net: split all the tap code out into net/tap.c

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 759 insertions, 0 deletions

diff --git a/net/tap.c b/net/tap.c
new file mode 100644
index 0000000..6b43d80
--- /dev/null
+++ b/net/tap.c
@@ -0,0 +1,759 @@
+/*
+ * 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 "net/tap.h"
+
+#include "config-host.h"
+
+#include <signal.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <net/if.h>
+
+#include "net.h"
+#include "sysemu.h"
+#include "qemu-char.h"
+#include "qemu-common.h"
+
+#ifdef __linux__
+#include "net/tap-linux.h"
+#endif
+
+#ifdef __NetBSD__
+#include <net/if_tap.h>
+#endif
+
+#ifdef CONFIG_BSD
+#if defined(__FreeBSD__) || defined(__DragonFly__)
+#include <libutil.h>
+#else
+#include <util.h>
+#endif
+#elif defined (__GLIBC__) && defined (__FreeBSD_kernel__)
+#include <freebsd/stdlib.h>
+#endif
+
+#if defined(__OpenBSD__)
+#include <util.h>
+#endif
+
+#ifdef __sun__
+#include <sys/stat.h>
+#include <sys/ethernet.h>
+#include <sys/sockio.h>
+#include <netinet/arp.h>
+#include <netinet/in.h>
+#include <netinet/in_systm.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h> // must come after ip.h
+#include <netinet/udp.h>
+#include <netinet/tcp.h>
+#include <net/if.h>
+#include <syslog.h>
+#include <stropts.h>
+#endif
+
+#if !defined(_AIX)
+
+/* Maximum GSO packet size (64k) plus plenty of room for
+ * the ethernet and virtio_net headers
+ */
+#define TAP_BUFSIZE (4096 + 65536)
+
+typedef struct TAPState {
+    VLANClientState *vc;
+    int fd;
+    char down_script[1024];
+    char down_script_arg[128];
+    uint8_t buf[TAP_BUFSIZE];
+    unsigned int read_poll : 1;
+    unsigned int write_poll : 1;
+    unsigned int has_vnet_hdr : 1;
+    unsigned int using_vnet_hdr : 1;
+    unsigned int has_ufo: 1;
+} 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  ? tap_can_send : NULL,
+                         s->read_poll  ? tap_send     : NULL,
+                         s->write_poll ? tap_writable : NULL,
+                         s);
+}
+
+static void tap_read_poll(TAPState *s, int enable)
+{
+    s->read_poll = !!enable;
+    tap_update_fd_handler(s);
+}
+
+static void tap_write_poll(TAPState *s, int enable)
+{
+    s->write_poll = !!enable;
+    tap_update_fd_handler(s);
+}
+
+static void tap_writable(void *opaque)
+{
+    TAPState *s = opaque;
+
+    tap_write_poll(s, 0);
+
+    qemu_flush_queued_packets(s->vc);
+}
+
+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, 1);
+        return 0;
+    }
+
+    return len;
+}
+
+static ssize_t tap_receive_iov(VLANClientState *vc, const struct iovec *iov,
+                               int iovcnt)
+{
+    TAPState *s = vc->opaque;
+    const struct iovec *iovp = iov;
+    struct iovec iov_copy[iovcnt + 1];
+    struct virtio_net_hdr hdr = { 0, };
+
+    if (s->has_vnet_hdr && !s->using_vnet_hdr) {
+        iov_copy[0].iov_base = &hdr;
+        iov_copy[0].iov_len =  sizeof(hdr);
+        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(VLANClientState *vc, const uint8_t *buf, size_t size)
+{
+    TAPState *s = vc->opaque;
+    struct iovec iov[2];
+    int iovcnt = 0;
+    struct virtio_net_hdr hdr = { 0, };
+
+    if (s->has_vnet_hdr) {
+        iov[iovcnt].iov_base = &hdr;
+        iov[iovcnt].iov_len  = sizeof(hdr);
+        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(VLANClientState *vc, const uint8_t *buf, size_t size)
+{
+    TAPState *s = vc->opaque;
+    struct iovec iov[1];
+
+    if (s->has_vnet_hdr && !s->using_vnet_hdr) {
+        return tap_receive_raw(vc, 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->vc);
+}
+
+#ifdef __sun__
+static ssize_t tap_read_packet(int tapfd, uint8_t *buf, int maxlen)
+{
+    struct strbuf sbuf;
+    int f = 0;
+
+    sbuf.maxlen = maxlen;
+    sbuf.buf = (char *)buf;
+
+    return getmsg(tapfd, NULL, &sbuf, &f) >= 0 ? sbuf.len : -1;
+}
+#else
+static ssize_t tap_read_packet(int tapfd, uint8_t *buf, int maxlen)
+{
+    return read(tapfd, buf, maxlen);
+}
+#endif
+
+static void tap_send_completed(VLANClientState *vc, ssize_t len)
+{
+    TAPState *s = vc->opaque;
+    tap_read_poll(s, 1);
+}
+
+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->has_vnet_hdr && !s->using_vnet_hdr) {
+            buf  += sizeof(struct virtio_net_hdr);
+            size -= sizeof(struct virtio_net_hdr);
+        }
+
+        size = qemu_send_packet_async(s->vc, buf, size, tap_send_completed);
+        if (size == 0) {
+            tap_read_poll(s, 0);
+        }
+    } while (size > 0);
+}
+
+/* sndbuf should be set to a value lower than the tx queue
+ * capacity of any destination network interface.
