Re: ifconfig v2

[David Young <dyoung%pobox.com@localhost>]

On Wed, Jun 12, 2013 at 05:07:06PM +0100, Robert Swindells wrote:
> 
> David Young wrote:
> >I find it hard to ignore the larger issue, though, which is that those
> >capability flags are only useful insofar as the NetBSD networking stack
> >and drivers are distrusted or buggy and some masochists like to turn
> >knobs until they find a combo that works. :-) Ordinarily a driver should
> >enable the offload capabilities that are known to work reliably, and it
> >should not advertise the buggy ones.
> 
> The offload features can't be used if the device is linked to another
> using bridge(4), there may be other combinations of pseudo-interfaces
> that cause problems too.

This is one of the bugs that needs to be fixed.  I agree that the
default capability-flag settings should not change until the various
bugs are fixed.

Same goes for the bpf bugs that der Mouse mentions.  Those are more
difficult to fix: how should TSO be treated by what is essentially a
diagnostic interface?  Turning off segmentation offload while a bpf tap
is active will change the performance of the system you're observing.
Tapping synthetic segmented packets is misleading.  You could tap
unsegmented packets, but how will an app distinguish those from real
packets?

Dave

-- 
David Young
dyoung%pobox.com@localhost    Urbana, IL    (217) 721-9981