Re: [PATCH 1/3] hwsim: remove 'optimization' sending to only known MACs

[Denis Kenzior <denkenz@gmail.com>]

Hi James,

>>
>> Suppose we have a setup with a single namespace, with 3 radios.
>>
>> Radio A with address aa
>> Radio B with address bb
>> Radio C with address cc
>>
>> When a _unicast_ frame with target 'cc' is seen by hwsim, it loops over A, B, 
>> C and compares the addresses.  If the addresses do not match, then no 
>> HWSIM_CMD_FRAME is issued for that radio.  So we'd only issue HWSIM_CMD_FRAME 
>> with Radio C's HWSIM_ATTR_ADDR_RECEIVER.
> 
> Ah ok, I see where you're coming from now. I overlooked that part. I can re-work 
> this and if the destination is a known radio then only forward to that radio. If 
> the destination is to an unknown radio I think we have to forward it regardless.
> 

Well, that's the part that is unclear to me.  See below.

>>
>> How does it help if namespace A receives a frame with target 'CC'? It doesn't 
>> know about Radio C, so how would radio C even receive the message? And if it 
>> somehow does anyway, then it would seem like the above dispatch logic is bogus 
>> in the first place?
> 
> If a client in namespace A sends a frame to target CC then the hwsim instance in 
> namespace A gets this frame. It doesn't know about target CC but the kernel 
> does. So it forwards into the kernel and target CC receives it.

So suppose client in namespace A sends something via Radio A to Radio C.  hwsim 
instance in namespace A will loop over the radios it knows about, which are A 
and B.  A is the source radio, so that should be ignored.  So with your proposed 
logic, hwsim in namespace A will send the frame to radio B with the target being 
Radio C.  But that would seem to be pointless?  If sending to radio B regardless 
of the target address is fine, why do we even bother with the dispatch logic at all?

Are you sure it isn't being sent to hwsim instances in all namespaces?

Regards,
-Denis