+ * Ethernet NICs generally have txqueuelen=1000, so 1Mb is
+ * a good default, given a 1500 byte MTU.
+ */
+#define TAP_DEFAULT_SNDBUF 1024*1024
+
+static int tap_set_sndbuf(TAPState *s, QemuOpts *opts)
+{
+    int sndbuf;
+
+    sndbuf = qemu_opt_get_size(opts, "sndbuf", TAP_DEFAULT_SNDBUF);
+    if (!sndbuf) {
+        sndbuf = INT_MAX;
+    }
+
+    if (ioctl(s->fd, TUNSETSNDBUF, &sndbuf) == -1 && qemu_opt_get(opts, "sndbuf")) {
+        qemu_error("TUNSETSNDBUF ioctl failed: %s\n", strerror(errno));
+        return -1;
+    }
+    return 0;
+}
+
+int tap_has_ufo(VLANClientState *vc)
+{
+    TAPState *s = vc->opaque;
+
+    assert(vc->type == NET_CLIENT_TYPE_TAP);
+
+    return s->has_ufo;
+}
+
+int tap_has_vnet_hdr(VLANClientState *vc)
+{
+    TAPState *s = vc->opaque;
+
+    assert(vc->type == NET_CLIENT_TYPE_TAP);
+
+    return s->has_vnet_hdr;
+}
+
+void tap_using_vnet_hdr(VLANClientState *vc, int using_vnet_hdr)
+{
+    TAPState *s = vc->opaque;
+
+    using_vnet_hdr = using_vnet_hdr != 0;
+
+    assert(vc->type == NET_CLIENT_TYPE_TAP);
+    assert(s->has_vnet_hdr == using_vnet_hdr);
+
+    s->using_vnet_hdr = using_vnet_hdr;
+}
+
+static int tap_probe_vnet_hdr(int fd)
+{
+    struct ifreq ifr;
+
+    if (ioctl(fd, TUNGETIFF, &ifr) != 0) {
+        qemu_error("TUNGETIFF ioctl() failed: %s\n", strerror(errno));
+        return 0;
+    }
+
+    return ifr.ifr_flags & IFF_VNET_HDR;
+}
+
+void tap_set_offload(VLANClientState *vc, int csum, int tso4,
+                     int tso6, int ecn, int ufo)
+{
+    TAPState *s = vc->opaque;
+    unsigned int offload = 0;
+
+    if (csum) {
+        offload |= TUN_F_CSUM;
+        if (tso4)
+            offload |= TUN_F_TSO4;
+        if (tso6)
+            offload |= TUN_F_TSO6;
+        if ((tso4 || tso6) && ecn)
+            offload |= TUN_F_TSO_ECN;
+        if (ufo)
+            offload |= TUN_F_UFO;
+    }
+
+    if (ioctl(s->fd, TUNSETOFFLOAD, offload) != 0) {
+        offload &= ~TUN_F_UFO;
+        if (ioctl(s->fd, TUNSETOFFLOAD, offload) != 0) {
+            fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
+                    strerror(errno));
+        }
+    }
+}
+
+static void tap_cleanup(VLANClientState *vc)
+{
+    TAPState *s = vc->opaque;
+
+    qemu_purge_queued_packets(vc);
+
+    if (s->down_script[0])
+        launch_script(s->down_script, s->down_script_arg, s->fd);
+
+    tap_read_poll(s, 0);
+    tap_write_poll(s, 0);
+    close(s->fd);
+    qemu_free(s);
+}
+
+/* fd support */
+
+static TAPState *net_tap_fd_init(VLANState *vlan,
+                                 const char *model,
+                                 const char *name,
+                                 int fd,
+                                 int vnet_hdr)
+{
+    TAPState *s;
+    unsigned int offload;
+
+    s = qemu_mallocz(sizeof(TAPState));
+    s->fd = fd;
+    s->has_vnet_hdr = vnet_hdr != 0;
+    s->using_vnet_hdr = 0;
+    s->vc = qemu_new_vlan_client(NET_CLIENT_TYPE_TAP,
+                                 vlan, NULL, model, name, NULL,
+                                 tap_receive, tap_receive_raw,
+                                 tap_receive_iov, tap_cleanup, s);
+    s->has_ufo = 0;
+    /* Check if tap supports UFO */
