netdev - Re: [PATCH RFC 2/2] net: dsa: bcm_sf2: implement HW bridging operations

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Message-ID: <20150219174640.GA6897@roeck-us.net>
Date:	Thu, 19 Feb 2015 09:46:40 -0800
From:	Guenter Roeck <linux@...ck-us.net>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	vivien.didelot@...oirfairelinux.com,
	jerome.oufella@...oirfairelinux.com, andrew@...n.ch,
	cphealy@...il.com
Subject: Re: [PATCH RFC 2/2] net: dsa: bcm_sf2: implement HW bridging
 operations

On Thu, Feb 19, 2015 at 09:27:23AM -0800, Florian Fainelli wrote:
> On 18/02/15 21:59, Guenter Roeck wrote:
> > On Wed, Feb 18, 2015 at 06:48:19PM -0800, Florian Fainelli wrote:
> >> On 17/02/15 11:26, Florian Fainelli wrote:
> >>> Update the Broadcom Starfighter 2 switch driver to implement the
> >>> join/leave/stp_update callbacks required for basic hardware bridging
> >>> support.
> >>>
> >>> There is not much to be done at the driver level but translating the
> >>> STP state from Linux to their HW values.
> >>>
> >>> Joining a bridge means that the joining port and the other port members
> >>> need to be in the same VLAN membership as the CPU, while leaving the
> >>> bridge puts the port back into a separate VLAN membership with only the
> >>> CPU.
> >>
> >> I found a couple additional issues while testing:
> >>
> >> - manipulating UP/DOWN state of interfaces that are part of a bridge
> >> would not restore their bridge membership
> >>
> >> - removing an interface from a bridge and bringing it back up would
> >> leave it in blocked state
> >>
> > Is this a problem with your implementation for sf2 or a generic problem
> > with the first patch, such as some missing state transitions ?
> 
> This is more of a side effect of having HW (an Ethernet switch) that can
> really block a given port, based on last night's discussion with Roopa,
> we can either fix this at the DSA level (in our case) or better fix this
> at the bridge layer, I will propose a fix for this shortly.
> 
> > 
> > For sf2, you might have to set the port state as well as the bridge
> > association in the port_setup function. That is of course just a
> > wild guess.
> 
> Right, that's what I ended up doing. Thanks!

Great.

Another question: How do you handle flushing the forwarding database ?

My current code for mv88e6352 flushes the forwarding database for a bridge
group if the port association for that group changes (whenever a port joins
or leaves a group, or whenever the state of a port in a group changes).
There is, however, another situation where the forwarding database may
have to be flushed - essentially on each topology change.

How do you handle this situation ? Is it a real problem or do I just
imagine that it is ?

Thanks,
Guenter
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