netdev - Re: [PATCH net] net: skb_scrub_packet(): Scrub offload_fwd

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Message-ID: <20181120114153.GB2264@nanopsycho>
Date:   Tue, 20 Nov 2018 12:41:53 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Petr Machata <petrm@...lanox.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Ido Schimmel <idosch@...lanox.com>
Subject: Re: [PATCH net] net: skb_scrub_packet(): Scrub offload_fwd_mark

Tue, Nov 20, 2018 at 12:39:56PM CET, petrm@...lanox.com wrote:
>When a packet is trapped and the corresponding SKB marked as
>already-forwarded, it retains this marking even after it is forwarded
>across veth links into another bridge. There, since it ingresses the
>bridge over veth, which doesn't have offload_fwd_mark, it triggers a
>warning in nbp_switchdev_frame_mark().
>
>Then nbp_switchdev_allowed_egress() decides not to allow egress from
>this bridge through another veth, because the SKB is already marked, and
>the mark (of 0) of course matches. Thus the packet is incorrectly
>blocked.
>
>Solve by resetting offload_fwd_mark() in skb_scrub_packet(). That
>function is called from tunnels and also from veth, and thus catches the
>cases where traffic is forwarded between bridges and transformed in a
>way that invalidates the marking.
>
>Fixes: 6bc506b4fb06 ("bridge: switchdev: Add forward mark support for stacked devices")
>Fixes: abf4bb6b63d0 ("skbuff: Add the offload_mr_fwd_mark field")
>Signed-off-by: Petr Machata <petrm@...lanox.com>
>Suggested-by: Ido Schimmel <idosch@...lanox.com>

Acked-by: Jiri Pirko <jiri@...lanox.com>