virnetdevtap.c

/*
 * Copyright (C) 2007-2014 Red Hat, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see
 * <http://www.gnu.org/licenses/>.
 *
 * Authors:
 *     Mark McLoughlin <markmc@redhat.com>
 *     Daniel P. Berrange <berrange@redhat.com>
 */

#include <config.h>

#include "virmacaddr.h"
#include "virnetdevtap.h"
#include "virnetdev.h"
#include "virnetdevbridge.h"
#include "virnetdevmidonet.h"
#include "virnetdevopenvswitch.h"
#include "virerror.h"
#include "virfile.h"
#include "viralloc.h"
#include "virlog.h"
#include "virstring.h"
#include "datatypes.h"

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <regex.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <fcntl.h>
#ifdef __linux__
# include <linux/if_tun.h>    /* IFF_TUN, IFF_NO_PI */
#elif defined(__FreeBSD__)
# include <net/if_mib.h>
# include <sys/sysctl.h>
#endif
#if defined(HAVE_GETIFADDRS) && defined(AF_LINK)
# include <ifaddrs.h>
#endif

#define VIR_FROM_THIS VIR_FROM_NONE

VIR_LOG_INIT("util.netdevtap");

/**
 * virNetDevTapGetName:
 * @tapfd: a tun/tap file descriptor
 * @ifname: a pointer that will receive the interface name
 *
 * Retrieve the interface name given a file descriptor for a tun/tap
 * interface.
 *
 * Returns 0 if the interface name is successfully queried, -1 otherwise
 */
int
virNetDevTapGetName(int tapfd ATTRIBUTE_UNUSED, char **ifname ATTRIBUTE_UNUSED)
{
#ifdef TUNGETIFF
    struct ifreq ifr;

    if (ioctl(tapfd, TUNGETIFF, &ifr) < 0) {
        virReportSystemError(errno, "%s",
                             _("Unable to query tap interface name"));
        return -1;
    }

    return VIR_STRDUP(*ifname, ifr.ifr_name) < 0 ? -1 : 0;
#else
    return -1;
#endif
}

/**
 * virNetDevTapGetRealDeviceName:
 * @ifname: the interface name
 *
 * Lookup real interface name (i.e. name of the device entry in /dev),
 * because e.g. on FreeBSD if we rename tap device to vnetN its device
 * entry still remains unchanged (/dev/tapX), but bhyve needs a name
 * that matches /dev entry.
 *
 * Returns the proper interface name or NULL if no corresponding interface
 * found.
 */
char*
virNetDevTapGetRealDeviceName(char *ifname ATTRIBUTE_UNUSED)
{
#ifdef IFDATA_DRIVERNAME
    int ifindex = 0;
    int name[6];
    size_t len = 0;
    char *ret = NULL;

    if ((ifindex = if_nametoindex(ifname)) == 0) {
        virReportSystemError(errno,
                             _("Unable to get interface index for '%s'"),
                             ifname);
        return NULL;
    }

    name[0] = CTL_NET;
    name[1] = PF_LINK;
    name[2] = NETLINK_GENERIC;
    name[3] = IFMIB_IFDATA;
    name[4] = ifindex;
    name[5] = IFDATA_DRIVERNAME;

    if (sysctl(name, 6, NULL, &len, 0, 0) < 0) {
        virReportSystemError(errno,
                             _("Unable to get driver name for '%s'"),
                             ifname);
        return NULL;
    }

    if (VIR_ALLOC_N(ret, len) < 0)
        return NULL;

    if (sysctl(name, 6, ret, &len, 0, 0) < 0) {
        virReportSystemError(errno,
                             _("Unable to get driver name for '%s'"),
                             ifname);
        VIR_FREE(ret);
        return NULL;
    }

    return ret;
#else
    return NULL;
#endif
}


/**
 * virNetDevProbeVnetHdr:
 * @tapfd: a tun/tap file descriptor
 *
 * Check whether it is safe to enable the IFF_VNET_HDR flag on the
 * tap interface.
 *
 * Setting IFF_VNET_HDR enables QEMU's virtio_net driver to allow
 * guests to pass larger (GSO) packets, with partial checksums, to
 * the host. This greatly increases the achievable throughput.
 *
 * It is only useful to enable this when we're setting up a virtio
 * interface. And it is only *safe* to enable it when we know for
 * sure that a) qemu has support for IFF_VNET_HDR and b) the running
 * kernel implements the TUNGETIFF ioctl(), which qemu needs to query
 * the supplied tapfd.
 *
 * Returns 1 if VnetHdr is supported, 0 if not supported
 */
#ifdef IFF_VNET_HDR
static int
virNetDevProbeVnetHdr(int tapfd)
{
# if defined(IFF_VNET_HDR) && defined(TUNGETFEATURES) && defined(TUNGETIFF)
    unsigned int features;
    struct ifreq dummy;

