interface.c

/*
 * interface.c: interface support functions
 *
 * Copyright (C) 2011 Red Hat, Inc.
 * Copyright (C) 2010 IBM Corp.
 * Copyright (C) 2010 Stefan Berger
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307  USA
 *
 * chgIfaceFlags originated from bridge.c
 *
 * Author: Stefan Berger <stefanb@us.ibm.com>
 */

#include <config.h>

#include <sys/socket.h>
#include <sys/ioctl.h>
#include <fcntl.h>
#include <netinet/in.h>

#ifdef __linux__
# include <linux/if.h>
# include <linux/sockios.h>
# include <linux/if_vlan.h>
#endif

#include "internal.h"

#include "util.h"
#include "interface.h"
#include "virterror_internal.h"
#include "virfile.h"
#include "memory.h"
#include "netlink.h"

#define VIR_FROM_THIS VIR_FROM_NET

#define ifaceError(code, ...) \
        virReportErrorHelper(VIR_FROM_NET, code, __FILE__, \
                             __FUNCTION__, __LINE__, __VA_ARGS__)

#if __linux__
static int
getFlags(int fd, const char *ifname, struct ifreq *ifr) {

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

    if (virStrncpy(ifr->ifr_name,
                   ifname, strlen(ifname), sizeof(ifr->ifr_name)) == NULL)
        return -ENODEV;

    if (ioctl(fd, SIOCGIFFLAGS, ifr) < 0)
        return -errno;

    return 0;
}


/**
 * ifaceGetFlags
 *
 * @ifname : name of the interface
 * @flags : pointer to short holding the flags on success
 *
 * Get the flags of the interface. Returns 0 on success, -errno on failure.
 */
int
ifaceGetFlags(const char *ifname, short *flags) {
    struct ifreq ifr;
    int rc;
    int fd = socket(PF_PACKET, SOCK_DGRAM, 0);

    if (fd < 0)
        return -errno;

    rc = getFlags(fd, ifname, &ifr);

    *flags = ifr.ifr_flags;

    VIR_FORCE_CLOSE(fd);

    return rc;
}


int
ifaceIsUp(const char *ifname, bool *up) {
    short flags = 0;
    int rc = ifaceGetFlags(ifname, &flags);

    if (rc < 0)
        return rc;

    *up = ((flags & IFF_UP) == IFF_UP);

    return 0;
}
#else

/* Note: Showstopper on cygwin is only missing PF_PACKET */

int

ifaceGetFlags(const char *ifname ATTRIBUTE_UNUSED,
              short *flags ATTRIBUTE_UNUSED) {
    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("ifaceGetFlags is not supported on non-linux platforms"));
    return -ENOSYS;
}

int
ifaceIsUp(const char *ifname ATTRIBUTE_UNUSED,
          bool *up ATTRIBUTE_UNUSED) {

    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("ifaceIsUp is not supported on non-linux platforms"));
    return -ENOSYS;
}

#endif /* __linux__ */

/*
 * chgIfaceFlags: Change flags on an interface
 *
 * @ifname : name of the interface
 * @flagclear : the flags to clear
 * @flagset : the flags to set
 *
 * The new flags of the interface will be calculated as
 * flagmask = (~0 ^ flagclear)
 * newflags = (curflags & flagmask) | flagset;
 *
 * Returns 0 on success, -errno on failure.
 */
#ifdef __linux__
static int chgIfaceFlags(const char *ifname, short flagclear, short flagset) {
    struct ifreq ifr;
    int rc = 0;
    short flags;
    short flagmask = (~0 ^ flagclear);
    int fd = socket(PF_PACKET, SOCK_DGRAM, 0);

    if (fd < 0)
        return -errno;

    rc = getFlags(fd, ifname, &ifr);
    if (rc < 0)
        goto cleanup;

    flags = (ifr.ifr_flags & flagmask) | flagset;

    if (ifr.ifr_flags != flags) {
        ifr.ifr_flags = flags;

        if (ioctl(fd, SIOCSIFFLAGS, &ifr) < 0)
            rc = -errno;
    }

cleanup:
    VIR_FORCE_CLOSE(fd);
    return rc;
}


/*
 * ifaceCtrl
 * @name: name of the interface
 * @up: true (1) for up, false (0) for down
 *
 * Function to control if an interface is activated (up, 1) or not (down, 0)
 *
 * Returns 0 on success, -errno on failure.
 */
int
ifaceCtrl(const char *name, bool up)
{
    return chgIfaceFlags(name,
                         (up) ? 0      : IFF_UP,
                         (up) ? IFF_UP : 0);
}

