network: Bring netdevs online later

Currently, MAC registration occurs during device creation, which is
early enough that, during live migration, you end up with duplicate
MAC addresses on still-running source and target devices, even though
the target device isn't actually being used yet.
This patch proposes to defer MAC registration until right before
the guest can actually use the device -- In other words, right
before starting guest CPUs.
Signed-off-by: NMatthew Rosato <mjrosato@linux.vnet.ibm.com>
Signed-off-by: NLaine Stump <laine@laine.org>

src/Makefile.am

@@ -733,7 +733,8 @@ QEMU_DRIVER_SOURCES =							\
 		qemu/qemu_monitor_text.h				\
 		qemu/qemu_monitor_json.c				\
 		qemu/qemu_monitor_json.h				\
-		qemu/qemu_driver.c qemu/qemu_driver.h
+		qemu/qemu_driver.c qemu/qemu_driver.h	\
+		qemu/qemu_interface.c qemu/qemu_interface.h
 
 XENAPI_DRIVER_SOURCES =						\
 		xenapi/xenapi_driver.c xenapi/xenapi_driver.h	\

src/lxc/lxc_process.c

@@ -297,6 +297,7 @@ char *virLXCProcessSetupInterfaceDirect(virConnectPtr conn,
     virNetDevVPortProfilePtr prof;
     virLXCDriverConfigPtr cfg = virLXCDriverGetConfig(driver);
     const char *linkdev = virDomainNetGetActualDirectDev(net);
+    unsigned int macvlan_create_flags = VIR_NETDEV_MACVLAN_CREATE_IFUP;
 
     /* XXX how todo bandwidth controls ?
      * Since the 'net-ifname' is about to be moved to a different
@@ -332,7 +333,8 @@ char *virLXCProcessSetupInterfaceDirect(virConnectPtr conn,
             prof,
             &res_ifname,
             VIR_NETDEV_VPORT_PROFILE_OP_CREATE,
-            cfg->stateDir, 0) < 0)
+            cfg->stateDir,
+            macvlan_create_flags) < 0)
         goto cleanup;
 
     ret = res_ifname;

src/qemu/qemu_hotplug.c

@@ -30,6 +30,7 @@
 #include "qemu_domain.h"
 #include "qemu_command.h"
 #include "qemu_hostdev.h"
+#include "qemu_interface.h"
 #include "domain_audit.h"
 #include "netdev_bandwidth_conf.h"
 #include "domain_nwfilter.h"
@@ -943,6 +944,10 @@ int qemuDomainAttachNetDevice(virConnectPtr conn,
             goto cleanup;
     }
 
+    /* Set device online immediately */
+    if (qemuInterfaceStartDevice(net) < 0)
+       goto cleanup;
+
     /* Set Bandwidth */
     if (virNetDevSupportBandwidth(actualType) &&
         virNetDevBandwidthSet(net->ifname,

src/qemu/qemu_interface.c

+/*
+ * qemu_interface.c: QEMU interface management
+ *
+ * Copyright IBM Corp. 2014
+ *
+ * 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:
+ *     Matthew J. Rosato <mjrosato@linux.vnet.ibm.com>
+ */
+
+#include <config.h>
+
+#include "qemu_interface.h"
+#include "virnetdev.h"
+#include "virnetdevtap.h"
+#include "virnetdevmacvlan.h"
+#include "virnetdevvportprofile.h"
+
+/**
+ * qemuInterfaceStartDevice:
+ * @net: net device to start
+ *
+ * Based upon the type of device provided, perform the appropriate
+ * work to completely activate the device and make it reachable from
+ * the rest of the network.
+ */
+int
+qemuInterfaceStartDevice(virDomainNetDefPtr net)
+{
+    int ret = -1;
+
+    switch (virDomainNetGetActualType(net)) {
+    case VIR_DOMAIN_NET_TYPE_BRIDGE:
+    case VIR_DOMAIN_NET_TYPE_NETWORK:
+        break;
+    case VIR_DOMAIN_NET_TYPE_DIRECT:
+        /* macvtap devices share their MAC address with the guest
+         * domain, and if they are set online prior to the domain CPUs
+         * being started, the host may send out traffic from this
+         * device that could confuse other entities on the network (in
+         * particular, if this new domain is the destination of a
+         * migration, and the source domain is still running, another
+         * host may mistakenly direct traffic for the guest to the
+         * destination domain rather than source domain). To prevent
+         * this, we create the macvtap device with IFF_UP false
+         * (i.e. "offline") then wait to bring it online until just as
+         * we are starting the domain CPUs.
+         */
+        if (virNetDevSetOnline(net->ifname, true) < 0)
+            goto cleanup;
+        break;
+
+    case VIR_DOMAIN_NET_TYPE_USER:
+    case VIR_DOMAIN_NET_TYPE_ETHERNET:
+    case VIR_DOMAIN_NET_TYPE_VHOSTUSER:
+    case VIR_DOMAIN_NET_TYPE_SERVER:
+    case VIR_DOMAIN_NET_TYPE_CLIENT:
+    case VIR_DOMAIN_NET_TYPE_MCAST:
+    case VIR_DOMAIN_NET_TYPE_INTERNAL:
+    case VIR_DOMAIN_NET_TYPE_HOSTDEV:
+    case VIR_DOMAIN_NET_TYPE_LAST:
+        /* these types all require no action */
+        break;
+    }
+
+    ret = 0;
+ cleanup:
+    return ret;
+}
+
+/**
+ * qemuInterfaceStartDevices:
+ * @def: domain definition
+ *
+ * Set all ifaces associated with this domain to the online state.
+ */
+int
+qemuInterfaceStartDevices(virDomainDefPtr def)
+{
+    size_t i;
+
+    for (i = 0; i < def->nnets; i++) {
+        if (qemuInterfaceStartDevice(def->nets[i]) < 0)
+            return -1;
+    }
+    return 0;
+}

