netdev - Re: [patch net-next-2.6] net: reinject arps into bonding slave instead of master

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Date:	Wed, 09 Mar 2011 15:49:49 +0100
From:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
To:	Jiri Pirko <jpirko@...hat.com>
CC:	Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org,
	davem@...emloft.net, shemminger@...ux-foundation.org,
	kaber@...sh.net, fubar@...ibm.com, eric.dumazet@...il.com
Subject: Re: [patch net-next-2.6] net: reinject arps into bonding slave	instead
 of master

Le 09/03/2011 08:45, Jiri Pirko a écrit :
> Tue, Mar 08, 2011 at 10:44:37PM CET, nicolas.2p.debian@...il.com wrote:
>> Le 08/03/2011 14:42, Andy Gospodarek a écrit :
>>> I'm pretty sure this patch will have the same catastrophic problem your
>>> last one did.  By cloning and setting skb2->dev = orig_dev you just
>>> inserted a frame identical to the one we received right back into the
>>> stack.  It only took a few minutes for my box to melt as one frame on
>>> the wire will cause an infinite number of frames to be received by the
>>> stack.
>>
>> I agree with Andy. We still keep one reinject (netif_rx), which is
>> probably better that two (__netif_receive_skb), but not enough.
>>
>> I really think we need a general framework for late delivery of final
>> packets to packet handler registered somewhere in the rx_handler
>> path.
>>
>> Jiri, is this patch the one you announced as "I have some kind nice
>> solution in mind and I'm going to submit that as a patch later (too
>> many patches are in the wind atm)" ?
>
>
> I did not had time to verify my thought yet but I think that the only
> think needed against my original patch (bonding: move processing of recv
> handlers into handle_frame()) is ro remove vlan_on_bond_hook, period.
>
> Because all incoming arps are seen by bond_handle_frame =>
> bond->recv_probe , even vlan ones - that would make eth0-bond0-bond0.5
> work and eth0-bond0-br0-bond0.5 as well. But again, need to verify this.

All incoming ARPs are seen by bond_handle_frame, even vlan ones, definitely true.

But as some of them *are* vlan ones, you will have to untag those "by hand" inside bond_handle_frame.

It might work, but I wouldn't support the idea, for two reasons :

- It would duplicate code, or at least, duplicate places where untagging happens.
- It would cause some vlan hacks to sit inside bond, which is not nice from a layering point of 
view. You recently advocated against breaking layering and you are right. We should avoid putting X 
related stuff into Y part of the network stack, as much as possible.

Again, I think we should try and find a generic way to have the final frame delivered to whoever 
needs it. And this way should not be limited to "vlan untagging" nor to bonding.

	Nicolas.
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