+    offload = TUN_F_CSUM | TUN_F_UFO;
+    if (ioctl(s->fd, TUNSETOFFLOAD, offload) == 0)
+       s->has_ufo = 1;
+    tap_set_offload(s->vc, 0, 0, 0, 0, 0);
+    tap_read_poll(s, 1);
+    return s;
+}
+
+#if defined (CONFIG_BSD) || defined (__FreeBSD_kernel__)
+static int tap_open(char *ifname, int ifname_size,
+                    int *vnet_hdr, int vnet_hdr_required)
+{
+    int fd;
+    char *dev;
+    struct stat s;
+
+    TFR(fd = open("/dev/tap", O_RDWR));
+    if (fd < 0) {
+        fprintf(stderr, "warning: could not open /dev/tap: no virtual network emulation\n");
+        return -1;
+    }
+
+    fstat(fd, &s);
+    dev = devname(s.st_rdev, S_IFCHR);
+    pstrcpy(ifname, ifname_size, dev);
+
+    fcntl(fd, F_SETFL, O_NONBLOCK);
+    return fd;
+}
+#elif defined(__sun__)
+#define TUNNEWPPA       (('T'<<16) | 0x0001)
+/*
+ * Allocate TAP device, returns opened fd.
+ * Stores dev name in the first arg(must be large enough).
+ */
+static int tap_alloc(char *dev, size_t dev_size)
+{
+    int tap_fd, if_fd, ppa = -1;
+    static int ip_fd = 0;
+    char *ptr;
+
+    static int arp_fd = 0;
+    int ip_muxid, arp_muxid;
+    struct strioctl  strioc_if, strioc_ppa;
+    int link_type = I_PLINK;;
+    struct lifreq ifr;
+    char actual_name[32] = "";
+
+    memset(&ifr, 0x0, sizeof(ifr));
+
+    if( *dev ){
+       ptr = dev;
+       while( *ptr && !qemu_isdigit((int)*ptr) ) ptr++;
+       ppa = atoi(ptr);
+    }
+
+    /* Check if IP device was opened */
+    if( ip_fd )
+       close(ip_fd);
+
+    TFR(ip_fd = open("/dev/udp", O_RDWR, 0));
+    if (ip_fd < 0) {
+       syslog(LOG_ERR, "Can't open /dev/ip (actually /dev/udp)");
+       return -1;
+    }
+
+    TFR(tap_fd = open("/dev/tap", O_RDWR, 0));
+    if (tap_fd < 0) {
+       syslog(LOG_ERR, "Can't open /dev/tap");
+       return -1;
+    }
+
+    /* Assign a new PPA and get its unit number. */
+    strioc_ppa.ic_cmd = TUNNEWPPA;
+    strioc_ppa.ic_timout = 0;
+    strioc_ppa.ic_len = sizeof(ppa);
+    strioc_ppa.ic_dp = (char *)&ppa;
+    if ((ppa = ioctl (tap_fd, I_STR, &strioc_ppa)) < 0)
+       syslog (LOG_ERR, "Can't assign new interface");
+
+    TFR(if_fd = open("/dev/tap", O_RDWR, 0));
+    if (if_fd < 0) {
+       syslog(LOG_ERR, "Can't open /dev/tap (2)");
+       return -1;
+    }
+    if(ioctl(if_fd, I_PUSH, "ip") < 0){
+       syslog(LOG_ERR, "Can't push IP module");
+       return -1;
+    }
+
+    if (ioctl(if_fd, SIOCGLIFFLAGS, &ifr) < 0)
+	syslog(LOG_ERR, "Can't get flags\n");
+
+    snprintf (actual_name, 32, "tap%d", ppa);
+    pstrcpy(ifr.lifr_name, sizeof(ifr.lifr_name), actual_name);
+
+    ifr.lifr_ppa = ppa;
+    /* Assign ppa according to the unit number returned by tun device */
+
+    if (ioctl (if_fd, SIOCSLIFNAME, &ifr) < 0)
+        syslog (LOG_ERR, "Can't set PPA %d", ppa);
+    if (ioctl(if_fd, SIOCGLIFFLAGS, &ifr) <0)
+        syslog (LOG_ERR, "Can't get flags\n");
+    /* Push arp module to if_fd */
+    if (ioctl (if_fd, I_PUSH, "arp") < 0)
+        syslog (LOG_ERR, "Can't push ARP module (2)");
+
+    /* Push arp module to ip_fd */
+    if (ioctl (ip_fd, I_POP, NULL) < 0)
+        syslog (LOG_ERR, "I_POP failed\n");
+    if (ioctl (ip_fd, I_PUSH, "arp") < 0)