src/qemu/qemu_interface.h

+/*
+ * qemu_interface.h: QEMU interface management
+ *
+ * Copyright IBM Corp. 2014
+ *
+ * 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:
+ *     Matthew J. Rosato <mjrosato@linux.vnet.ibm.com>
+ */
+
+#ifndef __QEMU_INTERFACE_H__
+# define __QEMU_INTERFACE_H__
+
+# include "domain_conf.h"
+
+int qemuInterfaceStartDevice(virDomainNetDefPtr net);
+int qemuInterfaceStartDevices(virDomainDefPtr def);
+
+#endif /* __QEMU_INTERFACE_H__ */

src/qemu/qemu_process.c

@@ -42,6 +42,7 @@
 #include "qemu_hostdev.h"
 #include "qemu_hotplug.h"
 #include "qemu_migration.h"
+#include "qemu_interface.h"
 
 #include "cpu/cpu.h"
 #include "datatypes.h"
@@ -3124,6 +3125,12 @@ qemuProcessStartCPUs(virQEMUDriverPtr driver, virDomainObjPtr vm,
     qemuDomainObjPrivatePtr priv = vm->privateData;
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
 
+    /* Bring up netdevs before starting CPUs */
+    if (reason != VIR_DOMAIN_RUNNING_UNPAUSED &&
+        reason != VIR_DOMAIN_RUNNING_SAVE_CANCELED &&
+        qemuInterfaceStartDevices(vm->def) < 0)
+       goto cleanup;
+
     VIR_DEBUG("Using lock state '%s'", NULLSTR(priv->lockState));
     if (virDomainLockProcessResume(driver->lockManager, cfg->uri,
                                    vm, priv->lockState) < 0) {

src/util/virnetdevmacvlan.c

@@ -899,9 +899,11 @@ int virNetDevMacVLanCreateWithVPortProfile(const char *tgifname,
         goto link_del_exit;
     }
 
-    if (virNetDevSetOnline(cr_ifname, true) < 0) {
-        rc = -1;
-        goto disassociate_exit;
+    if (flags & VIR_NETDEV_MACVLAN_CREATE_IFUP) {
+        if (virNetDevSetOnline(cr_ifname, true) < 0) {
+            rc = -1;
+            goto disassociate_exit;
+        }
     }
 
     if (flags & VIR_NETDEV_MACVLAN_CREATE_WITH_TAP) {

src/util/virnetdevmacvlan.h

@@ -44,6 +44,8 @@ typedef enum {
    VIR_NETDEV_MACVLAN_CREATE_NONE     = 0,
    /* Create with a tap device */
    VIR_NETDEV_MACVLAN_CREATE_WITH_TAP = 1 << 0,
+   /* Bring the interface up */
+   VIR_NETDEV_MACVLAN_CREATE_IFUP     = 1 << 1,
 } virNetDevMacVLanCreateFlags;
 
 int virNetDevMacVLanCreate(const char *ifname,