hw/virtio-net.c

   1 /*
   2  * Virtio Network Device
   3  *
   4  * Copyright IBM, Corp. 2007
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #include "virtio.h"
  15 #include "net.h"
  16 #include "qemu-timer.h"
  17 #include "virtio-net.h"
  18
  19 #define VIRTIO_NET_VM_VERSION    6
  20
  21 #define MAC_TABLE_ENTRIES    32
  22 #define MAX_VLAN    (1 << 12)   /* Per 802.1Q definition */
  23
  24 typedef struct VirtIONet
  25 {
  26     VirtIODevice vdev;
  27     uint8_t mac[ETH_ALEN];
  28     uint16_t status;
  29     VirtQueue *rx_vq;
  30     VirtQueue *tx_vq;
  31     VirtQueue *ctrl_vq;
  32     VLANClientState *vc;
  33     QEMUTimer *tx_timer;
  34     int tx_timer_active;
  35     int mergeable_rx_bufs;
  36     int promisc;
  37     int allmulti;
  38     struct {
  39         int in_use;
  40         uint8_t *macs;
  41     } mac_table;
  42     uint32_t *vlans;
  43 } VirtIONet;
  44
  45 /* TODO
  46  * - we could suppress RX interrupt if we were so inclined.
  47  */
  48
  49 static VirtIONet *to_virtio_net(VirtIODevice *vdev)
  50 {
  51     return (VirtIONet *)vdev;
  52 }
  53
  54 static void virtio_net_get_config(VirtIODevice *vdev, uint8_t *config)
  55 {
  56     VirtIONet *n = to_virtio_net(vdev);
  57     struct virtio_net_config netcfg;
  58
  59     netcfg.status = n->status;
  60     memcpy(netcfg.mac, n->mac, ETH_ALEN);
  61     memcpy(config, &netcfg, sizeof(netcfg));
  62 }
  63
  64 static void virtio_net_set_config(VirtIODevice *vdev, const uint8_t *config)
  65 {
  66     VirtIONet *n = to_virtio_net(vdev);
  67     struct virtio_net_config netcfg;
  68
  69     memcpy(&netcfg, config, sizeof(netcfg));
  70
  71     if (memcmp(netcfg.mac, n->mac, ETH_ALEN)) {
  72         memcpy(n->mac, netcfg.mac, ETH_ALEN);
  73         qemu_format_nic_info_str(n->vc, n->mac);
  74     }
  75 }
  76
  77 static void virtio_net_set_link_status(VLANClientState *vc)
  78 {
  79     VirtIONet *n = vc->opaque;
  80     uint16_t old_status = n->status;
  81
  82     if (vc->link_down)
  83         n->status &= ~VIRTIO_NET_S_LINK_UP;
  84     else
  85         n->status |= VIRTIO_NET_S_LINK_UP;
  86
  87     if (n->status != old_status)
  88         virtio_notify_config(&n->vdev);
  89 }
  90
  91 static void virtio_net_reset(VirtIODevice *vdev)
  92 {
  93     VirtIONet *n = to_virtio_net(vdev);
  94
  95     /* Reset back to compatibility mode */
  96     n->promisc = 1;
  97     n->allmulti = 0;
  98
  99     /* Flush any MAC and VLAN filter table state */
 100     n->mac_table.in_use = 0;
 101     memset(n->mac_table.macs, 0, MAC_TABLE_ENTRIES * ETH_ALEN);
 102     memset(n->vlans, 0, MAX_VLAN >> 3);
 103 }
 104
 105 static uint32_t virtio_net_get_features(VirtIODevice *vdev)
 106 {
 107     uint32_t features = (1 << VIRTIO_NET_F_MAC) |
 108                         (1 << VIRTIO_NET_F_STATUS) |
 109                         (1 << VIRTIO_NET_F_CTRL_VQ) |
 110                         (1 << VIRTIO_NET_F_CTRL_RX) |
 111                         (1 << VIRTIO_NET_F_CTRL_VLAN);
 112
 113     return features;
 114 }
 115
 116 static uint32_t virtio_net_bad_features(VirtIODevice *vdev)
 117 {
 118     uint32_t features = 0;
 119
 120     /* Linux kernel 2.6.25.  It understood MAC (as everyone must),
 121      * but also these: */
 122     features |= (1 << VIRTIO_NET_F_MAC);
 123     features |= (1 << VIRTIO_NET_F_GUEST_CSUM);
 124     features |= (1 << VIRTIO_NET_F_GUEST_TSO4);
