[N900] TUN support missing

Hi all. TUN network device support is missing in nokia-n900 (config-nokia-n900.armv7). It's essential for some software package functionality.

Solution

It's provided by CONFIG_TUN kernel config option. Location:

-> Device Drivers
  -> Network device support
    -> Network core driver support
         Universal TUN/TAP device driver support

Dependencies are NETDEVICES, NET_CORE, INET (already enabled).

Raw usage stats among pmaports:

$ git clone https://gitlab.postmarketos.org/postmarketos/pmaports ; cd pmaports/ ; \
  grep -hrE '^(#\s*)?CONFIG_TUN[^_]' pmaports/ | sort | uniq -c

      5 # CONFIG_TUN is not set
     23 CONFIG_TUN=m
    272 CONFIG_TUN=y

Testing

pmOS v21.12, linux 5.15.13

I've used standard process

$ pmbootstrap kconfig edit nokia-n900  # CONFIG_TUN enabled as a module
$ pmbootstrap build linux-nokia-n900 --force

~/.local/var/pmbootstrap/chroot_native/home/pmos/build/src/linux-5.15/drivers/net/tun.ko was then copied to the device, depmod'ed and insmod'ed, and worked. (tinc configuration is another unrelated topic).

Note: mknod /dev/net/tun c 10 200 must have been done as well.