ppp in 4.x apparently does a close(2) after opening the tun device;
i4brunppp starts up with only file descriptors 0 and 1 open (to the rbch
device) -> tun gets opened as 2 -> tun gets closed -> later use results
in EBADF. A quick fix to i4brunppp.c makes the thing work (I know, this
is ugly, but I needed it up quick...):
Submitted by: Juha-Matti Liukkonen <jml@cubical.fi>
34bc592815