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From: Thomas Glanzmann on 24 Nov 2009 09:18
Hello,
we have a T5220 with e1000 network cards and tcp checksum offloading
enabled. The problem is that the checksum is incorrectly computed for
some values:

(ad054764pc) [~] tshark -r zweiter.pcap -V frame.number == 46 | grep -i checksum
Header checksum: 0x4123 [correct]
Checksum: 0xffff [should be 0x0000 (see RFC 1624)]
[Good Checksum: False]
[Bad Checksum: False]

The problem is that I have DOS TCP stack that is RFC aware and ignores such
packets. Now my question is if someone hit this bug before and if there is
patch available and how to disable tcp offloading on Solaris 10 to circumvent
the problem.

This is on Solaris 10 Update 5 with all patches applied. The error is reproducable.

Thomas
From: Thomas Glanzmann on 24 Nov 2009 13:04
Hello,

* Thomas Glanzmann <sithglan(a)stud.uni-erlangen.de>:
> we have a T5220 with e1000 network cards and tcp checksum offloading
> enabled. The problem is that the checksum is incorrectly computed for
> some values:

> (ad054764pc) [~] tshark -r zweiter.pcap -V frame.number == 46 | grep -i checksum
> Header checksum: 0x4123 [correct]
> Checksum: 0xffff [should be 0x0000 (see RFC 1624)]
> [Good Checksum: False]
> [Bad Checksum: False]

there was a similar bug failed and fixed. A college confirmed that the
kernel patch is already applied the problem still pops up:

http://sunsolve.sun.com/search/document.do?assetkey=1-1-6533773-1

I also filed a bug report with Solaris and keep this thread updated.

Thomas
From: Martha Starkey on 25 Nov 2009 12:46
On 11/24/09 09:18, Thomas Glanzmann wrote:
> Hello,
> we have a T5220 with e1000 network cards and tcp checksum offloading
> enabled. The problem is that the checksum is incorrectly computed for
> some values:
>
> (ad054764pc) [~] tshark -r zweiter.pcap -V frame.number == 46 | grep -i checksum
> Header checksum: 0x4123 [correct]
> Checksum: 0xffff [should be 0x0000 (see RFC 1624)]
> [Good Checksum: False]
> [Bad Checksum: False]
>
> The problem is that I have DOS TCP stack that is RFC aware and ignores such
> packets. Now my question is if someone hit this bug before and if there is
> patch available and how to disable tcp offloading on Solaris 10 to circumvent
> the problem.

"TCP/IP: How to disable NIC hardware checksumming in Solaris[TM]."

http://sunsolve.sun.com/search/document.do?assetkey=1-61-214543-1

>
> This is on Solaris 10 Update 5 with all patches applied. The error is reproducable.
>
> Thomas
From: Oscar del Rio on 25 Nov 2009 12:52
Martha Starkey wrote:
>
> "TCP/IP: How to disable NIC hardware checksumming in Solaris[TM]."
>
> http://sunsolve.sun.com/search/document.do?assetkey=1-61-214543-1

Just to save some time to readers: these documents require Sun Contract
to access them.
From: Thomas Glanzmann on 25 Nov 2009 13:56
Hello Martha,

> "TCP/IP: How to disable NIC hardware checksumming in Solaris[TM]."

> http://sunsolve.sun.com/search/document.do?assetkey=1-61-214543-1

thank you a lot. For the people who don't have an account or find this using
google:

put that into /etc/system and reboot:

set ip:dohwcksum=0

Thomas
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