netdev - Re: [RFC PATCH net-next] bridge: ability to disable forwarding on a port

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Date:	Tue, 20 Jan 2015 05:59:04 -0800
From:	roopa <roopa@...ulusnetworks.com>
To:	"Samudrala, Sridhar" <sridhar.samudrala@...el.com>
CC:	Scott Feldman <sfeldma@...il.com>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>,
	"David S. Miller" <davem@...emloft.net>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Jiří Pírko <jiri@...nulli.us>,
	"Arad, Ronen" <ronen.arad@...el.com>, Thomas Graf <tgraf@...g.ch>,
	john fastabend <john.fastabend@...il.com>,
	"vyasevic@...hat.com" <vyasevic@...hat.com>,
	Netdev <netdev@...r.kernel.org>,
	Wilson Kok <wkok@...ulusnetworks.com>,
	Andy Gospodarek <gospo@...ulusnetworks.com>
Subject: Re: [RFC PATCH net-next] bridge: ability to disable forwarding on
 a port

On 1/19/15, 11:09 PM, Samudrala, Sridhar wrote:
>
> On 1/19/2015 10:20 PM, roopa wrote:
>> On 1/18/15, 11:37 PM, Scott Feldman wrote:
>>
>> <snip..>
>>>
>>> Not sure. I don't know the use case, but I think I might have heard 
>>> that
>>> there could be a case
>>>   where a switch port could be bridged with a vm's port running on the
>>> switch. (?)
>>>>
>>>> Ignoring the above usecase for a bit. And thinking through this 
>>>> again, It
>>>> appears that this check should
>>>> be only on the ingress port, no ?
>>>>
>>>> If the ingress bridge port is an offloaded port, don't flood or 
>>>> forward
>>>> because hardware has already done it.
>>>> And this is best done with the offload feature flag on the bridge 
>>>> port.
>>> That's assuming hardware did the flood.  Maybe your other option to
>>> mark the skb if already flooded by hw is best.  That's enough info for
>>> the bridge driver to make a decision to flood or not to the other
>>> ports, and it's an implementation decision for the driver/device to do
>>> the flood offload, if desired, and mark the skb if it did.
>>
>> Still thinking we can just use the offload feature flag here. How 
>> about  avoid forwarding only if both src and dst ports have
>> forwarding offloaded/accelerated by a switch asic  ?. That should 
>> cover all cases.
>>>
>>> Btw, you're still saying flood or forward, but in my mind we're
>>> talking about flood only: flood of unknown unicast or flood of
>>> bcast/mcast pkts.  Forwarding would be for known-unicast pkts, which
>>> should even involve the bridge driver since that forwarding is
>>> offloaded to the device.
>>
>> I was also taking into account pkts copied to the CPU due to an acl 
>> rule such as log.
>> These unicast pkts can come to cpu even if it is already forwarded in 
>> hw.
>
> Do you have a switch port netdev that corresponds to CPU port? Or are 
> they seen on the bridge device?
No we dont have a netdev for the CPU port. These show up on the netdev 
corresponding to the ingress front panel port.
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