Internet Protocol version 6 (IPv6) has been enabled by default in OpenBSD since 3.0. IPv6 privacy extensions have been enabled by default since OpenBSD 5.3.
To manually disable the use of IPv6 privacy extensions, determine the name of the installed network interfaces using the ifconfig command. Typical interfaces are em0 or fxp0.
To disable IPv6 privacy extensions on an inet6-enabled interface em0, execute the following:
ifconfig em0 –autoconfprivacy
The existing temporary privacy address will persist until it becomes invalid.
To enable IPv6 privacy extensions on an inet6-enabled interface em0, execute the following:
ifconfig em0 autoconfprivacy
A temporary privacy address will be generated and assigned to the interface em0. It will automatically be replaced by another temporary privacy address after 24 hours of use and after receipt of the next router advertisement for that interface’s prefix.
For more details, please look at the OpenBSD ifconfig manual page.
The recommended practice is to block all IPv6 inbound and outbound traffic in the pf packet filter, rather than attempting to disable it in the kernel.
1. Edit the file /etc/pf.conf
2. Add the following lines to the end of the file
block in inet6
block out inet6
3. Reboot (or, restart the pf.d script)
For more details, please look at the OpenBSD pf manual page.