#else

int
ifaceCtrl(const char *name ATTRIBUTE_UNUSED, bool up ATTRIBUTE_UNUSED)
{
    return -ENOSYS;
}

#endif /* __linux__ */

/**
 * ifaceCheck
 *
 * @reportError: whether to report errors or keep silent
 * @ifname: Name of the interface
 * @macaddr: expected MAC address of the interface; not checked if NULL
 * @ifindex: expected index of the interface; not checked if '-1'
 *
 * Determine whether a given interface is still available. If so,
 * it must have the given MAC address and if an interface index is
 * passed, it must also match the interface index.
 *
 * Returns 0 on success, -errno on failure.
 *   -ENODEV : if interface with given name does not exist or its interface
 *             index is different than the one passed
 *   -EINVAL : if interface name is invalid (too long)
 */
#ifdef __linux__
int
ifaceCheck(bool reportError, const char *ifname,
           const unsigned char *macaddr, int ifindex)
{
    struct ifreq ifr;
    int fd = -1;
    int rc = 0;
    int idx;

    if (macaddr != NULL) {
        fd = socket(PF_PACKET, SOCK_DGRAM, 0);
        if (fd < 0)
            return -errno;

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

        if (virStrncpy(ifr.ifr_name,
                       ifname, strlen(ifname), sizeof(ifr.ifr_name)) == NULL) {
            if (reportError)
                ifaceError(VIR_ERR_INTERNAL_ERROR,
                           _("invalid interface name %s"),
                           ifname);
            rc = -EINVAL;
            goto cleanup;
        }

        if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0) {
            if (reportError)
                ifaceError(VIR_ERR_INTERNAL_ERROR,
                           _("coud not get MAC address of interface %s"),
                           ifname);
            rc = -errno;
            goto cleanup;
        }

        if (memcmp(&ifr.ifr_hwaddr.sa_data, macaddr, VIR_MAC_BUFLEN) != 0) {
            rc = -ENODEV;
            goto cleanup;
        }
    }

    if (ifindex != -1) {
        rc = ifaceGetIndex(reportError, ifname, &idx);
        if (rc == 0 && idx != ifindex)
            rc = -ENODEV;
    }

 cleanup:
    VIR_FORCE_CLOSE(fd);

    return rc;
}

#else

int
ifaceCheck(bool reportError ATTRIBUTE_UNUSED,
           const char *ifname ATTRIBUTE_UNUSED,
           const unsigned char *macaddr ATTRIBUTE_UNUSED,
           int ifindex ATTRIBUTE_UNUSED)
{
    return -ENOSYS;
}

#endif /* __linux__ */


/**
 * ifaceGetIndex
 *
 * @reportError: whether to report errors or keep silent
 * @ifname : Name of the interface whose index is to be found
 * @ifindex: Pointer to int where the index will be written into
 *
 * Get the index of an interface given its name.
 *
 * Returns 0 on success, -errno on failure.
 *   -ENODEV : if interface with given name does not exist
 *   -EINVAL : if interface name is invalid (too long)
 */
#ifdef __linux__
int
ifaceGetIndex(bool reportError, const char *ifname, int *ifindex)
{
    int rc = 0;
    struct ifreq ifreq;
    int fd = socket(PF_PACKET, SOCK_DGRAM, 0);

    if (fd < 0)
        return -errno;

