Archipelago » qemu

/*

 * 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 "tap_int.h"

#include "config-host.h"

#include <sys/ioctl.h>

#include <sys/stat.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 int launch_script(const char *setup_script, const char *ifname, int fd);

static int tap_can_send(void *opaque);

static void tap_send(void *opaque);

static void tap_writable(void *opaque);

static void tap_update_fd_handler(TAPState *s)

{

    qemu_set_fd_handler2(s->fd,

                         s->read_poll && s->enabled ? tap_can_send : NULL,

                         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);

}

static int tap_can_send(void *opaque)

{

    TAPState *s = opaque;

    return qemu_can_send_packet(&s->nc);

}

#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;

    do {

        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);

        }

    } while (size > 0 && qemu_can_send_packet(&s->nc));

}

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;

}

int 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;

}

int 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);

}

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;

}

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;

}

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);

    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);

    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,

};

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 int launch_script(const char *setup_script, const char *ifname, int fd)

{

    int pid, status;

    char *args[3];

    char **parg;

    /* try to launch network script */

    pid = fork();

    if (pid == 0) {

        int open_max = sysconf(_SC_OPEN_MAX), i;

        for (i = 0; i < open_max; i++) {

            if (i != STDIN_FILENO &&

                i != STDOUT_FILENO &&

                i != STDERR_FILENO &&

                i != fd) {

                close(i);

            }

        }

        parg = args;

        *parg++ = (char *)setup_script;

        *parg++ = (char *)ifname;

        *parg = NULL;

        execv(setup_script, args);

        _exit(1);

    } else if (pid > 0) {

        while (waitpid(pid, &status, 0) != pid) {

            /* loop */

        }

        if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {

            return 0;

        }

    }

    fprintf(stderr, "%s: could not launch network script\n", setup_script);

    return -1;

}

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)

{

    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) {

        return -1;

    }

    /* try to launch bridge helper */

    pid = fork();

    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 = 0; i < open_max; i++) {

            if (i != STDIN_FILENO &&

                i != STDOUT_FILENO &&

                i != STDERR_FILENO &&

                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 if (pid > 0) {

        int fd;

        close(sv[1]);

        do {

            fd = recv_fd(sv[0]);

        } while (fd == -1 && errno == EINTR);

        close(sv[0]);

        while (waitpid(pid, &status, 0) != pid) {

            /* loop */

        }

        sigprocmask(SIG_SETMASK, &oldmask, NULL);

        if (fd < 0) {

            fprintf(stderr, "failed to recv file descriptor\n");

            return -1;

        }

        if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {

            return fd;

        }

    }

    fprintf(stderr, "failed to launch bridge helper\n");

    return -1;

}

int net_init_bridge(const NetClientOptions *opts, const char *name,

                    NetClientState *peer)

{

    const NetdevBridgeOptions *bridge;

    const char *helper, *br;

    TAPState *s;

    int fd, vnet_hdr;

    assert(opts->kind == NET_CLIENT_OPTIONS_KIND_BRIDGE);

    bridge = opts->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);

    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);

    if (!s) {

        close(fd);

        return -1;

    }

    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)

{

    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));

    if (fd < 0) {

        return -1;

    }

    if (setup_script &&

        setup_script[0] != '\0' &&

        strcmp(setup_script, "no") != 0 &&

        launch_script(setup_script, ifname, fd)) {

        close(fd);

        return -1;

    }

    return fd;

}

#define MAX_TAP_QUEUES 1024

static int 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)

{

    TAPState *s;

    s = net_tap_fd_init(peer, model, name, fd, vnet_hdr);

    if (!s) {

        close(fd);

        return -1;

    }

    if (tap_set_sndbuf(s->fd, tap) < 0) {

        return -1;

    }

    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)) {

        int vhostfd;

        if (tap->has_vhostfd) {

            vhostfd = monitor_handle_fd_param(cur_mon, vhostfdname);

            if (vhostfd == -1) {

                return -1;

            }

        } else {

            vhostfd = -1;

        }

        s->vhost_net = vhost_net_init(&s->nc, vhostfd,

                                      tap->has_vhostforce && tap->vhostforce);

        if (!s->vhost_net) {

            error_report("vhost-net requested but could not be initialized");

            return -1;

        }

    } else if (tap->has_vhostfd || tap->has_vhostfds) {

        error_report("vhostfd= is not valid without vhost");

        return -1;

    }

    return 0;

}

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)

{

    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;

    const char *vhostfdname;

    char ifname[128];

    assert(opts->kind == NET_CLIENT_OPTIONS_KIND_TAP);

    tap = opts->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_report("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) {

            error_report("ifname=, script=, downscript=, vnet_hdr=, "

                         "helper=, queues=, and fds= are invalid with fd=");

            return -1;

        }

        fd = monitor_handle_fd_param(cur_mon, tap->fd);

        if (fd == -1) {

            return -1;

        }

        fcntl(fd, F_SETFL, O_NONBLOCK);

        vnet_hdr = tap_probe_vnet_hdr(fd);

        if (net_init_tap_one(tap, peer, "tap", name, NULL,

                             script, downscript,

                             vhostfdname, vnet_hdr, fd)) {

            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_fd) {

            error_report("ifname=, script=, downscript=, vnet_hdr=, "

                         "helper=, queues=, and fd= 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_report("The number of fds passed does not match the "

                             "number of vhostfds passed");

                return -1;

            }

        }

        for (i = 0; i < nfds; i++) {

            fd = monitor_handle_fd_param(cur_mon, fds[i]);

            if (fd == -1) {

                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_report("vnet_hdr not consistent across given tap fds");

                return -1;

            }

            if (net_init_tap_one(tap, peer, "tap", name, ifname,

                                 script, downscript,

                                 tap->has_vhostfds ? vhost_fds[i] : NULL,

                                 vnet_hdr, fd)) {

                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_fds) {

            error_report("ifname=, script=, downscript=, and vnet_hdr= "

                         "queues=, and fds= are invalid with helper=");

            return -1;

        }

        fd = net_bridge_run_helper(tap->helper, DEFAULT_BRIDGE_INTERFACE);

        if (fd == -1) {

            return -1;

        }

        fcntl(fd, F_SETFL, O_NONBLOCK);

        vnet_hdr = tap_probe_vnet_hdr(fd);

        if (net_init_tap_one(tap, peer, "bridge", name, ifname,

                             script, downscript, vhostfdname,

                             vnet_hdr, fd)) {

            return -1;

        }

    } else {

        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);

            if (fd == -1) {

                return -1;

            }

            if (queues > 1 && i == 0 && !tap->has_ifname) {

                if (tap_fd_get_ifname(fd, ifname)) {

                    error_report("Fail to get ifname");

                    return -1;

                }

            }

            if (net_init_tap_one(tap, peer, "tap", name, ifname,

                                 i >= 1 ? "no" : script,

                                 i >= 1 ? "no" : downscript,

                                 vhostfdname, vnet_hdr, 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;

    }

}