Andrii Nakryiko <andrii@xxxxxxxxxx> writes: > Introduce 4 new netlink-based XDP APIs for attaching, detaching, and > querying XDP programs: > - bpf_xdp_attach; > - bpf_xdp_detach; > - bpf_xdp_query; > - bpf_xdp_query_id. > > These APIs replace bpf_set_link_xdp_fd, bpf_set_link_xdp_fd_opts, > bpf_get_link_xdp_id, and bpf_get_link_xdp_info APIs ([0]). The latter > don't follow a consistent naming pattern and some of them use > non-extensible approaches (e.g., struct xdp_link_info which can't be > modified without breaking libbpf ABI). > > The approach I took with these low-level XDP APIs is similar to what we > did with low-level TC APIs. There is a nice duality of bpf_tc_attach vs > bpf_xdp_attach, and so on. I left bpf_xdp_attach() to support detaching > when -1 is specified for prog_fd for generality and convenience, but > bpf_xdp_detach() is preferred due to clearer naming and associated > semantics. Both bpf_xdp_attach() and bpf_xdp_detach() accept the same > opts struct allowing to specify expected old_prog_fd. > > While doing the refactoring, I noticed that old APIs require users to > specify opts with old_fd == -1 to declare "don't care about already > attached XDP prog fd" condition. Otherwise, FD 0 is assumed, which is > essentially never an intended behavior. So I made this behavior > consistent with other kernel and libbpf APIs, in which zero FD means "no > FD". This seems to be more in line with the latest thinking in BPF land > and should cause less user confusion, hopefully. > > For querying, I left two APIs, both more generic bpf_xdp_query() > allowing to query multiple IDs and attach mode, but also > a specialization of it, bpf_xdp_query_id(), which returns only requested > prog_id. Uses of prog_id returning bpf_get_link_xdp_id() were so > prevalent across selftests and samples, that it seemed a very common use > case and using bpf_xdp_query() for doing it felt very cumbersome with > a highly branches if/else chain based on flags and attach mode. > > Old APIs are scheduled for deprecation in libbpf 0.8 release. > > [0] Closes: https://github.com/libbpf/libbpf/issues/309 > > Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx> Acked-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