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

    if (virStrncpy(ifreq.ifr_name, ifname, strlen(ifname),
                   sizeof(ifreq.ifr_name)) == NULL) {
        if (reportError)
            ifaceError(VIR_ERR_INTERNAL_ERROR,
                       _("invalid interface name %s"),
                       ifname);
        rc = -EINVAL;
        goto cleanup;
    }

    if (ioctl(fd, SIOCGIFINDEX, &ifreq) >= 0)
        *ifindex = ifreq.ifr_ifindex;
    else {
        if (reportError)
            ifaceError(VIR_ERR_INTERNAL_ERROR,
                       _("interface %s does not exist"),
                       ifname);
        rc = -ENODEV;
    }

cleanup:
    VIR_FORCE_CLOSE(fd);

    return rc;
}

#else

int
ifaceGetIndex(bool reportError,
              const char *ifname ATTRIBUTE_UNUSED,
              int *ifindex ATTRIBUTE_UNUSED)
{
    if (reportError) {
        ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
                   _("ifaceGetIndex is not supported on non-linux platforms"));
    }

    return -ENOSYS;
}

#endif /* __linux__ */

#ifdef __linux__
int
ifaceGetVlanID(const char *vlanifname, int *vlanid) {
    struct vlan_ioctl_args vlanargs = {
      .cmd = GET_VLAN_VID_CMD,
    };
    int rc = 0;
    int fd = socket(PF_PACKET, SOCK_DGRAM, 0);

    if (fd < 0)
        return -errno;

    if (virStrcpyStatic(vlanargs.device1, vlanifname) == NULL) {
        rc = -EINVAL;
        goto cleanup;
    }

    if (ioctl(fd, SIOCGIFVLAN, &vlanargs) != 0) {
        rc = -errno;
        goto cleanup;
    }

    *vlanid = vlanargs.u.VID;

 cleanup:
    VIR_FORCE_CLOSE(fd);

    return rc;
}

#else

int
ifaceGetVlanID(const char *vlanifname ATTRIBUTE_UNUSED,
               int *vlanid ATTRIBUTE_UNUSED) {

    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("ifaceGetVlanID is not supported on non-linux platforms"));

    return -ENOSYS;
}
#endif /* __linux__ */

/**
 * ifaceGetMacAddress:
 * @ifname: interface name to set MTU for
 * @macaddr: MAC address (VIR_MAC_BUFLEN in size)
 *
 * This function gets the @macaddr for a given interface @ifname.
 *
 * Returns 0 on success, -errno on failure.
 */
#ifdef __linux__
int
ifaceGetMacAddress(const char *ifname,
                   unsigned char *macaddr)
{
    struct ifreq ifr;
    int fd;
    int rc = 0;

    if (!ifname)
        return -EINVAL;

    fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd < 0)
        return -errno;

    memset(&ifr, 0, sizeof(struct ifreq));
    if (virStrcpyStatic(ifr.ifr_name, ifname) == NULL) {
        rc = -EINVAL;
        goto cleanup;
    }

    if (ioctl(fd, SIOCGIFHWADDR, (char *)&ifr) != 0) {
        rc = -errno;
        goto cleanup;
    }

    memcpy(macaddr, ifr.ifr_ifru.ifru_hwaddr.sa_data, VIR_MAC_BUFLEN);

cleanup:
    VIR_FORCE_CLOSE(fd);
    return rc;
}

#else

int
ifaceGetMacAddress(const char *ifname ATTRIBUTE_UNUSED,
                   unsigned char *macaddr ATTRIBUTE_UNUSED)
{
    return -ENOSYS;
}

#endif /* __linux__ */

/**
 * ifaceSetMacAddress:
 * @ifname: interface name to set MTU for
 * @macaddr: MAC address (VIR_MAC_BUFLEN in size)
 *
 * This function sets the @macaddr for a given interface @ifname. This
 * gets rid of the kernel's automatically assigned random MAC.
 *
 * Returns 0 on success, -errno on failure.
 */
#ifdef __linux__
int
ifaceSetMacAddress(const char *ifname,
                   const unsigned char *macaddr)
{
    struct ifreq ifr;
    int fd;
    int rc = 0;

    if (!ifname)
        return -EINVAL;

    fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd < 0)
        return -errno;

    memset(&ifr, 0, sizeof(struct ifreq));
    if (virStrcpyStatic(ifr.ifr_name, ifname) == NULL) {
        rc = -EINVAL;
        goto cleanup;
    }

