On Tue, 2020-11-10 at 23:53 +0000, Patel, Vedang wrote: > > With BTF formatted metadata it is up to the driver to advertise > > whatever it can/want :) > > so yes. > > I have a very basic question here. From what I understand about BTF, > I can generate a header file (using bpftool?) containing the BTF data > format provided by the driver. If so, how can I design an application > which can work with multiple NICs drivers without recompilation? I am > guessing there is some sort of “master list” of HW hints the drivers > will agree upon?
Hi Patel, as Jesper mentioned, some hints will be well defined in BTF format, by name, size and type, e.g.: u32 hash32; u16 vlan_tci; u64 timestamp; etc.. if the driver reports only well known hints, a program compiled with these can work in theory on any NIC that supports them. the BPF program loader/verifier in the kernel can check compatibility before loading a program on a NIC. now the question remains, What if different NICs/Drivers re-arrange those fields differently? this also can be solved by the BPF XDP program loader in the kernel at rung time, it can re-arrange the meta data offsets according to the current NIC directly in the byte code, but this is going to be a future work.
