netdev - Re: [patch net-next RFC 0/4] introduce infrastructure for support of switch chip datapath

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Date:	Tue, 25 Mar 2014 21:39:58 +0000
From:	tgraf <tgraf@...g.ch>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	Neil Horman <nhorman@...driver.com>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Jiri Pirko <jiri@...nulli.us>, netdev <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>, andy <andy@...yhouse.net>,
	dborkman <dborkman@...hat.com>, ogerlitz <ogerlitz@...lanox.com>,
	jesse <jesse@...ira.com>, pshelar <pshelar@...ira.com>,
	azhou <azhou@...ira.com>, Ben Hutchings <ben@...adent.org.uk>,
	Stephen Hemminger <stephen@...workplumber.org>,
	jeffrey.t.kirsher@...el.com, vyasevic <vyasevic@...hat.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Scott Feldman <sfeldma@...ulusnetworks.com>,
	Lennert Buytenhek <buytenh@...tstofly.org>,
	Felix Fietkau <nbd@...nwrt.org>
Subject: Re: [patch net-next RFC 0/4] introduce infrastructure for support of
 switch chip datapath

On 03/25/14 at 01:00pm, Florian Fainelli wrote:
> 2014-03-25 12:40 GMT-07:00 Neil Horman <nhorman@...driver.com>:
> > On Tue, Mar 25, 2014 at 11:33:22AM -0700, Florian Fainelli wrote:
> >> 2014-03-25 10:39 GMT-07:00 Neil Horman <nhorman@...driver.com>:
> >> > 1) Ports on a switch chip are accessed using net_device structures, but
> >> > registered to a private list contained within the switch device, rather than to
> >> > the net namespaces device list.
> >>
> >> I think this would be a good model for simple embedded switches that
> >> only support 802.1q VLANs for instance, since we won't be able to get
> >> any actual data to be sent/received to any per-port netdevice, those
> >> per-port netdevices would only be effective for control at the L2
> >> level.
> >>
> >> For switches that do support tags, I think we do want per-port
> >> netdevices to appear in the regular netdevices namespace as those
> >> might be able to get actual data sent to/received from by using these
> >> tags, at least momentarily until a higher-level entity decides
> >> otherwise (e.g: by bridging, disabling interfaces...).
> >>
> > Well, perhaps thats the answer then  - Augment the model to allow for the
> > registration of net_devices to private lists within a switch device, but don't
> > require it.  If a given chip supports the assignment of L3 data by the cpu, the
> > use of iptables etc, let the switch driver do so, its not like we can't do that
> > already, but for the smaller devices, keeping them tightly controled via the
> > switch driver in such a way that user space can only access them with permission
> > from the switch driver.
> >
> > Does that seem reasonable?
> 
> Sure that looks good, the switch driver will know what L2/L3 features
> it has, and the higher levels will know how to utilize that
> information to construct the net_devices stacking and namespacing.


I think all it takes is to correctly apply the existing separation
which is already available but not applied right now.

We already have the L2/L3 separation in place:

net_device vs in_device/inet6_dev/....

A pure L2 device that will never do L3 on the CPU would only
need to set a flag which we check before allocating a in_device
and therefore prevent from all the L3 configs to be exposed.
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