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

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

[Aras Vaichas]

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.

As a comparison, I used udhcpc from Busybox to make the DHCP request and I get
a 100% success rate.

There are some obvious differences between the requests from the two pieces of
software. (my test Windows Server 2003 DHCP server is on 10.1.1.1 and is
offering 10.1.1.2). As I am not a low level DHCP packet expert, perhaps someone
else can make sense of this. I will also start studying the BOOTP options
fields and try and understand if any of the U-Boot DHCP packet options are
incorrect.


** U-Boot DHCP sequence **

DHCP Discover:
Seconds Elapsed = 1
Your (client) IP address: 0.0.0.0 (0.0.0.0)
Next server IP address: 0.0.0.0 (0.0.0.0)
Option 53: DHCP Message Type = Discover
Option 57: Maximum DHCP Message Size = 576
Option 55: Parameter Request List
	1 = Subnet Mask
	3 = Router
	12 = Host name
	17 = Root Path

DHCP Request:
Seconds Elapsed = 1
Your (client) IP address: 10.1.1.2 (10.1.1.2)
Next server IP address: 10.1.1.1 (10.1.1.1)
Option 53: DHCP Message Type = DHCP Request
Option 57: Maximum DHCP Message Size = 576
Option 54: Server Identifier = 10.1.1.1
Option 50: Requested IP Address = 10.1.1.2
Option 55: Parameter Request List
	1 = Subnet Mask
	3 = Router
	12 = Host name
	17 = Root Path


** udhcpc DHCP sequence **

DHCP Discover:
Seconds Elapsed = 0
Your (client) IP address: 0.0.0.0 (0.0.0.0)
Next server IP address: 0.0.0.0 (0.0.0.0)
Option 53: DHCP Message Type = DHCP Discover
Option 61: Client Identifier
	Hardware type: Ethernet
	Client MAC address: ...
Option 60: Vendor class identifier = "udhcp 0.9.9-pre"
Option 55: Parameter Request List
	1 = Subnet Mask
	3 = Router
	6 = Domain Name Server
	12 = Host Name
	15 = Domain Name
	28 = Broadcast Address
	40 = Network Information Service Domain
	41 = Network Information Service Servers
	42 = Network Time Protocol Servers

DHCP Request:
Seconds Elapsed = 0
Your (client) IP address: 0.0.0.0 (0.0.0.0)
Next server IP address: 0.0.0.0 (0.0.0.0)
Option 53: DHCP Message Type = DHCP Request
Option 61: Client Identifier
	Hardware type: Ethernet
	Client MAC address: ...
Option 60: Vendor class identifier = "udhcp 0.9.9-pre"
Option 50: Requested IP Address = 10.1.1.2
Option 54: Server Identifier = 10.1.1.1
Option 55: Parameter Request List
	1 = Subnet Mask
	3 = Router
	6 = Domain Name Server
	12 = Host Name
	15 = Domain Name
	28 = Broadcast Address
	40 = Network Information Service Domain
	41 = Network Information Service Servers
	42 = Network Time Protocol Servers



regards,

Aras Vaichas

______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email 
______________________________________________________________________

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

[Aras Vaichas]

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

______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email 
______________________________________________________________________

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

[Wolfgang Denk]

In message <452C8358.40009@magellan-technology.com> you wrote:
>
> 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?

I don't want to add such a delay. The RFC does not include any timing
information, which means that packets can be sent immediately. 

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Q: Why do PCs have a reset button on the front?
A: Because they are expected to run Microsoft operating systems.

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

[Aras Vaichas]

Wolfgang Denk wrote:
> In message <452C8358.40009@magellan-technology.com> you wrote:
>> 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?
> 
> I don't want to add such a delay. The RFC does not include any timing
> information, which means that packets can be sent immediately. 

Wolfgang,

I fully understand that and no-one wants to have to include delays in their
system but unfortunately Microsoft didn't write their DHCP server code to allow
for a client which responds as quickly as U-Boot can.

No-one is ever going to be able to fix old copies of Windows Server, so I
suggest an interoperability patch which allows U-Boot to work better with
Windows Server DHCP service. A small delay at boot time is certainly a lot
cheaper than spending hours on the telephone for customer support.

Our product has a customer base of over 1000 units and most of those will,
unfortunately, use Windows Server 2000/2003 as their DHCP server. We've known
for a long time that certain DHCP servers were causing problems and we were
telling people that they should use a fixed IP address until they fixed their
DHCP service. It wasn't until we sent an engineer from Australia to France that
we knew the depth of this interoperability problem.

My testing shows that a delay of around 15ms before sending the "DHCP Request"
will work 100% of the time with the VMware Windows Server 2003 that I set up on
my PC so I am going to put a delay of 30ms in my U-Boot image for safety.

I will send a U-Boot upgrade package to several of our customer sites for
testing before I roll it out to all of our customers.


regards,

Aras Vaichas


--- current/net/bootp.c 2005-11-18 12:18:48.000000000 +1100
+++ u-boot-1.1.3-MAGARMv3/net/bootp.c   2006-10-11 16:35:51.000000000 +1000
@@ -844,6 +844,10 @@
        NetSetIP(iphdr, 0xFFFFFFFFL, PORT_BOOTPS, PORT_BOOTPC, iplen);

        debug ("Transmitting DHCPREQUEST packet: len = %d\n", pktlen);
+       // delay a small amount because Windows Server 2003 has problems if you
reply too quickly
+       // 15ms was proven to be OK on my at91rm9200 system, so I'll double it
just in case
+        udelay(30000);
+
        NetSendPacket(NetTxPacket, pktlen);
 }




______________________________________________________________________
This email has been scanned by the MessageLabs Email Security System.
For more information please visit http://www.messagelabs.com/email 
______________________________________________________________________

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

[Wolfgang Denk]

In message <452D825F.8040304@magellan-technology.com> you wrote:
>
> I fully understand that and no-one wants to have to include delays in their
> system but unfortunately Microsoft didn't write their DHCP server code to allow
> for a client which responds as quickly as U-Boot can.

;-)

> --- current/net/bootp.c 2005-11-18 12:18:48.000000000 +1100
> +++ u-boot-1.1.3-MAGARMv3/net/bootp.c   2006-10-11 16:35:51.000000000 +1000
> @@ -844,6 +844,10 @@
>         NetSetIP(iphdr, 0xFFFFFFFFL, PORT_BOOTPS, PORT_BOOTPC, iplen);
> 
>         debug ("Transmitting DHCPREQUEST packet: len = %d\n", pktlen);
> +       // delay a small amount because Windows Server 2003 has problems if you
> reply too quickly
> +       // 15ms was proven to be OK on my at91rm9200 system, so I'll double it
> just in case
> +        udelay(30000);
> +
>         NetSendPacket(NetTxPacket, pktlen);
>  }

Please submit a proper patch, i. e.

* Include a CHANGELOG entry
* Make sure not to violate the coding style (no C++ comments,
  indentation by TABs, line length < 70
* Make sure that your mailer does not wrap lines

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de
"Success covers a multitude of blunders."       - George Bernard Shaw

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

[Wolfgang Denk]

In message <452C3EEA.9010202@magellan-technology.com> you wrote:
> 
> 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.

Please update to the latest version, i. e. top of tree in git
repository.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
"UNIX was not designed to stop you from doing stupid things,  because
that would also stop you from doing clever things."       - Doug Gwyn