On Tue, Mar 18, 2025 at 02:58:18PM +0100, Michal Privoznik via Devel wrote:
From: Michal Privoznik <mprivozn@redhat.com>
If a guest changes MAC address on its vNIC, then QEMU emits NIC_RX_FILTER_CHANGED event (the event is emitted in other cases too, but that's not important right now). Now, domain XML allows users to chose whether to trust these events or not:
<interface trustGuestRxFilters='yes|no'/>
For the 'no' case no action is performed and the event is ignored. But for the 'yes' case, some host side features of corresponding vNIC (well tap/macvtap device) are tweaked to reflect changed MAC address. But what is missing is reflecting this new MAC address in domain XML.
Basically, what happens is: the host sees traffic with new MAC address, all tools inside the guest see the new MAC address (including 'virsh domifaddr --source agent') which makes it harder to match device in the guest with the one in the domain XML.
Therefore, report this new MAC address as another attribute of the <mac/> element:
<mac address="52:54:00:a4:6f:91" guestAddress="00:11:22:33:44:55"/>
IIUC, the "guestAddress" also influences things on the host - the macvtap device seems to get re-programmed with the MAC, so perhaps this is a slightly misleading name. How about 'activeAddress' / 'liveAddress' / 'currentAddress' With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|