Re: IP bad-len 0 ( on em0 )

On Wed, Apr 9, 2008 at 11:35 PM, Vitezslav Novy <vnovy_at_vnovy.net> wrote:
> Jack Vogel wrote:
>
> > On Wed, Apr 9, 2008 at 10:43 AM, Nikolay Pavlov <qpadla_at_gmail.com> wrote:
> >
> > > On Thursday 06 March 2008 01:35:43 Steven Hartland wrote:
> > >  > Did you ever get anywhere with this? Did Jack respond?
> > >
> > >  Nope. I've disabled tso.
> > >
> >
> >
> > I've looked into this a little, and then got interrupted with other
> issues. The
> > reason the thing is zero'ed is because the hardware is going to
> repacketize
> > this big wad that its been handled, it should be making new headers that
> > appear in the packets on the wire. So its not  yet clear to me what the
> > real brokenness is, you are actually SUPPOSED to zero that value and
> > csum according to documentation, but the rewritten headers should have
> > correct len's in them, so the question is why in some cases they do not.
> >
>
>  I think packets on wire have correct IP-len, but after sending packet to
> card, driver injects original long packet with zeroed IP-len to BPF.
>  So in tcpdump, we see packet with zero IP-len.
>
>
>  vita
>
>
>

ahhh, yes, that makes sense, hmmm, suggestions on what to do about it?

Jack