[Qemu-discuss] missing some fundamental concepts

[F. Heitkamp]

I have been trying to get a QEMU hosted virtual machine to connect to my 
host network.

I have a simple network configuration on my host.
It is configured on 192.168.0.0/16.

There is a dhcp and dns caching server running on the host
The host interface is enp9s0 and hast a static IP 192.168.0.2
Everything works fine. I have several computers and devices on my
network and they are able to obtain addresses from my host, and 
communicate with the outside world.

My virtual machine installation runs GNOME network manager and is able
to connect fine, i.e. obtain address vi a dhcp etc., to my network when
installed on a hard disk and booted on one of my other computers.

When I copy the installation to a image file I can boot it with qemu and
with default options it runs and I am able to run firefox and surf the
web etc.  The problem is the machine  is on the 10.0.2.0 net coming from 
QEMU using the slirp interface I suppose.

What I am trying to get working is to make the installation connect to
my host network so I can mount an NFS share to it.
My other boxes, on my network, are able to run the image, mount the NFS 
when running in VMWARE and Virtualbox.

I tried configuring the qemu command line with option:
  -netdev user,id=mynet0,net=192.168.0.0/16 -device e1000,netdev=mynet0

When the machine boots it gets an address 192.168.2.x hence is not on 
the  same subnet on my host. If I change the address and routing  to be 
on the same subnet it  still does not see my host network.

I tried using iproute2 utils to create a bridge and a tun/tap  device 
bridged to enp9s0  on my host.  However two problems occur, one I lose 
connectivity to the outside world, two, the bridge I create is not 
detected by my virtual  machine when running in qemu. Most of the 
bridging examples also  assign a static IP to the bridge.

I also have an unused Ethernet port/card on the host.
I am also avoiding libvirt, spice, etc for the time being in order to 
torture myself.

The problem seems deceptively simple:
Allow qemu to detect my host network and use the host dhcp server to 
obtain an IP address using either some sort of bridge or by passing the 
unused NIC on the host through qemu. None of my surfing has found 
solutions to these, at least in a way I understand.

Usually this means it is intuitively obvious or no one else wants  to do 
this.

Any suggestions welcome.

Fred