     s->vhost_net = NULL;
 352     return s;
 353 }
 354
 355 static int launch_script(const char *setup_script, const char *ifname, int fd)
 356 {
 357     int pid, status;
 358     char *args[3];
 359     char **parg;
 360
 361     /* try to launch network script */
 362     pid = fork();
 363     if (pid == 0) {
 364         int open_max = sysconf(_SC_OPEN_MAX), i;
 365
 366         for (i = 0; i < open_max; i++) {
 367             if (i != STDIN_FILENO &&
 368                 i != STDOUT_FILENO &&
 369                 i != STDERR_FILENO &&
 370                 i != fd) {
 371                 close(i);
 372             }
 373         }
 374         parg = args;
 375         *parg++ = (char *)setup_script;
 376         *parg++ = (char *)ifname;
 377         *parg = NULL;
 378         execv(setup_script, args);
 379         _exit(1);
 380     } else if (pid > 0) {
 381         while (waitpid(pid, &status, 0) != pid) {
 382             /* loop */
 383         }
 384
 385         if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
 386             return 0;
 387         }
 388     }
 389     fprintf(stderr, "%s: could not launch network script\n", setup_script);
 390     return -1;
 391 }
 392
 393 static int recv_fd(int c)
 394 {
 395     int fd;
 396     uint8_t msgbuf[CMSG_SPACE(sizeof(fd))];
 397     struct msghdr msg = {
 398         .msg_control = msgbuf,
 399         .msg_controllen = sizeof(msgbuf),
 400     };
 401     struct cmsghdr *cmsg;
 402     struct iovec iov;
 403     uint8_t req[1];
 404     ssize_t len;
 405
 406     cmsg = CMSG_FIRSTHDR(&msg);
 407     cmsg->cmsg_level = SOL_SOCKET;
 408     cmsg->cmsg_type = SCM_RIGHTS;
 409     cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
 410     msg.msg_controllen = cmsg->cmsg_len;
 411
 412     iov.iov_base = req;
 413     iov.iov_len = sizeof(req);
 414
 415     msg.msg_iov = &iov;
 416     msg.msg_iovlen = 1;
 417
 418     len = recvmsg(c, &msg, 0);
 419     if (len > 0) {
 420         memcpy(&fd, CMSG_DATA(cmsg), sizeof(fd));
 421         return fd;
 422     }
 423
 424     return len;
 425 }
 426
 427 static int net_bridge_run_helper(const char *helper, const char *bridge)
 428 {
 429     sigset_t oldmask, mask;
 430     int pid, status;
 431     char *args[5];
 432     char **parg;
 433     int sv[2];
 434
 435     sigemptyset(&mask);
 436     sigaddset(&mask, SIGCHLD);
 437     sigprocmask(SIG_BLOCK, &mask, &oldmask);
 438
 439     if (socketpair(PF_UNIX, SOCK_STREAM, 0, sv) == -1) {
 440         return -1;
 441     }
 442
 443     /* try to launch bridge helper */
 444     pid = fork();
 445     if (pid == 0) {
 446         int open_max = sysconf(_SC_OPEN_MAX), i;
 447         char fd_buf[6+10];
 448         char br_buf[6+IFNAMSIZ] = {0};
 449         char helper_cmd[PATH_MAX + sizeof(fd_buf) + sizeof(br_buf) + 15];
 450
 451         for (i = 0; i < open_max; i++) {
 452             if (i != STDIN_FILENO &&
 453                 i != STDOUT_FILENO &&
 454                 i != STDERR_FILENO &&
 455                 i != sv[1]) {
 456                 close(i);
 457             }
 458         }
 459
 460         snprintf(fd_buf, sizeof(fd_buf), "%s%d", "--fd=", sv[1]);
 461
 462         if (strrchr(helper, ' ') || strrchr(helper, '\t')) {
 463             /* assume helper is a command */
 464
 465             if (strstr(helper, "--br=") == NULL) {
 466                 snprintf(br_buf, sizeof(br_buf), "%s%s", "--br=", bridge);
 467             }
 468
 469             snprintf(helper_cmd, sizeof(helper_cmd), "%s %s %s %s",
 470                      helper, "--use-vnet", fd_buf, br_buf);
 471
 472             parg = args;
 473             *parg++ = (char *)"sh";
 474             *parg++ = (char *)"-c";
 475             *parg++ = helper_cmd;
 476             *parg++ = NULL;
 477
 478             execv("/bin/sh", args);
 479         } else {
 480             /* assume helper is just the executable path name */
 481
 482             snprintf(br_buf, sizeof(br_buf), "%s%s", "--br=", bridge);
 483
 484             parg = args;
 485             *parg++ = (char *)helper;
 486             *parg++ = (char *)"--use-vnet";
