text: /*
   * QEMU System Emulator
   *
   * Copyright (c) 2003-2008 Fabrice Bellard
   * Copyright (c) 2009 Red Hat, Inc.
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to deal
   * in the Software without restriction, including without limitation the rights
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   * copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
   * THE SOFTWARE.
   */
  
  #include "qemu/osdep.h"
  #include "tap_int.h"
  
  
  #include <sys/ioctl.h>
  #include <sys/wait.h>
  #include <sys/socket.h>
  #include <net/if.h>
  
  #include "net/net.h"
  #include "clients.h"
  #include "monitor/monitor.h"
  #include "sysemu/sysemu.h"
  #include "qemu-common.h"
  #include "qemu/error-report.h"
  
  #include "net/tap.h"
  
  #include "net/vhost_net.h"
  
  typedef struct TAPState {
      NetClientState nc;
      int fd;
      char down_script[1024];
      char down_script_arg[128];
      uint8_t buf[NET_BUFSIZE];
      bool read_poll;
      bool write_poll;
      bool using_vnet_hdr;
      bool has_ufo;
      bool enabled;
      VHostNetState *vhost_net;
      unsigned host_vnet_hdr_len;
  } TAPState;
  
  static void launch_script(const char *setup_script, const char *ifname,
                            int fd, Error **errp);
  
  static void tap_send(void *opaque);
  static void tap_writable(void *opaque);
  
  static void tap_update_fd_handler(TAPState *s)
  {
      qemu_set_fd_handler(s->fd,
                          s->read_poll && s->enabled ? tap_send : NULL,
                          s->write_poll && s->enabled ? tap_writable : NULL,
                          s);
  }
  
  static void tap_read_poll(TAPState *s, bool enable)
  {
      s->read_poll = enable;
      tap_update_fd_handler(s);
  }
  
  static void tap_write_poll(TAPState *s, bool enable)
  {
      s->write_poll = enable;
      tap_update_fd_handler(s);
  }
  
  static void tap_writable(void *opaque)
  {
      TAPState *s = opaque;
  
      tap_write_poll(s, false);
  
      qemu_flush_queued_packets(&s->nc);
  }
  
  static ssize_t tap_write_packet(TAPState *s, const struct iovec *iov, int iovcnt)
  {
      ssize_t len;
  
      do {
          len = writev(s->fd, iov, iovcnt);
      } while (len == -1 && errno == EINTR);
  
      if (len == -1 && errno == EAGAIN) {
          tap_write_poll(s, true);
          return 0;
      }
  
      return len;
  }
  
  static ssize_t tap_receive_iov(NetClientState *nc, const struct iovec *iov,
                                 int iovcnt)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      const struct iovec *iovp = iov;
      struct iovec iov_copy[iovcnt + 1];
      struct virtio_net_hdr_mrg_rxbuf hdr = { };
  
      if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
          iov_copy[0].iov_base = &hdr;
          iov_copy[0].iov_len =  s->host_vnet_hdr_len;
          memcpy(&iov_copy[1], iov, iovcnt * sizeof(*iov));
          iovp = iov_copy;
          iovcnt++;
      }
  
      return tap_write_packet(s, iovp, iovcnt);
  }
  
  static ssize_t tap_receive_raw(NetClientState *nc, const uint8_t *buf, size_t size)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      struct iovec iov[2];
      int iovcnt = 0;
      struct virtio_net_hdr_mrg_rxbuf hdr = { };
  
      if (s->host_vnet_hdr_len) {
          iov[iovcnt].iov_base = &hdr;
          iov[iovcnt].iov_len  = s->host_vnet_hdr_len;
          iovcnt++;
      }
  
      iov[iovcnt].iov_base = (char *)buf;
      iov[iovcnt].iov_len  = size;
      iovcnt++;
  
      return tap_write_packet(s, iov, iovcnt);
  }
  
  static ssize_t tap_receive(NetClientState *nc, const uint8_t *buf, size_t size)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      struct iovec iov[1];
  
      if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
          return tap_receive_raw(nc, buf, size);
      }
  
      iov[0].iov_base = (char *)buf;
      iov[0].iov_len  = size;
  
      return tap_write_packet(s, iov, 1);
  }
  
  #ifndef __sun__
  ssize_t tap_read_packet(int tapfd, uint8_t *buf, int maxlen)
  {
      return read(tapfd, buf, maxlen);
  }
  #endif
  
  static void tap_send_completed(NetClientState *nc, ssize_t len)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      tap_read_poll(s, true);
  }
  
