(Sorry for the double mail David, I missed the "reply all" button). On Friday, April 16, 2021 5:35 PM, David Ahern <dsahern@xxxxxxxxx> wrote: > On 4/16/21 5:03 AM, Konrad Zemek wrote: > > > So both vlan fields in the output struct bpf_fib_lookup are always zero. I > > haven't seen this commented on anywhere, including the discussion around > > introducing bpf_fib_lookup, so I assume it's an accidental oversight. > > The uapi was setup to cover the use case, but VLANs are not supported at > the moment. I'm surprised it's not marked as such in the bpf.h, the comments (or rather lack of) made me convinced that it works just as well as the MAC address fields. > On 4/16/21 5:03 AM, Konrad Zemek wrote: > > Do you have any proposals for a workaround? Right now I'm thinking of > > creating a BPF map that would map ifindex->vlan, populated in the userspace > > > > - but that assumes the output (struct bpf_fib_lookup*)->ifindex will be an > > index of the vlan device and not the physical device the vlan is attached > > on, which I'm not sure is the case yet. > > > > vlan netdevices do not support XDP redirect. > > It's not a trivial problem to handle VLANs or stacked devices in > general. I have working code here: > > https://github.com/dsahern/linux/commits/bpf/mpls-vlan-fwd > > but it is not ready for submitting upstream yet. The use case and > related ones need more work. They don't, but it's not that important for my use case. I have just one interface and all the VLANs are on that, so if I learn that a VLAN is needed it's just another thing I push in front of the tunnel frames that I already push. If I had multiple interfaces, I'd just need one more piece of info which is "what's the physical interface number this VLAN is attached on". XDP programs are already pretty specific to the infrastructure one's running, and already very manual with packet manipulation (which is actually a boon to a lot of things I'm doing), so I don't mind this not being a generic solution.
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