netdev - RE: [PATCH 3/3] gianfar: remove faulty filer optimizer

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Date:	Tue, 11 Aug 2015 14:00:23 +0000
From:	Manoil Claudiu <claudiu.manoil@...escale.com>
To:	Jakub Kicinski <moorray3@...pl>,
	"David S. Miller" <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Jakub Kicinski <kubakici@...pl>
Subject: RE: [PATCH 3/3] gianfar: remove faulty filer optimizer

>-----Original Message-----
>From: Jakub Kicinski [mailto:moorray3@...pl]
>Sent: Monday, August 10, 2015 11:12 PM
>To: David S. Miller; Manoil Claudiu-B08782
>Cc: netdev@...r.kernel.org; Jakub Kicinski
>Subject: [PATCH 3/3] gianfar: remove faulty filer optimizer
>
>From: Jakub Kicinski <kubakici@...pl>
>
>Current filer rule optimization is broken in several ways:
> (1) It destroys rule ordering.
> (2) It performs reads/writes beyond end of allocated tables.
> (3) It breaks badly for rules with more than 2 specifiers
>     (e.g. matching ip, port, tos).
> (4) We observed that the masking rules it generates do not
>     play well with clustering on P2020.  Only first rule
>     of the cluster would ever fire.  Given that optimizer
>     relies heavily on masking this is very hard to fix.
>
>The fact that nobody noticed (1), (3) or (4) makes me think
>that this feature is not very widely used and we should just
>remove it.

I'm not familiar with this filer classification code and its
author is no longer active apparently.   There is not much of a
choice here since this optimization feature is too complex and
poorly documented to be reviewed and validated in a reasonable
time span.
An example, a simple use case showing expected behavior vs.
actual behavior would help.

Thanks,
Claudiu

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