3.2-stable review patch. If anyone has any objections, please let me know. ------------------ From: Laszlo Ersek <lersek@xxxxxxxxxx> commit 08e34eb14fe4cfd934b5c169a7682a969457c4ea upstream. After a guest is live migrated, the xen-netfront driver emits a gratuitous ARP message, so that networking hardware on the target host's subnet can take notice, and public routing to the guest is re-established. However, if the packet appears on the backend interface before the backend is added to the target host's bridge, the packet is lost, and the migrated guest's peers become unable to talk to the guest. A sufficient two-parts condition to prevent the above is: (1) ensure that the backend only moves to Connected xenbus state after its hotplug scripts completed, ie. the netback interface got added to the bridge; and (2) ensure the frontend only queues the gARP when it sees the backend move to Connected. These two together provide complete ordering. Sub-condition (1) is already satisfied by commit f942dc2552b8 in Linus' tree, based on commit 6b0b80ca7165 from [1]. In general, the full condition is sufficient, not necessary, because, according to [2], live migration has been working for a long time without satisfying sub-condition (2). However, after 6b0b80ca7165 was backported to the RHEL-5 host to ensure (1), (2) still proved necessary in the RHEL-6 guest. This patch intends to provide (2) for upstream. The Reviewed-by line comes from [3]. [1] git://xenbits.xen.org/people/ianc/linux-2.6.git#upstream/dom0/backend/netback-history [2] http://old-list-archives.xen.org/xen-devel/2011-06/msg01969.html [3] http://old-list-archives.xen.org/xen-devel/2011-07/msg00484.html Signed-off-by: Laszlo Ersek <lersek@xxxxxxxxxx> Reviewed-by: Ian Campbell <ian.campbell@xxxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- drivers/net/xen-netfront.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -1707,7 +1707,6 @@ static void netback_changed(struct xenbu case XenbusStateInitialised: case XenbusStateReconfiguring: case XenbusStateReconfigured: - case XenbusStateConnected: case XenbusStateUnknown: case XenbusStateClosed: break; @@ -1718,6 +1717,9 @@ static void netback_changed(struct xenbu if (xennet_connect(netdev) != 0) break; xenbus_switch_state(dev, XenbusStateConnected); + break; + + case XenbusStateConnected: netif_notify_peers(netdev); break; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html