The idea for XDP-hints, which is XDP gaining access HW offload hints, dates back to Nov 2017. We believe the main reason XDP-hints work have stalled are that upstream we couldn't get consensus on the layout of the XDP metadata. BTF was not ready at that time.
We believe the flexibility of BTF can resolve the layout issues, especially since BTF have evolved to include support for kernel modules.
This talk is for hashing out upstream XDP-hints discussions and listening to
users/consumers of this facility.
There are multiple users of this facility that all needs to be satisfied:
- BPF-progs first obvious consumer (either XDP or TC hooks)
- XDP to SKB conversion (in veth and cpumap) for traditional HW offloads
- AF_XDP can consume BTF info in userspace to decode metadata area
- Chained BPF-progs can communicate state via metadata
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