bizarre em + TSO + MSS issue in RELENG_7

[Kip Macy]

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?

Thanks.
 -Kip