 125     features |= (1 << VIRTIO_NET_F_GUEST_TSO6);
 126     features |= (1 << VIRTIO_NET_F_GUEST_ECN);
 127
 128     return features & virtio_net_get_features(vdev);
 129 }
 130
 131 static void virtio_net_set_features(VirtIODevice *vdev, uint32_t features)
 132 {
 133     VirtIONet *n = to_virtio_net(vdev);
 134
 135     n->mergeable_rx_bufs = !!(features & (1 << VIRTIO_NET_F_MRG_RXBUF));
 136 }
 137
 138 static int virtio_net_handle_rx_mode(VirtIONet *n, uint8_t cmd,
 139                                      VirtQueueElement *elem)
 140 {
 141     uint8_t on;
 142
 143     if (elem->out_num != 2 || elem->out_sg[1].iov_len != sizeof(on)) {
 144         fprintf(stderr, "virtio-net ctrl invalid rx mode command\n");
 145         exit(1);
 146     }
 147
 148     on = ldub_p(elem->out_sg[1].iov_base);
 149
 150     if (cmd == VIRTIO_NET_CTRL_RX_MODE_PROMISC)
 151         n->promisc = on;
 152     else if (cmd == VIRTIO_NET_CTRL_RX_MODE_ALLMULTI)
 153         n->allmulti = on;
 154     else
 155         return VIRTIO_NET_ERR;
 156
 157     return VIRTIO_NET_OK;
 158 }
 159
 160 static int virtio_net_handle_mac(VirtIONet *n, uint8_t cmd,
 161                                  VirtQueueElement *elem)
 162 {
 163     struct virtio_net_ctrl_mac mac_data;
 164
 165     if (cmd != VIRTIO_NET_CTRL_MAC_TABLE_SET || elem->out_num != 3 ||
 166         elem->out_sg[1].iov_len < sizeof(mac_data) ||
 167         elem->out_sg[2].iov_len < sizeof(mac_data))
 168         return VIRTIO_NET_ERR;
 169
 170     n->mac_table.in_use = 0;
 171     memset(n->mac_table.macs, 0, MAC_TABLE_ENTRIES * ETH_ALEN);
 172
 173     mac_data.entries = ldl_le_p(elem->out_sg[1].iov_base);
 174
 175     if (sizeof(mac_data.entries) +
 176         (mac_data.entries * ETH_ALEN) > elem->out_sg[1].iov_len)
 177         return VIRTIO_NET_ERR;
 178
 179     if (mac_data.entries <= MAC_TABLE_ENTRIES) {
 180         memcpy(n->mac_table.macs, elem->out_sg[1].iov_base + sizeof(mac_data),
 181                mac_data.entries * ETH_ALEN);
 182         n->mac_table.in_use += mac_data.entries;
 183     } else {
 184         n->promisc = 1;
 185         return VIRTIO_NET_OK;
 186     }
 187
 188     mac_data.entries = ldl_le_p(elem->out_sg[2].iov_base);
 189
 190     if (sizeof(mac_data.entries) +
 191         (mac_data.entries * ETH_ALEN) > elem->out_sg[2].iov_len)
 192         return VIRTIO_NET_ERR;
 193
 194     if (mac_data.entries) {
 195         if (n->mac_table.in_use + mac_data.entries <= MAC_TABLE_ENTRIES) {
 196             memcpy(n->mac_table.macs + (n->mac_table.in_use * ETH_ALEN),
 197                    elem->out_sg[2].iov_base + sizeof(mac_data),
 198                    mac_data.entries * ETH_ALEN);
 199             n->mac_table.in_use += mac_data.entries;
 200         } else
 201             n->allmulti = 1;
 202     }
 203
 204     return VIRTIO_NET_OK;
 205 }
 206
 207 static int virtio_net_handle_vlan_table(VirtIONet *n, uint8_t cmd,
 208                                         VirtQueueElement *elem)
 209 {
 210     uint16_t vid;
 211
 212     if (elem->out_num != 2 || elem->out_sg[1].iov_len != sizeof(vid)) {
 213         fprintf(stderr, "virtio-net ctrl invalid vlan command\n");
 214         return VIRTIO_NET_ERR;
 215     }
 216
 217     vid = lduw_le_p(elem->out_sg[1].iov_base);
 218
 219     if (vid >= MAX_VLAN)
 220         return VIRTIO_NET_ERR;
 221
 222     if (cmd == VIRTIO_NET_CTRL_VLAN_ADD)
