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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.

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 +1,49 @@
+/*
+ * 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,
+                   const char *mode,
+                   char **res_ifname);
+
+int delMacvtapByMACAddress(virConnectPtr conn,
+                           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
Index: libvirt-macvtap/src/util/macvtap.c
===================================================================
--- /dev/null
+++ libvirt-macvtap/src/util/macvtap.c
@@ -0,0 +1,755 @@
+/*
+ * 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
+ *
+ */
+
+#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 "macvtap.h"
+#include "virterror_internal.h"
+
+#define VIR_FROM_THIS VIR_FROM_NONE
+
+#define ReportError(conn, code, fmt...)                                      \
+        virReportErrorHelper(conn, VIR_FROM_NONE, code, __FILE__,          \
+                               __FUNCTION__, __LINE__, fmt)
+
+#define MACVTAP_NAME_PREFIX	"macvtap"
+#define MACVTAP_NAME_PATTERN	"macvtap%d"
+
+static int nlOpen(virConnectPtr conn)
+{
+    int fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
+    if (fd < 0)
+        virReportSystemError(conn, errno,
+                             "%s",_("cannot open netlink socket"));
+    return fd;
+}
+
+
+static void nlClose(int fd)
+{
+    close(fd);
+}
+
+
+static
+int nlComm(virConnectPtr conn,
+           struct nlmsghdr *nlmsg,
+           char *respbuf, int *respbuflen)
+{
+    int rc = 0;
+    struct sockaddr_nl nladdr = {
+            .nl_family = AF_NETLINK,
+            .nl_pid    = 0,
+            .nl_groups = 0,
+    };
+    char rcvbuf[1024];
+    ssize_t nbytes;
+    size_t tocopy;
+    int fd = nlOpen(conn);
+
+    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(conn, errno,
+                             "%s", _("cannot send to netlink socket"));
+        rc = -1;
+        goto err_exit;
+    }
+
+    memset(rcvbuf, 0x0, sizeof(rcvbuf));
+    while (1) {
+        socklen_t addrlen = sizeof(nladdr);
+        nbytes = recvfrom(fd, &rcvbuf, sizeof(rcvbuf), 0,
+                          (struct sockaddr *)&nladdr, &addrlen);
+        if (nbytes < 0) {
+            if (errno == EAGAIN || errno == EINTR)
+                continue;
+            virReportSystemError(conn, errno, "%s",
+                                 _("error receiving from netlink socket"));
+            rc = -1;
+            goto err_exit;
+        }
+
+        tocopy = (nbytes < *respbuflen) ? nbytes : *respbuflen;
+        memcpy(respbuf, rcvbuf, tocopy);
+        *respbuflen = tocopy;
+        break;
+    }
+
+err_exit:
+    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)
+{
+    char nlmsgbuf[1024], recvbuf[1024];
+    struct nlmsghdr *nlm = (struct nlmsghdr *)nlmsgbuf, *resp;
+    struct nlmsgerr *err;
+    char rtattbuf[256];
+    struct rtattr *rta, *rta1;
+    struct ifinfomsg i = { .ifi_family = AF_UNSPEC };
+    int ifindex;
+    int recvbuflen = sizeof(recvbuf);
+
+    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_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_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;
+    }
+
+    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;
+    }
+
+    if (nlComm(conn, nlm, recvbuf, &recvbuflen) < 0)
+        return -1;
+
+    if (recvbuflen < NLMSG_LENGTH(0))
+        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;
+            return -1;
+        break;
+
+        default:
+            virReportSystemError(conn, -err->error,
+                                 _("error creating %s type of interface"),
+                                 type);
+            return -1;
+        }
+    break;
+
+    case NLMSG_DONE:
+    break;
+
+    default:
+        goto malformed_resp;
+    }
+
+    return 0;
+
+malformed_resp:
+    ReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                _("malformed netlink response message"));
+    return -1;
+
+buffer_too_small:
+    ReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                _("internal buffer is too small"));
+    return -1;
+}
+
+
+static int
+link_del(virConnectPtr conn,
+         const char *type,
+         const char *name)
+{
+    char nlmsgbuf[1024], recvbuf[1024];
+    struct nlmsghdr *nlm = (struct nlmsghdr *)nlmsgbuf, *resp;
+    struct nlmsgerr *err;
+    char rtattbuf[256];
+    struct rtattr *rta, *rta1;
+    struct ifinfomsg ifinfo = { .ifi_family = AF_UNSPEC };
+    int recvbuflen = sizeof(recvbuf);
+
+    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(conn, nlm, recvbuf, &recvbuflen) < 0)
+        return -1;
+
+    if (recvbuflen < NLMSG_LENGTH(0))
+        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(conn, -err->error,
+                                 _("error destroying %s interface"),
+                                 name);
+            return -1;
+        }
+    break;
+
+    case NLMSG_DONE:
+    break;
+
+    default:
+        goto malformed_resp;
+    }
+
+    return 0;
+
+malformed_resp:
+    ReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                _("malformed netlink response message"));
+    return -1;
+
+buffer_too_small:
+    ReportError(conn, VIR_ERR_INTERNAL_ERROR,
+                _("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 with virConnect object holding
+ * an error message, the file descriptor otherwise.
