netdev - Re: [PATCH net-next v2 2/3] net: dsa: mv88e6xxx: add support for bridge flags

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Date:   Tue, 19 Feb 2019 17:27:38 +0000
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Vivien Didelot <vivien.didelot@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 2/3] net: dsa: mv88e6xxx: add support for
 bridge flags

On Tue, Feb 19, 2019 at 12:23:04PM -0500, Vivien Didelot wrote:
> Hi Russell,
> 
> On Tue, 19 Feb 2019 17:00:59 +0000, Russell King - ARM Linux admin <linux@...linux.org.uk> wrote:
> > > to dsa_switch_ops and set BR_FLOOD | BR_MCAST_FLOOD from the DSA core,
> > > if the targeted driver has ds->ops->port_set_egress_flood. What do you think?
> > 
> > I've just changed my last patch to set these modes from
> > dsa_port_bridge_join() and dsa_port_bridge_leave(), and while testing,
> > I notice this on the ZII rev B board:
> > 
> > At boot (without anything connected to any of the switch ports):
> > 
> > br0: port 1(lan0) entered blocking state
> > br0: port 1(lan0) entered disabled state
> > device lan0 entered promiscuous mode
> > device eth1 entered promiscuous mode
> > br0: port 2(lan1) entered blocking state
> > br0: port 2(lan1) entered disabled state
> > device lan1 entered promiscuous mode
> > ...
> > 
> > I then removed lan0 from the bridge:
> > 
> > device lan0 left promiscuous mode
> > br0: port 1(lan0) entered disabled state
> > 
> > and then added it back:
> > 
> > br0: port 1(lan0) entered blocking state
> > br0: port 1(lan0) entered disabled state
> > device lan0 entered promiscuous mode
> > 
> > Now, you'd expect lan0 and lan1 to be configured the same at this
> > point, and the same as it was before lan0 was removed from the bridge?
> > lan0 is port 0, lan1 is port 1 on this switch - and the register debug
> > says:
> > 
> >     GLOBAL GLOBAL2 SERDES     0    1    2    3    4    5    6
> >  0:  c800       0    1140  500f 500f 500f 500f 500f 4e07 4d04
> > ...
> >  4:  40a8     258     1e0   43c  43d  43d   7c  430  53f 373f
> > 
> > Note that port 0 is in disabled state, but port 1 and 2 are in
> > blocking state... but wait, the kernel printed a message saying it was
> > in disabled state!
> > 
> > If I do the same for lan1, port 1 above changed from 0x43d to 0x433 as
> > expected, and then returns to 0x43c.
> > 
> > It looks like DSA isn't always in sync with bridge as per port state.
> 
> One thing we have to handle in DSA core are the unbridged ports. Such isolated
> ports must be in forwarding state if they are up, so that they can be used
> without a bridge, as a standard network interface.
> 
> Maybe it'd be simpler if the bridge code would put the interface down when
> unbridging it. That way we could remove the dsa_port_set_state_now(dp,
> BR_STATE_FORWARDING) hack from dsa_port_bridge_leave. Not sure if that makes
> sense though.

I'm not concerned about what happens when the port is removed from the
bridge above.

What I'm concerned about is the two different states when the port is
part of a bridge.

First time, the DSA switch is set to blocking mode, despite the kernel
saying the port is disabled.

Second time, the DSA switch is set to disabled mode, and the kernel
says the port is disabled.

Why is the port in blocking mode first time around?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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