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

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Date:	Thu, 15 Oct 2015 08:41:57 -0400
From:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...oirfairelinux.com,
	"David S. Miller" <davem@...emloft.net>,
	Guenter Roeck <linux@...ck-us.net>,
	Florian Fainelli <f.fainelli@...il.com>,
	Neil Armstrong <narmstrong@...libre.com>
Subject: Re: [PATCH net-next 0/4] net: dsa: mv88e6xxx: fix hardware bridging

On Oct. Thursday 15 (42) 04:52 AM, Andrew Lunn wrote:
> On Wed, Oct 14, 2015 at 09:28:55PM -0400, 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.
> 
> Hi Vivien 
> 
> This is a regression. Ports of the switch should work like normal
> Linux interfaces. And up until now, they did. This patchset changed
> that.
> 
> As Florian pointed out, these interfaces are separated from each
> other. So you need something like a bridge per port by default, which
> then gets removed and replaced when a port is added to a Linux bridge.

I'll fix this regression and try the exact same example you provided.

> We also need to take care of VLANs. When the port is not a member of a
> linux bridge, i expect all VLAN tagged frames to be received, as well
> as untagged frames. This is normal Linux behaviour. But i never got
> around to testing this with DSA.

Thanks for testing,
-v
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