On 07/11/2018 12:33 AM, Yegappan Lakshmanan wrote:

Hi all,

How do you add a VLAN tag to a libvirt SR-IOV VF network using the "virsh net-update" command? I couldn't find the section to pass to the "virsh net-update" command to add the VLAN tag.

I have the following libvirt network defined for a SR-IOV VF:

<network>   <name>GE0-0-SRIOV-1</name>   <uuid>7bc67166-c78e-4bcf-89ee-377dd9086631</uuid>   <forward mode='hostdev' managed='yes'>     <driver name='vfio'/>     <address type='pci' domain='0x0000' bus='0x02' slot='0x10' function='0x0'/>   </forward> </network>

I am trying to add VLAN 100 to this network. If I use the following command to add a VLAN tag to this network:

virsh net-update GE0-0-SRIOV-1 modify bridge --xml "<vlan trunk='no'><tag id='100'/></vlan>"> It fails as the section "bridge" doesn't support adding a VLAN tag.

Right. Because the <vlan> element in a network is not a part of the <bridge> element. It is a separate element all its own. the net-update command only supports updating a few very specific parts of the network definition, and the vlan element isn't one of those that's supported.

I have tried other section values like domain and all of them fail.

I don't remember the chronology, but it's very likely that support for net-update was added before vlan tagging was supported, and that net-update support for it was either forgotten or deemed impractical to implement when vlan tag support was later added.

I am able to add the VLAN to the portgroup section, but then the VLAN configuration is not propagated to the underlying physical PF interface.

Aha! This can be used to work around the absence of support for changing the <vlan> element directly under <network>. If the guest has "portgroup='blah'" in it's interface <source> element (or if the <portgroup> you change has "default='yes'", then any guest that is started after adding the portgroup should use the new vlan tag. However, the pre-existing interfaces of pre-existing guests will not have their vlan tag changed.

If I manually add the VLAN configuration using the "virsh net-edit" command and then connect a VM to this network, then the VLAN information is correctly propagated to the underlying physical NIC device.

Note that "virsh net-edit blah" is functionally the same as: virsh net-dumpxml blah --inactive >/tmp/blah.xml [modify /tmp/blah.xml] virsh net-define /tmp/blah.xml (and of course you'll have to net-destroy / net-start the network for the changes to take effect).

I need a way to automate this configuration.

Any pointers?

Thanks, Yegappan

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