[solved]QEMU/virt-manager/session: problem setting up virbr0

equaeghe · l33t Joined: 22 Feb 2005 Posts: 637

I'm using virt-manager for a Win11 VM. Currently, I'm using (default) user-mode networking, but I have the impression it has limitations I need to overcome (OneDrive connection in Windows does not work). I gather from various online docs that using a bridged network is the way to go and that I should select virbr0 as the interface. However, that does not work for me. I do not have the virbr0 interface and it is unclear to me what I would need to do to get it.

I read that I needed to set up a qemu:///system connection (I just have a qemu:///session one now) and that that would result in the virbr0 interface being created. However, when I try that, I get the message

alamahant · Advocate Joined: 23 Mar 2019 Posts: 3879

If you need your VMs to be on the same LAN as your host machine,then and only then you will need to manually create a bridge iface on top of your ethernet.
Do you need this?
Do you have ethernet or wifi?
Virbr0 etc are created by libvirt in order to provide NAT networking to your vms and you normally do not need to do anything manual.
As for libvirt, it has recently become modular.
Try

NeddySeagoon · Posted: Tue Apr 02, 2024 12:27 pm Post subject:

equaeghe,

virbr0 is not a bridge like you are thinking.

Its a NAT node with the IP address 192.168.122.1 on the VM side and provides NAT to your LAN, which is probably further NATed to the outside world.
This just works for outgoing (from the VM) initiated networking but incoming would need port forwarding.

OneDrive works behind NAT, so you shouldn't need a real bridge.

If you want a real bridge, add another (virtual) NIC to your guest and set that up as a bridge.
Make sure its used for the default route.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

equaeghe · l33t Joined: 22 Feb 2005 Posts: 637

@NeddySagoon: Thanks for your input. You were right that I didn't need anything special in terms of network; the OneDrive issue was not related to that (hadn't used it recently enough, so they had blocked that account…).

@alamahant: Your suggestion to enable some of libvirtd's services put me on the right track. In the end I enabled virtnetworkd.service, virtnodedevd.service, virtqemud.service, and virtstoraged.service (possibly overkill: I enabled things that were complained about as missing in my logs). Then virbr0 was auto-created in the qemu:///system connection I setup and I could reuse it in my qemu:///session connection after saying "allow virbr0" in /etc/qemu/bridge.conf.

N.B.: I was possibly also missing some kernel modules.I find out which to add to my config by looking at the ebuild of qemu and libvirt and checking the CONFIG_CHECKs being done.

My qemu VM setup has now surpassed my virtualbox VM setup, so I can ditch the latter and its inconvenient out-of-tree kernel module. :-)