 223         n->vlans[vid >> 5] |= (1U << (vid & 0x1f));
 224     else if (cmd == VIRTIO_NET_CTRL_VLAN_DEL)
 225         n->vlans[vid >> 5] &= ~(1U << (vid & 0x1f));
 226     else
 227         return VIRTIO_NET_ERR;
 228
 229     return VIRTIO_NET_OK;
 230 }
 231
 232 static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
 233 {
 234     VirtIONet *n = to_virtio_net(vdev);
 235     struct virtio_net_ctrl_hdr ctrl;
 236     virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
 237     VirtQueueElement elem;
 238
 239     while (virtqueue_pop(vq, &elem)) {
 240         if ((elem.in_num < 1) || (elem.out_num < 1)) {
 241             fprintf(stderr, "virtio-net ctrl missing headers\n");
 242             exit(1);
 243         }
 244
 245         if (elem.out_sg[0].iov_len < sizeof(ctrl) ||
 246             elem.in_sg[elem.in_num - 1].iov_len < sizeof(status)) {
 247             fprintf(stderr, "virtio-net ctrl header not in correct element\n");
 248             exit(1);
 249         }
 250
 251         ctrl.class = ldub_p(elem.out_sg[0].iov_base);
 252         ctrl.cmd = ldub_p(elem.out_sg[0].iov_base + sizeof(ctrl.class));
 253
 254         if (ctrl.class == VIRTIO_NET_CTRL_RX_MODE)
 255             status = virtio_net_handle_rx_mode(n, ctrl.cmd, &elem);
 256         else if (ctrl.class == VIRTIO_NET_CTRL_MAC)
 257             status = virtio_net_handle_mac(n, ctrl.cmd, &elem);
 258         else if (ctrl.class == VIRTIO_NET_CTRL_VLAN)
 259             status = virtio_net_handle_vlan_table(n, ctrl.cmd, &elem);
 260
 261         stb_p(elem.in_sg[elem.in_num - 1].iov_base, status);
 262
 263         virtqueue_push(vq, &elem, sizeof(status));
 264         virtio_notify(vdev, vq);
 265     }
 266 }
 267
 268 /* RX */
 269
 270 static void virtio_net_handle_rx(VirtIODevice *vdev, VirtQueue *vq)
 271 {
 272 }
 273
 274 static int do_virtio_net_can_receive(VirtIONet *n, int bufsize)
 275 {
 276     if (!virtio_queue_ready(n->rx_vq) ||
 277         !(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK))
 278         return 0;
 279
 280     if (virtio_queue_empty(n->rx_vq) ||
 281         (n->mergeable_rx_bufs &&
 282          !virtqueue_avail_bytes(n->rx_vq, bufsize, 0))) {
 283         virtio_queue_set_notification(n->rx_vq, 1);
 284         return 0;
 285     }
 286
 287     virtio_queue_set_notification(n->rx_vq, 0);
 288     return 1;
 289 }
 290
 291 static int virtio_net_can_receive(void *opaque)
 292 {
 293     VirtIONet *n = opaque;
 294
 295     return do_virtio_net_can_receive(n, VIRTIO_NET_MAX_BUFSIZE);
 296 }
 297
 298 static int iov_fill(struct iovec *iov, int iovcnt, const void *buf, int count)
 299 {
 300     int offset, i;
 301
 302     offset = i = 0;
 303     while (offset < count && i < iovcnt) {
 304         int len = MIN(iov[i].iov_len, count - offset);
 305         memcpy(iov[i].iov_base, buf + offset, len);
 306         offset += len;
 307         i++;
 308     }
 309
 310     return offset;
 311 }
 312
 313 static int receive_header(VirtIONet *n, struct iovec *iov, int iovcnt,
 314                           const void *buf, size_t size, size_t hdr_len)
 315 {
 316     struct virtio_net_hdr *hdr = (struct virtio_net_hdr *)iov[0].iov_base;
 317     int offset = 0;
 318
 319     hdr->flags = 0;
 320     hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
 321
 322     /* We only ever receive a struct virtio_net_hdr from the tapfd,
 323      * but we may be passing along a larger header to the guest.
