netdev - Re: [PATCH V2 00/12] Add basic VLAN support to bridges

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Date:	Wed, 19 Dec 2012 09:13:10 -0500
From:	Vlad Yasevich <vyasevic@...hat.com>
To:	Shmulik Ladkani <shmulik.ladkani@...il.com>
CC:	netdev@...r.kernel.org, shemminger@...tta.com, davem@...emloft.net,
	or.gerlitz@...il.com, jhs@...atatu.com, mst@...hat.com
Subject: Re: [PATCH V2 00/12] Add basic VLAN support to bridges

On 12/19/2012 03:10 AM, Shmulik Ladkani wrote:
> Thanks Vlad,
>
> On Tue, 18 Dec 2012 14:00:51 -0500 Vlad Yasevich <vyasevic@...hat.com> wrote:
>> A single vlan may also be designated as untagged.  Any untagged traffic
>> recieved by the port will be assigned to this vlan.
>
> Why the "untagged vlan" is per-bridge global?
> Usually, 802.1q switches define the PVID (port's VID) which controls
> the value of VID, in case ingress frame is either untagged or
> priority-tagged (per port configuration).
> This gives greater flexibility.

It's not.  There is a per port untagged pointer where you can designate 
which VLAN is untagged/native on a port.  The bride interface itself
can also function as a port, so it gets its own untagged pointer so
it can behave similar to port.

>
>> Any traffic exiting
>> the port with a VID matching the untagged vlan will exit untagged (the
>> bridge will strip the vlan header).  This is similar to "Native Vlan" support
>> available in most switches.
>
> 802.1q switches usually allow conifguring per-vlan, per-port
> tagged/untagged egress policy: each vid has its port membership map and
> an accompanying port egress-policy map.
> This gives great flexibility defining all sorts of configurations.

Right, and that's what's provided here.
  * Each VLAN has port membership map (net_bridge_vlan.portgroup).
  * Each port has a list of vlans configured as well 
(net_port_vlan.vlan_list).
  * Each port also has a single vlan that can be untagged 
(net_bridge_port.untagged).
  * The bridge also has a single untagged vlan (net_bridge.untagged)

The limitation (in switches as well) is that only a single VLAN
may be untagged on any 1 port.  If you have more then 1, you don't know
which VLAN the untagged traffic belongs to.

>
> Personally, I'd prefer a fully flexible vlan bridge allowing all sorts
> of configurations (as available in 802.1q switches).
>
> What's the reason limiting such configurations?

So, what do you see that's missing?

-vlad

>
> Regards,
> Shmulik
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