Make menuconfig.

Look for the line:

CONFIG_TUN=m

[/code]

in .config
If not present, add it.
It usually comes as a block here:
CONFIG_BLK_DEV_DM=y

CONFIG_DM_DEBUG=y

CONFIG_DM_CRYPT=y

# CONFIG_DM_SNAPSHOT is not set

# CONFIG_DM_MIRROR is not set

# CONFIG_DM_ZERO is not set

# CONFIG_DM_MULTIPATH is not set

# CONFIG_DM_DELAY is not set

CONFIG_DM_UEVENT=y

CONFIG_NETDEVICES=y

CONFIG_IFB=y

CONFIG_DUMMY=y

# CONFIG_BONDING is not set

# CONFIG_MACVLAN is not set

# CONFIG_EQUALIZER is not set

CONFIG_TUN=m

# CONFIG_VETH is not set

# CONFIG_PHYLIB is not set

CONFIG_NET_ETHERNET=y

CONFIG_MII=y

# CONFIG_AX88796 is not set

# CONFIG_SMC91X is not set

# CONFIG_DM9000 is not set

# CONFIG_ENC28J60 is not set

# CONFIG_ETHOC is not set

# CONFIG_SMC911X is not set

# CONFIG_SMSC911X is not set

# CONFIG_DNET is not set

[/code]

You can use the following code to quickly make a TUN module setting in a virgin .config:
sed s/'# CONFIG_TUN is not set'/'CONFIG_TUN=m'/ mconfig

cp mconfig .config[/code]

 
 
Joel G Mathew
Joel G Mathew, known in tech circles by the pseudonym Droidzone, is an opensource and programming enthusiast.
He is a full stack developer, whose favorite languages are currently Python and Vue.js. He is also fluent in Javascript, Flutter/Dart, Perl, PHP, SQL, C and bash shell scripting. He loves Linux, and can often be found tinkering with linux kernel code, and source code for GNU applications. He used to be an active developer on XDA forums, and his tinkered ROMS used to be very popular in the early 2000s.
His favorite pastime is grappling with GNU compilers, discovering newer Linux secrets, writing scripts, hacking roms, and programs (nothing illegal), reading, blogging. and testing out the latest gadgets.
When away from the tech world, Dr Joel G. Mathew is a practising ENT Surgeon, busy with surgeries and clinical practise.