netdev - Re: [PATCH next v2 0/7] Introduce l3

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Date:	Mon, 14 Mar 2016 10:57:01 -0700
From:	Mahesh Bandewar <maheshb@...gle.com>
To:	David Miller <davem@...emloft.net>
Cc:	mahesh@...dewar.net, Eric Dumazet <edumazet@...gle.com>,
	linux-netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH next v2 0/7] Introduce l3_dev pointer for L3 processing

On Sun, Mar 13, 2016 at 8:53 PM, David Miller <davem@...emloft.net> wrote:
> From: Mahesh Bandewar <maheshb@...gle.com>
> Date: Sun, 13 Mar 2016 19:29:58 -0700
>
>> On Sun, Mar 13, 2016 at 6:50 PM, David Miller <davem@...emloft.net> wrote:
>>> It doesn't matter whether doing so or not makes sense.
>>>
>>> You're going to have to find a way to do both, and also I'm concerned
>>> about how you're leaking the source namespace's "stuff" into the
>>> destination's.  That's very worrisome to me.
>>
>> If we add a new mode (e.g. L3s) and preserve current mode as is it,
>> then that should address your first concern.
>
> Also, I don't want all of this device translation stuff all over the
> place.
>
I could add skb->dev. Is that OK? Then non of this translation / helper-stuff
is required. I'm definitely open for suggestions.

> Furthermore, when you walk across the ns boundary, that old device has
> to disappear.  That's why that is the device assigned to skb->dev.
>
The layer boundaries are not that well maintained. We do check for the xfrm
policies in L4 and expect the skb->dev pointing to the L3 device. So unless we
have a way to derive a L3 dev from skb->dev, I don't think xfrm will
work. Unless
some Xfrm-expert asserts that this is not needed.

> Please stop pretending that this device switching is ok, it's not.