 324      */
 325     iov[0].iov_base += hdr_len;
 326     iov[0].iov_len  -= hdr_len;
 327
 328     return offset;
 329 }
 330
 331 static int receive_filter(VirtIONet *n, const uint8_t *buf, int size)
 332 {
 333     static const uint8_t bcast[] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
 334     static const uint8_t vlan[] = {0x81, 0x00};
 335     uint8_t *ptr = (uint8_t *)buf;
 336     int i;
 337
 338     if (n->promisc)
 339         return 1;
 340
 341     if (!memcmp(&ptr[12], vlan, sizeof(vlan))) {
 342         int vid = be16_to_cpup((uint16_t *)(ptr + 14)) & 0xfff;
 343         if (!(n->vlans[vid >> 5] & (1U << (vid & 0x1f))))
 344             return 0;
 345     }
 346
 347     if ((ptr[0] & 1) && n->allmulti)
 348         return 1;
 349
 350     if (!memcmp(ptr, bcast, sizeof(bcast)))
 351         return 1;
 352
 353     if (!memcmp(ptr, n->mac, ETH_ALEN))
 354         return 1;
 355
 356     for (i = 0; i < n->mac_table.in_use; i++) {
 357         if (!memcmp(ptr, &n->mac_table.macs[i * ETH_ALEN], ETH_ALEN))
 358             return 1;
 359     }
 360
 361     return 0;
 362 }
 363
 364 static void virtio_net_receive(void *opaque, const uint8_t *buf, int size)
 365 {
 366     VirtIONet *n = opaque;
 367     struct virtio_net_hdr_mrg_rxbuf *mhdr = NULL;
 368     size_t hdr_len, offset, i;
 369
 370     if (!do_virtio_net_can_receive(n, size))
 371         return;
 372
 373     if (!receive_filter(n, buf, size))
 374         return;
 375
 376     /* hdr_len refers to the header we supply to the guest */
 377     hdr_len = n->mergeable_rx_bufs ?
 378         sizeof(struct virtio_net_hdr_mrg_rxbuf) : sizeof(struct virtio_net_hdr);
 379
 380     offset = i = 0;
 381
 382     while (offset < size) {
 383         VirtQueueElement elem;
 384         int len, total;
 385         struct iovec sg[VIRTQUEUE_MAX_SIZE];
 386
 387         len = total = 0;
 388
 389         if ((i != 0 && !n->mergeable_rx_bufs) ||
 390             virtqueue_pop(n->rx_vq, &elem) == 0) {
 391             if (i == 0)
 392                 return;
 393             fprintf(stderr, "virtio-net truncating packet\n");
 394             exit(1);
 395         }
 396
 397         if (elem.in_num < 1) {
 398             fprintf(stderr, "virtio-net receive queue contains no in buffers\n");
 399             exit(1);
 400         }
 401
 402         if (!n->mergeable_rx_bufs && elem.in_sg[0].iov_len != hdr_len) {
 403             fprintf(stderr, "virtio-net header not in first element\n");
 404             exit(1);
 405         }
 406
 407         memcpy(&sg, &elem.in_sg[0], sizeof(sg[0]) * elem.in_num);
 408
 409         if (i == 0) {
 410             if (n->mergeable_rx_bufs)
 411                 mhdr = (struct virtio_net_hdr_mrg_rxbuf *)sg[0].iov_base;
 412
 413             offset += receive_header(n, sg, elem.in_num,
 414                                      buf + offset, size - offset, hdr_len);
 415             total += hdr_len;
 416         }
 417
 418         /* copy in packet.  ugh */
 419         len = iov_fill(sg, elem.in_num,
 420                        buf + offset, size - offset);
 421         total += len;
 422
 423         /* signal other side */
 424         virtqueue_fill(n->rx_vq, &elem, total, i++);
 425
 426         offset += len;
 427     }
 428
 429     if (mhdr)
 430         mhdr->num_buffers = i;
 431
 432     virtqueue_flush(n->rx_vq, i);
 433     virtio_notify(&n->vdev, n->rx_vq);
 434 }
 435
 436 /* TX */
 437 static void virtio_net_flush_tx(VirtIONet *n, VirtQueue *vq)
 438 {
 439     VirtQueueElement elem;
 440     int has_vnet_hdr = 0;
 441
 442     if (!(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK))
 443         return;
 444
 445     while (virtqueue_pop(vq, &elem)) {
 446         ssize_t len = 0;
 447         unsigned int out_num = elem.out_num;
 448         struct iovec *out_sg = &elem.out_sg[0];
 449         unsigned hdr_len;
 450
 451         /* hdr_len refers to the header received from the guest */
 452         hdr_len = n->mergeable_rx_bufs ?
