Messages in this thread | | | Date | Tue, 30 Jul 2019 21:00:01 +0200 | From | "Allan W. Nielsen" <> | Subject | Re: [PATCH] net: bridge: Allow bridge to joing multicast groups |
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The 07/30/2019 16:34, Andrew Lunn wrote: > The whole offloading story has been you use the hardware to accelerate > what the Linux stack can already do. It is true, I have been quite keen on finding a way to control the forwarding of L2-multicast which will work in the same way with and without HW acceleration (and which we can HW offlaod with the HW I'm working on).
> In this case, you want to accelerate Device Level Ring, DLR. It is actually not only for DLR, there are other ring protocols which has the same needs the same MRP (media redundancy protocol) is an other example.
I just used DLR as an example because this is the one we expect to implement the protocol for first. There are other just as important use-cases.
> But i've not yet seen a software implementation of DLR. Should we really be > considering first adding DLR to the SW bridge? We have actually (slowly) stared to work on a DLR SW implementation. We want to do this as a Linux driver instead of a user-space implementation, because there are other HW facilities we would like to offload (the HW has a automatic frame generator, which can generate the beacon frames, and a unit which can terminate the beacon frames, and generate an interrupt if the beacon frames are not received).
Our plan was to implement this in pure SW, and then look at how to HW offload it.
But this will take some time before we have anything meaning full to show.
> Make it an alternative to the STP code? I'm still working on learning the details of DLR, but I actually believe that it in some situations may co-exists with STP ;-)
DLR only works on ring topologies, but it is possible to connect a ring to a classic STP network. If doing so, then you are suppose to run DLR on the two ring ports, and (M)STP on the ports connecting to the remaining part of the network.
As far as I recall, this is called a gateway node. But supporting this is optional, and will properly not be supported in the first implementation.
> Once we have a generic implementation we can then look at how it can > be accelerated using switchdev. I agree with you that we need a SW implementation of DLR because we can offload the DLR protocol to HW.
But what we are looking at here, is to offload a non-aware-(DLR|MRP)-switch which happens to be placed in a network with these protocols running.
It is not really DLR specific, which is why it seems reasonable to implement this without a DLR SW implementation up front.
-- /Allan
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