  static void tap_send(void *opaque)
  {
      TAPState *s = opaque;
      int size;
      int packets = 0;
  
      while (true) {
          uint8_t *buf = s->buf;
  
          size = tap_read_packet(s->fd, s->buf, sizeof(s->buf));
          if (size <= 0) {
              break;
          }
  
          if (s->host_vnet_hdr_len && !s->using_vnet_hdr) {
              buf  += s->host_vnet_hdr_len;
              size -= s->host_vnet_hdr_len;
          }
  
          size = qemu_send_packet_async(&s->nc, buf, size, tap_send_completed);
          if (size == 0) {
              tap_read_poll(s, false);
              break;
          } else if (size < 0) {
              break;
          }
  
          /*
           * When the host keeps receiving more packets while tap_send() is
           * running we can hog the QEMU global mutex.  Limit the number of
           * packets that are processed per tap_send() callback to prevent
           * stalling the guest.
           */
          packets++;
          if (packets >= 50) {
              break;
          }
      }
  }
  
  static bool tap_has_ufo(NetClientState *nc)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
  
      assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
  
      return s->has_ufo;
  }
  
  static bool tap_has_vnet_hdr(NetClientState *nc)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
  
      assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
  
      return !!s->host_vnet_hdr_len;
  }
  
  static bool tap_has_vnet_hdr_len(NetClientState *nc, int len)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
  
      assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
  
      return !!tap_probe_vnet_hdr_len(s->fd, len);
  }
  
  static void tap_set_vnet_hdr_len(NetClientState *nc, int len)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
  
      assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
      assert(len == sizeof(struct virtio_net_hdr_mrg_rxbuf) ||
             len == sizeof(struct virtio_net_hdr));
  
      tap_fd_set_vnet_hdr_len(s->fd, len);
      s->host_vnet_hdr_len = len;
  }
  
  static void tap_using_vnet_hdr(NetClientState *nc, bool using_vnet_hdr)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
  
      assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
      assert(!!s->host_vnet_hdr_len == using_vnet_hdr);
  
      s->using_vnet_hdr = using_vnet_hdr;
  }
  
  static int tap_set_vnet_le(NetClientState *nc, bool is_le)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
  
      return tap_fd_set_vnet_le(s->fd, is_le);
  }
  
  static int tap_set_vnet_be(NetClientState *nc, bool is_be)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
  
      return tap_fd_set_vnet_be(s->fd, is_be);
  }
  
  static void tap_set_offload(NetClientState *nc, int csum, int tso4,
                       int tso6, int ecn, int ufo)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      if (s->fd < 0) {
          return;
      }
  
      tap_fd_set_offload(s->fd, csum, tso4, tso6, ecn, ufo);
  }
  
  static void tap_cleanup(NetClientState *nc)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      Error *err = NULL;
  
      if (s->vhost_net) {
          vhost_net_cleanup(s->vhost_net);
          s->vhost_net = NULL;
      }
  
      qemu_purge_queued_packets(nc);
  
      if (s->down_script[0]) {
          launch_script(s->down_script, s->down_script_arg, s->fd, &err);
          if (err) {
              error_report_err(err);
          }
      }
  
      tap_read_poll(s, false);
      tap_write_poll(s, false);
      close(s->fd);
      s->fd = -1;
  }
  
  static void tap_poll(NetClientState *nc, bool enable)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      tap_read_poll(s, enable);
      tap_write_poll(s, enable);
  }
  
  int tap_get_fd(NetClientState *nc)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
      return s->fd;
  }
  
  /* fd support */
  
  static NetClientInfo net_tap_info = {
      .type = NET_CLIENT_OPTIONS_KIND_TAP,
      .size = sizeof(TAPState),
      .receive = tap_receive,
      .receive_raw = tap_receive_raw,
      .receive_iov = tap_receive_iov,
      .poll = tap_poll,
      .cleanup = tap_cleanup,
      .has_ufo = tap_has_ufo,
      .has_vnet_hdr = tap_has_vnet_hdr,
      .has_vnet_hdr_len = tap_has_vnet_hdr_len,
      .using_vnet_hdr = tap_using_vnet_hdr,
      .set_offload = tap_set_offload,
      .set_vnet_hdr_len = tap_set_vnet_hdr_len,
      .set_vnet_le = tap_set_vnet_le,
      .set_vnet_be = tap_set_vnet_be,
  };
  