    /* To fill ifr.ifr_hdaddr.sa_family field */
    if (ioctl(fd, SIOCGIFHWADDR, &ifr) != 0) {
        rc = -errno;
        goto cleanup;
    }

    memcpy(ifr.ifr_hwaddr.sa_data, macaddr, VIR_MAC_BUFLEN);

    rc = ioctl(fd, SIOCSIFHWADDR, &ifr) == 0 ? 0 : -errno;

cleanup:
    VIR_FORCE_CLOSE(fd);
    return rc;
}

#else

int
ifaceSetMacAddress(const char *ifname ATTRIBUTE_UNUSED,
                   const unsigned char *macaddr ATTRIBUTE_UNUSED)
{
    return -ENOSYS;
}

#endif /* __linux__ */


/**
 * ifaceGetIPAddress:
 * @ifname: name of the interface whose IP address we want
 * @macaddr: MAC address (VIR_MAC_BUFLEN in size)
 *
 * This function gets the @macaddr for a given interface @ifname.
 *
 * Returns 0 on success, -errno on failure.
 */
#ifdef __linux__
int
ifaceGetIPAddress(const char *ifname,
                  virSocketAddrPtr addr)
{
    struct ifreq ifr;
    int fd;
    int rc = 0;

    if (!ifname || !addr)
        return -EINVAL;

    memset (addr, 0, sizeof(*addr));
    addr->data.stor.ss_family = AF_UNSPEC;

    fd = socket(AF_INET, SOCK_STREAM, 0);
    if (fd < 0)
        return -errno;

    memset(&ifr, 0, sizeof(struct ifreq));
    if (virStrcpyStatic(ifr.ifr_name, ifname) == NULL) {
        rc = -EINVAL;
        goto err_exit;
    }

    if (ioctl(fd, SIOCGIFADDR, (char *)&ifr) != 0) {
        rc = -errno;
        goto err_exit;
    }

    addr->data.stor.ss_family = AF_INET;
    addr->len = sizeof(addr->data.inet4);
    memcpy(&addr->data.inet4, &ifr.ifr_addr, addr->len);

err_exit:
    VIR_FORCE_CLOSE(fd);
    return rc;
}

#else

int
ifaceGetIPAddress(const char *ifname ATTRIBUTE_UNUSED,
                  virSocketAddrPtr addr ATTRIBUTE_UNUSED)
{
    return -ENOSYS;
}

#endif /* __linux__ */

/**
 * ifaceLinkAdd
 *
 * @type: The type of device, i.e., "macvtap"
 * @macaddress: The MAC address of the device
 * @macaddrsize: The size of the MAC address, typically '6'
 * @ifname: The name the interface is supposed to have; optional parameter
 * @srcdev: The name of the 'link' device
 * @macvlan_mode: The macvlan mode to use
 * @retry: Pointer to integer that will be '1' upon return if an interface
 *         with the same name already exists and it is worth to try
 *         again with a different name
 *
 * Create a macvtap device with the given properties.
 *
 * Returns 0 on success, -1 on fatal error.
 */
#if defined(__linux__) && WITH_MACVTAP
int
ifaceMacvtapLinkAdd(const char *type,
                    const unsigned char *macaddress, int macaddrsize,
                    const char *ifname,
                    const char *srcdev,
                    uint32_t macvlan_mode,
                    int *retry)
{
    int rc = 0;
    struct nlmsghdr *resp;
    struct nlmsgerr *err;
    struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
    int ifindex;
    unsigned char *recvbuf = NULL;
    unsigned int recvbuflen;
    struct nl_msg *nl_msg;
    struct nlattr *linkinfo, *info_data;

    if (ifaceGetIndex(true, srcdev, &ifindex) < 0)
        return -1;

