Re: [RFC 0/1] Allow MAC change on up interface

[Denis Kenzior <denkenz@gmail.com>]

Hi Johannes,

On 8/20/19 3:15 PM, Johannes Berg wrote:
> On Tue, 2019-08-20 at 14:58 -0500, Denis Kenzior wrote:
>>
>> But what actual complexity are we talking about here? If the kernel can
>> do this while the CONNECT is pending, why not?  It makes things simpler
>> and faster for userspace.  I don't see the downside unless you can
>> somehow objectively explain 'complexity'.
> 
> It's just extra code that we have to worry about. Right now you want it
> for CMD_CONNECT and CMD_AUTH. Somebody will come up with a reason to do
> it in CMD_ASSOC next, perhaps, who knows. Somebody else will say "oh,
> this is how it's done, so let's add it to CMD_JOIN_IBSS", because of
> course that's what they care about. OCB? Mesh? AP mode for tethering?
> Etc.

I don't buy the extra code argument.  If you want to do something useful 
you need to write 'extra code'.

The rest, I'm not sure why you are worried about them now?  For station 
there's a very clear & present use case.  If such a clear and present 
use case is presented for AP or Mesh, then deal with it then.

> 
> I don't see how this will not keep proliferating, and each new thing
> will come with its own dozen lines of code, a new feature flag, etc.

Such is life? :)

> 
> Relaxing and defining once and for all in which situations while the
> interface is up you can actually allow changing the address, and then
> having userspace do it that way is IMHO a better way to design the
> system, since it forgoes entirely all those questions of when and how
> and which new use cases will come up etc.
> 

That would be great in theory, but practically never works at least in 
my experience.  So maybe keep and open mind?  There is a clear need to 
make this path as fast as possible for STA.  There is no such need (yet) 
for the other cases you mentioned.

>> This was an RFC.  There isn't much point for us to cross all the 't's
>> and dot all the 'i's if you hate the idea in the first place.
> 
> Sure, but I cannot distinguish between "we only want it on CMD_CONNECT"
> and "we'll extend this once we agree" unless you actually say so. It'd
> help to communicate which t's and i's you didn't cross or dot.

Okay, I'll admit the RFC description could have been better.  But in the 
end you're human last I checked (at least I recall meeting you several 
times? ;)  How about a simple "Why do you think you need this?" first?

Regards,
-Denis