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[libvirt] [PATCH 4/5] macvtap support for libvirt -- helper code



This part adds the helper code to setup and tear down macvtap devices
using direct communication with the device driver via netlink sockets.
The rather short messages received from the netlink layer are now written 
into a dynamically allocated buffer.

Signed-off-by: Stefan Berger <stefanb us ibm com>



Index: libvirt-macvtap/src/util/macvtap.h
===================================================================
--- /dev/null
+++ libvirt-macvtap/src/util/macvtap.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2010 IBM Corporation
+ *
+ * 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
+ *
+ * Authors:
+ *     Stefan Berger <stefanb us ibm com>
+ */
+
+#ifndef __UTIL_MACVTAP_H__
+#define __UTIL_MACVTAP_H__
+
+#include <config.h>
+
+#if defined(WITH_MACVTAP)
+
+#include "internal.h"
+
+int openMacvtapTap(virConnectPtr conn,
+                   const char *ifname,
+                   const unsigned char *macaddress,
+                   const char *linkdev,
+                   int mode,
+                   char **res_ifname);
+
+int delMacvtapByMACAddress(const unsigned char *macaddress,
+                           int *hasBusyDev);
+
+#endif /* WITH_MACVTAP */
+
+#define MACVTAP_MODE_PRIVATE_STR  "private"
+#define MACVTAP_MODE_VEPA_STR     "vepa"
+#define MACVTAP_MODE_BRIDGE_STR   "bridge"
+
+
+#endif /* __UTIL_MACVTAP_H__ */
Index: libvirt-macvtap/src/util/macvtap.c
===================================================================
--- /dev/null
+++ libvirt-macvtap/src/util/macvtap.c
@@ -0,0 +1,800 @@
+/*
+ * Copyright (C) 2010 IBM Corporation
+ *
+ * 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
+ *
+ * Authors:
+ *     Stefan Berger <stefanb us ibm com>
+ *
+ * Notes:
+ * netlink: http://lovezutto.googlepages.com/netlink.pdf
+ *          iproute2 package
+ *
+ */
+
+#include <config.h>
+
+#if defined(WITH_MACVTAP)
+
+#include <stdio.h>
+#include <errno.h>
+#include <ctype.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <sys/socket.h>
+#include <sys/ioctl.h>
+
+#include <linux/if.h>
+#include <linux/netlink.h>
+#include <linux/rtnetlink.h>
+#include <linux/if_tun.h>
+
+#include "util.h"
+#include "memory.h"
+#include "macvtap.h"
+#include "conf/domain_conf.h"
+#include "virterror_internal.h"
+
+#define VIR_FROM_THIS VIR_FROM_NET
+
+#define ReportError(conn, code, fmt...)                                      \
+        virReportErrorHelper(conn, VIR_FROM_NET, code, __FILE__,          \
+                               __FUNCTION__, __LINE__, fmt)
+
+#define MACVTAP_NAME_PREFIX	"macvtap"
+#define MACVTAP_NAME_PATTERN	"macvtap%d"
+
+static int nlOpen(void)
+{
+    int fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+    if (fd < 0)
+        virReportSystemError(errno,
+                             "%s",_("cannot open netlink socket"));
+    return fd;
+}
+
+
+static void nlClose(int fd)
+{
+    close(fd);
+}
+
+
+/**
+ * nlComm:
+ * @nlmsg: pointer to netlink message
+ * @respbuf: pointer to pointer where response buffer will be allocated
+ * @respbuflen: pointer to integer holding the size of the response buffer
+ *      on return of the function.
+ *
+ * Send the given message to the netlink layer and receive response.
+ * Returns 0 on success, -1 on error. In case of error, no response
+ * buffer will be returned.
