Obviously the task is even easier than I had thought. Yesterday I
finally found the time to port the patch mentioned to
qemu-0.12.2. Once I had fired up a qemu virtual machine with
one virtual ethernet interface as
userspace-networking (using slirp code) and one virtual ethernet
connected to eth0 using pcap both connected to vlan=0 (behaves
like a bridge) on my sles11-linux-box I had exactly the desired behaviour.
(user-space nat, dhcp-server, dns-forwarding)
What is running inside the virtual-machine is of course
quite irrelevant. In fact the whole virtual-machine-stuff shouldn't be there
making the approach quite bloated and unnecessarily complicated to
port to freemantle-arm-scratchbox.
The commandline for this looks something like "qemu -boot d
-cdrom /windows/D/iso/SUSE_SLES-11-0-0.001.ISO -m 512
-net nic,model=e1000,vlan=0 -net pcap,ifname=eth0,vlan=0
-net nic,model=e1000,vlan=0 -net user,vlan=0".
So if somebody is willing to help it would be helpful to compile the
qemu-tools out of the qemu-0.12.2 package for
freemantel-arm-scratchbox.
The configuration which makes this work should also be fit for
compiling a qemu stripped down to just the networking stuff. I'm
thinking of something like qemu-img just for networking instead
of blockdevices.