Re: guessing when TSO is present

["ronnie sahlberg" <ronniesahlberg () gmail com>]

large segment offload (LSO)
can be easily detected by

TCP checksum==0    and being incorrect
and that the segment is much larger than the normal mtu.




On 4/7/06, Guy Harris <guy () alum mit edu> wrote:
> Hannes Gredler wrote:
> > checked in - thanks for the submission - /hannes
> >
> > On Wed, Jan 19, 2005 at 05:35:13PM -0800, Rick Jones wrote:
> > | A while back I think I posted something asking about what to do about
> TSO
> > | (large send) and how it generated "IP bad-len 0" output  when tracing on
> a
> > | TSO-enabled sender.
> > |
> > | I had a couple spare cycles, so I decided to just take a WAG at what
> might
> > | be done, which was to say that if the IP len was zero, just go ahead and
> > | guess that this was a TSO and set the len to the length parm pass-in to
> > | print-ip and hope.
> >
> > [ ... ]
> >
> > | basically, if the IP len is zero, ass-u-me that the segment is TSO and
> wing
> > | it.
> > |
> > | rick jones
>
> Should we make that the default, or would that be too risky?
>
> See
>
>  https://sourceforge.net/tracker/index.php?func=detail&aid=1437110&group_id=53066&atid=469573
>
> which I suspect is caused by TSO.
> -
> This is the tcpdump-workers list.
> Visit https://lists.sandelman.ca/ to unsubscribe.
-
This is the tcpdump-workers list.
Visit https://lists.sandelman.ca/ to unsubscribe.