Re: UEFI-PXE boot to grub2 with BIOS configured VLAN tagging?

[Andrei Borzenkov]

On Mon, Jan 9, 2017 at 1:16 PM, Christian Rohmann
<address@hidden> wrote:
> Hey Andrei, help-grub,
>
> On 01/06/17 17:12, Andrei Borzenkov wrote:
>>
>> The latter. There were patches to add tagged VLAN support (and they are
>> used by vendors, e.g. SUSE). Not sure what happens in case of netboot
>> though ... no, it adds core network support and ofnet driver support. No
>> UEFI patches.
>>
>> I am not sure how we should proceed with auto-configuration either. It
>> does not look like PXE_BASE_CODE_MODE structure contains information
>> about VLAN. So we probably need to somehow query interface. Someone
>> having such configuration is welcomed to provide patches :)
>>
>> ofnet is easier because we get this information directly from firmware.
>> On UEFI someone needs to find out how to get this information.
>
>
> Yeah, looking at http://dox.ipxe.org/structEFI__PXE__BASE__CODE__MODE.html
> it does not seems to contain any VLAN info for EFI boot as well.
>

This is not enough anyway, we query underlying interface for some
parameters already. We can just as well add additional query for VLAN
tags. I need example of device tree in such case though.

> I am just wondering if the VLAN defined prior to booting (i.e. via the
> UEFI-BIOS) is transparent to the software doing the network boot and the NIC
> simply tags all frames.

Jein :)  This would work if application (grub) used UEFI APIs to
access files over network. But grub works with physical underlying
adapter and bypasses (or, actually, actively unbinds) all other
protocols, including VLAN. So we need to query, which VLAN was used to
bootstrap grub, and configure it later using our own grub tools.

> iPXE does have VLAN support though, so somehow
> configuration of VLANs is possible, see http://ipxe.org/buildcfg/vlan_cmd .
>

The question is not how to configure VLAN, but how to detect, which
VLAN was used to bootstrap us. grub patches I mentioned simply
explicitly send tagged VLAN packets over base interface, so they
should work on every platform. Revisiting these patches, they do not
add user interface (commands) to configure VLAN interfaces though.

http://git.savannah.gnu.org/cgit/grub.git/commit/?h=pfsmorigo/vlantag