bizarre em + TSO + MSS issue in RELENG_7

[Mike Andrews]

On Sat, 17 Nov 2007, Kip Macy wrote:

> On Nov 17, 2007 2:33 PM, Mike Andrews <mandrews at bit0.com> wrote:
>> On Sat, 17 Nov 2007, Kip Macy wrote:
>>
>>> On Nov 17, 2007 10:33 AM, Denis Shaposhnikov <dsh at vlink.ru> wrote:
>>>> On Sat, 17 Nov 2007 00:42:54 -0500 (EST)
>>>> Mike Andrews <mandrews at bit0.com> wrote:
>>>>
>>>>> Has anyone run into problems with MSS not being respected when using
>>>>> TSO, specifically on em cards?
>>>>
>>>> Yes, I wrote about this problem on the beginning of 2007, see
>>>>
>>>>     http://tinyurl.com/3e5ak5
>>>>
>>>
>>> if_em.c:3502
>>>        /*
>>>         * Payload size per packet w/o any headers.
>>>         * Length of all headers up to payload.
>>>         */
>>>        TXD->tcp_seg_setup.fields.mss = htole16(mp->m_pkthdr.tso_segsz);
>>>        TXD->tcp_seg_setup.fields.hdr_len = hdr_len;
>>>
>>>
>>> Please print out the value of tso_segsz here. It appears to be being
>>> set correctly. The only thing I can think of is that t_maxopd is not
>>> correct. As tso_segsz is correct here:
>>
>>
>> It repeatedly prints 1368 during a 1 meg file transfer over a connection
>> with a 1380 MSS.  Any other printf's I can add?  I'm working on a web page
>> with tcpdump / firewall log output illustrating the issue...
>
> Mike -
> Denis' tcpdump output doesn't show oversized segments, something else
> appears to be happening there. Can you post your tcpdump output
> somewhere?


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