    *retry = 0;

    nl_msg = nlmsg_alloc_simple(RTM_NEWLINK,
                                NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL);
    if (!nl_msg) {
        virReportOOMError();
        return -1;
    }

    if (nlmsg_append(nl_msg,  &ifinfo, sizeof(ifinfo), NLMSG_ALIGNTO) < 0)
        goto buffer_too_small;

    if (nla_put_u32(nl_msg, IFLA_LINK, ifindex) < 0)
        goto buffer_too_small;

    if (nla_put(nl_msg, IFLA_ADDRESS, macaddrsize, macaddress) < 0)
        goto buffer_too_small;

    if (ifname &&
        nla_put(nl_msg, IFLA_IFNAME, strlen(ifname)+1, ifname) < 0)
        goto buffer_too_small;

    if (!(linkinfo = nla_nest_start(nl_msg, IFLA_LINKINFO)))
        goto buffer_too_small;

    if (nla_put(nl_msg, IFLA_INFO_KIND, strlen(type), type) < 0)
        goto buffer_too_small;

    if (macvlan_mode > 0) {
        if (!(info_data = nla_nest_start(nl_msg, IFLA_INFO_DATA)))
            goto buffer_too_small;

        if (nla_put(nl_msg, IFLA_MACVLAN_MODE, sizeof(macvlan_mode),
                    &macvlan_mode) < 0)
            goto buffer_too_small;

        nla_nest_end(nl_msg, info_data);
    }

    nla_nest_end(nl_msg, linkinfo);

    if (nlComm(nl_msg, &recvbuf, &recvbuflen, 0) < 0) {
        rc = -1;
        goto cleanup;
    }

    if (recvbuflen < NLMSG_LENGTH(0) || recvbuf == NULL)
        goto malformed_resp;

    resp = (struct nlmsghdr *)recvbuf;

    switch (resp->nlmsg_type) {
    case NLMSG_ERROR:
        err = (struct nlmsgerr *)NLMSG_DATA(resp);
        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
            goto malformed_resp;

        switch (err->error) {

        case 0:
            break;

        case -EEXIST:
            *retry = 1;
            rc = -1;
            break;

        default:
            virReportSystemError(-err->error,
                                 _("error creating %s type of interface"),
                                 type);
            rc = -1;
        }
        break;

    case NLMSG_DONE:
        break;

    default:
        goto malformed_resp;
    }

cleanup:
    nlmsg_free(nl_msg);

    VIR_FREE(recvbuf);

    return rc;

malformed_resp:
    nlmsg_free(nl_msg);

    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("malformed netlink response message"));
    VIR_FREE(recvbuf);
    return -1;

buffer_too_small:
    nlmsg_free(nl_msg);

    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("allocated netlink buffer is too small"));
    return -1;
}

#else

int
ifaceMacvtapLinkAdd(const char *type ATTRIBUTE_UNUSED,
                    const unsigned char *macaddress ATTRIBUTE_UNUSED,
                    int macaddrsize ATTRIBUTE_UNUSED,
                    const char *ifname ATTRIBUTE_UNUSED,
                    const char *srcdev ATTRIBUTE_UNUSED,
                    uint32_t macvlan_mode ATTRIBUTE_UNUSED,
                    int *retry ATTRIBUTE_UNUSED)
{
    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
# if defined(__linux__) && !WITH_MACVTAP
               _("ifaceMacvtapLinkAdd is not supported since the include "
                 "files were too old"));
# else
               _("ifaceMacvtapLinkAdd is not supported on non-linux "
                 "platforms"));
# endif

    return -1;
}

#endif


/**
 * ifaceLinkDel
 *
 * @ifname: Name of the interface
 *
 * Tear down an interface with the given name.
 *
 * Returns 0 on success, -1 on fatal error.
 */
#if defined( __linux__) && WITH_MACVTAP
int
ifaceLinkDel(const char *ifname)
{
    int rc = 0;
    struct nlmsghdr *resp;
    struct nlmsgerr *err;
    struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
    unsigned char *recvbuf = NULL;
    unsigned int recvbuflen;
    struct nl_msg *nl_msg;

    nl_msg = nlmsg_alloc_simple(RTM_DELLINK,
                                NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL);
    if (!nl_msg) {
        virReportOOMError();
        return -1;
    }

    if (nlmsg_append(nl_msg,  &ifinfo, sizeof(ifinfo), NLMSG_ALIGNTO) < 0)
        goto buffer_too_small;

    if (nla_put(nl_msg, IFLA_IFNAME, strlen(ifname)+1, ifname) < 0)
        goto buffer_too_small;

