On Sat, 6 Feb 2021 01:05:21 +0200 Vladimir Oltean wrote: > On Fri, Feb 05, 2021 at 02:42:55PM -0800, Florian Fainelli wrote: > > How does the mirred action deal with that case? How does it know that > > packets delivered to the DSA master should be sent towards a foreign > > address, do I need to set-up two mirred rules? One that set-ups the > > filter on say sw0p0 to redirect egress to eth0 (DSA master) and another > > one to ingress filter on eth0 and egress mirror to eth1 (USB ethernet > > dongle)? > > [ I should have posted this as RFC, somebody asked me if it's possible, > I only tested ingress mirroring, saw something come out, and posted this. > I didn't even study act_mirred.c to see why I got anything at all ]
Let me mark it as RFC, then :) > For ingress mirroring there should be nothing special about the mirror > packets, it's just more traffic in the ingress data path where the qdisc > hook already exists. For ingress the only possible corner case seems to be if the filter has SKIP_SW set, then HW will send to CPU but SW will ignore. That's assuming the frame still comes on the CPU appropriately tagged. > For egress mirroring I don't think there's really any way for the mirred > action to take over the packets from what is basically the ingress qdisc > and into the egress qdisc of the DSA interface such that they will be > redirected to the selected mirror. I hadn't even thought about egress > mirroring. I suppose with more API, we could have DSA do introspection > into the frame header, see it's an egress-mirrored packet, and inject it > into the egress qdisc of the net device instead of doing netif_rx. IMHO it's not very pretty but FWIW some "SmartNIC" drivers already do a similar thing. But to be clear that's just an optimization, right? The SW should still be able to re-process and come to the same decisions as the switch, provided SKIP_SW was not set? > The idea with 2 mirrors might work however it's not amazing and I was > thinking that if we bother to do something at all, we could as well try > to think it through and come up with something that's seamless for the > user.
