Re: [PATCH RFC 2/2] net: dsa: bcm_sf2: implement HW bridging operations

[roopa <roopa@cumulusnetworks.com>]

On 2/19/15, 6:18 PM, Andrew Lunn wrote:
>>> Remember that we are dealing with hardware switch chips. Those chips
>>> won't time out fdb entries just because the kernel's bridge driver
>>> thinks that it should.
>> Oh, they dont..?
> To some extent, it is better to think of these as two switches
> connected to each other, not one switch. The HW switch needs help with
> STP, but otherwise it is a fully functional and autonomous switch.
yes, exactly.
>
> This is going to make displaying the forwarding database interesting,
> because the SW bridge fdb and the HW bridge fdb are each subsets of
> the big picture and possible even contradictory since they are not
> updated atomically.
>
What we do on our switches is,
- disable SW bridge learning
- enable HW bridge learning
- we keep the SW bridge fdb in sync with the HW fdb, which leads to:
         - HW learnt entries are pushed to SW bridge fdb
         - SW static fdb entries (added by the user) are pushed to HW