netdev - Re: [RFC patch net-next-2.6] net: allow multiple rx

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Date:	Fri, 01 Jul 2011 16:57:07 +0200
From:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
To:	Michał Mirosław <mirqus@...il.com>
CC:	Jiri Pirko <jpirko@...hat.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	netdev@...r.kernel.org, davem@...emloft.net, kaber@...sh.net,
	fubar@...ibm.com, eric.dumazet@...il.com, andy@...yhouse.net
Subject: Re: [RFC patch net-next-2.6] net: allow multiple rx_handler registration

Le 01/07/2011 08:36, Michał Mirosław a écrit :
> 2011/6/30 Jiri Pirko<jpirko@...hat.com>:
>> Thu, Jun 30, 2011 at 06:27:12PM CEST, shemminger@...tta.com wrote:
>>> On Thu, 30 Jun 2011 17:16:49 +0200
>>> Jiri Pirko<jpirko@...hat.com>  wrote:
>>>
>>>> For some net topos it is necessary to have multiple "soft-net-devices"
>>>> hooked on one netdev. For example very common is to have
>>>> eth<->(br+vlan). Vlan is not using rh_handler (yet) but also for example
>>>> macvlan would be useful to have hooked on same netdev as br.
>>>>
>>>> This patch introduces rx_handler list. size struct net_device stays
>>>> intact. Measured performance regression on eth-br topo is ~1% (on received
>>>> pkts generated by pktgen) and on eth-bond topo it is ~0.25%
>>>>
>>>> On br I think that the performance can be brought back maybe by using per-cpu
>>>> variables to store port in rx_path (I must check this)
>>>>
>>>> Please comment.
>>>>
>>>> Signed-off-by: Jiri Pirko<jpirko@...hat.com>
>>>
>>> I am ok with the infrastructure, but why should Vlan use rh_handle.
>>
>> Well why it shoudln't. It would fit into what rx_handler is here for - the
>> code would be more unified. Also net_device struct would lose struct
>> vlan_group __rcu *vlgrp pointer (and reducing net_device size is always
>> good thing).
>>
>>> It is wrong to allow macvlan and bridge to share same device.
>>> Right now the code blocks users from doing lots of stupid things.
>>
>> Right, this is since rx_handler was introduced. Before that all these
>> stupid configs were allowed. It's possible easily to forbid unwanted
>> configs by checking priv flags.
>
> We could introduce a catch-all macvlan/vlan device that would take
> addresses/VLANs which are not covered by other configured
> macvlans/vlans. This would allow clearer configuration and would make
> the evaluation order explicit. As a bonus, this will give another
> device to put tcpdump on. ;-)

'Sounds like what I had in mind in http://marc.info/?l=linux-netdev&m=130622112921245&w=2 .

	Nicolas.

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