 453             sizeof(struct virtio_net_hdr_mrg_rxbuf) :
 454             sizeof(struct virtio_net_hdr);
 455
 456         if (out_num < 1 || out_sg->iov_len != hdr_len) {
 457             fprintf(stderr, "virtio-net header not in first element\n");
 458             exit(1);
 459         }
 460
 461         /* ignore the header if GSO is not supported */
 462         if (!has_vnet_hdr) {
 463             out_num--;
 464             out_sg++;
 465             len += hdr_len;
 466         } else if (n->mergeable_rx_bufs) {
 467             /* tapfd expects a struct virtio_net_hdr */
 468             hdr_len -= sizeof(struct virtio_net_hdr);
 469             out_sg->iov_len -= hdr_len;
 470             len += hdr_len;
 471         }
 472
 473         len += qemu_sendv_packet(n->vc, out_sg, out_num);
 474
 475         virtqueue_push(vq, &elem, len);
 476         virtio_notify(&n->vdev, vq);
 477     }
 478 }
 479
 480 static void virtio_net_handle_tx(VirtIODevice *vdev, VirtQueue *vq)
 481 {
 482     VirtIONet *n = to_virtio_net(vdev);
 483
 484     if (n->tx_timer_active) {
 485         virtio_queue_set_notification(vq, 1);
 486         qemu_del_timer(n->tx_timer);
 487         n->tx_timer_active = 0;
 488         virtio_net_flush_tx(n, vq);
 489     } else {
 490         qemu_mod_timer(n->tx_timer,
 491                        qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL);
 492         n->tx_timer_active = 1;
 493         virtio_queue_set_notification(vq, 0);
 494     }
 495 }
 496
 497 static void virtio_net_tx_timer(void *opaque)
 498 {
 499     VirtIONet *n = opaque;
 500
 501     n->tx_timer_active = 0;
 502
 503     /* Just in case the driver is not ready on more */
 504     if (!(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK))
 505         return;
 506
 507     virtio_queue_set_notification(n->tx_vq, 1);
 508     virtio_net_flush_tx(n, n->tx_vq);
 509 }
 510
 511 static void virtio_net_save(QEMUFile *f, void *opaque)
 512 {
 513     VirtIONet *n = opaque;
 514
 515     virtio_save(&n->vdev, f);
 516
 517     qemu_put_buffer(f, n->mac, ETH_ALEN);
 518     qemu_put_be32(f, n->tx_timer_active);
 519     qemu_put_be32(f, n->mergeable_rx_bufs);
 520     qemu_put_be16(f, n->status);
 521     qemu_put_be32(f, n->promisc);
 522     qemu_put_be32(f, n->allmulti);
 523     qemu_put_be32(f, n->mac_table.in_use);
 524     qemu_put_buffer(f, n->mac_table.macs, n->mac_table.in_use * ETH_ALEN);
 525     qemu_put_buffer(f, (uint8_t *)n->vlans, MAX_VLAN >> 3);
 526 }
 527
 528 static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
 529 {
 530     VirtIONet *n = opaque;
 531
 532     if (version_id < 2 || version_id > VIRTIO_NET_VM_VERSION)
 533         return -EINVAL;
 534
 535     virtio_load(&n->vdev, f);
 536
 537     qemu_get_buffer(f, n->mac, ETH_ALEN);
 538     n->tx_timer_active = qemu_get_be32(f);
 539     n->mergeable_rx_bufs = qemu_get_be32(f);
 540
 541     if (version_id >= 3)
 542         n->status = qemu_get_be16(f);
 543
 544     if (version_id >= 4) {
 545         n->promisc = qemu_get_be32(f);