+ */
+static
+int nlComm(struct nlmsghdr *nlmsg,
+           char **respbuf, int *respbuflen)
+{
+    int rc = 0;
+    struct sockaddr_nl nladdr = {
+            .nl_family = AF_NETLINK,
+            .nl_pid    = 0,
+            .nl_groups = 0,
+    };
+    int rcvChunkSize = 1024; // expecting less than that
+    int rcvoffset = 0;
+    ssize_t nbytes;
+    int fd = nlOpen();
+
+    if (fd < 0)
+        return -1;
+
+    nlmsg->nlmsg_flags |= NLM_F_ACK;
+
+    nbytes = sendto(fd, (void *)nlmsg, nlmsg->nlmsg_len, 0,
+                    (struct sockaddr *)&nladdr, sizeof(nladdr));
+    if (nbytes < 0) {
+        virReportSystemError(errno,
+                             "%s", _("cannot send to netlink socket"));
+        rc = -1;
+        goto err_exit;
+    }
+
+    while (1) {
+        if (VIR_REALLOC_N(*respbuf, rcvoffset+rcvChunkSize) < 0) {
+            virReportOOMError();
+            rc = -1;
+            goto err_exit;
+        }
+
+        socklen_t addrlen = sizeof(nladdr);
+        nbytes = recvfrom(fd, &((*respbuf)[rcvoffset]), rcvChunkSize, 0,
+                          (struct sockaddr *)&nladdr, &addrlen);
+        if (nbytes < 0) {
+            if (errno == EAGAIN || errno == EINTR)
+                continue;
+            virReportSystemError(errno, "%s",
+                                 _("error receiving from netlink socket"));
+            rc = -1;
+            goto err_exit;
+        }
+        rcvoffset += nbytes;
+        break;
+    }
+    *respbuflen = rcvoffset;
+
+err_exit:
+    if (rc == -1) {
+        VIR_FREE(*respbuf);
+        *respbuf = NULL;
+        *respbuflen = 0;
+    }
+
+    nlClose(fd);
+    return rc;
+}
+
+
+static struct rtattr *
+rtattrCreate(char *buffer, int bufsize, int type,
+             const void *data, int datalen)
+{
+    struct rtattr *r = (struct rtattr *)buffer;
+    r->rta_type = type;
+    r->rta_len  = RTA_LENGTH(datalen);
+    if (r->rta_len > bufsize)
+        return NULL;
+    memcpy(RTA_DATA(r), data, datalen);
+    return r;
+}
+
+
+static void
+nlInit(struct nlmsghdr *nlm, int flags, int type)
+{
+    nlm->nlmsg_len = NLMSG_LENGTH(0);
+    nlm->nlmsg_flags = flags;
+    nlm->nlmsg_type = type;
+}
+
+
+static void
+nlAlign(struct nlmsghdr *nlm)
+{
+    nlm->nlmsg_len = NLMSG_ALIGN(nlm->nlmsg_len);
+}
+
+
+static void *
+nlAppend(struct nlmsghdr *nlm, int totlen, const void *data, int datalen)
+{
+    char *pos;
+    nlAlign(nlm);
+    if (nlm->nlmsg_len + NLMSG_ALIGN(datalen) > totlen)
+        return NULL;
+    pos = (char *)nlm + nlm->nlmsg_len;
+    memcpy(pos, data, datalen);
+    nlm->nlmsg_len += datalen;
+    nlAlign(nlm);
+    return pos;
+}
+
+
+static int
+getIfIndex(virConnectPtr conn,
+           const char *ifname,
+           int *idx)
+{
+    int rc = 0;
+    struct ifreq ifreq;
+    int fd = socket(PF_PACKET, SOCK_DGRAM, 0);
+
+    if (fd < 0)
+        return errno;
+
+    if (virStrncpy(ifreq.ifr_name, ifname, strlen(ifname),
+                   sizeof(ifreq.ifr_name)) == NULL) {
+        if (conn)
+            ReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                        _("invalid interface name %s"),
+                        ifname);
+        rc = EINVAL;
+        goto err_exit;
+    }
+    if (ioctl(fd, SIOCGIFINDEX, &ifreq) >= 0)
+        *idx = ifreq.ifr_ifindex;
+    else {
+        if (conn)
+            ReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                        _("interface %s does not exist"),
+                        ifname);
+        rc = ENODEV;
+    }
+
+err_exit:
+    close(fd);
+
+    return rc;
+}
+
+
+/*
+ * chgIfFlags: 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.