+        syslog (LOG_ERR, "Can't push ARP module (3)\n");
+    /* Open arp_fd */
+    TFR(arp_fd = open ("/dev/tap", O_RDWR, 0));
+    if (arp_fd < 0)
+       syslog (LOG_ERR, "Can't open %s\n", "/dev/tap");
+
+    /* Set ifname to arp */
+    strioc_if.ic_cmd = SIOCSLIFNAME;
+    strioc_if.ic_timout = 0;
+    strioc_if.ic_len = sizeof(ifr);
+    strioc_if.ic_dp = (char *)&ifr;
+    if (ioctl(arp_fd, I_STR, &strioc_if) < 0){
+        syslog (LOG_ERR, "Can't set ifname to arp\n");
+    }
+
+    if((ip_muxid = ioctl(ip_fd, I_LINK, if_fd)) < 0){
+       syslog(LOG_ERR, "Can't link TAP device to IP");
+       return -1;
+    }
+
+    if ((arp_muxid = ioctl (ip_fd, link_type, arp_fd)) < 0)
+        syslog (LOG_ERR, "Can't link TAP device to ARP");
+
+    close (if_fd);
+
+    memset(&ifr, 0x0, sizeof(ifr));
+    pstrcpy(ifr.lifr_name, sizeof(ifr.lifr_name), actual_name);
+    ifr.lifr_ip_muxid  = ip_muxid;
+    ifr.lifr_arp_muxid = arp_muxid;
+
+    if (ioctl (ip_fd, SIOCSLIFMUXID, &ifr) < 0)
+    {
+      ioctl (ip_fd, I_PUNLINK , arp_muxid);
+      ioctl (ip_fd, I_PUNLINK, ip_muxid);
+      syslog (LOG_ERR, "Can't set multiplexor id");
+    }
+
+    snprintf(dev, dev_size, "tap%d", ppa);
+    return tap_fd;
+}
+
+static int tap_open(char *ifname, int ifname_size,
+                    int *vnet_hdr, int vnet_hdr_required)
+{
+    char  dev[10]="";
+    int fd;
+    if( (fd = tap_alloc(dev, sizeof(dev))) < 0 ){
+       fprintf(stderr, "Cannot allocate TAP device\n");
+       return -1;
+    }
+    pstrcpy(ifname, ifname_size, dev);
+    fcntl(fd, F_SETFL, O_NONBLOCK);
+    return fd;
+}
+#elif defined (_AIX)
+static int tap_open(char *ifname, int ifname_size,
+                    int *vnet_hdr, int vnet_hdr_required)
+{
+    fprintf (stderr, "no tap on AIX\n");
+    return -1;
+}
+#else
+static int tap_open(char *ifname, int ifname_size,
+                    int *vnet_hdr, int vnet_hdr_required)
+{
+    struct ifreq ifr;
+    int fd, ret;
+
+    TFR(fd = open("/dev/net/tun", O_RDWR));
+    if (fd < 0) {
+        fprintf(stderr, "warning: could not open /dev/net/tun: no virtual network emulation\n");
+        return -1;
+    }
+    memset(&ifr, 0, sizeof(ifr));
+    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
+
+    if (*vnet_hdr) {
+        unsigned int features;
+
+        if (ioctl(fd, TUNGETFEATURES, &features) == 0 &&
+            features & IFF_VNET_HDR) {
+            *vnet_hdr = 1;
+            ifr.ifr_flags |= IFF_VNET_HDR;
+        }
+
+        if (vnet_hdr_required && !*vnet_hdr) {
+            qemu_error("vnet_hdr=1 requested, but no kernel "
+                       "support for IFF_VNET_HDR available");
+            close(fd);
+            return -1;
+        }
+    }
+
+    if (ifname[0] != '\0')
+        pstrcpy(ifr.ifr_name, IFNAMSIZ, ifname);
+    else
+        pstrcpy(ifr.ifr_name, IFNAMSIZ, "tap%d");
+    ret = ioctl(fd, TUNSETIFF, (void *) &ifr);
+    if (ret != 0) {
+        fprintf(stderr, "warning: could not configure /dev/net/tun: no virtual network emulation\n");
+        close(fd);
+        return -1;
+    }
+    pstrcpy(ifname, ifname_size, ifr.ifr_name);
+    fcntl(fd, F_SETFL, O_NONBLOCK);
+    return fd;
+}
+#endif
+
+static int launch_script(const char *setup_script, const char *ifname, int fd)
