netdev - Re: [PATCH net-next v2 01/12] net: bridge: multicast: Propagate br_mc_disabled

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Date:   Wed, 30 Jan 2019 17:00:57 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Ido Schimmel <idosch@...lanox.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "vivien.didelot@...il.com" <vivien.didelot@...il.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Jiri Pirko <jiri@...lanox.com>,
        "ilias.apalodimas@...aro.org" <ilias.apalodimas@...aro.org>,
        "ivan.khoronzhuk@...aro.org" <ivan.khoronzhuk@...aro.org>,
        "roopa@...ulusnetworks.com" <roopa@...ulusnetworks.com>,
        "nikolay@...ulusnetworks.com" <nikolay@...ulusnetworks.com>
Subject: Re: [PATCH net-next v2 01/12] net: bridge: multicast: Propagate
 br_mc_disabled_update() return

On 1/29/19 11:36 PM, Ido Schimmel wrote:
> On Tue, Jan 29, 2019 at 04:55:37PM -0800, Florian Fainelli wrote:
>> Some Ethernet switches might not be able to support disabling multicast
>> flooding globally when e.g: several bridges span the same physical
>> device, propagate the return value of br_mc_disabled_update() such that
>> this propagates correctly to user-space.
>>
>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>> ---
>>  net/bridge/br_multicast.c | 23 ++++++++++++++++-------
>>  1 file changed, 16 insertions(+), 7 deletions(-)
>>
>> diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
>> index 3aeff0895669..aff5e003d34f 100644
>> --- a/net/bridge/br_multicast.c
>> +++ b/net/bridge/br_multicast.c
>> @@ -813,20 +813,22 @@ static void br_ip6_multicast_port_query_expired(struct timer_list *t)
>>  }
>>  #endif
>>  
>> -static void br_mc_disabled_update(struct net_device *dev, bool value)
>> +static int br_mc_disabled_update(struct net_device *dev, bool value)
>>  {
>>  	struct switchdev_attr attr = {
>>  		.orig_dev = dev,
>>  		.id = SWITCHDEV_ATTR_ID_BRIDGE_MC_DISABLED,
>> -		.flags = SWITCHDEV_F_DEFER,
>> +		.flags = SWITCHDEV_F_DEFER | SWITCHDEV_F_SKIP_EOPNOTSUPP,
> 
> Actually, since the operation is deferred I don't think the return value
> from the driver is ever checked. Can you test it?

You are right, you get a WARN() from switchdev_attr_port_set_now(), but
this does not propagate back to the caller, so you can still create a
bridge device and enslave a device successfully despite getting warnings
on the console.

> 
> I think it would be good to convert the attributes to use the switchdev
> notifier like commit d17d9f5e5143 ("switchdev: Replace port obj add/del
> SDO with a notification") did for objects. Then you can have your
> listener veto the operation in the same context it is happening.

Alright, working on it. Would you do that just for the attr_set, or for
attr_get as well (to be symmetrical)?
-- 
Florian