[libvirt] [PATCH] network: Defer online of macvtap during qemu migration

[Matthew Rosato]

When generating macvtaps via virNetDevMacVLanCreateWithVPortProfile,
the macvtap device is unconditionally set to the up state.  However,
during migration, this results in a case where both the source and
target system are simultaneously up with the same MAC address.  This
patch defers bringing the target macvtap up until later in the
migration to shrink this window.

Signed-off-by: Matthew Rosato <mjrosato at linux.vnet.ibm.com>
---
 src/qemu/qemu_migration.c   |   18 ++++++++++++++++++
 src/util/virnetdevmacvlan.c |   11 ++++++++---
 2 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/qemu/qemu_migration.c b/src/qemu/qemu_migration.c
index a9f7fea..aee803a 100644
--- a/src/qemu/qemu_migration.c
+++ b/src/qemu/qemu_migration.c
@@ -56,6 +56,7 @@
 #include "virhook.h"
 #include "virstring.h"
 #include "virtypedparam.h"
+#include "virnetdev.h"
 
 #define VIR_FROM_THIS VIR_FROM_QEMU
 
@@ -4468,6 +4469,8 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
     virCapsPtr caps = NULL;
     unsigned short port;
+    virDomainNetDefPtr net;
+    size_t i;
 
     VIR_DEBUG("driver=%p, dconn=%p, vm=%p, cookiein=%s, cookieinlen=%d, "
               "cookieout=%p, cookieoutlen=%p, flags=%lx, retcode=%d",
@@ -4574,6 +4577,21 @@ qemuMigrationFinish(virQEMUDriverPtr driver,
         }
 
         if (!(flags & VIR_MIGRATE_PAUSED) && !(flags & VIR_MIGRATE_OFFLINE)) {
+            /* Macvtaps were previously left offline, bring them online now */
+            for (i = 0; i < vm->def->nnets; i++) {
+                net = vm->def->nets[i];
+                if (virDomainNetGetActualType(net) == VIR_DOMAIN_NET_TYPE_DIRECT) {
+                    if (virNetDevSetOnline(net->ifname, true) < 0) {
+                        ignore_value(virNetDevVPortProfileDisassociate(net->ifname,
+                                                                       virDomainNetGetActualVirtPortProfile(net),
+                                                                       &net->mac,
+                                                                       virDomainNetGetActualDirectDev(net),
+                                                                       -1,
+                                                                       VIR_NETDEV_VPORT_PROFILE_OP_MIGRATE_IN_FINISH));
+                        ignore_value(virNetDevMacVLanDelete(net->ifname));
+                    }
+                }
+            }
             /* run 'cont' on the destination, which allows migration on qemu
              * >= 0.10.6 to work properly.  This isn't strictly necessary on
              * older qemu's, but it also doesn't hurt anything there
diff --git a/src/util/virnetdevmacvlan.c b/src/util/virnetdevmacvlan.c
index 7bbf540..3da845b 100644
--- a/src/util/virnetdevmacvlan.c
+++ b/src/util/virnetdevmacvlan.c
@@ -898,9 +898,14 @@ int virNetDevMacVLanCreateWithVPortProfile(const char *tgifname,
         goto link_del_exit;
     }
 
-    if (virNetDevSetOnline(cr_ifname, true) < 0) {
-        rc = -1;
-        goto disassociate_exit;
+    /* If this device is being created as part of an inbound
+     * migration, leave the device offline for now.
+     */
+    if (vmOp != VIR_NETDEV_VPORT_PROFILE_OP_MIGRATE_IN_START) {
+        if (virNetDevSetOnline(cr_ifname, true) < 0) {
+            rc = -1;
+            goto disassociate_exit;
+        }
     }
 
     if (withTap) {
-- 
1.7.9.5