    if (ioctl(tapfd, TUNGETFEATURES, &features) != 0) {
        VIR_INFO("Not enabling IFF_VNET_HDR; "
                 "TUNGETFEATURES ioctl() not implemented");
        return 0;
    }

    if (!(features & IFF_VNET_HDR)) {
        VIR_INFO("Not enabling IFF_VNET_HDR; "
                 "TUNGETFEATURES ioctl() reports no IFF_VNET_HDR");
        return 0;
    }

    /* The kernel will always return -1 at this point.
     * If TUNGETIFF is not implemented then errno == EBADFD.
     */
    if (ioctl(tapfd, TUNGETIFF, &dummy) != -1 || errno != EBADFD) {
        VIR_INFO("Not enabling IFF_VNET_HDR; "
                 "TUNGETIFF ioctl() not implemented");
        return 0;
    }

    VIR_INFO("Enabling IFF_VNET_HDR");

    return 1;
# else
    (void) tapfd;
    VIR_INFO("Not enabling IFF_VNET_HDR; disabled at build time");
    return 0;
# endif
}
#endif


#ifdef TUNSETIFF
/**
 * virNetDevTapCreate:
 * @ifname: the interface name
 * @tunpath: path to the tun device (if NULL, /dev/net/tun is used)
 * @tapfds: array of file descriptors return value for the new tap device
 * @tapfdSize: number of file descriptors in @tapfd
 * @flags: OR of virNetDevTapCreateFlags. Only one flag is recognized:
 *
 *   VIR_NETDEV_TAP_CREATE_VNET_HDR
 *     - Enable IFF_VNET_HDR on the tap device
 *   VIR_NETDEV_TAP_CREATE_PERSIST
 *     - The device will persist after the file descriptor is closed
 *
 * Creates a tap interface. The caller must use virNetDevTapDelete to
 * remove a persistent TAP device when it is no longer needed. In case
 * @tapfdSize is greater than one, multiqueue extension is requested
 * from kernel.
 *
 * Returns 0 in case of success or -1 on failure.
 */
int virNetDevTapCreate(char **ifname,
                       const char *tunpath,
                       int *tapfd,
                       size_t tapfdSize,
                       unsigned int flags)
{
    size_t i;
    struct ifreq ifr;
    int ret = -1;
    int fd;

    if (!tunpath)
        tunpath = "/dev/net/tun";

    memset(&ifr, 0, sizeof(ifr));
    for (i = 0; i < tapfdSize; i++) {
        if ((fd = open(tunpath, O_RDWR)) < 0) {
            virReportSystemError(errno,
                                 _("Unable to open %s, is tun module loaded?"),
                                 tunpath);
            goto cleanup;
        }

        memset(&ifr, 0, sizeof(ifr));

        ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
        /* If tapfdSize is greater than one, request multiqueue */
        if (tapfdSize > 1) {
# ifdef IFF_MULTI_QUEUE
            ifr.ifr_flags |= IFF_MULTI_QUEUE;
# else
            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                           _("Multiqueue devices are not supported on this system"));
            goto cleanup;
# endif
        }

# ifdef IFF_VNET_HDR
        if ((flags &  VIR_NETDEV_TAP_CREATE_VNET_HDR) &&
            virNetDevProbeVnetHdr(fd))
            ifr.ifr_flags |= IFF_VNET_HDR;
# endif

        if (virStrcpyStatic(ifr.ifr_name, *ifname) == NULL) {
            virReportSystemError(ERANGE,
                                 _("Network interface name '%s' is too long"),
                                 *ifname);
            goto cleanup;

