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...

Thanks for the quick follow-up. That means that maxopd is not getting
initialized correctly, which means I'm going to have add some logging
to tcp_input. Which means it will have to wait until this evening at
the earliest. This does, however, mean that em is off the hook. It is
just doing what it is told.

 -Kip