  static TAPState *net_tap_fd_init(NetClientState *peer,
                                   const char *model,
                                   const char *name,
                                   int fd,
                                   int vnet_hdr)
  {
      NetClientState *nc;
      TAPState *s;
  
      nc = qemu_new_net_client(&net_tap_info, peer, model, name);
  
      s = DO_UPCAST(TAPState, nc, nc);
  
      s->fd = fd;
      s->host_vnet_hdr_len = vnet_hdr ? sizeof(struct virtio_net_hdr) : 0;
      s->using_vnet_hdr = false;
      s->has_ufo = tap_probe_has_ufo(s->fd);
      s->enabled = true;
      tap_set_offload(&s->nc, 0, 0, 0, 0, 0);
      /*
       * Make sure host header length is set correctly in tap:
       * it might have been modified by another instance of qemu.
       */
      if (tap_probe_vnet_hdr_len(s->fd, s->host_vnet_hdr_len)) {
          tap_fd_set_vnet_hdr_len(s->fd, s->host_vnet_hdr_len);
      }
      tap_read_poll(s, true);
      s->vhost_net = NULL;
      return s;
  }
  
  static void launch_script(const char *setup_script, const char *ifname,
                            int fd, Error **errp)
  {
      int pid, status;
      char *args[3];
      char **parg;
  
      /* try to launch network script */
      pid = fork();
      if (pid < 0) {
          error_setg_errno(errp, errno, "could not launch network script %s",
                           setup_script);
          return;
      }
      if (pid == 0) {
          int open_max = sysconf(_SC_OPEN_MAX), i;
  
          for (i = 3; i < open_max; i++) {
              if (i != fd) {
                  close(i);
              }
          }
          parg = args;
          *parg++ = (char *)setup_script;
          *parg++ = (char *)ifname;
          *parg = NULL;
          execv(setup_script, args);
          _exit(1);
      } else {
          while (waitpid(pid, &status, 0) != pid) {
              /* loop */
          }
  
          if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
              return;
          }
          error_setg(errp, "network script %s failed with status %d",
                     setup_script, status);
      }
  }
  
  static int recv_fd(int c)
  {
      int fd;
      uint8_t msgbuf[CMSG_SPACE(sizeof(fd))];
      struct msghdr msg = {
          .msg_control = msgbuf,
          .msg_controllen = sizeof(msgbuf),
      };
      struct cmsghdr *cmsg;
      struct iovec iov;
      uint8_t req[1];
      ssize_t len;
  
      cmsg = CMSG_FIRSTHDR(&msg);
      cmsg->cmsg_level = SOL_SOCKET;
      cmsg->cmsg_type = SCM_RIGHTS;
      cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
      msg.msg_controllen = cmsg->cmsg_len;
  
      iov.iov_base = req;
      iov.iov_len = sizeof(req);
  
      msg.msg_iov = &iov;
      msg.msg_iovlen = 1;
  
      len = recvmsg(c, &msg, 0);
      if (len > 0) {
          memcpy(&fd, CMSG_DATA(cmsg), sizeof(fd));
          return fd;
      }
  
      return len;
  }
  
  static int net_bridge_run_helper(const char *helper, const char *bridge,
                                   Error **errp)
  {
      sigset_t oldmask, mask;
      int pid, status;
      char *args[5];
      char **parg;
      int sv[2];
  
      sigemptyset(&mask);
      sigaddset(&mask, SIGCHLD);
      sigprocmask(SIG_BLOCK, &mask, &oldmask);
  
      if (socketpair(PF_UNIX, SOCK_STREAM, 0, sv) == -1) {
          error_setg_errno(errp, errno, "socketpair() failed");
          return -1;
      }
  
      /* try to launch bridge helper */
      pid = fork();
      if (pid < 0) {
          error_setg_errno(errp, errno, "Can't fork bridge helper");
          return -1;
      }
      if (pid == 0) {
          int open_max = sysconf(_SC_OPEN_MAX), i;
          char fd_buf[6+10];
          char br_buf[6+IFNAMSIZ] = {0};
          char helper_cmd[PATH_MAX + sizeof(fd_buf) + sizeof(br_buf) + 15];
  
          for (i = 3; i < open_max; i++) {
              if (i != sv[1]) {
                  close(i);
              }
          }
  
          snprintf(fd_buf, sizeof(fd_buf), "%s%d", "--fd=", sv[1]);
  
          if (strrchr(helper, ' ') || strrchr(helper, '\t')) {
              /* assume helper is a command */
  