        }

        if (ioctl(fd, TUNSETIFF, &ifr) < 0) {
            virReportSystemError(errno,
                                 _("Unable to create tap device %s"),
                                 NULLSTR(*ifname));
            goto cleanup;
        }

        if (i == 0) {
            /* In case we are looping more than once, set other
             * TAPs to have the same name */
            VIR_FREE(*ifname);
            if (VIR_STRDUP(*ifname, ifr.ifr_name) < 0)
                goto cleanup;
        }

        if ((flags & VIR_NETDEV_TAP_CREATE_PERSIST) &&
            ioctl(fd, TUNSETPERSIST, 1) < 0) {
            virReportSystemError(errno,
                                 _("Unable to set tap device %s to persistent"),
                                 NULLSTR(*ifname));
            goto cleanup;
        }
        tapfd[i] = fd;
    }

    ret = 0;

 cleanup:
    if (ret < 0) {
        VIR_FORCE_CLOSE(fd);
        while (i--)
            VIR_FORCE_CLOSE(tapfd[i]);
    }

    return ret;
}


int virNetDevTapDelete(const char *ifname,
                       const char *tunpath)
{
    struct ifreq try;
    int fd;
    int ret = -1;

    if (!tunpath)
        tunpath = "/dev/net/tun";

    if ((fd = open(tunpath, O_RDWR)) < 0) {
        virReportSystemError(errno,
                             _("Unable to open %s, is tun module loaded?"),
                             tunpath);
        return -1;
    }

    memset(&try, 0, sizeof(struct ifreq));
    try.ifr_flags = IFF_TAP|IFF_NO_PI;

    if (virStrcpyStatic(try.ifr_name, ifname) == NULL) {
        virReportSystemError(ERANGE,
                             _("Network interface name '%s' is too long"),
                             ifname);
        goto cleanup;
    }

    if (ioctl(fd, TUNSETIFF, &try) < 0) {
        virReportSystemError(errno, "%s",
                             _("Unable to associate TAP device"));
        goto cleanup;
    }

    if (ioctl(fd, TUNSETPERSIST, 0) < 0) {
        virReportSystemError(errno, "%s",
                             _("Unable to make TAP device non-persistent"));
        goto cleanup;
    }

    ret = 0;

 cleanup:
    VIR_FORCE_CLOSE(fd);
    return ret;
}
#elif defined(SIOCIFCREATE2) && defined(SIOCIFDESTROY) && defined(IF_MAXUNIT)
int virNetDevTapCreate(char **ifname,
                       const char *tunpath ATTRIBUTE_UNUSED,
                       int *tapfd,
                       size_t tapfdSize,
                       unsigned int flags ATTRIBUTE_UNUSED)
{
    int s;
    struct ifreq ifr;
    int ret = -1;
    char *newifname = NULL;

    if (tapfdSize > 1) {
        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                       _("Multiqueue devices are not supported on this system"));
        goto cleanup;
    }

    /* As FreeBSD determines interface type by name,
     * we have to create 'tap' interface first and
     * then rename it to 'vnet'
     */
    if ((s = virNetDevSetupControl("tap", &ifr)) < 0)
        return -1;

    if (ioctl(s, SIOCIFCREATE2, &ifr) < 0) {
        virReportSystemError(errno, "%s",
                             _("Unable to create tap device"));
        goto cleanup;
    }

    /* In case we were given exact interface name (e.g. 'vnetN'),
     * we just rename to it. If we have format string like
     * 'vnet%d', we need to find the first available name that
     * matches this pattern
     */
    if (strstr(*ifname, "%d") != NULL) {
        size_t i;
        for (i = 0; i <= IF_MAXUNIT; i++) {
            char *newname;
            if (virAsprintf(&newname, *ifname, i) < 0)
                goto cleanup;

            if (virNetDevExists(newname) == 0) {
                newifname = newname;
                break;
            }

            VIR_FREE(newname);
        }
        if (newifname) {
            VIR_FREE(*ifname);
            *ifname = newifname;
        } else {
            virReportError(VIR_ERR_INTERNAL_ERROR,
                           _("Failed to generate new name for interface %s"),
                           ifr.ifr_name);
            goto cleanup;
        }
    }

    if (tapfd) {
        char *dev_path = NULL;
        if (virAsprintf(&dev_path, "/dev/%s", ifr.ifr_name) < 0)
            goto cleanup;

        if ((*tapfd = open(dev_path, O_RDWR)) < 0) {
            virReportSystemError(errno,
                                 _("Unable to open %s"),
                                 dev_path);
            VIR_FREE(dev_path);
            goto cleanup;
        }

