bpf_obj_get_info() to retreive prog_tag from the kernel based on prog_fd (kernel 4.13+)
bpf_prog_compute_tag() to compute prog_tag from a set of bpf_insns (kernel independent)
bpf_prog_get_tag() to retrieve prog_tag from /proc/pid/fdinfo/fd (kernel 4.10+)
Signed-off-by: Alexei Starovoitov <ast@fb.com>