[U-Boot-Users] dhcp problems with Windows Server

[Aras Vaichas <arasv@magellan-technology.com>]

Aras Vaichas wrote:
> Hello,
> 
> I'm seeing problems with the DHCP mechanism in U-Boot and the DHCP server on
> Windows Server 2000/2003. We use U-Boot 1.2 on an at91rm9200 based platform
> with the DM9161 PHY.
> 
> Now I understand that this may not be a U-Boot problem, but for the sake of
> interoperability it may be a good idea to try and fix it as many people use
> Windows Server ...
> 
> Normally we use Un*x DHCP servers and I get 100% success rate but with the
> Microsoft version of DHCP I see about a 75% success rate. i.e. 1 in 4 requests
> will fail.
> 
> Looking at the packets with Ethereal, it looks like the DHCP server isn't
> sending the final "DHCP ACK" for the "DHCP Request" from the U-Boot. Something
> that U-Boot is sending in the "DHCP Request" to the Windows Server is causing
> it to fail occasionally.

Sorry to answer my own question, but I've found the problem and a solution.

The problem appears to be that Windows Server is occasionally too slow to be
able to process the DHCP request. If the time between Windows Server sending
the "DHCP Offer" and U-Boot sending the "DHCP Request" is too short, the
Microsoft DHCP server fails to send the DHCP ACK.

I discovered this when I compiled debugging in to net/bootp.c and I proved it
when I delayed the "DHCP Request" by a small amount (using a printf).

e.g. a DHCP discovery request

U-Boot:	DHCP Discover?
Windows Server DHCP server: DHCP Offer = a.b.c.d
** insert small delay here **
U-Boot: DHCP Request = a.b.c.d?
Windows Server DHCP server: DHCP ACK

I'm not sure what the actual delay should be and I'm not sure where it should
go. Wolfgang, can you suggest a place to put a delay, and should it be wrapped
in a CONFIG_ option?



regards,

Aras Vaichas

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