        VIR_FREE(dev_path);
    }

    if (virNetDevSetName(ifr.ifr_name, *ifname) == -1)
        goto cleanup;


    ret = 0;
 cleanup:
    VIR_FORCE_CLOSE(s);

    return ret;
}

int virNetDevTapDelete(const char *ifname,
                       const char *tunpath ATTRIBUTE_UNUSED)
{
    int s;
    struct ifreq ifr;
    int ret = -1;

    if ((s = virNetDevSetupControl(ifname, &ifr)) < 0)
        return -1;

    if (ioctl(s, SIOCIFDESTROY, &ifr) < 0) {
        virReportSystemError(errno,
                             _("Unable to remove tap device %s"),
                             ifname);
        goto cleanup;
    }

    ret = 0;
 cleanup:
    VIR_FORCE_CLOSE(s);
    return ret;
}

#else
int virNetDevTapCreate(char **ifname ATTRIBUTE_UNUSED,
                       const char *tunpath ATTRIBUTE_UNUSED,
                       int *tapfd ATTRIBUTE_UNUSED,
                       size_t tapfdSize ATTRIBUTE_UNUSED,
                       unsigned int flags ATTRIBUTE_UNUSED)
{
    virReportSystemError(ENOSYS, "%s",
                         _("Unable to create TAP devices on this platform"));
    return -1;
}
int virNetDevTapDelete(const char *ifname ATTRIBUTE_UNUSED,
                       const char *tunpath ATTRIBUTE_UNUSED)
{
    virReportSystemError(ENOSYS, "%s",
                         _("Unable to delete TAP devices on this platform"));
    return -1;
}
#endif


/**
 * virNetDevTapAttachBridge:
 * @tapname: the tap interface name (or name template)
 * @brname: the bridge name
 * @macaddr: desired MAC address
 * @virtPortProfile: bridge/port specific configuration
 * @virtVlan: vlan tag info
 * @mtu: requested MTU for port (or 0 for "default")
 * @actualMTU: MTU actually set for port (after accounting for bridge's MTU)
 *
 * This attaches an existing tap device (@tapname) to a bridge
 * (@brname).
 *
 * Returns 0 in case of success or -1 on failure
 */
int
virNetDevTapAttachBridge(const char *tapname,
                         const char *brname,
                         const virMacAddr *macaddr,
                         const unsigned char *vmuuid,
                         virNetDevVPortProfilePtr virtPortProfile,
                         virNetDevVlanPtr virtVlan,
                         unsigned int mtu,
                         unsigned int *actualMTU)
{
    /* If an MTU is specified for the new device, set it before
     * attaching the device to the bridge, as it may affect the MTU of
     * the bridge (in particular if it is the first device attached to
     * the bridge, or if it is smaller than the current MTU of the
     * bridge). If MTU isn't specified for the new device (i.e. 0),
     * we need to set the interface MTU to the current MTU of the
     * bridge (to avoid inadvertantly changing the bridge's MTU).
     */
    if (mtu > 0) {
        if (virNetDevSetMTU(tapname, mtu) < 0)
            goto error;
    } else {
        if (virNetDevSetMTUFromDevice(tapname, brname) < 0)
            goto error;
    }
    if (actualMTU) {
        int retMTU = virNetDevGetMTU(tapname);

        if (retMTU < 0)
            goto error;

        *actualMTU = retMTU;
    }


    if (virtPortProfile) {
        if (virtPortProfile->virtPortType == VIR_NETDEV_VPORT_PROFILE_MIDONET) {
            if (virNetDevMidonetBindPort(tapname, virtPortProfile) < 0)
                goto error;
        } else if (virtPortProfile->virtPortType == VIR_NETDEV_VPORT_PROFILE_OPENVSWITCH) {
            if (virNetDevOpenvswitchAddPort(brname, tapname, macaddr, vmuuid,
                                            virtPortProfile, virtVlan) < 0)
                goto error;
        }
    } else {
        if (virNetDevBridgeAddPort(brname, tapname) < 0)
            goto error;
    }

    return 0;

 error:
    return -1;
}


/**
 * virNetDevTapCreateInBridgePort:
 * @brname: the bridge name
 * @ifname: the interface name (or name template)
 * @macaddr: desired MAC address
 * @tunpath: path to the tun device (if NULL, /dev/net/tun is used)
 * @tapfd: array of file descriptor return value for the new tap device
 * @tapfdSize: number of file descriptors in @tapfd
 * @virtPortProfile: bridge/port specific configuration
 * @coalesce: optional coalesce parameters
 * @mtu: requested MTU for port (or 0 for "default")
 * @actualMTU: MTU actually set for port (after accounting for bridge's MTU)
 * @flags: OR of virNetDevTapCreateFlags:

