How are network numbers selected for TUN device ?

[Benjamin Herrenschmidt]

Hi Samuel !

I noticed the tun device automatically gets assigned a NAT network
of 192.168.x.0, where x is apparently always 2 here.

The problem is that my work internal network is already 192.168.2.0
(and my home one is 10.0.1.0). I used to have MOL use 192.168.4.0
back with 0.9.63 when I used my own tunconfig scripts.

How is that network number selected ? I didn't (yet) find a simple
way to force the scripts to use 192.168.4.0

Ben.