Easily doable via AFWall settings and for mobile data by selecting IPv4 only, but it doesn’t prevent the phone from obtaining an IPv6 address when connected to wifi offering IPv6.

From CanMan1’s brief tutorial:

Required:

• rooted device
• 2 paths must exist:

1. ls -l /proc/sys/net/ipv6/conf/wlan0/accept_ra
2. ls -l /proc/sys/net/ipv6/conf/all/disable_ipv6

Launch ADB as root after connecting the device to a PC via USB:

adb root

Now launch the shell to log into the phone:

adb shell

DO NOT run the following command unless you are logged into your device, you’ll see a prompt like so, if you are:

deviceName:/

Remount the filesystem as read-write (otherwise you’ll get readonly errors):

mount -o remount,rw /system

Create the disable script:

cd /etc/init.d && nano 00disable_ipv6

Paste the script from CanMan1:

#!/system/bin/sh
# Disable IPv6
echo 0 > /proc/sys/net/ipv6/conf/wlan0/accept_ra
echo 1 > /proc/sys/net/ipv6/conf/all/disable_ipv6

CNTRL + W to save > Y to accept

Create the re-enable script, if you decide to enable IPv6:

nano 00disable_ipv6_reset

Paste the script from CanMan1:

#!/system/bin/sh
# Enable. IPv6
echo 1 > /proc/sys/net/ipv6/conf/wlan0/accept_ra
echo 0 > /proc/sys/net/ipv6/conf/all/disable_ipv6

Make them executable:

chmod +x 00disable_ipv6 && chmod +x 00disable_ipv6_reset

Run to make it active:

./00disable_ipv6

Done.

This patch will not survive reboots or ROM flashes. Repeat steps above to re-enable.

To confirm its operative, navigate to network settings where you previously obtained an IPv6 address.