Unusual Packet Capture Between Linux and Windows

On 10/11/2011 3:08 PM, Andy Furniss wrote:
> Billy Mays wrote:
>
>> eth1 is the one that seems to be having the problem, while eth0 is an
>> interface I know to work (just to clarify the output below). I ran
>> ethtool on both of my interfaces and included only the differences
>> between them. I must admit I am not familiar with specifics of what they
>> do:
>>
>> Offload parameters for eth1:
>>
>> tx-checksumming: on
>> scatter-gather: on
>> tcp-segmentation-offload: on
>> generic-segmentation-offload: on
>>
>>
>> Offload parameters for eth0:
>>
>> tx-checksumming: off
>> scatter-gather: off
>> tcp-segmentation-offload: off
>> generic-segmentation-offload: off
>>
>>
>>
>> Which of these are safe to change? Would any of these possibly be the
>> source of my error?
>
> I would try
>
> ethtool -K eth1 tso off
>
> tcp-segmentation-offload means that you nic is doing some of the work to
> do with tcp that the kernel netcode usually does. This could be why you
> see different dumps as tcpdump will be seeing the packets before the nic
> has segmented them.
>
> It should be safe to turn off the others (tx sg gso) if you need to test
> further.
>
>


Trying to disable anything but gso seems to be disabled:

root@af:/# ethtool -K eth1 tso off
Cannot set device tcp segmentation offload settings: Operation not supported
root@af:/# ethtool -K eth1 gso off
root@af:/# ethtool -K eth1 rx off
Cannot set device rx csum settings: Operation not supported
root@af:/# ethtool -K eth1 tx off
Cannot set device tx csum settings: Operation not supported





How can these settings be turned on, but not able to be turned off?
Would it be easier to just spend $20 and get a new nic?

Bill

Billy Mays wrote:

> Trying to disable anything but gso seems to be disabled:
>
> root@af:/# ethtool -K eth1 tso off
> Cannot set device tcp segmentation offload settings: Operation not
> supported
> root@af:/# ethtool -K eth1 gso off
> root@af:/# ethtool -K eth1 rx off
> Cannot set device rx csum settings: Operation not supported
> root@af:/# ethtool -K eth1 tx off
> Cannot set device tx csum settings: Operation not supported

Hmm, maybe search for you nic/driver and see if a bug has been
reported/fixed.

> How can these settings be turned on, but not able to be turned off?
> Would it be easier to just spend $20 and get a new nic?

It may be quicker/less hassle - but I have no idea if it will actually
fix your main problem. With tso off at least the tcpdumps should match.

On 10/13/2011 5:52 AM, Andy Furniss wrote:
> Billy Mays wrote:
>
>> Trying to disable anything but gso seems to be disabled:
>>
>> root@af:/# ethtool -K eth1 tso off
>> Cannot set device tcp segmentation offload settings: Operation not
>> supported
>> root@af:/# ethtool -K eth1 gso off
>> root@af:/# ethtool -K eth1 rx off
>> Cannot set device rx csum settings: Operation not supported
>> root@af:/# ethtool -K eth1 tx off
>> Cannot set device tx csum settings: Operation not supported
>
> Hmm, maybe search for you nic/driver and see if a bug has been
> reported/fixed.
>
>> How can these settings be turned on, but not able to be turned off?
>> Would it be easier to just spend $20 and get a new nic?
>
> It may be quicker/less hassle - but I have no idea if it will actually
> fix your main problem. With tso off at least the tcpdumps should match.
>

For the sake of posterity, I believe I fixed the problem by updating my
kernel from 2.6.32-21-generic-pae to 2.6.38-11-generic-pae. Hope this
helps someone in the future.

Bill