+ */
+static int chgIfFlags(const char *ifname, short flagclear, short flagset) {
+    struct ifreq ifr;
+    int rc = 0;
+    int flags;
+    short flagmask = (~0 ^ flagclear);
+    int fd = socket(PF_PACKET, SOCK_DGRAM, 0);
+
+    if (fd < 0)
+        return errno;
+
+    if (virStrncpy(ifr.ifr_name,
+                   ifname, strlen(ifname), sizeof(ifr.ifr_name)) == NULL) {
+        rc = ENODEV;
+        goto err_exit;
+    }
+
+    if (ioctl(fd, SIOCGIFFLAGS, &ifr) < 0) {
+        rc = errno;
+        goto err_exit;
+    }
+
+    flags = (ifr.ifr_flags & flagmask) | flagset;
+
+    if (ifr.ifr_flags != flags) {
+        ifr.ifr_flags = flags;
+
+        if (ioctl(fd, SIOCSIFFLAGS, &ifr) < 0)
+            rc = errno;
+    }
+
+err_exit:
+    close(fd);
+    return rc;
+}
+
+/*
+ * ifUp
+ * @name: name of the interface
+ * @up: 1 for up, 0 for down
+ *
+ * Function to control if an interface is activated (up, 1) or not (down, 0)
+ *
+ * Returns 0 in case of success or an errno code in case of failure.
+ */
+static int
+ifUp(const char *name, int up)
+{
+    return chgIfFlags(name,
+                      (up) ? 0      : IFF_UP,
+                      (up) ? IFF_UP : 0);
+}
+
+
+static int
+link_add(virConnectPtr conn,
+         const char *type,
+         const unsigned char *macaddress, int macaddrsize,
+         const char *ifname,
+         const char *srcdev,
+         uint32_t macvlan_mode,
+         int *retry)
+{
+    int rc = 0;
+    char nlmsgbuf[256];
+    struct nlmsghdr *nlm = (struct nlmsghdr *)nlmsgbuf, *resp;
+    struct nlmsgerr *err;
+    char rtattbuf[64];
+    struct rtattr *rta, *rta1, *li;
+    struct ifinfomsg i = { .ifi_family = AF_UNSPEC };
+    int ifindex;
+    char *recvbuf = NULL;
+    int recvbuflen;
+
+    if (getIfIndex(conn, srcdev, &ifindex) != 0)
+        return -1;
+
+    *retry = 0;
+
+    memset(&nlmsgbuf, 0, sizeof(nlmsgbuf));
+
+    nlInit(nlm, NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL, RTM_NEWLINK);
+
+    if (!nlAppend(nlm, sizeof(nlmsgbuf), &i, sizeof(i)))
+        goto buffer_too_small;
+
+    rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_LINK,
+                       &ifindex, sizeof(ifindex));
+    if (!rta)
+        goto buffer_too_small;
+
+    if (!nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len))
+        goto buffer_too_small;
+
+    rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_ADDRESS,
+                       macaddress, macaddrsize);
+    if (!rta)
+        goto buffer_too_small;
+
+    if (!nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len))
+        goto buffer_too_small;
+
+    if (ifname) {
+        rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_IFNAME,
+                           ifname, strlen(ifname) + 1);
+        if (!rta)
+            goto buffer_too_small;
+
+        if (!nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len))
+            goto buffer_too_small;
+    }
+
+    rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_LINKINFO, NULL, 0);
+    if (!rta)
+        goto buffer_too_small;
+
+    if (!(li = nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len)))
+        goto buffer_too_small;
+
+    rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_INFO_KIND,
+                       type, strlen(type));
+    if (!rta)
+        goto buffer_too_small;
+
+    if (!nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len))
+        goto buffer_too_small;
+
+    if (macvlan_mode > 0) {
