need help configuring network passthrough for QEMU KVMs

Shadow_Fury

i'm trying to follow this guide on the gentoo wiki to try to set up a network bridge using iptables.

i've gotten down to the guest configuration section, but the VM is not detecting the network. i'm using aQEMU to manage the vm, but i'm pretty sure i've got that set correctly. what confuses me is how to carry out this instruction on the wiki:

alamahant · Advocate Joined: 23 Mar 2019 Posts: 3879

Do not use tun-tap manually.
Just create a linux bridge on the host with the host's ethernet interface as its slave.
Then assign this bridge to your qemu guests
It works fine this way foe qemu-libvirt.
Do you have an ethernet interface?
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Shadow_Fury · Posted: Fri Jan 14, 2022 6:09 pm Post subject:

well, the physical interface of the host is called eno1, i've reated a bridge br0, as well as a tap interface: tap0.

i'm a little unsuer how to proceed though.

alamahant · Advocate Joined: 23 Mar 2019 Posts: 3879

Shadow_Fury · Posted: Fri Jan 14, 2022 7:36 pm Post subject:

i'm pretty new to command line networking, so i'm not sure what you mean by sole slave, or how to check that.

i've followed all of the instructions in the wiki article, and that is all i know on the matter.

aslo, i'm not using sole qemu. i'm using a graphical overlay called "aQEMU" yes, the name is a bit confusing.

the way you set network interfaces there, is by selecting a "connection type" (one of: {nic, user, channel, tap, socket, multicast socket}), and then configuring some parameters. in my case, the only parameter i have set is the "ifname, and i've set it to tap0.

i have no idea how to proceed, so it would be helpful if i was provided with the commands i need to run.

*just to clarify, i have virt-manager installed, i just don't use it. this is because, since my system is pretty much a pure qt5/kde system, virt-manager compiled without gtk, so no GUI. aQEMU is qt based so it works well with my system. i'm fine to switch if it doesn't work, though preferably to something that will respect my window decoration/other aesthetics, since a white gtk window in no way fits with my system theme (not least because the entire system is dark mode)

Shadow_Fury · Posted: Sun Jan 16, 2022 12:13 am Post subject:

so, update. I tried re-compiling virt-manager with gtk, and this indeed gave me a GUI (that, indeed didn't follow my system style)

this however, fails even earlier. specifically, it fails to connect to qemu://system, thus meaning i cannot even create a VM, mutch less connect it to a network.
any help is appreciated

alamahant · Advocate Joined: 23 Mar 2019 Posts: 3879

Plz start libvirtd and make sure your user is member of the group "libvirt"
Do you have libvirt emerged?
Now you dont need ANY tap/tun interfaces.
Just create a bridge out of your ethernet and assign this bridge to your virt-manager guests.
If you need help creating the bridge plz let us know.
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Shadow_Fury · Posted: Sun Jan 16, 2022 1:18 am Post subject:

now virt-manager just hangs when trying to connect. i've started libvirtd via openRC, and added my user to the libvirt group, what should i do? it did manage to connect once, but after the system rebooted, it stopped working

edit: got it to connect to qemu/kvm, but now creating a disk hangs, and actually connecting to qemu/kvm takes a good couple of minutes

nevermind, VM created correctly. still, the process seemed unusually slow

alamahant · Advocate Joined: 23 Mar 2019 Posts: 3879

It shouldnt take all this time.
Plz post

NeddySeagoon · Posted: Sun Jan 16, 2022 11:06 am Post subject:

Shadow_Fury,

Ethernet bridging and Ethernet pass through are two different things.

A bridge is the software equivalent of an Ethernet hub. All packets on the bridge get sent to all the ports on the bridge.
The host may or may not have an IP on the bridge.

Pass through removes the device from the host and donates it to the guest. This needs hardware support on the host and the hardware being passed through.
I spent a week trying to make this word only to discover a hardware bug in my four port network card that made it impossible, so I did bridging instead.

At the outset, it's essential that your eno1 interface does not get an IP address of its own, so your /etc/conf.d/net file on the host needs

Shadow_Fury · Posted: Sun Jan 16, 2022 11:54 am Post subject:

it seems networking is fine now, the NAT interface provided in virt-manager works out of the box.

Dominique_71 · Posted: Thu Mar 17, 2022 3:57 pm Post subject:

I am installing Debian into qemu and I try both aqemu and virt-manager. aqemu was not updated from 2 years ago and it use outdated qemu options, which imply I didn't succeeded to get it to work with the network. virt-manager is the way to go. It's network connection just worked out of the box.

Also, at that time with my ~amd64 gentoo system, the group the user must be in is not livirt (group don't exist) but wheel.

NeddySeagoon · Posted: Thu Mar 17, 2022 9:25 pm Post subject:

Shadow_Fury,

Both ways work. For remote inbound connections to the VM, the bridge is easier to work with.

The default NAT interface does not support IPv6, if that matters to you.
_________________
Regards,

NeddySeagoon

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