netdev - Re: [PATCH net 2/2] net/sched: fix corrupted L2 header with MPLS 'push' and 'pop' actions

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Message-ID: <20191011073437.uwtftvhofrrm5r5v@netronome.com>
Date:   Fri, 11 Oct 2019 09:34:38 +0200
From:   Simon Horman <simon.horman@...ronome.com>
To:     Davide Caratti <dcaratti@...hat.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        John Hurley <john.hurley@...ronome.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Lorenzo Bianconi <lorenzo@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH net 2/2] net/sched: fix corrupted L2 header with MPLS
 'push' and 'pop' actions

On Thu, Oct 10, 2019 at 08:43:53PM +0200, Davide Caratti wrote:
> the following script:
> 
>  # tc qdisc add dev eth0 clsact
>  # tc filter add dev eth0 egress protocol ip matchall \
>  > action mpls push protocol mpls_uc label 0x355aa bos 1
> 
> causes corruption of all IP packets transmitted by eth0. On TC egress, we
> can't rely on the value of skb->mac_len, because it's 0 and a MPLS 'push'
> operation will result in an overwrite of the first 4 octets in the packet
> L2 header (e.g. the Destination Address if eth0 is an Ethernet); the same
> error pattern is present also in the MPLS 'pop' operation. Fix this error
> in act_mpls data plane, computing 'mac_len' as the difference between the
> network header and the mac header (when not at TC ingress), and use it in
> MPLS 'push'/'pop' core functions.
> 
> CC: Lorenzo Bianconi <lorenzo@...nel.org>
> Fixes: 2a2ea50870ba ("net: sched: add mpls manipulation actions to TC")
> Signed-off-by: Davide Caratti <dcaratti@...hat.com>

Reviewed-by: Simon Horman <simon.horman@...ronome.com>