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

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Date:	Wed, 9 Mar 2011 16:09:40 +0100
From:	Jiri Pirko <jpirko@...hat.com>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.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

Wed, Mar 09, 2011 at 03:49:49PM CET, nicolas.2p.debian@...il.com wrote:
>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.

Hmm. For hw vlan accel this would not be needed. But for
non-hw-vlan-accel the frame is wrapped when going thru handle_frame.
And yes, in that case untagging would be necessary. Unless the vlan
untagging happening now in ptype_base handler is moved in rx path
somewhere before __netif_receive_skb. That would result in two things:

1) Bond would be able to scope vlan packets
2) The rx path for hw-vlan-accel and non-hw-vlan-accel would be the same
   (should be desirable + one reinjection would be avoided for
    non-hw-vlan-accel)
>
>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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