              if (strstr(helper, "--br=") == NULL) {
                  snprintf(br_buf, sizeof(br_buf), "%s%s", "--br=", bridge);
              }
  
              snprintf(helper_cmd, sizeof(helper_cmd), "%s %s %s %s",
                       helper, "--use-vnet", fd_buf, br_buf);
  
              parg = args;
              *parg++ = (char *)"sh";
              *parg++ = (char *)"-c";
              *parg++ = helper_cmd;
              *parg++ = NULL;
  
              execv("/bin/sh", args);
          } else {
              /* assume helper is just the executable path name */
  
              snprintf(br_buf, sizeof(br_buf), "%s%s", "--br=", bridge);
  
              parg = args;
              *parg++ = (char *)helper;
              *parg++ = (char *)"--use-vnet";
              *parg++ = fd_buf;
              *parg++ = br_buf;
              *parg++ = NULL;
  
              execv(helper, args);
          }
          _exit(1);
  
      } else {
          int fd;
          int saved_errno;
  
          close(sv[1]);
  
          do {
              fd = recv_fd(sv[0]);
          } while (fd == -1 && errno == EINTR);
          saved_errno = errno;
  
          close(sv[0]);
  
          while (waitpid(pid, &status, 0) != pid) {
              /* loop */
          }
          sigprocmask(SIG_SETMASK, &oldmask, NULL);
          if (fd < 0) {
              error_setg_errno(errp, saved_errno,
                               "failed to recv file descriptor");
              return -1;
          }
          if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
              error_setg(errp, "bridge helper failed");
              return -1;
          }
          return fd;
      }
  }
  
  int net_init_bridge(const NetClientOptions *opts, const char *name,
                      NetClientState *peer, Error **errp)
  {
      const NetdevBridgeOptions *bridge;
      const char *helper, *br;
      TAPState *s;
      int fd, vnet_hdr;
  
      assert(opts->type == NET_CLIENT_OPTIONS_KIND_BRIDGE);
      bridge = opts->u.bridge;
  
      helper = bridge->has_helper ? bridge->helper : DEFAULT_BRIDGE_HELPER;
      br     = bridge->has_br     ? bridge->br     : DEFAULT_BRIDGE_INTERFACE;
  
      fd = net_bridge_run_helper(helper, br, errp);
      if (fd == -1) {
          return -1;
      }
  
      fcntl(fd, F_SETFL, O_NONBLOCK);
      vnet_hdr = tap_probe_vnet_hdr(fd);
      s = net_tap_fd_init(peer, "bridge", name, fd, vnet_hdr);
  
      snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s,br=%s", helper,
               br);
  
      return 0;
  }
  
  static int net_tap_init(const NetdevTapOptions *tap, int *vnet_hdr,
                          const char *setup_script, char *ifname,
                          size_t ifname_sz, int mq_required, Error **errp)
  {
      Error *err = NULL;
      int fd, vnet_hdr_required;
  
      if (tap->has_vnet_hdr) {
          *vnet_hdr = tap->vnet_hdr;
          vnet_hdr_required = *vnet_hdr;
      } else {
          *vnet_hdr = 1;
          vnet_hdr_required = 0;
      }
  
      TFR(fd = tap_open(ifname, ifname_sz, vnet_hdr, vnet_hdr_required,
                        mq_required, errp));
      if (fd < 0) {
          return -1;
      }
  
      if (setup_script &&
          setup_script[0] != '\0' &&
          strcmp(setup_script, "no") != 0) {
          launch_script(setup_script, ifname, fd, &err);
          if (err) {
              error_propagate(errp, err);
              close(fd);
              return -1;
          }
      }
  
      return fd;
  }
  
  #define MAX_TAP_QUEUES 1024
  
  static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState *peer,
                               const char *model, const char *name,
                               const char *ifname, const char *script,
                               const char *downscript, const char *vhostfdname,
                               int vnet_hdr, int fd, Error **errp)
  {
      Error *err = NULL;
      TAPState *s = net_tap_fd_init(peer, model, name, fd, vnet_hdr);
      int vhostfd;
  
      tap_set_sndbuf(s->fd, tap, &err);
      if (err) {
          error_propagate(errp, err);
          return;
      }
  
      if (tap->has_fd || tap->has_fds) {
          snprintf(s->nc.info_str, sizeof(s->nc.info_str), "fd=%d", fd);
      } else if (tap->has_helper) {
          snprintf(s->nc.info_str, sizeof(s->nc.info_str), "helper=%s",
                   tap->helper);
      } else {
          snprintf(s->nc.info_str, sizeof(s->nc.info_str),
                   "ifname=%s,script=%s,downscript=%s", ifname, script,
                   downscript);
  
