netdev - Re: [PATCH net-next 0/2] flower: add MPLS matching support

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Date:   Tue, 25 Apr 2017 08:47:00 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Simon Horman <simon.horman@...ronome.com>,
        Jakub Kicinski <kubakici@...pl>
Cc:     David Miller <davem@...emloft.net>, benjamin.lahaise@...ronome.com,
        netdev@...r.kernel.org, bcrl@...ck.org,
        Jiri Pirko <jiri@...nulli.us>
Subject: Re: [PATCH net-next 0/2] flower: add MPLS matching support

On 17-04-25 07:55 AM, Simon Horman wrote:
[..]
>
> I agree something should be done wrt BOS. If the LABEL and TC are to
> be left as-is then I think a similar treatment of BOS - that is masking it
> - makes sense.
>
> I also agree with statements made earlier in the thread that it is unlikely
> that the unused bits of these attributes will be used - as opposed to a
> bitmask of flag values which seems ripe for re-use for future flags.
>

For your use case, I think you are fine if you just do the mask in the
kernel. A mask  to a user value implies "I am ignoring the rest
of these bits - I dont  care if you set them "

> I would like to add to the discussion that I think in future it would
> be good to expand the features provided by this patch to support supplying
> a mask as part of the match - as flower supports for other fields such
> as IP addresses. But I think the current scheme of masking out invalid bits
> should also work in conjunction with user-supplied masks.
>

The challenge we have right now is "users do stoopid or malicious
things". So are you going to accept the wrong bitmap + mask?

cheers,
jamal