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

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Date:	Fri, 1 Jul 2011 08:36:30 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Jiri Pirko <jpirko@...hat.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>, netdev@...r.kernel.org,
	davem@...emloft.net, kaber@...sh.net, fubar@...ibm.com,
	eric.dumazet@...il.com, nicolas.2p.debian@...il.com,
	andy@...yhouse.net
Subject: Re: [RFC patch net-next-2.6] net: allow multiple rx_handler registration

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. ;-)

Best Regards,
Michał Mirosław
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