Wired and Wireless with Etables

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Wired and Wireless with Etables

Ray Joseph
I would like to determine how to configure dom0 to use either wireless or wired connections automatically depending upon which are available. 

The machine will come up in Xen when configured as either wired or wireless.  This may not be relevant, but Xen will not boot if wireless is configured and no wireless is available, nor if both are configured and set to the bridge set to wired and wireless is not available.

 

I am trying to get Xen4.9 up and Debian 9 on a Toshiba laptop with only a wireless and a wired (enx0) connection through a docking station.  I am trying to use:  https://wiki.debian.org/BridgeNetworkConnections#Bridging_with_a_wireless_NIC

This laptop is a personal workstation implementing a variety of vms and OSs. Testing wireless internet connection is using JetPack 4G AP and I intend to use various public/private wireless APs. 

 

It seems the way to do this is to bond wlan0 and eth0 as bond0, then build a bridge for domus with bond0.  Etables requires the bridge MAC to be defined in the rules.  I do not know how to assign a MAC to the bridge since I don't know which interface came up.

 

How can I set up bridging without knowing which interface is up?

Thanks,
Ray

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Re: Wired and Wireless with Etables

Simon Hobson-2

On 1 Jul 2017, at 13:16, Ray Joseph <[hidden email]> wrote:

> I would like to determine how to configure dom0 to use either wireless or wired connections automatically depending upon which are available.
>
> The machine will come up in Xen when configured as either wired or wireless.  This may not be relevant, but Xen will not boot if wireless is configured and no wireless is available, nor if both are configured and set to the bridge set to wired and wireless is not available.

Does it give any clues as to what the problem may be ? It doesn't sound right, because the networking isn't done by Xen.

> It seems the way to do this is to bond wlan0 and eth0 as bond0, then build a bridge for domus with bond0.

No, just no. Do not try introducing bonding as it just isn't what you need.

> Etables requires the bridge MAC to be defined in the rules.  I do not know how to assign a MAC to the bridge since I don't know which interface came up.

As I said to you in reply to your off-list response - for ETHERNET networking you do **NOT** need to do any of that ebtables stuff. Really, you do NOT need to do anything.

> How can I set up bridging without knowing which interface is up?

Lets get some basics in first.
The bridge can exist without any devices attached to it. Devices can be dynamically added and removed as needed - and this the default action by Xen as guests are created (VIF created and added to bridge)/destroyed (VIF removed from bridge and destroyed).
You can assign an IP to the bridge regardless of whether any devices are attached to it.
You can attach an ethernet interface without it being connected to anything (ie cable unplugged).
I don't know if that is the case with a WiFi interface - try it and see.

So it should be sufficient to create a bridge and add both the ethernet and WiFi interfaces to it. The host should then be able to network using either interface depending on which is connected. You should leave STP turned on, otherwise you'll find a network loop that will kill your network if you have both WiFi and Ethernet connected to the same network.

Now, back to running Xen over that bridge.

Over ethernet, you do NOT need any ebtable rules - it just works out of the box as it were.
You *may* need the ebtables rules when using WiFi (you may find you don't) - but it's safe to leave these in place as they won't have any effect on traffic over the ethernet interface.
So it should be perfectly safe to configure the bridge with the ebtables rules for using WiFi whichever interface is in use. Furthermore, it should be safe to configure the MAC address of the bridge to be that of the WiFi interface even when using ethernet.


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