 487             *parg++ = fd_buf;
 488             *parg++ = br_buf;
 489             *parg++ = NULL;
 490
 491             execv(helper, args);
 492         }
 493         _exit(1);
 494
 495     } else if (pid > 0) {
 496         int fd;
 497
 498         close(sv[1]);
 499
 500         do {
 501             fd = recv_fd(sv[0]);
 502         } while (fd == -1 && errno == EINTR);
 503
 504         close(sv[0]);
 505
 506         while (waitpid(pid, &status, 0) != pid) {
 507             /* loop */
 508         }
 509         sigprocmask(SIG_SETMASK, &oldmask, NULL);
 510         if (fd < 0) {
 511             fprintf(stderr, "failed to recv file descriptor\n");
 512             return -1;
 513         }
 514
 515         if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
 516             return fd;
 517         }
 518     }
 519     fprintf(stderr, "failed to launch bridge helper\n");
 520     return -1;
 521 }
 522
 523 int net_init_bridge(const NetClientOptions *opts, const char *name,
 524                     NetClientState *peer)
 525 {
 526     const NetdevBridgeOptions *bridge;
 527     const char *helper, *br;
 528
 529     TAPState *s;
 530     int fd, vnet_hdr;
 531
 532     assert(opts->kind == NET_CLIENT_OPTIONS_KIND_BRIDGE);
 533     bridge = opts->bridge;
 534
 535     helper = bridge->has_helper ? bridge->helper : DEFAULT_BRIDGE_HELPER;
 536     br     = bridge->has_br     ? bridge->br     : DEFAULT_BRIDGE_INTERFACE;
 537
 538     fd = net_bridge_run_helper(helper, br);
 539     if (fd == -1) {
 540         return -1;
 541     }
 542
 543     fcntl(fd, F_SETFL, O_NONBLOCK);
 544
 545     vnet_hdr = tap_probe_vnet_hdr(fd);
 546
 547     s = net_tap_fd_init(peer, "bridge", name, fd, vnet_hdr);
 548     if (!s) {
 549         close(fd);
 550         return -1;
 551     }
 552
 553     snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s,br=%s", helper,
 554              br);
 555
 556     return 0;
 557 }
 558
 559 static int net_tap_init(const NetdevTapOptions *tap, int *vnet_hdr,
 560                         const char *setup_script, char *ifname,
 561                         size_t ifname_sz, int mq_required)
 562 {
 563     int fd, vnet_hdr_required;
 564
 565     if (tap->has_vnet_hdr) {
 566         *vnet_hdr = tap->vnet_hdr;
 567         vnet_hdr_required = *vnet_hdr;
 568     } else {
 569         *vnet_hdr = 1;
 570         vnet_hdr_required = 0;
 571     }
 572
 573     TFR(fd = tap_open(ifname, ifname_sz, vnet_hdr, vnet_hdr_required,
 574                       mq_required));
 575     if (fd < 0) {
 576         return -1;
 577     }
 578
 579     if (setup_script &&
 580         setup_script[0] != '\0' &&
 581         strcmp(setup_script, "no") != 0 &&
 582         launch_script(setup_script, ifname, fd)) {
 583         close(fd);
 584         return -1;
 585     }
 586
 587     return fd;
 588 }
 589
 590 #define MAX_TAP_QUEUES 1024
 591
 592 static int net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
 593                             const char *model, const char *name,
 594                             const char *ifname, const char *script,
 595                             const char *downscript, const char *vhostfdname,
 596                             int vnet_hdr, int fd)
 597 {
 598     TAPState *s;
 599
 600     s = net_tap_fd_init(peer, model, name, fd, vnet_hdr);
 601     if (!s) {
 602         close(fd);
 603         return -1;
 604     }
 605
 606     if (tap_set_sndbuf(s->fd, tap) < 0) {
 607         return -1;
 608     }
 609
 610     if (tap->has_fd || tap->has_fds) {
 611         snprintf(s->nc.info_str, sizeof(s->nc.info_str), "fd=%d", fd);
 612     } else if (tap->has_helper) {
 613         snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s",
 614                  tap->helper);
 615     } else {
 616         snprintf(s->nc.info_str, sizeof(s->nc.info_str),
 617                  "ifname=%s,script=%s,downscript=%s", ifname, script,
 618                  downscript);
 619
 620         if (strcmp(downscript, "no") != 0) {
 621             snprintf(s->down_script, sizeof(s->down_script), "%s", downscript);
