netdev - Re: [PATCH v2 net] net: bridge: Clear offload_fwd_mark when passing frame up bridge interface.

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Date:   Thu, 19 May 2022 00:43:12 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Andrew Lunn <andrew@...n.ch>, netdev <netdev@...r.kernel.org>
Cc:     Ido Schimmel <idosch@...lanox.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH v2 net] net: bridge: Clear offload_fwd_mark when passing
 frame up bridge interface.

On 18/05/2022 03:58, Andrew Lunn wrote:
> It is possible to stack bridges on top of each other. Consider the
> following which makes use of an Ethernet switch:
> 
>        br1
>      /    \
>     /      \
>    /        \
>  br0.11    wlan0
>    |
>    br0
>  /  |  \
> p1  p2  p3
> 
> br0 is offloaded to the switch. Above br0 is a vlan interface, for
> vlan 11. This vlan interface is then a slave of br1. br1 also has a
> wireless interface as a slave. This setup trunks wireless lan traffic
> over the copper network inside a VLAN.
> 
> A frame received on p1 which is passed up to the bridge has the
> skb->offload_fwd_mark flag set to true, indicating that the switch has
> dealt with forwarding the frame out ports p2 and p3 as needed. This
> flag instructs the software bridge it does not need to pass the frame
> back down again. However, the flag is not getting reset when the frame
> is passed upwards. As a result br1 sees the flag, wrongly interprets
> it, and fails to forward the frame to wlan0.
> 
> When passing a frame upwards, clear the flag. This is the Rx
> equivalent of br_switchdev_frame_unmark() in br_dev_xmit().
> 
> Fixes: f1c2eddf4cb6 ("bridge: switchdev: Use an helper to clear forward mark")
> Signed-off-by: Andrew Lunn <andrew@...n.ch>
> ---
> 
> v2:
> Extended the commit message with Ido obsersation of the equivelance of
> br_dev_xmit().
> 
> Fixed up the comment.
> 
> This code has passed Ido test setup.
> 

Acked-by: Nikolay Aleksandrov <razor@...ckwall.org>