From: Flavio Leitner <redacted>
Date: Tue, 26 Mar 2019 17:57:07 -0300

The request_module() is quite expensive and triggers the
usermode helper in userspace. Instead, load only if the
module is not present and keep module references to avoid
problems.

The first patch standardize the module alias which is already
there, but not in a formal way.

The second patch adds an API to point to the NAT helper.

The following patches will register each NAT helper using
the new API.

The last patch fixes openvswitch to use the new API to
load and reference the NAT helper and also report an error
if the operation fails.

These are mostly netfilter changes so I would like to see some
reviews/ACKs from netfilter folks.

Thanks.