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

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Message-ID: <CAE4R7bBY2jF5PfOZOOtKGDRc22-kTr1731kiEpk+O2oE21KgEA@mail.gmail.com>
Date:	Sat, 21 Feb 2015 11:43:32 -0800
From:	Scott Feldman <sfeldma@...il.com>
To:	Florian Fainelli <f.fainelli@...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

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?

-scott
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