    if (nlComm(nl_msg, &recvbuf, &recvbuflen, 0) < 0) {
        rc = -1;
        goto cleanup;
    }

    if (recvbuflen < NLMSG_LENGTH(0) || recvbuf == NULL)
        goto malformed_resp;

    resp = (struct nlmsghdr *)recvbuf;

    switch (resp->nlmsg_type) {
    case NLMSG_ERROR:
        err = (struct nlmsgerr *)NLMSG_DATA(resp);
        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
            goto malformed_resp;

        if (err->error) {
            virReportSystemError(-err->error,
                                 _("error destroying %s interface"),
                                 ifname);
            rc = -1;
        }
        break;

    case NLMSG_DONE:
        break;

    default:
        goto malformed_resp;
    }

cleanup:
    nlmsg_free(nl_msg);

    VIR_FREE(recvbuf);

    return rc;

malformed_resp:
    nlmsg_free(nl_msg);

    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("malformed netlink response message"));
    VIR_FREE(recvbuf);
    return -1;

buffer_too_small:
    nlmsg_free(nl_msg);

    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("allocated netlink buffer is too small"));
    return -1;
}

#else

int
ifaceLinkDel(const char *ifname ATTRIBUTE_UNUSED)
{
    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
# if defined(__linux__) && !WITH_MACVTAP
               _("ifaceLinkDel is not supported since the include files "
                 "were too old"));
# else
               _("ifaceLinkDel is not supported on non-linux platforms"));
# endif
    return -1;
}

#endif


#if defined(__linux__) && defined(IFLA_PORT_MAX)

static struct nla_policy ifla_policy[IFLA_MAX + 1] =
{
  [IFLA_VF_PORTS] = { .type = NLA_NESTED },
};

/**
 * ifaceMacvtapLinkDump
 *
 * @nltarget_kernel: whether to send the message to the kernel or another
 *                   process
 * @ifname: The name of the interface; only use if ifindex < 0
 * @ifindex: The interface index; may be < 0 if ifname is given
 * @nlattr: pointer to a pointer of netlink attributes that will contain
 *          the results
 * @recvbuf: Pointer to the buffer holding the returned netlink response
 *           message; free it, once not needed anymore
 * @getPidFunc: Pointer to a function that will be invoked if the kernel
 *              is not the target of the netlink message but it is to be
 *              sent to another process.
 *
 * Get information about an interface given its name or index.
 *
 * Returns 0 on success, -1 on fatal error.
 */
int
ifaceMacvtapLinkDump(bool nltarget_kernel, const char *ifname, int ifindex,
                     struct nlattr **tb, unsigned char **recvbuf,
                     uint32_t (*getPidFunc)(void))
{
    int rc = 0;
    struct nlmsghdr *resp;
    struct nlmsgerr *err;
    struct ifinfomsg ifinfo = {
        .ifi_family = AF_UNSPEC,
        .ifi_index  = ifindex
    };
    unsigned int recvbuflen;
    uint32_t pid = 0;
    struct nl_msg *nl_msg;

    *recvbuf = NULL;

    nl_msg = nlmsg_alloc_simple(RTM_GETLINK, NLM_F_REQUEST);
    if (!nl_msg) {
        virReportOOMError();
        return -1;
    }

    if (nlmsg_append(nl_msg,  &ifinfo, sizeof(ifinfo), NLMSG_ALIGNTO) < 0)
        goto buffer_too_small;

    if (ifindex < 0 && ifname) {
        if (nla_put(nl_msg, IFLA_IFNAME, strlen(ifname)+1, ifname) < 0)
            goto buffer_too_small;
    }

    if (!nltarget_kernel) {
        pid = getPidFunc();
        if (pid == 0) {
            rc = -1;
            goto cleanup;
        }
    }

    if (nlComm(nl_msg, recvbuf, &recvbuflen, pid) < 0) {
        rc = -1;
        goto cleanup;
    }

    if (recvbuflen < NLMSG_LENGTH(0) || *recvbuf == NULL)
        goto malformed_resp;

    resp = (struct nlmsghdr *)*recvbuf;

