netdev - Re: [PATCH net-next] net/sched: act_police: more accurate MTU policing

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Message-ID: <YgabcluXWaQY9tVv@t14s.localdomain>
Date:   Fri, 11 Feb 2022 14:22:58 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        Oz Shlomo <ozsh@...dia.com>,
        Eelco Chaudron <echaudro@...hat.com>
Subject: Re: [PATCH net-next] net/sched: act_police: more accurate MTU
 policing

On Thu, Feb 10, 2022 at 06:56:08PM +0100, Davide Caratti wrote:
> in current Linux, MTU policing does not take into account that packets at
> the TC ingress have the L2 header pulled. Thus, the same TC police action
> (with the same value of tcfp_mtu) behaves differently for ingress/egress.
> In addition, the full GSO size is compared to tcfp_mtu: as a consequence,
> the policer drops GSO packets even when individual segments have the L2 +
> L3 + L4 + payload length below the configured valued of tcfp_mtu.
> 
> Improve the accuracy of MTU policing as follows:
>  - account for mac_len for non-GSO packets at TC ingress.
>  - compare MTU threshold with the segmented size for GSO packets.
> Also, add a kselftest that verifies the correct behavior.
> 
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>