netdev - Re: Port STP state after removing port from bridge

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Message-ID: <CAE4R7bAN7QrJcjUCbAJ86tb9YDNGJfYeq3fdqh-a3Xnc+4S+Zg@mail.gmail.com>
Date:	Fri, 20 Feb 2015 07:03:24 -0800
From:	Scott Feldman <sfeldma@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Florian Fainelli <f.fainelli@...il.com>,
	netdev <netdev@...r.kernel.org>,
	Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: Port STP state after removing port from bridge

On Fri, Feb 20, 2015 at 2:00 AM, Jiri Pirko <jiri@...nulli.us> wrote:
> Fri, Feb 20, 2015 at 05:45:01AM CET, sfeldma@...il.com wrote:
>>On Wed, Feb 18, 2015 at 11:39 PM, Florian Fainelli <f.fainelli@...il.com>
>>wrote:
>>
>>> Hi,
>>>
>>> It just occured to me that the following sequence:
>>>
>>> brctl addbr br0
>>> brctl addif br0 port0
>>> ... STP happens
>>> brctl delif br0 port0
>>>
>>> will leave port0 in STP disabled state, because the bridge code will
>>> set the STP state to DISABLED, and only a down/up sequence can bring
>>> it back to FORWARDING.
>>>
>>> Is this something that we should somehow fix? As an user it seems a
>>> little convoluted having to do a down/up sequence to restore things. I
>>> believe however that it is valid for the bridge layer to mark a port
>>> as DISABLED when removing it. This is typically not noticed or even
>>> remotely a problem with software bridges because we cannot enforce an
>>> actual STP state at the HW level.
>>>
>>> Let me know your thoughts.
>>>
>>>
>>The fix in rocker would be:
>>
>>diff --git a/drivers/net/ethernet/rocker/rocker.c
>>b/drivers/net/ethernet/rocker/rocker.c
>>index 34389b6a..e2004fb 100644
>>--- a/drivers/net/ethernet/rocker/rocker.c
>>+++ b/drivers/net/ethernet/rocker/rocker.c
>>@@ -4456,8 +4456,10 @@ static int rocker_port_bridge_leave(struct
>>rocker_port *rocker_port)
>>                rocker_port_internal_vlan_id_get(rocker_port,
>>                                                 rocker_port->dev->ifindex);
>>        err = rocker_port_vlan(rocker_port, 0, 0);
>>+       if (err)
>>+               return err;
>>
>>-       return err;
>>+       return rocker_port_stp_update(rocker_port, BR_STATE_FORWARDING);
>> }
>>
>>
>>This will return the port back to it's initial state of
>>BR_STATE_FORWARDING, after it's removed from the bridge.
>>
>>I'll include this patch in the rocker pile to be pushed later.
>>
>>-scott
>
>
> I'm not sure, but wouldn't it be nicer it the bridge code would set
> state to disabled before the port is removed from the bridge?

When the port is removed from a bridge, for example with brctl delif,
the bridge driver puts port in BR_STATE_DISABLED and then sends
netdevice event NETDEV_CHANGEUPPER.  In response to
NETDEV_CHANGEUPPER, the rocker driver is returning port back to
BR_STATE_FORWARDING (the initial state for an un-bridged port).  So
this preserves bridge behavior for non-switchdev uses.  Does this
answer the question, or did I miss understand your question?

-scott
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