 *   VIR_NETDEV_TAP_CREATE_IFUP
 *     - Bring the interface up
 *   VIR_NETDEV_TAP_CREATE_VNET_HDR
 *     - Enable IFF_VNET_HDR on the tap device
 *   VIR_NETDEV_TAP_CREATE_USE_MAC_FOR_BRIDGE
 *     - Set this interface's MAC as the bridge's MAC address
 *   VIR_NETDEV_TAP_CREATE_PERSIST
 *     - The device will persist after the file descriptor is closed
 *
 * This function creates a new tap device on a bridge. @ifname can be either
 * a fixed name or a name template with '%d' for dynamic name allocation.
 * in either case the final name for the bridge will be stored in @ifname.
 * If the @tapfd parameter is supplied, the open tap device file descriptor
 * will be returned, otherwise the TAP device will be closed. The caller must
 * use virNetDevTapDelete to remove a persistent TAP device when it is no
 * longer needed.
 *
 * Returns 0 in case of success or -1 on failure
 */
int virNetDevTapCreateInBridgePort(const char *brname,
                                   char **ifname,
                                   const virMacAddr *macaddr,
                                   const unsigned char *vmuuid,
                                   const char *tunpath,
                                   int *tapfd,
                                   size_t tapfdSize,
                                   virNetDevVPortProfilePtr virtPortProfile,
                                   virNetDevVlanPtr virtVlan,
                                   virNetDevCoalescePtr coalesce,
                                   unsigned int mtu,
                                   unsigned int *actualMTU,
                                   unsigned int flags)
{
    virMacAddr tapmac;
    char macaddrstr[VIR_MAC_STRING_BUFLEN];
    size_t i;

    if (virNetDevTapCreate(ifname, tunpath, tapfd, tapfdSize, flags) < 0)
        return -1;

    /* We need to set the interface MAC before adding it
     * to the bridge, because the bridge assumes the lowest
     * MAC of all enslaved interfaces & we don't want it
     * seeing the kernel allocate random MAC for the TAP
     * device before we set our static MAC.
     */
    virMacAddrSet(&tapmac, macaddr);
    if (!(flags & VIR_NETDEV_TAP_CREATE_USE_MAC_FOR_BRIDGE)) {
        if (macaddr->addr[0] == 0xFE) {
            /* For normal use, the tap device's MAC address cannot
             * match the MAC address used by the guest. This results
             * in "received packet on vnetX with own address as source
             * address" error logs from the kernel.
             */
            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                           _("Unable to use MAC address starting with "
                             "reserved value 0xFE - '%s' - "),
                           virMacAddrFormat(macaddr, macaddrstr));
            goto error;
        }
        tapmac.addr[0] = 0xFE; /* Discourage bridge from using TAP dev MAC */
    }

    if (virNetDevSetMAC(*ifname, &tapmac) < 0)
        goto error;

    if (virNetDevTapAttachBridge(*ifname, brname, macaddr, vmuuid,
                                 virtPortProfile, virtVlan, mtu, actualMTU) < 0) {
        goto error;
    }

    if (virNetDevSetOnline(*ifname, !!(flags & VIR_NETDEV_TAP_CREATE_IFUP)) < 0)
        goto error;

    if (virNetDevSetCoalesce(*ifname, coalesce, false) < 0)
        goto error;

    return 0;

 error:
    for (i = 0; i < tapfdSize && tapfd[i] >= 0; i++)
        VIR_FORCE_CLOSE(tapfd[i]);

    return -1;
}

/*-------------------- interface stats --------------------*/

/**
 * virNetDevTapInterfaceStats:
 * @ifname: interface
 * @stats: where to store statistics
 * @swapped: whether to swap RX/TX fields
 *
 * Fetch RX/TX statistics for given named interface (@ifname) and
 * store them at @stats. The returned statistics are always from
 * domain POV. Because in some cases this means swapping RX/TX in
 * the stats and in others this means no swapping (consider TAP
 * vs macvtap) caller might choose if the returned stats should
 * be @swapped or not.
 *
 * Returns 0 on success, -1 otherwise (with error reported).
 */
#ifdef __linux__
int
virNetDevTapInterfaceStats(const char *ifname,
                           virDomainInterfaceStatsPtr stats,
                           bool swapped)
{
    int ifname_len;
    FILE *fp;
    char line[256], *colon;

    fp = fopen("/proc/net/dev", "r");
    if (!fp) {
        virReportSystemError(errno, "%s",
                             _("Could not open /proc/net/dev"));
        return -1;
    }

    ifname_len = strlen(ifname);

    while (fgets(line, sizeof(line), fp)) {
        long long dummy;
        long long rx_bytes;
        long long rx_packets;
        long long rx_errs;
        long long rx_drop;
        long long tx_bytes;
        long long tx_packets;
        long long tx_errs;
        long long tx_drop;