 622             snprintf(s->down_script_arg, sizeof(s->down_script_arg),
 623                      "%s", ifname);
 624         }
 625     }
 626
 627     if (tap->has_vhost ? tap->vhost :
 628         vhostfdname || (tap->has_vhostforce && tap->vhostforce)) {
 629         int vhostfd;
 630
 631         if (tap->has_vhostfd) {
 632             vhostfd = monitor_handle_fd_param(cur_mon, vhostfdname);
 633             if (vhostfd == -1) {
 634                 return -1;
 635             }
 636         } else {
 637             vhostfd = -1;
 638         }
 639
 640         s->vhost_net = vhost_net_init(&s->nc, vhostfd,
 641                                       tap->has_vhostforce && tap->vhostforce);
 642         if (!s->vhost_net) {
 643             error_report("vhost-net requested but could not be initialized");
 644             return -1;
 645         }
 646     } else if (tap->has_vhostfd || tap->has_vhostfds) {
 647         error_report("vhostfd= is not valid without vhost");
 648         return -1;
 649     }
 650
 651     return 0;
 652 }
 653
 654 static int get_fds(char *str, char *fds[], int max)
 655 {
 656     char *ptr = str, *this;
 657     size_t len = strlen(str);
 658     int i = 0;
 659
 660     while (i < max && ptr < str + len) {
 661         this = strchr(ptr, ':');
 662
 663         if (this == NULL) {
 664             fds[i] = g_strdup(ptr);
 665         } else {
 666             fds[i] = g_strndup(ptr, this - ptr);
 667         }
 668
 669         i++;
 670         if (this == NULL) {
 671             break;
 672         } else {
 673             ptr = this + 1;
 674         }
 675     }
 676
 677     return i;
 678 }
 679
 680 int net_init_tap(const NetClientOptions *opts, const char *name,
 681                  NetClientState *peer)
 682 {
 683     const NetdevTapOptions *tap;
 684     int fd, vnet_hdr = 0, i = 0, queues;
 685     /* for the no-fd, no-helper case */
 686     const char *script = NULL; /* suppress wrong "uninit'd use" gcc warning */
 687     const char *downscript = NULL;
 688     const char *vhostfdname;
 689     char ifname[128];
 690
 691     assert(opts->kind == NET_CLIENT_OPTIONS_KIND_TAP);
 692     tap = opts->tap;
 693     queues = tap->has_queues ? tap->queues : 1;
 694     vhostfdname = tap->has_vhostfd ? tap->vhostfd : NULL;
 695
 696     if (tap->has_fd) {
 697         if (tap->has_ifname || tap->has_script || tap->has_downscript ||
 698             tap->has_vnet_hdr || tap->has_helper || tap->has_queues ||
 699             tap->has_fds) {
 700             error_report("ifname=, script=, downscript=, vnet_hdr=, "
 701                          "helper=, queues=, and fds= are invalid with fd=");
 702             return -1;
 703         }
 704
 705         fd = monitor_handle_fd_param(cur_mon, tap->fd);
 706         if (fd == -1) {
 707             return -1;
 708         }
 709
 710         fcntl(fd, F_SETFL, O_NONBLOCK);
 711
 712         vnet_hdr = tap_probe_vnet_hdr(fd);
 713
 714         if (net_init_tap_one(tap, peer, "tap", name, NULL,
 715                              script, downscript,
 716                              vhostfdname, vnet_hdr, fd)) {
 717             return -1;
 718         }
 719     } else if (tap->has_fds) {
 720         char *fds[MAX_TAP_QUEUES];
 721         char *vhost_fds[MAX_TAP_QUEUES];
 722         int nfds, nvhosts;
 723
 724         if (tap->has_ifname || tap->has_script || tap->has_downscript ||
 725             tap->has_vnet_hdr || tap->has_helper || tap->has_queues ||
 726             tap->has_fd) {
 727             error_report("ifname=, script=, downscript=, vnet_hdr=, "
 728                          "helper=, queues=, and fd= are invalid with fds=");
 729             return -1;
 730         }
 731
 732         nfds = get_fds(tap->fds, fds, MAX_TAP_QUEUES);
 733         if (tap->has_vhostfds) {
 734             nvhosts = get_fds(tap->vhostfds, vhost_fds, MAX_TAP_QUEUES);
 735             if (nfds != nvhosts) {
 736                 error_report("The number of fds passed does not match the "
 737                              "number of vhostfds passed");
 738                 return -1;
 739             }
 740         }
