Re: [Qemu-devel] replies

[Renzo Davoli]

> I don't know why qemu uses "tunX". You'd think it would be better off using 
> the
> "tapX" device instead. "tunX" is like "tapX" only it is point-to-point (no
> ethernet frames). tun is meant for ip tunnelling and passes ip frames while
> tap is for ethernet tunnelling.
> 
> If I understand right tunX will only support ip (and tcp/ip and udp/ip and 
> etc)
> while tap also supports ipx, ipv6, etc. Not 100% sure on this point. renzo 
> could
> probably answer better on this than I could.

Tap would be the more appropriate as entire packets with data-link header 
are exchanged.
> 
> > 
> > 2. Can I do traffic shaping / policing against TUN/TAP device attached to 
> > Qemu 
> > guest system? And if I can do it, should I attach the shaper against  
> > tun/tap 
> > or vde switch? 
> > 
VDE does not handle traffic shaping/filtering. It is an emulated
Ethernet with switches and cables. Consistently with the real world
counterpart it is not its role to do that.

You can do filtering/shaping on the linux box that works as a router.
Tap0 for it is a standard interface thus all the iptables options can be
applied.
> 
I am leaving for a conference. Dunno how frequently I'll be able to read
my mail and answer....

If you have spare time and need something to read for the sleep instead
of counting jumping sheeps, I have published a techreport on VDE (no
commands, philosophy only, what you can do with it) 
http://www.cs.unibo.it/techreports/2004/2004-12.pdf

ciao
        renzo