+        rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_INFO_DATA,
+                           NULL, 0);
+        if (!rta)
+            goto buffer_too_small;
+
+        if (!(rta1 = nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len)))
+            goto buffer_too_small;
+
+        rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_MACVLAN_MODE,
+                           &macvlan_mode, sizeof(macvlan_mode));
+        if (!rta)
+            goto buffer_too_small;
+
+        if (!nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len))
+            goto buffer_too_small;
+
+        rta1->rta_len = (char *)nlm + nlm->nlmsg_len - (char *)rta1;
+    }
+
+    li->rta_len = (char *)nlm + nlm->nlmsg_len - (char *)li;
+
+    if (nlComm(nlm, &recvbuf, &recvbuflen) < 0)
+        return -1;
+
+    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;
+    }
+
+    VIR_FREE(recvbuf);
+
+    return rc;
+
+malformed_resp:
+    ReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                _("malformed netlink response message"));
+    VIR_FREE(recvbuf);
+    return -1;
+
+buffer_too_small:
+    ReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                _("internal buffer is too small"));
+    return -1;
+}
+
+
+static int
+link_del(const char *type,
+         const char *name)
+{
+    int rc = 0;
+    char nlmsgbuf[256];
+    struct nlmsghdr *nlm = (struct nlmsghdr *)nlmsgbuf, *resp;
+    struct nlmsgerr *err;
+    char rtattbuf[64];
+    struct rtattr *rta, *rta1;
+    struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
+    char *recvbuf = NULL;
+    int recvbuflen;
+
+    memset(&nlmsgbuf, 0, sizeof(nlmsgbuf));
+
+    nlInit(nlm, NLM_F_REQUEST | NLM_F_CREATE | NLM_F_EXCL, RTM_DELLINK);
+
+    if (!nlAppend(nlm, sizeof(nlmsgbuf), &ifinfo, sizeof(ifinfo)))
+        goto buffer_too_small;
+
+    rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_LINKINFO, NULL, 0);
+    if (!rta)
+        goto buffer_too_small;
+
+    if (!(rta1 = nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len)))
+        goto buffer_too_small;
+
+    rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_INFO_KIND,
+                       type, strlen(type));
+    if (!rta)
+        goto buffer_too_small;
+
+    if (!nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len))
+        goto buffer_too_small;
+
+    rta1->rta_len = (char *)nlm + nlm->nlmsg_len - (char *)rta1;
+
+    rta = rtattrCreate(rtattbuf, sizeof(rtattbuf), IFLA_IFNAME,
+                       name, strlen(name)+1);
+    if (!rta)
+        goto buffer_too_small;
+
+    if (!nlAppend(nlm, sizeof(nlmsgbuf), rtattbuf, rta->rta_len))
+        goto buffer_too_small;
+
+    if (nlComm(nlm, &recvbuf, &recvbuflen) < 0)
+        return -1;
+
+    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;
+
+        default:
+            virReportSystemError(-err->error,
+                                 _("error destroying %s interface"),
+                                 name);
+            rc = -1;
+        }
+    break;
+
+    case NLMSG_DONE:
+    break;
+
+    default:
+        goto malformed_resp;
+    }
+
+    VIR_FREE(recvbuf);
+
+    return rc;
+
+malformed_resp:
+    ReportError(NULL, VIR_ERR_INTERNAL_ERROR,
+                "%s", _("malformed netlink response message"));
+    VIR_FREE(recvbuf);
+    return -1;
+
+buffer_too_small:
+    ReportError(NULL, VIR_ERR_INTERNAL_ERROR,
+                "%s", _("internal buffer is too small"));
+    return -1;
+}
+
+
+/* Open the macvtap's tap device.
