lkml.org 
[lkml]   [2017]   [Sep]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH net-next 2/2] net: dsa: lan9303: Add basic offloading of unicast traffic
From
Date
Den 22. sep. 2017 22:08, skrev Andrew Lunn:
>>> I'm wondering how this is supposed to work. Please add a good comment
>>> here, since the hardware is forcing you to do something odd.
>>>
>>> Maybe it would be a good idea to save the STP state in chip. And then
>>> when chip->is_bridged is set true, change the state in the hardware to
>>> the saved value?
>>>
>>> What happens when port 0 is added to the bridge, there is then a
>>> minute pause and then port 1 is added? I would expect that as soon as
>>> port 0 is added, the STP state machine for port 0 will start and move
>>> into listening and then forwarding. Due to hardware limitations it
>>> looks like you cannot do this. So what state is the hardware
>>> effectively in? Blocking? Forwarding?
>>>
>>> Then port 1 is added. You can then can respect the states. port 1 will
>>> do blocking->listening->forwarding, but what about port 0? The calls
>>> won't get repeated? How does it transition to forwarding?
>>>
>>> Andrew
>>>
>>
>> I see your point with the "minute pause" argument. Although a bit
>> contrived use case, it is easy to fix by caching the STP state, as
>> you suggest. So I can do that.
>
> I don't think it is contrived. I've done bridge configuration by hand
> for testing purposes. I've also set the forwarding delay to very small
> values, so there is a clear race condition here.
>
>> How does other DSA HW chips handle port separation? Knowing that
>> could perhaps help me know what to look for.
>
> They have better hardware :-)
>
> Generally each port is totally independent. You can change the STP
> state per port without restrictions.
>
We can indeed change the STP state per lan9303 port "without
restrictions".

The point is: Once both external ports are in "forwarding", I see no way
to prevent traffic flowing directly between the external ports.


> Andrew
>

Egil

\
 
 \ /
  Last update: 2017-09-23 11:59    [W:0.070 / U:2.764 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site