+ */
+static
+int openTap(virConnectPtr conn,
+            const char *ifname,
+            int retries)
+{
+    FILE *file;
+    char path[256];
+    int ifindex;
+    char tapname[50];
+    int tapfd;
+
+    snprintf(path, sizeof(path), "/sys/class/net/%s/ifindex", ifname);
+    file = fopen(path, "r");
+
+    if (!file) {
+        virReportSystemError(conn, errno,
+                             _("cannot open macvtap file %s to determine "
+                               "interface index"), path);
+        return -1;
+    }
+
+    if (fscanf(file, "%d", &ifindex) != 1) {
+        virReportSystemError(conn, errno,
+                             "%s",_("cannot determine macvtap's tap device "
+                             "interface index"));
+        fclose(file);
+        return -1;
+    }
+
+    fclose(file);
+
+    snprintf(tapname, sizeof(tapname), "/dev/tap%d", ifindex);
+
+    while (1) {
+        // may need to wait for udev to be done
+        tapfd = open(tapname, O_RDWR);
+        if (tapfd < 0 && retries--) {
+            usleep(20000);
+            continue;
+        }
+        break;
+    }
+
+    if (tapfd < 0)
+        virReportSystemError(conn, errno,
+                             _("cannot open macvtap tap device %s"),
+                             tapname);
+
+    return tapfd;
+}
+
+
+static uint32_t
+modeFromString(const char *mode_str)
+{
+    if (!mode_str)
+        return 0;
+    if (STREQ(mode_str, MACVTAP_MODE_PRIVATE_STR))
+        return MACVLAN_MODE_PRIVATE;
+    if (STREQ(mode_str, MACVTAP_MODE_VEPA_STR))
+        return MACVLAN_MODE_VEPA;
+    if (STREQ(mode_str, MACVTAP_MODE_BRIDGE_STR))
+        return MACVLAN_MODE_BRIDGE;
+    return 0;
+}
+
+
+/* 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,
+               const char *mode_str,
+               char **res_ifname)
+{
+    const char *type = "macvtap";
+    int c, rc;
+    char ifname[IFNAMSIZ];
+    int retries, do_retry = 0;
+    uint32_t mode = modeFromString(mode_str);
+    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(conn, errno,
+                                 _("Interface %s already exists"), tgifname);
+            return -1;
+        }
+        cr_ifname = tgifname;
+        rc = link_add(conn, type, macaddress, 6, tgifname, linkdev,
+                      mode, &do_retry);
+        if (rc)
+            return -1;
+    } else {
+create_name:
+        retries = 5;
+        for (c = 0; c < 255; c++) {
+            snprintf(ifname, sizeof(ifname), MACVTAP_NAME_PATTERN, c);
+            if (getIfIndex(NULL, ifname, &ifindex) == ENODEV) {
+                rc = link_add(conn, type, macaddress, 6, ifname, linkdev,
+                              mode, &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(conn, errno,
+                             _("cannot 'up' interface %s"), cr_ifname);
+        rc = -1;
+        goto link_del_exit;
+    }
+
+    rc = openTap(conn, cr_ifname, 10);
+
+    if (rc > 0)
+        *res_ifname = strdup(cr_ifname);
+    else
+        goto link_del_exit;
+
+    return rc;
+
+link_del_exit:
+    link_del(conn, 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.
+ * @conn: Pointer to a virConnect object
+ * @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 with
+ * error message attached to the virConnect object.
+ */
+int
+delMacvtapByMACAddress(virConnectPtr conn,
+                       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(conn, errno, "%s",
+                             _("cannot open file to read network interfaces "
+                             "from"));
+        return -1;
+    }
+
+    int sock = socket(AF_INET, SOCK_DGRAM, 0);
+    if (sock < 0) {
+        virReportSystemError(conn, 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(conn, ifname, 0);
+                    if (tapfd > 0) {
+                        close(tapfd);
+                        ifUp(ifname, 0);
+                        if (link_del(conn, "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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