          if (strcmp(downscript, "no") != 0) {
              snprintf(s->down_script, sizeof(s->down_script), "%s", downscript);
              snprintf(s->down_script_arg, sizeof(s->down_script_arg),
                       "%s", ifname);
          }
      }
  
      if (tap->has_vhost ? tap->vhost :
          vhostfdname || (tap->has_vhostforce && tap->vhostforce)) {
          VhostNetOptions options;
  
          options.backend_type = VHOST_BACKEND_TYPE_KERNEL;
          options.net_backend = &s->nc;
  
          if (vhostfdname) {
              vhostfd = monitor_fd_param(cur_mon, vhostfdname, &err);
              if (vhostfd == -1) {
                  error_propagate(errp, err);
                  return;
              }
          } else {
              vhostfd = open("/dev/vhost-net", O_RDWR);
              if (vhostfd < 0) {
                  error_setg_errno(errp, errno,
                                   "tap: open vhost char device failed");
                  return;
              }
          }
          options.opaque = (void *)(uintptr_t)vhostfd;
  
          s->vhost_net = vhost_net_init(&options);
          if (!s->vhost_net) {
              error_setg(errp,
                         "vhost-net requested but could not be initialized");
              return;
          }
      } else if (vhostfdname) {
          error_setg(errp, "vhostfd= is not valid without vhost");
      }
  }
  
  static int get_fds(char *str, char *fds[], int max)
  {
      char *ptr = str, *this;
      size_t len = strlen(str);
      int i = 0;
  
      while (i < max && ptr < str + len) {
          this = strchr(ptr, ':');
  
          if (this == NULL) {
              fds[i] = g_strdup(ptr);
          } else {
              fds[i] = g_strndup(ptr, this - ptr);
          }
  
          i++;
          if (this == NULL) {
              break;
          } else {
              ptr = this + 1;
          }
      }
  
      return i;
  }
  
  int net_init_tap(const NetClientOptions *opts, const char *name,
                   NetClientState *peer, Error **errp)
  {
      const NetdevTapOptions *tap;
      int fd, vnet_hdr = 0, i = 0, queues;
      /* for the no-fd, no-helper case */
      const char *script = NULL; /* suppress wrong "uninit'd use" gcc warning */
      const char *downscript = NULL;
      Error *err = NULL;
      const char *vhostfdname;
      char ifname[128];
  
      assert(opts->type == NET_CLIENT_OPTIONS_KIND_TAP);
      tap = opts->u.tap;
      queues = tap->has_queues ? tap->queues : 1;
      vhostfdname = tap->has_vhostfd ? tap->vhostfd : NULL;
  
      /* QEMU vlans does not support multiqueue tap, in this case peer is set.
       * For -netdev, peer is always NULL. */
      if (peer && (tap->has_queues || tap->has_fds || tap->has_vhostfds)) {
          error_setg(errp, "Multiqueue tap cannot be used with QEMU vlans");
          return -1;
      }
  
      if (tap->has_fd) {
          if (tap->has_ifname || tap->has_script || tap->has_downscript ||
              tap->has_vnet_hdr || tap->has_helper || tap->has_queues ||
              tap->has_fds || tap->has_vhostfds) {
              error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
                         "helper=, queues=, fds=, and vhostfds= "
                         "are invalid with fd=");
              return -1;
          }
  
          fd = monitor_fd_param(cur_mon, tap->fd, &err);
          if (fd == -1) {
              error_propagate(errp, err);
              return -1;
          }
  
          fcntl(fd, F_SETFL, O_NONBLOCK);
  
          vnet_hdr = tap_probe_vnet_hdr(fd);
  
          net_init_tap_one(tap, peer, "tap", name, NULL,
                           script, downscript,
                           vhostfdname, vnet_hdr, fd, &err);
          if (err) {
              error_propagate(errp, err);
              return -1;
          }
      } else if (tap->has_fds) {
          char *fds[MAX_TAP_QUEUES];
          char *vhost_fds[MAX_TAP_QUEUES];
          int nfds, nvhosts;
  
          if (tap->has_ifname || tap->has_script || tap->has_downscript ||
              tap->has_vnet_hdr || tap->has_helper || tap->has_queues ||
              tap->has_vhostfd) {
              error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
                         "helper=, queues=, and vhostfd= "
                         "are invalid with fds=");
              return -1;
          }
  