+ * @conn: Pointer to virConnect object
+ * @name: Name of the macvtap interface
+ * @retries : Number of retries in case udev for example may need to be
+ *            waited for to create the tap chardev
+ * Returns negative value in case of error, the file descriptor otherwise.
+ */
+static
+int openTap(const char *ifname,
+            int retries)
+{
+    FILE *file;
+    char path[64];
+    int ifindex;
+    char tapname[50];
+    int tapfd;
+
+    if (snprintf(path, sizeof(path),
+                 "/sys/class/net/%s/ifindex", ifname) >= sizeof(path)) {
+        virReportSystemError(errno,
+                             "%s",
+                             _("buffer for ifindex path is too small"));
+        return -1;
+    }
+
+    file = fopen(path, "r");
+
+    if (!file) {
+        virReportSystemError(errno,
+                             _("cannot open macvtap file %s to determine "
+                               "interface index"), path);
+        return -1;
+    }
+
+    if (fscanf(file, "%d", &ifindex) != 1) {
+        virReportSystemError(errno,
+                             "%s",_("cannot determine macvtap's tap device "
+                             "interface index"));
+        fclose(file);
+        return -1;
+    }
+
+    fclose(file);
+
+    if (snprintf(tapname, sizeof(tapname),
+                 "/dev/tap%d", ifindex) >= sizeof(tapname)) {
+        virReportSystemError(errno,
+                             "%s",
+                             _("internal buffer for tap device is too small"));
+        return -1;
+    }
+
+    while (1) {
+        // may need to wait for udev to be done
+        tapfd = open(tapname, O_RDWR);
+        if (tapfd < 0 && retries > 0) {
+            retries--;
+            usleep(20000);
+            continue;
+        }
+        break;
+    }
+
+    if (tapfd < 0)
+        virReportSystemError(errno,
+                             _("cannot open macvtap tap device %s"),
+                             tapname);
+
+    return tapfd;
+}
+
+
+static uint32_t
+macvtapModeFromInt(enum virDomainNetdevMacvtapType mode)
+{
+    switch (mode) {
+    case VIR_DOMAIN_NETDEV_MACVTAP_MODE_PRIVATE:
+        return MACVLAN_MODE_PRIVATE;
+    break;
+
+    case VIR_DOMAIN_NETDEV_MACVTAP_MODE_BRIDGE:
+        return MACVLAN_MODE_BRIDGE;
+    break;
+
+    case VIR_DOMAIN_NETDEV_MACVTAP_MODE_VEPA:
+    default:
+        return MACVLAN_MODE_VEPA;
+    }
+}
+
+
+/* openMacvtapTap:
+ * Create an instance of a macvtap device and open its tap character
+ * device.
+ * @conn: Pointer to virConnect object
+ * @tgifname: Interface name that the macvtap is supposed to have. May
+ *    be NULL if this function is supposed to choose a name
+ * @macaddress: The MAC address for the macvtap device
+ * @linkdev: The interface name of the NIC to connect to the external bridge
+ * @mode_str: String describing the mode. Valid are 'bridge', 'vepa' and
+ *     'private'.
+ * @res_ifname: Pointer to a string pointer where the actual name of the
+ *     interface will be stored into if everything succeeded. It is up
+ *     to the caller to free the string.
+ *
+ * Returns file descriptor of the tap device in case of success,
+ * negative value otherwise with error message attached to the 'conn'
+ * object.
