[ipxe-devel] SAN Boot Windows XP with USB-NIC.

Fri Mar 18 09:24:11 UTC 2011

Hi, Michael,

Add some of my observations.

My NB has an on board NIC. It can successfully sanboot windows xp. I 
captured the wireshark trace of the successful case and compare it to 
USB-NIC case.

Please open the attached wireshark trace files. For the same read command, 
frame 3 looks a bit different. Refer to the [Protocols in frame] field, the 
success case is "eth:ip:tcp:iscsi", the USB-NIC case is "eth:ip:tcp".

Do you have idea about why server side respond different for the same read 
command? Thanks very much!

Regards,
Jerry

----- Original Message ----- 
From: "jerrycheng-hinet" <jaspers.cheng at msa.hinet.net>
To: "Michael Brown" <mbrown at fensystems.co.uk>; <ipxe-devel at ipxe.org>
Cc: <Muralidhar.Appalla at emulex.com>
Sent: Friday, March 18, 2011 12:39 AM
Subject: Re: [ipxe-devel] SAN Boot Windows XP with USB-NIC.

>
> Thanks, Michael,
>
>> You need to prevent your server's network card from sending packets that
>> are
>> too large for the USB NIC to receive.  To do this, you can either:
>>
>> a) set the MTU on the server's NIC down to the standard Ethernet value of
>> 1500
>> bytes, or
>>
>> b) disable TCP segmentation offload (TSO) on the server's NIC.
>>
>> Let me know what happens!
>
> What I did to change the setting:
> a) ifconfig eth0 mtu 1500
> b) ethtool -K eth0 tso off
>
> I tried both ways with 2 different NICs (INTEL PRO/1000 PT Quad Port 
> Server
> Adapter and Realtek RTL8186C). Unfortunately, the result remained the 
> same.
> Please see attached trace file for more details.
>
> I don't know why the both ways did not take effect. If you have any ideas,
> please feel free to tell me. Thanks a lot!
>
> Regards,
> Jerry
>
> ----- Original Message ----- 
> From: "Michael Brown" <mbrown at fensystems.co.uk>
> To: <ipxe-devel at ipxe.org>
> Cc: "jerrycheng-hinet" <jaspers.cheng at msa.hinet.net>;
> <Muralidhar.Appalla at emulex.com>
> Sent: Thursday, March 17, 2011 9:20 AM
> Subject: Re: [ipxe-devel] SAN Boot Windows XP with USB-NIC.
>
>
>> On Tuesday 15 Mar 2011 18:06:05 jerrycheng-hinet wrote:
>>> > i.e. assume that the NIC supports interrupts if *either* the
>>> > ServiceFlags
>>> > indicate SUPPORTED_IRQ *or* the IRQ number is non-zero.
>>>
>>> I have tried to add above code to undinet.c. It seemed to work for my
>>> USB-NIC.
>>
>> Yes; unfortunately it would break undionly.kpxe running on an Emulex NIC.
>> Since the bug is in the PXE stack of your USB NIC (which is incorrectly
>> advertising that it does not use interrupts), I can't justify breaking 
>> the
>> Emulex NICs in order to make your USB NIC work.  We need to find some
>> other
>> solution.
>>
>>> So far, the sanboot seemed to get into trouble in NTDETECT.com. The
>>> screen
>>> showed "NTDETECT FAILED", then NB power reset happened .
>>>
>>> I have opened debug messages of "undinet, int13, autoboot, sanboot_cmd,
>>> iscsi" and captured the trace of whole booting process by wireshark.
>>>
>>> If you are available, please take a look at attached wireshark trace
>>> and.give me some suggestions? Thanks very much!
>>
>> Thanks for the packet trace!  It hadn't occurred to me to use 
>> DEBUG=syslog
>> as
>> a means of annotating a wireshark capture with inline debug output; it's
>> quite
>> a neat trick.
>>
>> It looks at a first glance as though the NIC suddenly goes deaf to 
>> packets
>> within a specific TCP connection.  For example, packet 1947 shows that
>> iPXE
>> must have received packet 1946 but not packet 1945. It then appears that
>> iPXE
>> ignores the retransmissions in packets 1948, 1949, 1950, 1959, 1960 and
>> 1961,
>> at which point the INT13 layer times out and closes the iSCSI connection.
>> iPXE then immediately successfully re-opens the iSCSI connection, which
>> proceeds happily until packet 2021, where the same pattern occurs.
>>
>> The troublesome packets are the first packets within their respective
>> connections to have a size which is greater than a standard Ethernet MTU.
>> Everything we see is wholly consistent with these large packets being
>> dropped
>> before they are received by iPXE.
>>
>> I think the problem is that you have the MTU on the server set to greater
>> than
>> 1500.  iPXE requests a TCP MSS of 1460 bytes, but I think the TCP offload
>> on
>> your server's network card may be ignoring that.
>>
>> You need to prevent your server's network card from sending packets that
>> are
>> too large for the USB NIC to receive.  To do this, you can either:
>>
>> a) set the MTU on the server's NIC down to the standard Ethernet value of
>> 1500
>> bytes, or
>>
>> b) disable TCP segmentation offload (TSO) on the server's NIC.
>>
>> Let me know what happens!
>>
>> Michael
> 
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