Bridging setup on bootup on Debian/Ubuntu

The following should pretty much work on any Debian based systems. Note that it only creates a single tuntap device. It also requires the uml-utilities and bridge-utils packages.

Also, replace <userid> with either username or numeric userid (since the interface is created before the network is active, if the user does not exist on the local system, use the numeric id instead).

/etc/network/interfaces

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual

auto br0
iface br0 inet dhcp
pre-up tunctl -u <userid> -t tap0
pre-up ifconfig tap0 0.0.0.0 promisc up
bridge_ports eth0 tap0
post-down tunctl -d tap0