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

[Matthew Rosato]

On 05/05/2014 12:26 PM, Matthew Rosato wrote:
> 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>

Forgot to mention that this patch is associated with what Wangrui
reported here:

http://www.redhat.com/archives/libvir-list/2014-March/msg01054.html

and follows Viktor's suggested solution mentioned here:

http://www.redhat.com/archives/libvir-list/2014-March/msg01654.html


> ---
>  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) {
>