Re: [PATCH net] net: skb_scrub_packet(): Scrub offload_fwd_mark

[Jiri Pirko <jiri@resnulli.us>]

Tue, Nov 20, 2018 at 12:39:56PM CET, petrm@mellanox.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@mellanox.com>
>Suggested-by: Ido Schimmel <idosch@mellanox.com>

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