+ *
+ */
+int
+openMacvtapTap(virConnectPtr conn,
+               const char *tgifname,
+               const unsigned char *macaddress,
+               const char *linkdev,
+               int mode,
+               char **res_ifname)
+{
+    const char *type = "macvtap";
+    int c, rc;
+    char ifname[IFNAMSIZ];
+    int retries, do_retry = 0;
+    uint32_t macvtapMode = macvtapModeFromInt(mode);
+    const char *cr_ifname;
+    int ifindex;
+
+    *res_ifname = NULL;
+
+    if (tgifname) {
+        if(getIfIndex(NULL, tgifname, &ifindex) == 0) {
+            if (STRPREFIX(tgifname,
+                          MACVTAP_NAME_PREFIX)) {
+                goto create_name;
+            }
+            virReportSystemError(errno,
+                                 _("Interface %s already exists"), tgifname);
+            return -1;
+        }
+        cr_ifname = tgifname;
+        rc = link_add(conn, type, macaddress, 6, tgifname, linkdev,
+                      macvtapMode, &do_retry);
+        if (rc)
+            return -1;
+    } else {
+create_name:
+        retries = 5;
+        for (c = 0; c < 8192; c++) {
+            snprintf(ifname, sizeof(ifname), MACVTAP_NAME_PATTERN, c);
+            if (getIfIndex(NULL, ifname, &ifindex) == ENODEV) {
+                rc = link_add(conn, type, macaddress, 6, ifname, linkdev,
+                              macvtapMode, &do_retry);
+                if (rc == 0)
+                    break;
+
+                if (do_retry && --retries)
+                    continue;
+                return -1;
+            }
+        }
+        cr_ifname = ifname;
+    }
+
+    rc = ifUp(cr_ifname, 1);
+    if (rc != 0) {
+        virReportSystemError(errno,
+                             _("cannot 'up' interface %s"), cr_ifname);
+        rc = -1;
+        goto link_del_exit;
+    }
+
+    rc = openTap(cr_ifname, 10);
+
+    if (rc > 0)
+        *res_ifname = strdup(cr_ifname);
+    else
+        goto link_del_exit;
+
+    return rc;
+
+link_del_exit:
+    link_del(type, ifname);
+
+    return rc;
+}
+
+
+/* Delete a macvtap type of interface given the MAC address. This
+ * function will delete all macvtap type of interfaces that have the
+ * given MAC address.
+ * @macaddress : Pointer to 6 bytes holding the MAC address of the
+ *    macvtap device(s) to destroy
+ *
+ * Returns 0 in case of success, negative value in case of error.
+ */
+int
+delMacvtapByMACAddress(const unsigned char *macaddress,
+                       int *hasBusyDev)
+{
+    struct ifreq ifr;
+    FILE *file;
+    char *ifname, *pos;
+    char buffer[1024];
+    off_t oldpos = 0;
+    int tapfd;
+
+    *hasBusyDev = 0;
+
+    file = fopen("/proc/net/dev", "r");
+
+    if (!file) {
+        virReportSystemError(errno, "%s",
+                             _("cannot open file to read network interfaces "
+                             "from"));
+        return -1;
+    }
+
+    int sock = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sock < 0) {
+        virReportSystemError(errno, "%s",
+                             _("cannot open socket"));
+        goto sock_err;
+    }
+
+    while (NULL != (ifname = fgets(buffer, sizeof(buffer), file))) {
+        if (isspace(ifname[0]))
+            ifname++;
+        if ((pos = strchr(ifname, ':')) != NULL) {
+            pos[0] = 0;
+            if (virStrncpy(ifr.ifr_name, ifname, strlen(ifname),
+                           sizeof(ifr.ifr_name)) == NULL)
+                continue;
+            if (ioctl(sock, SIOCGIFHWADDR, (char *)&ifr) >= 0) {
+                if (memcmp(&ifr.ifr_hwaddr.sa_data[0], macaddress, 6) == 0) {
+                    tapfd = openTap(ifname, 0);
+                    if (tapfd > 0) {
+                        close(tapfd);
+                        ifUp(ifname, 0);
+                        if (link_del("macvtap", ifname) == 0)
+                            fseeko(file, oldpos, SEEK_SET);
+                    } else {
+                        *hasBusyDev = 1;
+                    }
+                }
+            }
+        }
+        oldpos = ftello(file);
+    }
+
+    close(sock);
+sock_err:
+    fclose(file);
+
+    return 0;
+}
+
+#endif

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