netdev - Re: [PATCH net-next 01/18] net: skb_scrub_packet(): Scrub offload_fwd

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Date:   Mon, 19 Nov 2018 22:41:10 +0000
From:   Petr Machata <petrm@...lanox.com>
To:     David Miller <davem@...emloft.net>
CC:     Ido Schimmel <idosch@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "shuah@...nel.org" <shuah@...nel.org>,
        Jiri Pirko <jiri@...lanox.com>,
        "roopa@...ulusnetworks.com" <roopa@...ulusnetworks.com>,
        mlxsw <mlxsw@...lanox.com>
Subject: Re: [PATCH net-next 01/18] net: skb_scrub_packet(): Scrub
 offload_fwd_mark

David Miller <davem@...emloft.net> writes:

> From: Ido Schimmel <idosch@...lanox.com>
> Date: Mon, 19 Nov 2018 16:11:07 +0000
>
>> From: Petr Machata <petrm@...lanox.com>
>> 
>> 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.
>> 
>> Signed-off-by: Petr Machata <petrm@...lanox.com>
>> Suggested-by: Ido Schimmel <idosch@...lanox.com>
>> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
>
> As a bug fix this seems relevant for 'net' instead of 'net-next'.

Sure, I'll send for net.

Thanks,
Petr