    switch (resp->nlmsg_type) {
    case NLMSG_ERROR:
        err = (struct nlmsgerr *)NLMSG_DATA(resp);
        if (resp->nlmsg_len < NLMSG_LENGTH(sizeof(*err)))
            goto malformed_resp;

        if (err->error) {
            virReportSystemError(-err->error,
                                 _("error dumping %s (%d) interface"),
                                 ifname, ifindex);
            rc = -1;
        }
        break;

    case GENL_ID_CTRL:
    case NLMSG_DONE:
        if (nlmsg_parse(resp, sizeof(struct ifinfomsg),
                        tb, IFLA_MAX, ifla_policy)) {
            goto malformed_resp;
        }
        break;

    default:
        goto malformed_resp;
    }

    if (rc != 0)
        VIR_FREE(*recvbuf);

cleanup:
    nlmsg_free(nl_msg);

    return rc;

malformed_resp:
    nlmsg_free(nl_msg);

    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("malformed netlink response message"));
    VIR_FREE(*recvbuf);
    return -1;

buffer_too_small:
    nlmsg_free(nl_msg);

    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
               _("allocated netlink buffer is too small"));
    return -1;
}

#else

int
ifaceMacvtapLinkDump(bool nltarget_kernel ATTRIBUTE_UNUSED,
                     const char *ifname ATTRIBUTE_UNUSED,
                     int ifindex ATTRIBUTE_UNUSED,
                     struct nlattr **tb ATTRIBUTE_UNUSED,
                     unsigned char **recvbuf ATTRIBUTE_UNUSED,
                     uint32_t (*getPidFunc)(void) ATTRIBUTE_UNUSED)
{
    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
# if defined(__linux__) && !defined(IFLA_PORT_MAX)
               _("ifaceMacvtapLinkDump is not supported since the include "
                 "files were too old"));
# else
               _("ifaceMacvtapLinkDump is not supported on non-linux "
                 "platforms"));
# endif

    return -1;
}

#endif


/**
 * ifaceGetNthParent
 *
 * @ifindex : the index of the interface or -1 if ifname is given
 * @ifname : the name of the interface; ignored if ifindex is valid
 * @nthParent : the nth parent interface to get
 * @parent_ifindex : pointer to int
 * @parent_ifname : pointer to buffer of size IFNAMSIZ
 * @nth : the nth parent that is actually returned; if for example eth0.100
 *        was given and the 100th parent is to be returned, then eth0 will
 *        most likely be returned with nth set to 1 since the chain does
 *        not have more interfaces
 *
 * Get the nth parent interface of the given interface. 0 is the interface
 * itself.
 *
 * Return 0 on success, != 0 otherwise
 */
#if defined(__linux__) && WITH_MACVTAP
int
ifaceGetNthParent(int ifindex, const char *ifname, unsigned int nthParent,
                  int *parent_ifindex, char *parent_ifname,
                  unsigned int *nth)
{
    int rc;
    struct nlattr *tb[IFLA_MAX + 1] = { NULL, };
    unsigned char *recvbuf = NULL;
    bool end = false;
    unsigned int i = 0;

    *nth = 0;

    if (ifindex <= 0 && ifaceGetIndex(true, ifname, &ifindex) < 0)
        return -1;

    while (!end && i <= nthParent) {
        rc = ifaceMacvtapLinkDump(true, ifname, ifindex, tb, &recvbuf, NULL);
        if (rc)
            break;

        if (tb[IFLA_IFNAME]) {
            if (!virStrcpy(parent_ifname, (char*)RTA_DATA(tb[IFLA_IFNAME]),
                           IFNAMSIZ)) {
                ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
                           _("buffer for root interface name is too small"));
                VIR_FREE(recvbuf);
                return -1;
            }
            *parent_ifindex = ifindex;
        }

        if (tb[IFLA_LINK]) {
            ifindex = *(int *)RTA_DATA(tb[IFLA_LINK]);
            ifname = NULL;
        } else
            end = true;

