Why wireless interface cannot be attached to a Linux host bridge?

[Laine Stump]

On 7/7/20 11:26 AM, ryotaro kobayashi wrote:
> Hello, everyone.
> 
> I'm from japan and using machine translation, so I apologize if it's 
> hard to read.
> 
> I am currently trying to build a virtual environment using Ubuntu and kvm.
> 
> However, I found out from the following page that the virtual machine 
> cannot use the bridge network because I am using a wireless network.
> 
> https://wiki.libvirt.org/page/Networking
> 
> I am having trouble with this because my PC is using a wireless LAN.
> 
> On that page it says "wireless interfaces cannot be attached to a Linux 
> host bridge",  I Can you tell me why this is so?
> 
> Is it a limitation of the NIC driver for the wireless LAN?

Not really.

> Or is it a limitation of libvirt?

Definitely not. Completely out of libvirt's control.


It is a limitation of

1) the way that almost all wireless connections work (only traffic 
to/from a single MAC address is allowed on a particular wireless 
connection).

(Yes, I know there are some wireless modes that allow multiple MAC 
addresses on a single association. But those modes aren't supported by 
most wireless APs or clients.)

2) Because of (1), the Linux kernel doesn't allow wireless network 
devices to be attached to a Linux host bridge device.


Some people have had success with IPv6 by enabling proxy ARP on the 
bridge device and wireless interface (without directly attaching them to 
each other, then manually adding a host route pointing to the guest's 
IP. It might be possible to do something similar for IPv4 using proxy 
ARP, but I personally haven't played with the idea.