tcp_output() might generate invalid TSO frames

[Jack Vogel]

No, the problem Mike is having is due to an issue in our new shared code
in how we get the mac address, we changed it to support alt mac addresses,
and it works find on our hardware, there is an issue in the vmware
emulation.

Nevertheless, if there's a problem in the TSO code it would be nice to get
that fixed.

Jack


On Wed, Apr 15, 2009 at 11:06 AM, Kip Macy <kmacy at freebsd.org> wrote:

> Interesting. That might explain a problem that Mike Silbersack is
> seeing with the latest em driver on vmware.
>
> I don't know of any NICs that actually choke on such frames.
> Nonetheless, it is silly behavior. I'll try to see if we can get this
> fixed before 7.2.
>
> Thanks,
> Kip
>
> On Wed, Apr 15, 2009 at 8:40 AM, Renaud Lienhart <renaud at vmware.com>
> wrote:
> > Hi,
> >
> > We're having trouble virtualizing FreeBSD 7+ on ESX because of an issue
> > with the stack's TSO implementation: it sometimes generates TSO packets
> > whose payload size is actually smaller than the MSS.
> >
> > The faulty logic is described, along with a patch, in PR #132832. It
> > has been opened for a while now, without any apparent activity, which
> > is why I'm reaching the mailing list directly.
> >
> > ESX currently drops these packets as many physical nics are known to
> > choke on such frames, which effectively limits FreeBSD guests'
> > performance.
> > I don't know about other virtualization stacks' behavior.
> >
> > http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/132832
> >
> > Thanks for your time,
> >
> >        Renaud
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>
>
> --
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