Re: [RFC PATCH net-next 3/5] net: dsa: tag_rtl8_4: add realtek 8 byte protocol 4 tag

[Alvin Šipraga]

On 8/23/21 1:45 AM, Vladimir Oltean wrote:
> On Sun, Aug 22, 2021 at 11:37:28PM +0000, Alvin Šipraga wrote:
>>>>>> +	skb->offload_fwd_mark = 1;
>>>>>
>>>>> At the very least, please use
>>>>>
>>>>> 	dsa_default_offload_fwd_mark(skb);
>>>>>
>>>>> which does the right thing when the port is not offloading the bridge.
>>>>
>>>> Sure. Can you elaborate on what you mean by "at the very least"? Can it
>>>> be improved even further?
>>>
>>> The elaboration is right below. skb->offload_fwd_mark should be set to
>>> zero for packets that have been forwarded only to the host (like packets
>>> that have hit a trapping rule). I guess the switch will denote this
>>> piece of info through the REASON code.
>>
>> Yes, I think it will be communicated in REASON too. I haven't gotten to
>> deciphering the contents of this field since it has not been needed so
>> far: the ports are fully isolated and all bridging is done in software.
> 
> In that case, setting skb->offload_fwd_mark to true is absolutely wrong,
> since the bridge is told that no software forwarding should be done
> between ports, as it was already done in hardware (see nbp_switchdev_allowed_egress).
> 
> I wonder how this has ever worked? Are you completely sure that bridging
> is done in software?

You are absolutely right, and indeed I checked just now and the bridging 
is not working at all.

Deleting the line (i.e. skb->offload_fwd_mark = 0) restores the expected 
bridging behaviour.

Based on what you have said, do I understand correctly that 
offload_fwd_mark shouldn't be set until bridge hardware offloading has 
been implemented?

Thanks for your detailed review so far.