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

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Date:	Sat, 21 Feb 2015 12:26:24 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Scott Feldman <sfeldma@...il.com>
Cc:	Jiri Pirko <jiri@...nulli.us>, netdev <netdev@...r.kernel.org>,
	Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: Port STP state after removing port from bridge

2015-02-21 11:43 GMT-08:00 Scott Feldman <sfeldma@...il.com>:
> On Fri, Feb 20, 2015 at 9:04 AM, Florian Fainelli <f.fainelli@...il.com> wrote:
>> On 20/02/15 07:03, Scott Feldman wrote:
>>> 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?
>>
>> I think what we want is a solution at the bridge level, we have rocker
>> now updating the STP state to BR_STATE_FORWARDING when a given
>> rocker_port leaves a bridge, and I also had a similar change in DSA.
>>
>> Something like this maybe (untested):
>>
>> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
>> index b087d278c679..d693a2a10b3c 100644
>> --- a/net/bridge/br_if.c
>> +++ b/net/bridge/br_if.c
>> @@ -242,6 +242,8 @@ static void del_nbp(struct net_bridge_port *p)
>>
>>         spin_lock_bh(&br->lock);
>>         br_stp_disable_port(p);
>> +       if (dev->features & NETIF_F_HW_SWITCH_OFFLOAD)
>> +               br_set_state(p, BR_STATE_FORWARDING);
>>         spin_unlock_bh(&br->lock);
>>
>>         br_ifinfo_notify(RTM_DELLINK, p);
>
> Acked-by: Scott Feldman <sfeldma@...il.com>
>
> I like it.  I tested your version with rocker and it works great.  (I
> removed my version).  Would you push this one when things open up?

Ok, thanks for testing!
-- 
Florian
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