[VLAN] Adding VLANs to downed interfaces

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Stephen Hemminger wrote:
> On Wed, 30 Aug 2006 15:33:23 -0400
> John Kamenik <jkamenik@xxxxxxxxxx> wrote:
>> I have a question about applying VLANs to downed interfaces.  I know  
>> that the kernel will not let you do it, and was wondering why?  I  
>> have created a patch that removes this limitation and applied it to  
>> my system and everything works as I would expect it to.  Was this a  
>> fix to a bug I am not currently seeing?
>> I am using the 2.6.17 kernel and the attached patch is based on it.   
>> The only file changed was the net/8021q/vlan.c file.  The  
>> "register_vlan_device" no longer makes a test to determine if the  
>> real (parent) interface is up.
>> John T. Kamenik (Software Eng.)
>> jkamenik@xxxxxxxxxx
>> (301) 975 - 1000 (ext. 168)
>> Patton Electronics Co.
>> 7622 Rickenbacker Dr.
>> Gaithersburg, Md 20879
> I would be concerned about devices that do vlan acceleration.
> The act of adding a vlan causes the device to have to talk to
> the hardware.  Often, the data structures for the hardware are
> not allocated until after the device is brought up.
> So if you did this on drivers like sky2, e1000, forcedeth, r8169,
> s2io, ... your change would crash.

Would this be any different from bouncing an e100 ethX interface when 
VLANs were configured on it?  I can't see why we shouldn't be able to 
relax that restriction and allow vlans on downed interfaces....


Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc

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