CentOS 7 Airwall Agent crashes after provisioning

Issue

It has become common security practice in CentOS to disable IPv6 in the kernel.

This can causes the Airwall Agent to fail after it is provisioned. The error is similar to this:

Oct 14 07:18:52 corpkvm01 hip: Reading config file: /etc/tnw/profiles/profile-123123/hip.conf
Oct 14 07:18:52 corpkvm01 systemd: hip.service: main process exited, code=exited, status=1/FAILURE
Oct 14 07:18:52 corpkvm01 systemd: Unit hip.service entered failed state.
Oct 14 07:18:52 corpkvm01 systemd: hip.service failed.
Oct 14 07:19:22 corpkvm01 systemd: hip.service holdoff time over, scheduling restart.
Oct 14 07:19:22 corpkvm01 systemd: Stopped Airwall Agent.

Workaround

Enable IPv6 on CentOS 7. The Airwall Agent uses IPv6 internally and requires the kernel to allow IPv6 addresses be present on the system.