bogus 0 len IP packet, was: Hang in VOP_LOCK1_APV on 8-STABLE with NFS.

[Ronald Klop]

On Sat, 22 Jan 2011 00:01:47 +0100, Ronald Klop  
<ronald-freebsd8 at klop.yi.org> wrote:

> On Tue, 18 Jan 2011 09:38:04 +0100, <sthaug at nethelp.no> wrote:
>
>>> > So, does anyone have an idea why the IP length field would be set to  
>>> 0
>>> > for these TCP/IP packets?
>>> >
>>> > Here's some info from Ronald w.r.t. his hardware. (All I can think  
>>> of is
>>> > that he could try disabling TSO, etc?)
>>> >
>>> > Thanks in advance for any help with this, rick
>>> >
>>>
>>> It seems that issue came from TSO. Driver will set ip_len and
>>> ip_sum field to 0 before passing the TCP segment to controller.
>>> The failed length were 4446, 5858, 3034 and 4310 and the total
>>> number of such frames are more than 35k within 90 seconds. Since
>>> failed length 4310 is continuously repeated I guess there is edge
>>> case where em(4) didn't free failed TCP segment for TSO.
>>> I remember there was commit to HEAD(r217295) which could be related
>>> with this issue.
>>
>> I'm seeing the same problem with Broadcom NetXtreme (bce) cards:
>>
>> bce0 at pci0:3:0:0:        class=0x020000 card=0x03421014 chip=0x164c14e4  
>> rev=0x12 hdr=0x00
>>     vendor     = 'Broadcom Corporation'
>>     device     = 'Broadcom NetXtreme II Gigabit Ethernet Adapter  
>> (BCM5708)'
>>     class      = network
>>     subclass   = ethernet
>>
>> This is with 8.2-PRERELEASE. Turning off TSO (ifconfig bce0 -tso)
>> removes the problem.
>>
>> Steinar Haug, Nethelp consulting, sthaug at nethelp.no
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>
> I tried -tso and -txcsum in various combinations, but it didn't solve  
> the problem. I wil look for another brand of network card to try. But  
> this has to wait till monday when I'm at the office again.

I also used another network card (rl0) and it has the same problem with  
NFS. I'm going to change some network cables to see if that helps. I have  
some hints that there might be something wrong with that.

Ronald.