Heinrich Schuchardt xypron.glpk at gmx.de
Tue Aug 6 18:52:09 UTC 2019

On 8/6/19 7:02 PM, Peter Jones wrote:
> On Tue, Aug 06, 2019 at 09:44:14AM +0100, Leif Lindholm wrote:
>> +Peter Jones (sorry Peter)
> + Javier Martinez Canillas
>> On Tue, Aug 06, 2019 at 08:34:58AM +0200, Heinrich Schuchardt wrote:
>>> iPXE uses the EFI simple network protocol to execute DHCP.
>> OK.
>>> Can GRUB already do the same when the EFI_PXE_BASE_CODE_PROTOCOL is not
>>> present?
>> Yes. As of very recently (proper* DHCP support was only merged in
>> March 2019, so is included in 2.04 release, prior to that it
>> technically performed BOOTP).
>> SNP means you do your own networking - it gives you access to the raw
>> (usually) Ethernet packets.
>> * proper as in "it now conceptually does the correct thing", not as in
>>    "I have extensively tested this".
>>> What I do not understand about GRUB's grub_net_configure_by_dhcp_ack()
>>> is that it silently assumes IPv4 being used without even checking. This
>>> contradicts the definition of the PXE base code protocol in the UEFI
>>> standard:
>> Well, it would not surprise me if this function predates GRUB's UEFI
>> support.
>> It actually gets even slightly messier when you look at what GRUB does
>> when netbooting itself; it starts out using MNP (and hence IP
>> addresses assigned by UEFI) to load its modules, switching to SNP once
>> it loads efinet.mod.
>>> EFI_PXE_BASE_CODE_PACKET DhcpAck is a union:
>>> typedef union {
>>>   UINT8                             Raw[1472];
>>> Should the check be done in grub_efi_net_config_real()?
>> Possibly. I've cc:d Peter since he's the last person I know who took a
>> proper look at this.
> That's actually what we've got in our current patch set, based on
> Michael Chang at SuSE's https work.  Javier Martinez (cc'd) is working
> on getting those ready for upstream, but in the mean time, check out the
> patches nearby to:
> https://github.com/rhboot/grub2/commit/4f977935a9271727bf21889526fdf82f0fc8fed9

Thank you for the link.

There are currently no plans to implement these device paths in U-Boot:

* IPv4 Device Path
* IPv6 Device Path
* Uniform Resource Identifiers (URI) Device Path

I assume that these device paths would only be installed on handles
implementing the EFI DHCPv4 Protocol or the EFI DHCPv6 Protocol but
could not identify the relevant information in the specification.

Best regards


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