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Based on: Subj: libbpf: Helpers to access XDP hints based on BTF definitions https://lore.kernel.org/all/20210803010331.39453-15-ederson.desouza@intel.com/ From: Ederson de Souza <ederson.desouza@intel.com> Ederson says: A new set of functions to help get the BTF definition of XDP hints structure and get the information based on it. `xsk_umem__btf_id` helps retrieve the BTF id of XDP metadata. `xsk_btf__init` sets up a context based on the BTF, including a hashmap, so that subsequent queries are faster. `xsk_btf__read` returns a pointer to the position in the XDP metadata containing a given field. `xsk_btf__has_field` checks the presence of a field in the BTF. `xsk_btf__free` frees up the context. Besides those, a macro `XSK_BTF_READ_INTO` acts as a convenient helper to read the field contents into a given variable. Note that currently, the hashmap used to speed-up offset location into the BTF doesn't use the field name as a string as key to the hashmap. It directly uses the pointer value instead, as it is expected that most of time, field names will be addressed by a shared constant string residing on read-only memory, thus saving some time. If this assumption is not entirely true, this optimisation needs to be rethought (or discarded altogether). Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>