[libvirt] [PATCHv2 0/4] support <vlan> element for interfaces and networks

danpb raised a (valid) objection about the XML format in the first version of these patches, so I've redone it to be like this: <vlan trunk='yes'> <tag id='42'/> <tag id='30'/> </vlan> The downside is that for a single vlan tag, it's more verbose: <vlan> <tag id='42'/> </vlan> On the other hand, it's more consistent. The rest of the patches in the series were unchanged (and even the data definition is unchanged). === The purpose of these patches is to define a data type that can properly describe an interface's vlan configuration (including multiple vlans for trunking), provide XML parser and formatter to translate to and from the new data type, add the new <vlan> element to both domain <interface> and to <network> in appropriate places, and to provide the new vlan data to the hypervisor driver. Once these 4 patches are applied, all that will be left to support vlan configuration for any network connection that supports it, is to request the vlan data for the interface with virDomainNetGetActualVlan(netdef). If that function returns NULL, there is no vlan config for this interface; if it's non-zero, it is a pointer to virNetDevVlan, and you can grab the data from there. Since I currently know of only two types of network connection we will be able to easily support this for (sr-iov VFs using PCI passthrough, and openvswitch), any type other than those will refuse to start if a vlan has been requested (see PATCH 4/4). This covers validation for the qemu and lxc drivers (since they use common code), but I'm not sure about xen, esx, or any other driver - they will likely require extra code to either implement transparent vlan configuration, or log an error if it's requested (my guess is that, in spite of our best efforts, *many* people will misunderstand the limitations of this functionality, and try to put all sorts of interfaces on vlans; it will be much friendlier to inform them of the problem rather than simply ignore the vlan config.