Subject: Re: [RFC PATCH] xfrm: fix handling of XFRM policies mark and mask.

From: Steffen Klassert <[email-masked]>
Date: Thu, 7 Feb 2013 13:54:37 +0100

On Thu, Feb 07, 2013 at 12:08:22PM +0100, Emmanuel Thierry wrote:
> 
> This is a nice idea, however you keep the insertion asymmetric. The usage of xfrm marks in non-conflicting cases will be made possible, but it stays disturbing for a user as the initial example will still have the same behavior:
> * Inserting the marked one then the unmarked will succeed
> * Inserting the unmarked then the marked one will fail
> This gives to the user the feeling of an indeterministic behavior of the xfrm module.

This was intended. Inserting the marked one then the unmarked
is a working scenario. Some users might rely on it, so we can't
change this as you proposed.

On the other hand, inserting the unmarked one then the marked
might result in a wrong policy lookup, so we can't allow this.
The only possibility we have, is inserting with different
priorites and that's what I'm proposing.

I fear we have to live with that asymmetric behaviour if
both policies have the same priority.