Re: [Qemu-devel] using -net dump with tap networking

[Stefan Hajnoczi]

On Tue, Feb 19, 2013 at 09:53:07AM +0100, Markus Armbruster wrote:
> Stefan Hajnoczi <address@hidden> writes:
> 
> > On Tue, Feb 19, 2013 at 12:37:28PM +1100, Alexey Kardashevskiy wrote:
> >> On 14/02/13 21:26, Stefan Hajnoczi wrote:
> >> 
> >> >>>>Now I want to enable network dump. With the old "-net" syntax I could 
> >> >>>>do
> >> >>>>that with "-net dump" but I cannot with the new syntax, tried many
> >> >>>>variants, none works. What would the correct syntax be for the case 
> >> >>>>above?
> >> 
> >> The question was about new "-netdev" interface.
> >> 
> >> >I would do:
> >> >
> >> >qemu-system-ppc64 ...
> >> >       -net tap,ifname=tap0,script=qemu-ifup.sh
> >> >       -net nic,model=virtio
> >> >       -net dump,file=./dump.lan.qemu.virtio
> >> >
> >> 
> >> The answer is about old "-net" interface which I know how to use.
> >> 
> >> Does this mean that there is no way to use "dump" with "-netdev tap"?
> >
> > It is not possible using just -netdev/-device.  The closest you can get
> > is:
> >
> >   $ qemu -netdev hubport,hubid=1,id=hubport0 \
> >          -device virtio-net-pci,netdev=hubport0,... \
> >      -net tap,vlan=1,... \
> >      -net dump,vlan=1,...
> 
> Care to explain briefly how hubport works, and how it's connected to the
> legacy "vlan" feature?

-netdev hubport instantiates a new port on a hub with "vlan" number
hubid=<number>.

hubport is a -netdev, so it allows you to hook up a NIC to a hub using
-netdev/-device syntax.

This is just playing games with syntax, we still have a hub in between
the virtio-net-pci, tap, and dump devices.  I didn't check if the
offload features get plumbed through, but I wouldn't count on it.

Stefan