+{
+    sigset_t oldmask, mask;
+    int pid, status;
+    char *args[3];
+    char **parg;
+
+    sigemptyset(&mask);
+    sigaddset(&mask, SIGCHLD);
+    sigprocmask(SIG_BLOCK, &mask, &oldmask);
+
+    /* 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 */
+        }
+        sigprocmask(SIG_SETMASK, &oldmask, NULL);
+
+        if (WIFEXITED(status) && WEXITSTATUS(status) == 0) {
+            return 0;
+        }
+    }
+    fprintf(stderr, "%s: could not launch network script\n", setup_script);
+    return -1;
+}
+
+static int net_tap_init(QemuOpts *opts, int *vnet_hdr)
+{
+    int fd, vnet_hdr_required;
+    char ifname[128] = {0,};
+    const char *setup_script;
+
+    if (qemu_opt_get(opts, "ifname")) {
+        pstrcpy(ifname, sizeof(ifname), qemu_opt_get(opts, "ifname"));
+    }
+
+    *vnet_hdr = qemu_opt_get_bool(opts, "vnet_hdr", 1);
+    if (qemu_opt_get(opts, "vnet_hdr")) {
+        vnet_hdr_required = *vnet_hdr;
+    } else {
+        vnet_hdr_required = 0;
+    }
+
+    TFR(fd = tap_open(ifname, sizeof(ifname), vnet_hdr, vnet_hdr_required));
+    if (fd < 0) {
+        return -1;
+    }
+
+    setup_script = qemu_opt_get(opts, "script");
+    if (setup_script &&
+        setup_script[0] != '\0' &&
+        strcmp(setup_script, "no") != 0 &&
+        launch_script(setup_script, ifname, fd)) {
+        close(fd);
+        return -1;
+    }
+
+    qemu_opt_set(opts, "ifname", ifname);
+
+    return fd;
+}
+
+int net_init_tap(QemuOpts *opts, Monitor *mon, const char *name, VLANState *vlan)
+{
+    TAPState *s;
+    int fd, vnet_hdr;
+
+    if (qemu_opt_get(opts, "fd")) {
+        if (qemu_opt_get(opts, "ifname") ||
+            qemu_opt_get(opts, "script") ||
+            qemu_opt_get(opts, "downscript") ||
+            qemu_opt_get(opts, "vnet_hdr")) {
+            qemu_error("ifname=, script=, downscript= and vnet_hdr= is invalid with fd=\n");
+            return -1;
+        }
+
+        fd = net_handle_fd_param(mon, qemu_opt_get(opts, "fd"));
+        if (fd == -1) {
+            return -1;
+        }
+
+        fcntl(fd, F_SETFL, O_NONBLOCK);
+
+        vnet_hdr = tap_probe_vnet_hdr(fd);
+    } else {
+        if (!qemu_opt_get(opts, "script")) {
+            qemu_opt_set(opts, "script", DEFAULT_NETWORK_SCRIPT);
+        }
+
+        if (!qemu_opt_get(opts, "downscript")) {
+            qemu_opt_set(opts, "downscript", DEFAULT_NETWORK_DOWN_SCRIPT);
+        }
+
+        fd = net_tap_init(opts, &vnet_hdr);
+    }
+
+    s = net_tap_fd_init(vlan, "tap", name, fd, vnet_hdr);
+    if (!s) {
+        close(fd);
+        return -1;
+    }
+
+    if (tap_set_sndbuf(s, opts) < 0) {
+        return -1;
+    }
+
+    if (qemu_opt_get(opts, "fd")) {
+        snprintf(s->vc->info_str, sizeof(s->vc->info_str), "fd=%d", fd);
+    } else {
+        const char *ifname, *script, *downscript;
+
+        ifname     = qemu_opt_get(opts, "ifname");
+        script     = qemu_opt_get(opts, "script");
+        downscript = qemu_opt_get(opts, "downscript");
+
+        snprintf(s->vc->info_str, sizeof(s->vc->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 (vlan) {
+        vlan->nb_host_devs++;
+    }
+
+    return 0;
+}
+
+#endif /* !defined(_AIX) */