        VIR_FREE(recvbuf);

        i++;
    }

    *nth = i - 1;

    return rc;
}

#else

int
ifaceGetNthParent(int ifindex ATTRIBUTE_UNUSED,
                  const char *ifname ATTRIBUTE_UNUSED,
                  unsigned int nthParent ATTRIBUTE_UNUSED,
                  int *parent_ifindex ATTRIBUTE_UNUSED,
                  char *parent_ifname ATTRIBUTE_UNUSED,
                  unsigned int *nth ATTRIBUTE_UNUSED)
{
    ifaceError(VIR_ERR_INTERNAL_ERROR, "%s",
# if defined(__linux__) && !WITH_MACVTAP
               _("ifaceGetNthParent is not supported since the include files "
                 "were too old"));
# else
               _("ifaceGetNthParent is not supported on non-linux platforms"));
# endif
    return -1;
}

#endif

/**
 * ifaceReplaceMacAddress:
 * @macaddress: new MAC address for interface
 * @linkdev: name of interface
 * @stateDir: directory to store old MAC address
 *
 * Returns 0 on success, -errno on failure.
 *
 */
int
ifaceReplaceMacAddress(const unsigned char *macaddress,
                       const char *linkdev,
                       const char *stateDir)
{
    unsigned char oldmac[6];
    int rc;

    rc = ifaceGetMacAddress(linkdev, oldmac);

    if (rc < 0) {
        virReportSystemError(rc,
                             _("Getting MAC address from '%s' "
                               "to '%02x:%02x:%02x:%02x:%02x:%02x' failed."),
                             linkdev,
                             oldmac[0], oldmac[1], oldmac[2],
                             oldmac[3], oldmac[4], oldmac[5]);
    } else {
        char *path = NULL;
        char macstr[VIR_MAC_STRING_BUFLEN];

        if (virAsprintf(&path, "%s/%s",
                        stateDir,
                        linkdev) < 0) {
            virReportOOMError();
            return -errno;
        }
        virFormatMacAddr(oldmac, macstr);
        if (virFileWriteStr(path, macstr, O_CREAT|O_TRUNC|O_WRONLY) < 0) {
            virReportSystemError(errno, _("Unable to preserve mac for %s"),
                                 linkdev);
            return -errno;
        }
    }

    rc = ifaceSetMacAddress(linkdev, macaddress);
    if (rc < 0) {
        virReportSystemError(rc,
                             _("Setting MAC address on  '%s' to "
                               "'%02x:%02x:%02x:%02x:%02x:%02x' failed."),
                             linkdev,
                             macaddress[0], macaddress[1], macaddress[2],
                             macaddress[3], macaddress[4], macaddress[5]);
    }

    return rc;
}

/**
 * ifaceRestoreMacAddress:
 * @linkdev: name of interface
 * @stateDir: directory containing old MAC address
 *
 * Returns 0 on success, -errno on failure.
 *
 */
int
ifaceRestoreMacAddress(const char *linkdev,
                       const char *stateDir)
{
    int rc;
    char *oldmacname = NULL;
    char *macstr = NULL;
    char *path = NULL;
    unsigned char oldmac[6];

    if (virAsprintf(&path, "%s/%s",
                    stateDir,
                    linkdev) < 0) {
        virReportOOMError();
        return -errno;
    }

    if (virFileReadAll(path, VIR_MAC_STRING_BUFLEN, &macstr) < 0) {
        return -errno;
    }

    if (virParseMacAddr(macstr, &oldmac[0]) != 0) {
        ifaceError(VIR_ERR_INTERNAL_ERROR,
                   _("Cannot parse MAC address from '%s'"),
                   oldmacname);
        VIR_FREE(macstr);
        return -EINVAL;
    }

    /*reset mac and remove file-ignore results*/
    rc = ifaceSetMacAddress(linkdev, oldmac);
    if (rc < 0) {
        virReportSystemError(rc,
                             _("Setting MAC address on  '%s' to "
                               "'%02x:%02x:%02x:%02x:%02x:%02x' failed."),
                             linkdev,
                             oldmac[0], oldmac[1], oldmac[2],
                             oldmac[3], oldmac[4], oldmac[5]);
    }
    ignore_value(unlink(path));
    VIR_FREE(macstr);

    return rc;
}