          nfds = get_fds(tap->fds, fds, MAX_TAP_QUEUES);
          if (tap->has_vhostfds) {
              nvhosts = get_fds(tap->vhostfds, vhost_fds, MAX_TAP_QUEUES);
              if (nfds != nvhosts) {
                  error_setg(errp, "The number of fds passed does not match "
                             "the number of vhostfds passed");
                  return -1;
              }
          }
  
          for (i = 0; i < nfds; i++) {
              fd = monitor_fd_param(cur_mon, fds[i], &err);
              if (fd == -1) {
                  error_propagate(errp, err);
                  return -1;
              }
  
              fcntl(fd, F_SETFL, O_NONBLOCK);
  
              if (i == 0) {
                  vnet_hdr = tap_probe_vnet_hdr(fd);
              } else if (vnet_hdr != tap_probe_vnet_hdr(fd)) {
                  error_setg(errp,
                             "vnet_hdr not consistent across given tap fds");
                  return -1;
              }
  
              net_init_tap_one(tap, peer, "tap", name, ifname,
                               script, downscript,
                               tap->has_vhostfds ? vhost_fds[i] : NULL,
                               vnet_hdr, fd, &err);
              if (err) {
                  error_propagate(errp, err);
                  return -1;
              }
          }
      } else if (tap->has_helper) {
          if (tap->has_ifname || tap->has_script || tap->has_downscript ||
              tap->has_vnet_hdr || tap->has_queues || tap->has_vhostfds) {
              error_setg(errp, "ifname=, script=, downscript=, vnet_hdr=, "
                         "queues=, and vhostfds= are invalid with helper=");
              return -1;
          }
  
          fd = net_bridge_run_helper(tap->helper, DEFAULT_BRIDGE_INTERFACE,
                                     errp);
          if (fd == -1) {
              return -1;
          }
  
          fcntl(fd, F_SETFL, O_NONBLOCK);
          vnet_hdr = tap_probe_vnet_hdr(fd);
  
          net_init_tap_one(tap, peer, "bridge", name, ifname,
                           script, downscript, vhostfdname,
                           vnet_hdr, fd, &err);
          if (err) {
              error_propagate(errp, err);
              close(fd);
              return -1;
          }
      } else {
          if (tap->has_vhostfds) {
              error_setg(errp, "vhostfds= is invalid if fds= wasn't specified");
              return -1;
          }
          script = tap->has_script ? tap->script : DEFAULT_NETWORK_SCRIPT;
          downscript = tap->has_downscript ? tap->downscript :
              DEFAULT_NETWORK_DOWN_SCRIPT;
  
          if (tap->has_ifname) {
              pstrcpy(ifname, sizeof ifname, tap->ifname);
          } else {
              ifname[0] = '\0';
          }
  
          for (i = 0; i < queues; i++) {
              fd = net_tap_init(tap, &vnet_hdr, i >= 1 ? "no" : script,
                                ifname, sizeof ifname, queues > 1, errp);
              if (fd == -1) {
                  return -1;
              }
  
              if (queues > 1 && i == 0 && !tap->has_ifname) {
                  if (tap_fd_get_ifname(fd, ifname)) {
                      error_setg(errp, "Fail to get ifname");
                      close(fd);
                      return -1;
                  }
              }
  
              net_init_tap_one(tap, peer, "tap", name, ifname,
                               i >= 1 ? "no" : script,
                               i >= 1 ? "no" : downscript,
                               vhostfdname, vnet_hdr, fd, &err);
              if (err) {
                  error_propagate(errp, err);
                  close(fd);
                  return -1;
              }
          }
      }
  
      return 0;
  }
  
  VHostNetState *tap_get_vhost_net(NetClientState *nc)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_TAP);
      return s->vhost_net;
  }
  
  int tap_enable(NetClientState *nc)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      int ret;
  
      if (s->enabled) {
          return 0;
      } else {
          ret = tap_fd_enable(s->fd);
          if (ret == 0) {
              s->enabled = true;
              tap_update_fd_handler(s);
          }
          return ret;
      }
  }
  
  int tap_disable(NetClientState *nc)
  {
      TAPState *s = DO_UPCAST(TAPState, nc, nc);
      int ret;
  
      if (s->enabled == 0) {
          return 0;
      } else {
          ret = tap_fd_disable(s->fd);
          if (ret == 0) {
              qemu_purge_queued_packets(nc);
              s->enabled = false;
              tap_update_fd_handler(s);
          }
          return ret;
      }
  }
  