We address this problem by introducing a new network backend: -net bridge. This
backend is less flexible than -net tap because it relies on a helper with
elevated privileges to do the heavy lifting of allocating and attaching a tap
device to a bridge. We use a special purpose helper because we don't want
to elevate the privileges of more generic tools like brctl.
From a user perspective, to use bridged networking with a guest, you simply use:
qemu -hda linux.img -net bridge -net nic
I know that this patch is less than a day old and untested, but would it
be reasonable to make this the "default" network configuration at some
point in the future? This certainly seems to be what I want 99% of the
time when I launch qemu or kvm by hand from the command line.