 546         n->allmulti = qemu_get_be32(f);
 547     }
 548
 549     if (version_id >= 5) {
 550         n->mac_table.in_use = qemu_get_be32(f);
 551         /* MAC_TABLE_ENTRIES may be different from the saved image */
 552         if (n->mac_table.in_use <= MAC_TABLE_ENTRIES) {
 553             qemu_get_buffer(f, n->mac_table.macs,
 554                             n->mac_table.in_use * ETH_ALEN);
 555         } else if (n->mac_table.in_use) {
 556             qemu_fseek(f, n->mac_table.in_use * ETH_ALEN, SEEK_CUR);
 557             n->promisc = 1;
 558             n->mac_table.in_use = 0;
 559         }
 560     }
 561
 562     if (version_id >= 6)
 563         qemu_get_buffer(f, (uint8_t *)n->vlans, MAX_VLAN >> 3);
 564
 565     if (n->tx_timer_active) {
 566         qemu_mod_timer(n->tx_timer,
 567                        qemu_get_clock(vm_clock) + TX_TIMER_INTERVAL);
 568     }
 569
 570     return 0;
 571 }
 572
 573 static void virtio_net_cleanup(VLANClientState *vc)
 574 {
 575     VirtIONet *n = vc->opaque;
 576
 577     unregister_savevm("virtio-net", n);
 578
 579     qemu_free(n->mac_table.macs);
 580     qemu_free(n->vlans);
 581
 582     qemu_del_timer(n->tx_timer);
 583     qemu_free_timer(n->tx_timer);
 584
 585     virtio_cleanup(&n->vdev);
 586 }
 587
 588 VirtIODevice *virtio_net_init(DeviceState *dev)
 589 {
 590     VirtIONet *n;
 591     static int virtio_net_id;
 592
 593     n = (VirtIONet *)virtio_common_init("virtio-net", VIRTIO_ID_NET,
 594                                         sizeof(struct virtio_net_config),
 595                                         sizeof(VirtIONet));
 596
 597     n->vdev.get_config = virtio_net_get_config;
 598     n->vdev.set_config = virtio_net_set_config;
 599     n->vdev.get_features = virtio_net_get_features;
 600     n->vdev.set_features = virtio_net_set_features;
 601     n->vdev.bad_features = virtio_net_bad_features;
 602     n->vdev.reset = virtio_net_reset;
 603     n->rx_vq = virtio_add_queue(&n->vdev, 256, virtio_net_handle_rx);
 604     n->tx_vq = virtio_add_queue(&n->vdev, 256, virtio_net_handle_tx);
 605     n->ctrl_vq = virtio_add_queue(&n->vdev, 16, virtio_net_handle_ctrl);
 606     qdev_get_macaddr(dev, n->mac);
 607     n->status = VIRTIO_NET_S_LINK_UP;
 608     n->vc = qdev_get_vlan_client(dev,
 609                                  virtio_net_receive,
 610                                  virtio_net_can_receive,
 611                                  virtio_net_cleanup, n);
 612     n->vc->link_status_changed = virtio_net_set_link_status;
 613
 614     qemu_format_nic_info_str(n->vc, n->mac);
 615
 616     n->tx_timer = qemu_new_timer(vm_clock, virtio_net_tx_timer, n);
 617     n->tx_timer_active = 0;
 618     n->mergeable_rx_bufs = 0;
 619     n->promisc = 1; /* for compatibility */
 620
 621     n->mac_table.macs = qemu_mallocz(MAC_TABLE_ENTRIES * ETH_ALEN);
 622
 623     n->vlans = qemu_mallocz(MAX_VLAN >> 3);
 624
 625     register_savevm("virtio-net", virtio_net_id++, VIRTIO_NET_VM_VERSION,
 626                     virtio_net_save, virtio_net_load, n);
 627
 628     return &n->vdev;
 629 }