linux-kernel - Re: [PATCH net-next 0/4] net: dsa: mv88e6xxx: fix hardware bridging

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Message-ID: <20151015123926.GA25443@ketchup.mtl.sfl>
Date:	Thu, 15 Oct 2015 08:39:26 -0400
From:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel@...oirfairelinux.com,
	"David S. Miller" <davem@...emloft.net>,
	Guenter Roeck <linux@...ck-us.net>,
	Neil Armstrong <narmstrong@...libre.com>
Subject: Re: [PATCH net-next 0/4] net: dsa: mv88e6xxx: fix hardware bridging

On Oct. Wednesday 14 (42) 06:44 PM, Florian Fainelli wrote:
> On 14/10/15 18:28, Vivien Didelot wrote:
> > On Oct. Thursday 15 (42) 12:46 AM, Andrew Lunn wrote:
> >> On Sun, Oct 11, 2015 at 06:08:34PM -0400, Vivien Didelot wrote:
> >>> DSA and its drivers currently hook the NETDEV_CHANGEUPPER net_device event in
> >>> order to configure the VLAN map of every port.
> >>>
> >>> This VLAN map is a feature of these switch chips to hardcode and restrict which
> >>> output ports a given input port can egress frames to.
> >>>
> >>> A Linux bridge is a simple untagged VLAN propagated by the bridge code itself.
> >>> With a proper 802.1Q support, a driver does not need this hook anymore, and
> >>> will simply program the related VLAN object.
> >>>
> >>> This patchset improves the hardware bridging code in the mv88e6xxx driver with
> >>> a strict 802.1Q mode.
> >>
> >> Hi Vivien
> >>
> >> I just tested this as part of net-next/master, and found a problem....
> >>
> >> If i do:
> >>
> >> ip link set lan0 up
> >> ip addr add 192.168.10.2/24 dev lan0
> >>
> >> It will not ping. Looking in sys/kernel/debug/dsa0/stats i see
> >> broadcast packets, probably ARP, being received at the port.
> >> But they are not being forwarded out the CPU port.
> >>
> >> If however i do
> >>
> >> brctl addbr br0
> >> brctl addif br0 lan0
> >> ip addr add 192.168.10.2/24 dev br0
> >> ip link set br0 up
> >>
> >> i can ping.
> >>
> >> So it looks like we are too restrictive by default. You should be able
> >> to use interfaces as they are, without a bridge.
> > 
> > Correct, if the ports are not in a VLAN by default, they cannot talk.
> 
> The expectation for DSA devices, if no bridge device is configured is to
> have each port be able to talk to the CPU port only, but this has to
> work out of the box.

OK, I might have forgotten this requirement. I also just noticed that
you mentioned it in Documentation/networking/dsa/dsa.txt. Thanks for the
reminder.

> > 
> > If you want to, I think the special VLAN 0 can be used for that
> > purpose. IIRC, in a given configuration, Linux add the interfaces
> > (thus programs the hardware) with VLAN 0. I'm not sure when, maybe
> > when the .ndo_vlan_rx_add_vid is implemented, I need to give it a
> > shot.
> 
> But if you do that, won't that put all DSA ports into VLAN 0? Would
> not that break isolation between each ports as expected for a DSA
> switch?

You're correct, then VLAN 0 is not an option. I have something else in
mind, fix coming soon.

> > 
> > Otherwise, I can send you a patch configuring the VLAN 0 on switch
> > setup if this is the behavior we want.

Thanks,
-v
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