 741
 742         for (i = 0; i < nfds; i++) {
 743             fd = monitor_handle_fd_param(cur_mon, fds[i]);
 744             if (fd == -1) {
 745                 return -1;
 746             }
 747
 748             fcntl(fd, F_SETFL, O_NONBLOCK);
 749
 750             if (i == 0) {
 751                 vnet_hdr = tap_probe_vnet_hdr(fd);
 752             } else if (vnet_hdr != tap_probe_vnet_hdr(fd)) {
 753                 error_report("vnet_hdr not consistent across given tap fds");
 754                 return -1;
 755             }
 756
 757             if (net_init_tap_one(tap, peer, "tap", name, ifname,
 758                                  script, downscript,
 759                                  tap->has_vhostfds ? vhost_fds[i] : NULL,
 760                                  vnet_hdr, fd)) {
 761                 return -1;
 762             }
 763         }
 764     } else if (tap->has_helper) {
 765         if (tap->has_ifname || tap->has_script || tap->has_downscript ||
 766             tap->has_vnet_hdr || tap->has_queues || tap->has_fds) {
 767             error_report("ifname=, script=, downscript=, and vnet_hdr= "
 768                          "queues=, and fds= are invalid with helper=");
 769             return -1;
 770         }
 771
 772         fd = net_bridge_run_helper(tap->helper, DEFAULT_BRIDGE_INTERFACE);
 773         if (fd == -1) {
 774             return -1;
 775         }
 776
 777         fcntl(fd, F_SETFL, O_NONBLOCK);
 778         vnet_hdr = tap_probe_vnet_hdr(fd);
 779
 780         if (net_init_tap_one(tap, peer, "bridge", name, ifname,
 781                              script, downscript, vhostfdname,
 782                              vnet_hdr, fd)) {
 783             return -1;
 784         }
 785     } else {
 786         script = tap->has_script ? tap->script : DEFAULT_NETWORK_SCRIPT;
 787         downscript = tap->has_downscript ? tap->downscript :
 788             DEFAULT_NETWORK_DOWN_SCRIPT;
 789
 790         if (tap->has_ifname) {
 791             pstrcpy(ifname, sizeof ifname, tap->ifname);
 792         } else {
 793             ifname[0] = '\0';
 794         }
 795
 796         for (i = 0; i < queues; i++) {
 797             fd = net_tap_init(tap, &vnet_hdr, i >= 1 ? "no" : script,
 798                               ifname, sizeof ifname, queues > 1);
 799             if (fd == -1) {
 800                 return -1;
 801             }
 802
 803             if (queues > 1 && i == 0 && !tap->has_ifname) {
 804                 if (tap_fd_get_ifname(fd, ifname)) {
 805                     error_report("Fail to get ifname");
 806                     return -1;
 807                 }
 808             }
 809
 810             if (net_init_tap_one(tap, peer, "tap", name, ifname,
 811                                  i >= 1 ? "no" : script,
 812                                  i >= 1 ? "no" : downscript,
 813                                  vhostfdname, vnet_hdr, fd)) {
 814                 return -1;
 815             }
 816         }
 817     }
 818
 819     return 0;
 820 }
 821
 822 VHostNetState *tap_get_vhost_net(NetClientState *nc)
 823 {
 824     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 825     assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
 826     return s->vhost_net;
 827 }
 828
 829 int tap_enable(NetClientState *nc)
 830 {
 831     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 832     int ret;
 833
 834     if (s->enabled) {
 835         return 0;
 836     } else {
 837         ret = tap_fd_enable(s->fd);
 838         if (ret == 0) {
 839             s->enabled = true;
 840             tap_update_fd_handler(s);
 841         }
 842         return ret;
 843     }
 844 }
 845
 846 int tap_disable(NetClientState *nc)
 847 {
 848     TAPState *s = DO_UPCAST(TAPState, nc, nc);
 849     int ret;
 850
 851     if (s->enabled == 0) {
 852         return 0;
 853     } else {
 854         ret = tap_fd_disable(s->fd);
 855         if (ret == 0) {
 856             qemu_purge_queued_packets(nc);
 857             s->enabled = false;
 858             tap_update_fd_handler(s);
 859         }
 860         return ret;
 861     }
 862 }