netdev - Re: [PATCH] net/vlan: withdraw VLAN ID attribute from GVRP on VLAN device stop

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Date:	Mon, 26 Mar 2012 09:38:43 -0400
From:	"Ward, David - 0663 - MITLL" <david.ward@...mit.edu>
To:	"jorge@...2.net" <jorge@...2.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net/vlan: withdraw VLAN ID attribute from GVRP on VLAN
 device stop

On 26/03/12 07:29, Jorge Boncompte [DTI2] wrote:
> El 26/03/2012 0:43, David Ward escribió:
>> When a VLAN device is stopped which has VLAN_FLAG_GVRP set, the VLAN
>> ID attribute that was previously declared by GVRP must be withdrawn.
>>
> 	Hmm, maybe I am missing something but I think it only makes sense to withdrawn
> the attribute when you delete the interface, and vlan_dev_stop() it's called if
> you just put the interface down. It's better for the network convergence to not
> signal the switches just for this. IMHO.

If I bring a VLAN interface down, then I stop participating in the 
VLAN.  If my NIC still receives traffic for the VLAN, I drop it.  So to 
remove unnecessary load on the (potentially shared) network link and 
remove unnecessary local processing by the kernel of packets I know I am 
going to drop, I should tell the switch that I am no longer interested 
in receiving the VLAN traffic.  Which is the whole point of GVRP.  Right?

In any case, we currently register the attribute when the interface is 
brought up, not when it is created.  However we do it, the attribute 
declaration/withdrawal should be symmetric.

>
>> Signed-off-by: David Ward<david.ward@...mit.edu>
>> ---
>>   net/8021q/vlan_dev.c |    3 +++
>>   1 files changed, 3 insertions(+), 0 deletions(-)
>>
>> diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
>> index 9988d4a..df86dd0 100644
>> --- a/net/8021q/vlan_dev.c
>> +++ b/net/8021q/vlan_dev.c
>> @@ -319,6 +319,9 @@ static int vlan_dev_stop(struct net_device *dev)
>>   	struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
>>   	struct net_device *real_dev = vlan->real_dev;
>>
>> +	if (vlan->flags&  VLAN_FLAG_GVRP)
>> +		vlan_gvrp_request_leave(dev);
>> +
>>   	dev_mc_unsync(real_dev, dev);
>>   	dev_uc_unsync(real_dev, dev);
>>   	if (dev->flags&  IFF_ALLMULTI)--
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