Documentation/networking/net_failover.rst

1 .. SPDX-License-Identifier: GPL-2.0
15 The failover netdev acts a master device and controls 2 slave devices. The
17 a passthru/vf device with the same MAC gets registered as 'primary' slave
19 'pci' device. The user accesses the network interface via 'failover' netdev.
28 virtio-net accelerated datapath: STANDBY mode
31 net_failover enables hypervisor controlled accelerated datapath to virtio-net
35 feature on the virtio-net interface and assign the same MAC address to both
36 virtio-net and VF interfaces.
45     <model type='virtio'/>
49     <alias name='ua-backup0'/>
56     <teaming type='transient' persistent='ua-backup0'/>
59 In this configuration, the first device definition is for the virtio-net
60 interface and this acts as the 'persistent' device indicating that this
63 virtio-net device is set to 'down' to ensure that the 'failover' netdev prefers
64 the VF passthrough device for normal communication. The virtio-net device will
67 The second device definition is for the VF passthrough interface. Here the
68 'teaming' tag is provided with type 'transient' indicating that this device may
69 periodically be unplugged. A second attribute - 'persistent' is provided and
70 points to the alias name declared for the virtio-net device.
88 virtio-net interface, and ens11 is the slave 'primary' VF passthrough interface.
91 like systemd-networkd, ifupdown, etc, do not understand the 'net_failover'
92 device; and on the first boot, the VM might end up with both 'failover' device
96 received only on the 'failover' device.
98 Below is the patch snippet used with 'cloud-ifupdown-helper' script found on
102   @@ -27,6 +27,8 @@ do_setup() {
106   +    if [ -d "/sys/class/net/${INTERFACE}/master" ]; then exit 0; fi
108        if ifup --no-act "$INTERFACE" > /dev/null 2>&1; then
113 Live Migration of a VM with SR-IOV VF & virtio-net in STANDBY mode
117 with VMs that have direct attached SR-IOV VF devices by automatic failover to
123 device to the VM. This is not the VF that was passthrough'd to the VM (seen in
133     <teaming type='transient' persistent='ua-backup0'/>
139   DOMAIN=vm-01
143   TAP_IF=vmtap01        # virtio-net interface in the VM.
149   # Set the virtio-net interface up.
150   virsh domif-setlink $DOMAIN $TAP_IF up
153   virsh detach-device --live --config $DOMAIN $VF_XML
158   # the VF -> br0 -> vnet interface path.
163   virsh migrate --live --persistent $DOMAIN qemu+ssh://$REMOTE_HOST/system
174 completes, and it reattaches the VF to the VM and brings down the virtio-net
178   # reattach-vf.sh
183   virsh attach-device --config --live vm01 vf.xml
184   virsh domif-setlink vm01 vmtap01 down