        /* The line looks like:
         *   "   eth0:..."
         * Split it at the colon.
         */
        colon = strchr(line, ':');
        if (!colon) continue;
        *colon = '\0';
        if (colon-ifname_len >= line &&
            STREQ(colon-ifname_len, ifname)) {
            if (sscanf(colon+1,
                       "%lld %lld %lld %lld %lld %lld %lld %lld %lld %lld %lld %lld %lld %lld %lld %lld",
                       &rx_bytes, &rx_packets, &rx_errs, &rx_drop,
                       &dummy, &dummy, &dummy, &dummy,
                       &tx_bytes, &tx_packets, &tx_errs, &tx_drop,
                       &dummy, &dummy, &dummy, &dummy) != 16)
                continue;

            if (swapped) {
                stats->rx_bytes = tx_bytes;
                stats->rx_packets = tx_packets;
                stats->rx_errs = tx_errs;
                stats->rx_drop = tx_drop;
                stats->tx_bytes = rx_bytes;
                stats->tx_packets = rx_packets;
                stats->tx_errs = rx_errs;
                stats->tx_drop = rx_drop;
            } else {
                stats->rx_bytes = rx_bytes;
                stats->rx_packets = rx_packets;
                stats->rx_errs = rx_errs;
                stats->rx_drop = rx_drop;
                stats->tx_bytes = tx_bytes;
                stats->tx_packets = tx_packets;
                stats->tx_errs = tx_errs;
                stats->tx_drop = tx_drop;
            }

            VIR_FORCE_FCLOSE(fp);
            return 0;
        }
    }
    VIR_FORCE_FCLOSE(fp);

    virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                   _("/proc/net/dev: Interface not found"));
    return -1;
}
#elif defined(HAVE_GETIFADDRS) && defined(AF_LINK)
int
virNetDevTapInterfaceStats(const char *ifname,
                           virDomainInterfaceStatsPtr stats,
                           bool swapped)
{
    struct ifaddrs *ifap, *ifa;
    struct if_data *ifd;
    int ret = -1;

    if (getifaddrs(&ifap) < 0) {
        virReportSystemError(errno, "%s",
                             _("Could not get interface list"));
        return -1;
    }

    for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
        if (!ifa->ifa_addr)
            continue;

        if (ifa->ifa_addr->sa_family != AF_LINK)
            continue;

        if (STREQ(ifa->ifa_name, ifname)) {
            ifd = (struct if_data *)ifa->ifa_data;
            if (swapped) {
                stats->tx_bytes = ifd->ifi_ibytes;
                stats->tx_packets = ifd->ifi_ipackets;
                stats->tx_errs = ifd->ifi_ierrors;
                stats->tx_drop = ifd->ifi_iqdrops;
                stats->rx_bytes = ifd->ifi_obytes;
                stats->rx_packets = ifd->ifi_opackets;
                stats->rx_errs = ifd->ifi_oerrors;
# ifdef HAVE_STRUCT_IF_DATA_IFI_OQDROPS
                stats->rx_drop = ifd->ifi_oqdrops;
# else
                stats->rx_drop = 0;
# endif
            } else {
                stats->tx_bytes = ifd->ifi_obytes;
                stats->tx_packets = ifd->ifi_opackets;
                stats->tx_errs = ifd->ifi_oerrors;
# ifdef HAVE_STRUCT_IF_DATA_IFI_OQDROPS
                stats->tx_drop = ifd->ifi_oqdrops;
# else
                stats->tx_drop = 0;
# endif
                stats->rx_bytes = ifd->ifi_ibytes;
                stats->rx_packets = ifd->ifi_ipackets;
                stats->rx_errs = ifd->ifi_ierrors;
                stats->rx_drop = ifd->ifi_iqdrops;
            }

            ret = 0;
            break;
        }
    }

    if (ret < 0)
        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                       _("Interface not found"));

    freeifaddrs(ifap);
    return ret;
}
#else
int
virNetDevTapInterfaceStats(const char *ifname ATTRIBUTE_UNUSED,
                           virDomainInterfaceStatsPtr stats ATTRIBUTE_UNUSED,
                           bool swapped ATTRIBUTE_UNUSED)
{
    virReportError(VIR_ERR_OPERATION_INVALID, "%s",
                   _("interface stats not implemented on this platform"));
    return -1;
}

#endif /* __linux__ */