Jakub Sitnicki revisits storing custom BPF data tied to an skb's lifetime.
In this talk Jakub will recap what he's already established on the XDP/skb metadata feature (scope, accessible hooks, wipe conditions, and driver contract) and then discuss two approaches for paths where XDP metadata isn't supported: a BPF map side-stash available today, and an RFC for embedding a BPF metadata buffer in an skb extension chunk. Jakub will compare both from the BPF-hook interface and overhead perspectives, and explain why alternatives (extending metadata lifetime, BPF local storage) failed.
The latter will delve into skb extension internals—compiling out unneeded extensions and avoiding hot-path allocations—and finally the talk closes with open user-API questions: whether a new socket option or cmsg type is needed, how users exchange metadata today and its limits, and how metadata maps to L7 abstractions like streams and requests.
Come and engage Jakub!
cheers, jamal