On 09/06/2017 09:42 AM, Andrew Lunn wrote: >>> On the switch asics we work with, the driver has information if the >>> packet was >>> forwarded in hardware. This is per packet reason code telling why the >>> CPU is seeing the packet. >>> The driver can use this information to reset skb->offload_fwd_mark to >>> allow software forward. > >> I am not positive this is universally available across different >> switch vendors. > > It is not universally available. We cannot rely on it being available > with switches supported by DSA. > > We have a few choices: > > 1) We assume anything the switch forwards to the CPU has also been > sent out whatever ports of the switch it needs to. Set > offload_fwd_mark. > > 2) We assume anything the switch forwards to the CPU has not gone > anywhere else, and the bridge needs to send it out whatever ports > it thinks. Don't set offload_fwd_mark. > > 3) We define some rules about what packets the switch should handle, > and then do some deep packet inspection to decide if > offload_fwd_mark should be set or not. > > I don't see 3) being possible. We are dealing with a fixed silicon > data path, not something which is fully programmable. > > So it is down to 1) or 2). I've been assuming 1), but maybe we need to > discuss that as well.
At the very least we should probably move the skb->offload_fwd_mark setting down into the individual taggers since they should be in a better position to set it or not based on the switch device they are driving, this should address, on a per-switch basis whether 2) or 3) applies to a given switch. That being said, I have a feeling that the Marvell switches behave a tiny bit differently than others in that they do not flood broadcast by default in a given L2 domain. On b53/bcm_sf2 there is the ability to disable the reception of broadcast frames on the management/CPU port, and while there is the ability to configure which ports should be flooded in case of unicast/multicast lookup failures, I don't see anything for Broadcast, so I am assuming this will get forwarded by default. Will test with your patch set later on time permitting. -- Florian
